12z Model Comparisons

[Roger J Smith]

I'd like to add my thanks to all those who worked on this particular comparison thread as well as all other model evaluation threads on NW. It has broadened my understanding considerably, and at the same time led to some conclusions of my own, which I'll share here for whatever use they may be (slim to none? we'll see) ...

From the forecast competition, I have come to the conclusion that the GFS is generally the best bet, although it pays to compromise with the GEM or the ECM when they vary considerably from it. The most important factoid I can offer is that the models generally show marked degradation in accuracy nowadays between day 6 and day 8. In other words, you're further ahead in a competition situation to wait out day 7 and use day 6, it improves the forecast by more than the arbitrary score bonus you lose which amounts to about 2-3 C degrees in the scoring system or 12 hours in the timing of pressure or precip events. If you see what I'm getting at, the state of the art for longer term medium range forecasts is now about 6 days from this experience. After that, the improvement is not worth waiting for in scoring terms as John has things set up. And I think that's a valuable perspective on how to use 5-7 day forecast models.

The other rather significant point I could offer here is that the present operational status of the GFS and other models seems to point in the same direction as my research -- there is something "out there" introducing new energy cycles that our very impressive modern technology cannot easily solve or forecast, because it has not yet begun to arrive in the system. I think you'll see from first principles that if energy from outside the system is guiding weather systems, but this energy has a life cycle of about 10-15 days, then its first significant appearance in the "time zero" condition will be around 5 to 7.5 days ahead of the event. This may further explain what my research has been pointing towards, events in the magnetic field that can only be predicted from a cause-and-effect theory, and not from an empirical model.

So all of this research rather tends to reinforce my notion that my own research is on the right track and I really hope that sooner or later this concept will "turn on the light bulb" in the profession in general -- some sort of super model that goes out to day 5 or 6 using the current equations and techniques, then shapes the further development more and more from the theoretical base of timing, could open the door to an accuracy level in the 7-15 day period or further, similar to the current 5-6 day accuracy. In other words, no more Fantasy Island as we now understand that term.

Well, there's no doubt that this is somewhat of a vast leap forward in conceptual thinking and I wish there was some easy way that I could demonstrate this. I tried to do that in December with a map 30 days in advance that some agreed was about as accurate as the usual 5-6 day GFS type forecast. I will try to work out some way of operationally testing out this idea in general in the next few months, but severe blocking like we had in Jan-Feb tends to throw a monkey wrench into my technique, so I have been thinking of going at this in the easier summer to autumn part of the year, getting some experience to refine the method, then seeing if a working 7-15 day adjusted GFS might be within reach. If so, there's no telling how far the thing could be pushed before longer-range trends degraded the accuracy.

Big idea, long post, and probably a fairly long pause before anything else happens. I'm working on this whenever I can, though. One thing for certain, I have made more progress by stumbling into NW by accident than I could have foreseen a year ago when I was trading insults with Bill Farkin on the Beeb site. That was then, this is now.

[BLAST FROM THE PAST]

Big idea, long post, and probably a fairly long pause before anything else happens. I'm working on this whenever I can, though. One thing for certain, I have made more progress by stumbling into NW by accident than I could have foreseen a year ago when I was trading insults with Bill Farkin on the Beeb site. That was then, this is now.

[Thundery wintry showers]

Yes, for all of those who are unclear, that was an April Fool's joke- caught a fair few out it would seem!

I started this thing up partly to satisfy my own curiosity as to how the models are doing and it would be as much a shame for myself as anyone else if I stopped keeping this up. There may well come a time when I find that my time and resources are too limited- but such a time is unlikely to arise until at least the autumn.

PS much appreciated from JACKONE- that will certainly make comparisons results easier come five days' time.

[Thundery wintry showers]

Model Comparisons for T+144, T+120 and T+96 on 4 April 2006.

T+96 (to Saturday 8th April)

GFS: 995mb low over Scotland, cyclonic west to north-westerlies over England and Wales. Sun and wintry showers.

UKMO: 995mb low to the W of Scandinavia, north-westerlies for Britain with a long track from the Arctic. Sun and wintry showers.

ECMWF: 995mb low over Shetland, WNW winds over Britain. Sun, wintry showers.

NOGAPS: 990mb low to the N of Shetland, WNW winds over Britain. Sun, wintry showers.

JMA: 995mb low off Shetland, NW winds over Britain, sun, wintry showers likely.

GEM: 990mb low over NW Scandinavia, W winds in the S, N winds in the N, wintry showers.

Sunshine and April showers is the unanimous verdict for Saturday, with all models agreeing on winds from a north-westerly quarter. All models suggest temperatures that would support some wintriness especially in the north.

T+120 (to Sunday 9th April)

GFS: 1000mb low over S Scandinavia, northerly winds and wintry showers. 1030mb mid Atlantic high.

UKMO: 995mb Scandinavian Low, 1030mb high off W Ireland, northerly winds and wintry showers.

ECMWF: 1005mb low over W Scandinavia, strong 1030mb high in mid Atlantic, wintry/showery northerlies over Britain.

NOGAPS: Undefined

JMA: 1000mb low over Scandinavia, 1030mb mid Atlantic high and northerlies and wintry showers.

GEM: 1000mb low to the N and over Scandinavia, 1030mb high to the WSW, northerlies and wintry showers.

Unanimous verdict: northerly winds, sun, wintry showers.

T+144 (to Monday 10th April)

GFS: 1005mb Scandinavian Low, 1025mb high in mid Atlantic extending to W Ireland, with slack northerlies over Britain. Cold.

UKMO: 1035mb high to the SW, anticyclonic NW winds, 1005mb lows to the N and NE. Warmer in the far W, cold in central and E areas.

ECMWF: 1030mb high to the SW with 1025mb ridge into SW Britain. North-easterlies over all but the far north of Scotland (westerlies) Cold.

NOGAPS: 1025-1030mb high to the SW, 1020mb ridge over to NW Britain. North-easterlies in the S, light winds elsewhere. Cold.

JMA: 1030mb high to the SW, ridge over to SW Britain. Very slack N winds in the south, westerlies elsewhere, warmer air pushing in.

GEM: 1035mb high to the SW, anticyclonic WNW winds over Britain, still in cold air.

Agreement that after a few bright showery days, the setup will topple as a ridge of high pressure moves in from the W and SW.

[Thundery wintry showers]

Model Comparisons for T+144, T+120 and T+96 on 5 April 2006.

T+96 (to Sunday 9th April)

GFS: 1030mb high to the West, 995mb E Scandinavia Low, northerlies over Britain.

UKMO: 1030mb high to the west, 1000mb Scandinavian Low and northerlies.

ECMWF: 1030mb high to the west, 1000mb Scandinavian Low and northerlies.

NOGAPS: 1025mb high to the west, 995mb lows over Scandinavia and to the N, NNW winds over Britain.

JMA: 1030mb high to the west, 1000mb Scandinavian Low and northerlies.

GEM: 1030mb high to the west, 995mb low over Scandinavia and north-westerlies over Britain.

Almost unanimous agreement on a northerly, with only NOGAPS and GEM going for a north-westerly type regime.

T+120 (to Monday 10th April)

GFS: 980mb low west of Iceland, 1030mb high to the SW throwing up a ridge over Britain, northerlies in the S, westerlies in the N.

UKMO: Still 1010mb Scandinavian Low and low pressure way out to the west of Iceland. A 1030mb high with a ridge over Britain, NNE winds for all but the far N (westerlies)

ECMWF: 1005mb Scandinavian Low, 995mb low west of Iceland, 1030mb high to the SW, ridge over Britain with toppling northerlies.

NOGAPS: 1000mb Scandinavian Low, 980mb low west of Iceland, toppling NNE winds in the SE, westerlies elsewhere.

JMA: 1005mb Scandinavia Low, 985mb low W of Iceland, 1035mb high to the SW with a toppling ridge. NNE winds in the E, W winds elsewhere.

GEM: 1005mb Euro Low, 1030mb High to the W/NW, toppling NE winds over Britain.

All models are agreed on a toppler situation but disagree as to the timing of the toppling and where the high will be during the toppling.

T+144 (to Tuesday 11th April)

GFS: 975mb Icelandic Low, 1030mb high to the south, strong westerly winds.

UKMO: 990mb lows north of Iceland, 1030mb high covering SW Britain, and light WSW winds.

ECMWF: 1030mb high way out to the SW, 985mb low west of Iceland, and WSW winds over Britain.

NOGAPS: 975mb low west of Iceland, 1020mb ridge of high pressure covering SE England from a 1030mb Azores High, and SW winds.

JMA: 965mb low E of Iceland, 1030mb high covering extreme S of England, westerly winds.

GEM: 1025mb high over Britain connected to 1030mb Azores High. Anticyclonic.

The toppling will complete according to the models, but outputs vary from having the high over Britain to having it well away to the SW with westerlies powering in.

[Thundery wintry showers]

I have fallen behind with these model comparisons; here in one fell swoop, I will bring it up-to-date. The system has changed slightly in that I will be saving the images to my hard drive on an evening, and updating the comparison the next day. This will allow for more leeway in situations where I have limited time on an evening, and also give me the actual charts to compare T+0 to (as opposed to just my descriptions)

Model Comparisons for T+144, T+120 and T+96 on 6 April 2006.

T+96 (to Monday 10th April)

GFS: 975mb low west of Iceland, toppling northerly over southern Britain, westerlies in the north, 1030mb high to the SW.

UKMO: Big 975mb low west of Iceland, 1030mb high to the SW, westerlies over most of Britain, still northerlies in extreme south.

ECMWF: 1030mb high to the SW, 980mb Icelandic Low, westerlies for most, but northerlies in extreme south.

NOGAPS: 975mb low west of Iceland, 1030mb high quite a way out to the SW, westerlies.

JMA: 975mb low west of Iceland, 1030mb high to the SW, 1020mb ridge over Britain, light WSW winds.

GEM: 1035mb high to the SW, toppling NE winds for most parts, westerlies for extreme north.

Toppling is a certainty according to the models; but specifics vary.

T+120 (to Tuesday 11th April)

GFS: 985mb Icelandic Low, 1030mb high to the SW, strong WNW winds over Britain.

UKMO: 980mb low east of Iceland, 1030mb high to the SW, strong WNW winds over Britain.

ECMWF: 980mb Icelandic Low, 1030mb high to the SW, westerlies over Britain.

NOGAPS: 975mb low SE of Iceland, 1030mb high well away to the SW, WNW winds over Britain, cyclonic.

JMA: 975mb low W of Iceland, 1035mb high well away to the SW, 1005mb low over N Scotland, westerlies over Britain.

GEM: 985mb low E of Iceland, 1030mb high well to the SW but with 1020mb ridge into S England. Westerlies in the north.

All models apart from GEM suggest unsettled weather trying to take over from the west.

T+144 (to Wednesday 12th April)

GFS: 990mb low to the N, 1025mb high to the S and SW, strong WNW winds.

UKMO: 985mb low to the N, 1030mb high to the S/SW and WNW winds, high pressure in charge for the south.

ECMWF: 995mb lows to the north, 1025mb high to the south with 1030mb centre in the Azores, WNW winds, high pressure in charge over the south.

NOGAPS: 985mb low to the N dominating our weather with westerlies, 1030mb high well away to the SW.

JMA: 985mb Icelandic Low, 1030mb high well to the SW, WNW winds and low pressure in charge.

GEM: 975mb low to E of Iceland, 1035mb high well out to the SW, westerlies over Britain.

Pressure will be high to the SW and low to the N- but which will prevail for the British Isles.

[Thundery wintry showers]

Model Comparisons for T+144, T+120 and T+96 on 7 April 2006.

T+96 (to Tuesday 11th April)

GFS: 980mb Icelandic Low, 1030mb high to the S/SW, WNW winds over Britain.

UKMO: 980mb low just E of Iceland, WNW winds over Britain, 1030mb high to the SW.

ECMWF: 980mb low over Iceland, 1030mb high to the SW, WNW winds over Britain.

NOGAPS: 975mb low W of Iceland, WNW winds over Britain, 1030mb high well to the SW.

JMA: 980mb Icelandic Low, 1015mb high to the E, 1030mb High to the SW, SW winds over Britain.

GEM: 965mb Icelandic Low, 1030mb high well to the SW, westerlies over Britain.

Looks like the UKMO and ECMWF and GEM backed down from their anticyclonic outlook.

T+120 (to Wednesday 12th April)

GFS: 990mb low E of Iceland, 1020mb high to the S just covering the south coast, strong westerlies.

UKMO: 990mb low E of Iceland, 1025mb high to the SW, strong westerlies.

ECMWF: 995mb low E of Iceland, 1025mb high to the SW, moderate westerlies.

NOGAPS: 980mb low W of Iceland, 995mb low to the NE, WNW winds over Britain.

JMA: 1015mb Scandinavian High, 1030mb high to the SW, 980mb low W of Iceland. Light winds.

GEM: 970mb low E of Iceland, weak 1020mb High to the South and westerlies.

Westerlies look set to be the outcome according to this set of models.

T+144 (to Thursday 13th April)

GFS: 990mb low to the N, 1015mb high to the SE, and light to moderate WSW winds, a long southerly drag extending towards southern Britain.

UKMO: 985mb low to the N, 1015mb high to the south, strong westerlies.

ECMWF: 970mb low off N Scotland with very strong winds, westerlies, 10154mb high to the S.

NOGAPS: 980mb low to the NW, 990mb low over Scotland, WNW winds. Low pressure firmly in charge.

JMA: 970mb low S of Iceland and westerlies.

GEM: 975mb low to E of Iceland, strong WSW winds over Britain.

GFS goes for a potential southerly plume, the others suggest that it will be unsettled, probably with a continuation of the traditional April showers theme.

[Thundery wintry showers]

Model Comparisons for T+144, T+120 and T+96 on 8 April 2006.

T+96 (to Wedensday 12th April April)

GFS: 990mb low to the E of Iceland, 1000mb low to the NE, WNW winds over Britain.

UKMO: 990mb low over Iceland and moderate westerlies.

ECMWF: 990mb lows E of Iceland and off NW Scotland, strong cyclonic WSW winds.

NOGAPS: Unavailable

JMA: 990mb Icelandic Low, westerlies (moderate) over Britain.

GEM: 985mb low to the north and moderate westerlies.

It appears that ECMWF is out on its own with this deep low to the north and strong to gale force winds, other models suggesting moderate westerlies.

T+120 (to Thursday 13th April)

GFS: 990mb low to the N, 1015mb high to the SE and light WSW winds. Long southerly drag just to the south.

UKMO: 985mb low over Scotland, very strong cyclonic westerlies further south.

ECMWF: 990mb low to the north- a very large low. Cyclonic westerlies.

NOGAPS:

JMA: 970mb low off NW Scotland and strong westerlies.

GEM: 985mb low off N Scotland and cyclonic westerlies.

GFS is sticking by its more settled/warmer outlook from yesterday but remains at odds with the other models.

T+144 (to Friday 14th April)

GFS: 990mb low off W Scandinavia with moderate WNW winds.

UKMO: 990mb low off W Scandinavia, 980mb Icelandic Low and westerlies.

ECMWF: 990mb Scandinavian Low, 985mb Icelandic Low. Westerlies.

NOGAPS:

JMA: 980mb low covering Shetland, cyclonic W/WNW winds over Britain.

GEM: 990mb Scandinavian Low, 985mb Icelandic low, WNW winds.

A very zonal outlook in the truest sense of the word, with westerlies dominant and lows moving west to east. GFS is traditionally good in this kind of setup but it remains to be seen whether the GFS has fallen down in accuracy even in this kind of setup.

[Thundery wintry showers]

Model Comparisons for T+144, T+120 and T+96 on 9 April 2006.

T+96 (to Thursday 13th April)

GFS: 975mb low just off N Scotland with very strong westerlies.

UKMO: 975mb low just off N Scotland with very strong westerlies, more cyclonic than on the GFS.

ECMWF: 985mb low just to the W of W Norway, with strong WNW winds over Britain and slack high pressure over Europe.

NOGAPS: As ECMWF, but with winds of a westerly direction over Britain rather than WNW due to slightly different orientation of the low.

JMA: Deep 985mb low just to the NNW of Scotland with cyclonic, strong to gale force WSW winds over Britain.

GEM: 985mb low centred over southern Norway, with low at 990mb generally to the north, and WNW winds over Britain.

Some disagreement over low positioning, but it looks like there will be west to WNW winds and it will be unsettled with either rain, or sunshine and April showers.

T+120 (to Friday 14th April)

GFS: 990mb low W of Iceland, 985mb low just NW of western Norway, and moderate WNW winds over Britain. 1020mb high over the Azores and slack high pressure over Europe.

UKMO: 980mb Icelandic Low, 985mb low W of Norway, with weak 1015mb high over Europe. Westerlies and a weak ridge of high pressure over Britain.

ECMWF: Three 990mb lows to the north, with slack westerlies over Britain and a weak ridge of high pressure, 1020mb centre over the Med.

NOGAPS: Again similar to ECMWF, but with the 1020mb high more pronounced and sending warm southerlies into southern Britain, slack westerlies in the north.

JMA: 1000mb low over SW Norway and 990mb Icelandic Low, NW winds over Britain.

GEM: 985mb low centred over Sweden and NW winds over Britain.

JMA and GEM and to a lesser extent GFS look quite showery with north-westerly winds. UKMO and ECMWF think that a ridge of high pressure will affect Britain while NOGAPS goes for a southerly plume. Whatever happens, indications are that Good Friday will be sunny, either with or without showers.

T+144 (to Saturday 15th April)

GFS: 990mb low over Iceland, westerly winds over Britain.

UKMO: 990mb low to the SW of Iceland with westerly winds.

ECMWF: 995mb low to the south and SE of Iceland, southerlies in the east, westerlies in the west, slack regime, southerly plume just to the east.

NOGAPS: 990mb low S of Iceland, southerly plume affecting Britain but with low pressure in charge, 1000mb low to the South.

JMA: 1025mb high to the SW controlling the weather in the South, more unsettled in the North with westerly winds and 990mb Icelandic Low.

GEM: 995-1000mb low complex to the north, WNW winds over Britain and a high to the SW.

Much disagreement into the Easter weekend.

[Thundery wintry showers]

I missed the 10th April, but can update the 12th quite easily. Had trouble saving anything to my hard drive on 11 April- WZ seemed to have messed up most of the runs.

Model Comparisons for T+144, T+120 and T+96 on 12 April 2006.

T+96 (to Sunday 16th April)

GFS: No GFS available- for some unknown reason it saved a random combination of 9/10 April runs onto my hard drive! Why?

UKMO: 990mb low to the W of Norway, moderate westerlies in the north, slack 1010mb pressure over southern Britain with 1010mb low in the Channel.

ECMWF: 985mb low to the W of Norway feeding in slack NW winds and 1025mb high to the SW. Quite a cyclonic outlook.

NOGAPS: 985mb low to the W of Norway, cyclonic westerlies over Britain and high pressure well to the south.

JMA: Almost identical to the ECMWF but with the low to the north at 990mb.

GEM: 985mb low to the W of Norway feeding in cyclonic westerlies, but 1025mb Azores High trying to influence the extreme south.

The outlook for Easter Sunday is quite settled in the south according to UKMO, but on other models looks showery and quite cool with westerly or north-westerly winds.

T+120 (to Monday 17th April)

GFS:

UKMO: 985mb low over west coast of Norway, 1010mb Icelandic Low and 1010mb low in North Sea, slack northerlies over Britain.

ECMWF: 990mb low covering west coast of Norway, cyclonic NW winds but 1025mb Azores High close by.

NOGAPS: 985mb low, west coast of Norway, with cyclonic WNW winds of cold origin.

JMA: 990mb lows centred over Scandinavia, moderate westerlies, weak 1015mb high over the extreme south.

GEM: 985mb low over SW Norway, WNW winds over Britain but 1020mb Azores High influencing the extreme south;.

Again the outlook is quite showery with NW winds, but some models have the Azores High playing a significant role in southern parts.

T+144 (to Tuesday 18th April)

GFS:

UKMO: 995mb low over Scandinavia, 1005mb extension to Iceland, moderate W winds, 1020mb high extending influence into the south.

ECMWF: 990mb Scandinavian Low, more cyclonic WNW winds, still 1025mb Azores High.

NOGAPS: 985mb low to the W of Norway, light cyclonic westerlies, looking showery.

JMA: 995mb low off SE Norway with NW winds over Britain, cyclonic in nature.

GEM: 990mb Scandinavian Lows, slack WNW winds and high pressure at 1020mb to the W of Spain ridging north.

Looks like it will continue to be a battle between showery NWs and the Azores High.

[Thundery wintry showers]

Some good news: the problems with downloading the images has been sorted and 13-15 April are now available:

Model Comparisons for T+144, T+120 and T+96 on 13 April 2006.

T+96 (to Monday 17th April)

GFS: 990mb Scandinavian Low, 1025mb Azores High and light WNW winds, high in charge over southern England.

UKMO: 990mb over west coast of Norway and 1025mb Azores High. Less "flat" a WNW pattern than GFS with a more cyclonic, showery looking regime.

ECMWF: 990mb low to the W of Norway, 1025mb Azores High with anticyclonic WNW winds in the south, but a more cyclonic influence in the north.

NOGAPS: Unavailable.

JMA: 990mb low over west coast of Norway, slack WNW winds over Britain, 1025mb Azores High.

GEM: 985mb Scandinavian Low, 1020mb Azores High, strong westerly winds.

Good agreement among the models on a WNW pattern, but disagreement on the exact positioning of the low to our north.

T+120 (to Tuesday 18th April)

GFS: 1020mb high to our south with a ridge into southern England, moderate westerlies and a ridge of high pressure firmly in charge.

UKMO: 990mb low off W Norway, a moderate westerly flow over Britain with slack high pressure to the south.

ECMWF: 985mb low off W Norway, 1000mb low to the NW, 1020mb ridge of high pressure extending into S England. Westerlies.

NOGAPS:

JMA: 990mb low over NW Norway, slack westerlies over Britain, high pressure at 1025mb to the SW.

GEM: Slack 1015mb high to the south, WSW winds, 1000mb low to the NW, 990mb Scandinavian Low.

The outlook is one of moderate westerly winds, possibly with high pressure dominating over the south.

T+144 (to Wednesday 19th April)

GFS: Very deep 975mb low off W Scotland, gale force westerlies over Britain, extremely windy looking pattern.

UKMO: 1005mb lows to the NW and NE, moderate westerlies, high pressure to the south.

ECMWF: Deep 990mb low to the north, with very strong westerly winds over Britain but not as excessively so as on the GFS, still a slack high to the S.

NOGAPS:

JMA: 995mb low off W Scotland, and south-westerly winds over Britain.

GEM: 990mb low off W Scotland and strong SSW winds over Britain.

GFS and ECMWF go for strong westerlies, UKMO for moderate westerlies, and JMA and GEM for strong south/south-westerlies. The excessively deep low shown by GFS should not be trusted.

[Thundery wintry showers]

Some good news: the problems with downloading the images has been sorted and 13-15 April are now available:

Model Comparisons for T+144, T+120 and T+96 on 14 April 2006.

T+96 (to Tuesday 18th April)

GFS: 985mb low W of Norway, 995mb low to the NW, moderate westerly winds.

UKMO: 990mb low W of Norway and moderate westerly winds, slack high pressure to the south.

ECMWF: 990mb low W of Norway, moderate westerlies over Britain, slack 1020mb high to the south.

NOGAPS: Unavailable.

JMA: 990mb low off NW Norway, 1020mb Azores High the dominant feature especially for southern England, with moderate westerly winds.

GEM: 990mb low off W Scandinavia, moderate westerlies over Britain.

Good agreement that moderate westerly winds will dominate.

T+120 (to Wednesday 19th April)

GFS: Deep 985mb low to the north, strong to gale force westerlies, very similar to yesterday's ECMWF T+144.

UKMO: 985mb low to the NW, not really yet affecting Britain, with moderate WSW winds, 990mb low still W of Norway.

ECMWF: 1000mb low over N Scotland, much shallower than yesterday's at T+144. Cyclonic westerly winds, moderate.

NOGAPS:

JMA: 995mb low off N Scotland, 1000mb low in the Atlantic, a conveyor belt of mild WSW winds.

GEM: Slack 1000mb low over western Scotland with moderate SW winds, veering northerly in the far NW.

Some disagreement here, though a zonal pattern is generally agreed upon.

T+144 (to Thursday 20th April)

GFS: 990mb lows to the NW and over Scandinavia, strong SW winds.

UKMO: 970mb low off NW Scotland and strong WSW winds, gales in NW Scotland.

ECMWF: Deep 990mb low to the SW with very strong S winds over the south-western part of Britain, light winds elsewhere.

NOGAPS: T+144 is here: 990mb low off W Ireland and strong southerlies over Britain, cyclonic in nature.

JMA: 985mb low over Northern Ireland with strong SSW winds over Britain.

GEM: Very slack low pressure over Britain, centred at 1000mb off NE Scotland. Very light westerlies, veering northerly to the NW.

Quite a wide split at T+144.

[Thundery wintry showers]

Model Comparisons for T+144, T+120 and T+96 on 15 April 2006.

T+96 (to Wednesday 19th April)

GFS: Slack 1000mb low to the NW and moderate WSW winds over Britain.

UKMO: 1005mb low over Wales, very slack WSW airflow over Britain.

ECMWF: 1010mb lows to the N, 1020mb high to the SW and very slack westerlies.

NOGAPS: 995mb low over N England and a very cyclonic outlook.

JMA: 990mb low off W Norway, with 1005mb low over Iceland and slack WSW winds.

GEM: SW winds, 1000mb low off W Scotland, 995mb low off W Scandinavia.

Light WSW/SW winds seems to be the outlook except for NOGAPS.

T+120 (to Thursday 20th April)

GFS: 995mb low off NW Scotland, secondary low in the Channel, moderate SW winds.

UKMO: 1000mb Icelandic Low, 1005mb low to the SW and moderate WSW winds.

ECMWF: Azores High at 1025mb getting closer with 1020mb isobar covering the south, very slack westerlies.

NOGAPS: 990mb low off SW Norway,light winds in the W, NW winds elsewhere.

JMA: 995mb low over central England, cyclonic outlook.

GEM: 995mb low over East Anglia, N winds elsewhere, very cyclonic.

A secondary depression is likely to track close to Britain according to all models bar NOGAPS and, interestingly, ECMWF.

T+144 (to Friday 21st April)

GFS: 1000mb low off East Anglia with 1005mb extension up the North Sea and strong northerly winds over Britain, not of especially cold origin though.

UKMO: 1000mb low in the North Sea, strong northerlies over Britain.

ECMWF: 1025mb high from the Azores covering all but the far N of Scotland (light westerlies). High pressure outlook.

NOGAPS: 1010mb low to the S, 990mb Scandinavian Low, ridge of high pressure over Britain in a generally northerly flow.

JMA: 1000mb low in the North Sea, very strong northerlies over Britain.

GEM: 1005mb low in the north sea and very strong northerlies over Britain.

Most go for northerlies, but the ECMWF is out on its own with a high pressure outlook- will it be right?

[Thundery wintry showers]

Model Comparisons for T+144, T+120 and T+96 on 15 April 2006.

T+96 (to Thursday 20th April)

GFS: 995mb low over NW Scotland with strong SW winds over Britain.

UKMO: Deep 985mb low over W Scotland, very strong WSW winds over Britain.

ECMWF: 1005mb low to the north, 1010mb secondary low to the SW, westerly winds.

NOGAPS: 990mb low to the W of Scotland, with WSW winds over Britain, strengthening to strong SWs in the west.

JMA: Ridiculously deep 965mb low S of Iceland with strong WSW winds over Britain.

GEM: 990mb lows to the N and NW, WSW winds over Britain but strong SWs approaching the west.

The secondary low is generally positioned to our NW, I suspect that JMA may have overdeepened it a tad, while ECMWF has this low a lot further south than the other models.

T+120 (to Friday 21st April)

GFS: 990mb low off NE Scotland with very strong north-westerly winds over Britain.

UKMO: 1000mb low in the North Sea, strong northerlies for Britain.

ECMWF: 1005mb Scandinavian Low, moderate northerlies for Britain, strong 1030mb Azores High.

NOGAPS: Very deep 985mb low over NE England and a cyclonic outlook, very windy everywhere.

JMA: 975mb low over NW Scotland with strong to gale force south-westerly winds, cyclonic.

GEM: 985mb low over W England, very cyclonic and windy.

UKMO and ECMWF put the low to the E with northerlies, the GFS puts it to the NE with north-westerlies, the JMA has it to the NW with very strong SWs, and NOGAPS and GEM plant it over the British Isles. It will be interesting to see which model has it right.

T+144 (to Saturday 22nd April)

GFS: 995mb Scandinavian Low, 1000mb low to the NW, westerlies over Britain, a messy picture. 1025mb Azores High.

UKMO: 1000mb low to the north, 1030mb Azores High and westerly winds.

ECMWF: 970mb Icelandic Low with wet/windy westerlies over Britain, 1030mb Azores High.

NOGAPS: 995mb low in the North Sea and 1010mb ridge of high pressure over the south.

JMA: 1000mb low in the North Sea and moderate northerlies.

GEM: 990mb low off East Anglia, cyclonic northerlies over Britain.

JMA and GEM go for northerlies, the GFS, UKMO and ECMWF go for a strong Azores high but lows to the north meaning a warm, damp westerly flow. Notable is that the ECMWF has strongly backtracked from yesterday's high pressure outlook.

[Thundery wintry showers]

Model Comparisons for T+144, T+120 and T+96 on 17 April 2006.

T+96 (to Friday 21st April)

GFS: Low at 1005mb over France, 980mb low west of Iceland, 1030mb Azores High, northerlies over Britain.

UKMO: 1010mb low over France, with northerlies in the west, light easterlies elsewhere.

ECMWF: 1010mb low over W France, slack northerly winds over Britain.

NOGAPS: Unavailable again.

JMA: 1010mb low over N France, light northerlies for Britain.

GEM: 1000mb low over N France, quite cyclonic, light NE winds over Britain.

The models are agreed on a low over France, with north or east winds over Britain but not of a very cold origin.

T+120 (to Saturday 22nd April)

GFS: 980mb Icelandic Low, 1025mb Azores High ridging into S England, westerlies over Britain.

UKMO: 975mb Icelandic Low, 1030mb Azores High, WSW winds.

ECMWF: 970mb Icelandic Low, 1030mb Azores High and WSW winds.

NOGAPS:

JMA: 990mb Icelandic Lows, 1030mb Azores High, warm WSW winds.

GEM: 1005mb low centred over E France, 990mb Icelandic Low, 1030mb Icelandic High, northerlies for most but turning westerly in the west.

Apart from GEM, all models have warm westerlies over Britain, probably with a lot of cloud.

T+144 (to Sunday 23rd April)

GFS: 1025mb high to the south, 990mb lows to the north, ridge of high pressure and slack westerlies over Britain.

UKMO: 1030mb Azores High, 975mb low to the east of Iceland, westerly winds over Britain.

ECMWF: 980mb lows to the north, weak secondary lows over S England, with light westerlies further north.

NOGAPS:

JMA:980mb Icelandic Low, 1030mb Azores High ridging towards Britain, with warm WSW winds.

GEM: 975mb Icelandic Low, 1025mb high to the south, slack westerlies.

A consistent outlook from the models, with a warm westerly regime but probably not much sunshine.

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Model Comparisons for T+144, T+120 and T+96 on 18 April 2006.

T+96 (to Saturday 22nd April)

GFS: 975mb low just W of Iceland, 1025mb Azores High, strong westerlies, particularly strong in the north.

UKMO: 970mb Icelandic Low, a generally WSW flow but high pressure over the southeast.

ECMWF: 970mb Icelandic Low, westerlies over Britain but high pressure prevailing in the south.

NOGAPS: Unavailable again.

JMA: 975mb Icelandic Low, WSW winds, but high pressure dominant in the south.

GEM: 980mb low west of Iceland, NE winds for most of Britain with the Azores High penetrating east, 1010mb low over E France.

It looks like GEM is out on its own, with all other models going for low pressure over Iceland and WSW winds; all going for high pressure in the south bar GFS, and a WSW regime.

T+120 (to Sunday 23rd April)

GFS: 980mb Icelandic Low, moderate WSW winds over Britain, of warm origin in the south but looking windy/showery in the north.

UKMO: 970mb Icelandic Low and westerly winds. Pressure still high over the south.

ECMWF: 970mb Icelandic Low, SW winds in the north, but slack pressure gradient in the south at 1010-1015mb.

NOGAPS:

JMA: 975mb low NE of Iceland, westerlies over Britain, still high pressure close to the south.

GEM: 970mb Icelandic Low, 1025mb Azores High and westerly winds over Britain.

Very good agreement on a westerly pattern with an Icelandic Low.

T+144 (to Monday 24th April)

GFS: 985mb low to the north, continued WSW winds.

UKMO: 980mb low just E of Iceland, now cyclonic with low pressure and westerly winds.

ECMWF: 975mb Icelandic Low, WSW winds, the low extending towards the SE.

NOGAPS: 995mb low in the North Sea and 1010mb ridge of high pressure over the south.

JMA: 985mb Icelandic Low, a flat westerly pattern with 1020-1025mb high to the south.

GEM: Big 985mb Icelandic Low, WSW winds over Britain.

Still good agreement among the models, with westerly winds continuing to prevail.

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Model Comparisons for T+144, T+120 and T+96 on 19 April 2006.

T+96 (to Sunday 23rd April)

GFS: 975mb Icelandic Low, strong WSW winds in the north but high pressure in the south, probably promising some warm sunny weather.

UKMO: 970mb low just E of Iceland, high pressure over most of Britain but strong WSW winds in northern Scotland.

ECMWF: 965mb low just E of Iceland, high pressure, but WSW winds in northern Scotland.

NOGAPS: Unavailable again.

JMA: 980mb low NE of Iceland, 985mb low W of Iceland, with high pressure over the entire of the British Isles and WSW winds off northern Scotland.

GEM: Large 980mb Icelandic Low, westerlies over Britain, high pressure away to the south.

It looks like GEM is out on its own again- all other models say high pressure over England & Wales.

T+120 (to Monday 24th April)

GFS: 980mb Icelandic Low, SW winds in the north, but high pressure again dominant over the SE.

UKMO: 985mb low W of Iceland, 980mb low to the NE of Iceland, and high pressure in the south, WSW winds for most.

ECMWF: 985mb low SW of Iceland, 975mb low NE of Iceland and SW winds, high pressure at 1030mb over Russia.

NOGAPS:

JMA: 975mb low W of Iceland, SW winds over Britain, and high pressure.

GEM: 980mb low to the west of Iceland, high pressure ridge over southern Britain (1020mb) and WSW winds.

Very good agreement on a SW pattern with high pressure in charge for the south.

T+144 (to Tuesday 25th April)

GFS: 980mb low over E Iceland, with WSW winds becoming more pronounced, a front moving in from the west.

UKMO: 990mb Icelandic Low and strong SW winds over Britain, low pressure moving closer.

ECMWF: 985mb low NE of Iceland, SW winds, and low pressure moving closer.

NOGAPS: 995mb low in the North Sea and 1010mb ridge of high pressure over the south.

JMA: 980mb low just N of Iceland, moderate SW winds, low pressure getting closer but making less impression than on the other models.

GEM: 985mb Icelandic Low, SW winds, low pressure approaching from the west.

Good agreement that by Tuesday, conditions will be turning more unsettled from the west.

[Thundery wintry showers]

I hope people don't mind this, but with regards this thread for "12Z Model Comparisons", I have decided to revert to a format where T+96 and T+120 and T+144 are presented as a summary of the differences between the models, rather than saying what each individual model says in turn.

This is partly because the former format was mainly for use when I didn't download the runs to my hard drive, and so needed a description in this thread to compare the actual outcome with, whereas now that I have the images on my hard drive each time, I don't need a description. The other reason is that detailing each of the models in turn was by far the most time-consuming aspect of this particular thread.

I have no intention of changing anything with the "Model Comparisons Results" thread though- that will remain as it has always been.

Model Comparisons for T+144, T+120 and T+96 on 20 April 2006.

NOGAPS was unavailable.

T+96 (to Monday 24th April)

There is strong agreement among the models on a 970-975mb Icelandic Low, a 1030mb High over the Baltic, and a slack high pressure area over most of Britain, with strong SSW winds in the far northwest. However, the UKMO has a more elongated 980mb Icelandic Low and the SSW flow affecting the whole of Britain.

T+120 (to Tuesday 25th April)

At T+120, there is somewhat more divergence. The GFS goes for a flat 975mb Icelandic low and WSW winds over Britain, a pattern agreed with by the UKMO. ECMWF and GEM have high pressure holding on in the SE, with a conveyor belt of warm SW winds elsewhere, and JMA has high pressure persisting over the British Isles, with the Icelandic Low rather less deep than on the other models, at only 985mb.

T+144 (to Wednesday 26th April)

At T+144, there is more of a split among the models. The GFS has a slack westerly flow with a 1010mb low over N Scotland, an outcome agreed with by the ECMWF, while the UKMO has a deep 980mb low to the north, and a strong WNW flow over Britain. Meanwhile, GEM goes with high pressure holding on in southern Britain and lowest pressure at 970mb still over Iceland, and JMA also sticks with high pressure in the SE, with more of a SW flow for north-western areas. Hence it is GFS, ECMWF and UKMO (low pressure and westerlies) vs GEM and JMA (high pressure).

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Model Comparisons for T+144, T+120 and T+96 on 21 April 2006.

NOGAPS was unavailable.

T+96 (to Tuesday 25th April)

The GFS goes for a very deep 965mb Icelandic Low at T+96, with SW winds in the northwest, and high pressure in the southeast, with a slack 1015-1020mb Euro High. UKMO and GEM are in broad agreement, but with a slacker Icelandic Low (980mb) with ECMWF having the low at 975mb and the same pattern. JMA has more of a SSW flow with the low centred to the W of Iceland at 980mb, while NOGAPS goes for a more progressive cyclonic westerly pattern with a 980mb Icelandic Low.

NOGAPS is probably the odd one out here, the others say high pressure will cling on in the SE.

T+120 (to Wednesday 26th April)

GFS has a weak 1005mb low over N Scotland, with 985mb Icelandic Low and 1025mb Azores High, and showery looking WNW winds. UKMO is the same but without the Icelandic Low. ECMWF has an Icelandic Low, but no low over N Scotland, and a WSW flow with high pressure over the south.

NOGAPS has a slack westerly flow over Britain, while GEM goes for a strong ridge from the Azores High into southern Britain, and JMA has a slack westerly flow penetrating from the west, and a weak 995mb Icelandic Low.

GEM seems to be the odd one out with its high pressure scenario.

T+144 (to Thursday 27th April)

GFS has a strong 1005mb low over N Scotland at T+144, with strong WNW winds over Britain, and a 1030mb Azores High. UKMO is similar but with a 1000mb low centred off Shetland, and the high a little closer.

ECMWF goes for north-westerlies with the Azores High extending into SW England, a scenario agreed with by the NOGAPS. JMA has a 1010mb low over NE Scotland and north-westerlies, while GEM persists in sticking high pressure over the southern half of Britain.

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Model Comparisons for T+144, T+120 and T+96 on 22 April 2006.

T+96 (to Wednesday 26th April)

GFS and ECMWF both have a strong 1025mb Azores High just to the SW, and low pressure quite a way away to the north, with light-moderate westerly winds over Britain. The UKMO, JMA and GEM beg to differ, with 1005mb low pressure just N of Scotland and moderate-strong WNW winds, which would be showery. NOGAPS opts for an intermediate scenario; low pressure at 990mb off N Scotland, 1025mb Azores High and a high pressure outlook for the S, showery WNW'lys for the north.

So it is the anticyclonic GFS & ECMWF vs the cyclonic UKMO, JMA and GEM.

T+120 (to Thursday 27th April)

GFS has a 1030mb Azores High on our doorstep, just over SW England, with light westerlies elsewhere, and a highly anticyclonic outlook. Other models are not as anticyclonic in outlook, with ECMWF keeping the high just off SW England, and strong NW winds for the north-eastern quarter of Britain with a 1005mb low just W of Scandinavia. UKMO and JMA are quite similar to the ECMWF, with 1005-1010mb low pressure just north of Scotland, showery WNW winds in the north, but high pressure dominating in the south. NOGAPS unavailable at T+120.

GEM looks decidedly cyclonic with a 1000mb low just off NE Scotland and showery NW winds,

Overall, the GFS seems to be more anticyclonic than the other models.

T+144 (to Friday 28th April)

GFS is anticyclonic again, with a 1030mb Azores High covering almost the entire country. The JMA is not dissimilar with the high situated over SW England and only light westerlies. The UKMO continues the theme of 1010mb low to the N of Scotland and 1035mb Azores High displaced into the mid-Atlantic, with some showery north-westerlies for the north.

ECMWF and NOGAPS go for a solution with high pressure just to the W and light northerlies, while GEM continues with low pressure in charge and a showery north-westerly.

b]Model Comparisons for T+144, T+120 and T+96 on 23 April 2006.

NOGAPS was unavailable.

T+96 (to Thursday 27th April)

GFS continues with yesterday's anticyclonic outlook, with a 1030mb high centred just off SW England, and moderate westerlies in the north, but an anticyclonic outlook everywhere, particularly the south. UKMO and ECMWF give very similar outlooks to the GFS, so they appear to have fallen into line with GFS this time.

JMA positions the high to the SW but gives light north-westerlies over Britain, while GEM begs to differ, putting the high in the mid Atlantic and giving Britain NNW winds.

T+120 (to Friday 28th April)

GFS positions the (1035mb) high in the mid Atlantic, giving an anticyclonic northerly flow. I reckon that there would be anticyclonic gloom for many areas if that came off. Again, the UKMO and ECMWF agree strongly with the GFS output. GEM has the high further west and at 1030mb, with a cool/unsettled northerly regime, while JMA has the high only at 1030mb, but further east than the other models, so only very light northerlies for Britain.

T+144 (to Saturday 29th April)

GFS has a strong 1030mb Azores High that ridges into southern Britain, promising more anticyclonic weather, with moderate westerlies in Scotland. The ECMWF, again, agrees with the GFS outcome. The UKMO has the high over Ireland with light northerlies, while GEM and JMA both have the high in the mid Atlantic with northerlies over Britain and low pressure over Scandinavia and the North Sea- an outlook that reminds me of early June 1995.

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Model Comparisons for T+144, T+120 and T+96 on 25 April 2006.

T+96 (to Saturday 29th April)

GFS has a 1025mb Azores High ridging in towards Ireland, with northerlies for the eastern half of Britain, and a low to the ESE, a conclusion broadly agreed with by the ECMWF.

UKMO has the high stronger, at 1030mb, with a 1010mb low over S Scandinavia, and NNW winds over Britain.

NOGAPS, however, has a 1030mb high almost right over the British Isles.

GEM and JMA have the high at only 1025mb and the low quite prominent to the East, meaning a more unsettled northerly regime.

T+120 (to Sunday 30th April)

GFS has a 1000mb Icelandic Low, and a slack 1015mb high to the south, with WSW winds moving eastwards over the British isles.

UKMO has the Icelandic Low much deeper, at 985mb, and some pretty strong westerly winds over the British Isles.

ECMWF has 1020mb high to the SE and as a ridge from the Azores, with high pressure in the S but westerlies in the N.

NOGAPS is unavailable, while GEM and JMA remain in good agreement, with the low to the NW being slacker, and westerly winds over Britain.

T+144 (to Monday 1st May)

At T+144, GFS deepens the Icelandic Low to 990mb, and has a 1005mb low over NW Scotland and light westerlies over Britain.

UKMO looks completely different, with 990-995mb lows over N Scotland and strong, showery looking WNW winds over Britain. NOGAPS and GEM broadly agrees with UKMO but with the low centred more over Iceland.

ECMWF has slack pressure over Britain, with a 1005mb low over southern Britain.

JMA has a slack low right over Britain at at 1000mb.

So it looks like turning more unsettled from the north-west, but models disagree on the specifics.

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Model Comparisons for T+144, T+120 and T+96 on 26 April 2006.

T+96 (to Sunday 30th April)

GFS still has 995mb Icelandic Low, and WSW winds for the north, but there is also a 1010mb low over the near Continent, with light easterly winds for the south.

UKMO has the Icelandic Low at 1000mb, and a 1010mb low in the North Sea, giving a slack regime over Britain, and looking quite unsettled.

ECMWF looks similar to UKMO, but with the low in the North Sea further south, just off East Anglia.

NOGAPS has the 1010mb low actually over East Anglia, so shows northerlies for Britain, with the exception of N Scotland (easterlies)

JMA has a 1010mb low over the far SE, with southerly winds in the west, and easterlies elsewhere. GEM is unavailable.

T+120 (to Monday 1st May)

GFS has a flabby 1005mb low over the west and south of Britain, with easterly winds across the northern half of Britain.

UKMO prefers a westerly scenario, with a 1005mb low over N Scotland, and westerly winds for Britain.

ECMWF has a very strong Scandinavian High, but pressure over Britain is slack with light easterlies for the north-eastern quarter of the country.

NOGAPS opts for 1005mb lows over England and Wales, with easterly winds in Scotland, again going for a strong Scandinavian High. This conclusion is broadly agreed with by JMA.

GEM has a strong 975mb Icelandic Low and westerlies- broad agreement with UKMO, but with a much deeper Icelandic Low.

T+144 (to Tuesday 2nd May)

GFS goes for strong southerly winds, with a 985mb low west of Ireland.

UKMO looks quite similar, but with a deeper (980mb) low over Ireland itself and very strong southerly winds.

ECMWF continues the theme of slack pressure gradient, however, with a strong Scandinavian High, and low pressure well away to the west.

NOGAPS has a 1000mb low over the W and SW of Britain, and has SSE winds covering the eastern parts of Britain.

JMA has light southerlies, and a very deep 980mb low well away to the SW, but as yet not affecting Britain.

GEM prefers a showery SSW flow, with a 980mb low south of Iceland.

Perhaps a warmer outlook then towards T+144, with southerly winds, at any rate it does look like turning more unsettled.

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Model Comparisons for T+144, T+120 and T+96 on 27 April 2006.

T+96 (to Monday 1st May

GFS has a 995mb low over Southern England, with pretty strong easterlies over the north, and a strong Scandinavian High. Looks like a pretty drab cold dull wet Bank Holiday Monday from that outlook.

UKMO has a slack 1000mb low over Britain- similar to JMA's 25 April T+144- and westerly regimes trying to push away the Scandinavian High.

ECMWF sticks by its outlook of the past couple of days, with slack low pressure over the south, and light easterlies for northern Scotland.

NOGAPS unavailable at T+96.

JMA has 1000mb lows in the English Channel and an easterly flow, assisted by a strong Scandinavian High.

GEM is in agreement with ECMWF.

T+120 (to Tuesday 2nd May)

GFS has a deep 980mb low to the W of Ireland with southerly winds over Britain, and looks quite similar to yesterday's UKMO at T+144.

UKMO has a 985mb low off W Ireland, with very strong southerlies over Britain.

ECMWF has light southerlies over Britain, and a 990mb low just off W Ireland, overall less cyclonic than the GFS and UKMO.

NOGAPS seems to be in broad agreement with the GFS, but with the low even deeper, at 975mb.

JMA has the low at 980mb much further south than the other models, to the W of France and has SE winds over Britain, light/moderate.

GEM goes for cyclonic southerlies with the low at 990mb west of Ireland.

T+144 (to Wednesday 3rd May)

GFS has a 970mb low to the west of Scotland- very deep, with strong SW winds sweeping in over Britain.

UKMO looks similar but with the low at 985mb and further south, and strong SSW winds.

ECMWF also has southerlies, but with the low further to the SW, and a long draw of southerlies from Spain.

NOGAPS is similar to ECMWF.

JMA is almost identical to ECMWF, the low quite deep at 975mb but off SW Ireland, and with a long southerly drag over Britain.

GEM has a 985mb low W of Ireland, and a southerly drag over Britain.

So southerlies is the outlook, with GFS and UKMO going with a cyclonic outlook, and the other models showing a block to the east holding firm.

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Model Comparisons for T+144, T+120 and T+96 on 28 April 2006.

T+96 (to Tuesday 2nd May

GFS has a strong 975mb low off western Ireland, with strong southerly winds over the British Isles.

UKMO has the low at 980mb and slightly further north than GFS, but the outlook is exactly the same- strong southerly winds over Britain.

ECMWF agrees with the GFS and UKMO, having the low at the same intensity and position as the UKMO, and strong southerlies.

NOGAPS has the main low much further west, at 980mb, and also has a slack secondary low over Britain at 1005mb, giving rise to light winds.

JMA has 985mb low, much further south than GFS, UKMO or ECMWF- situated just off south-west England, with only moderate to strong southerlies over Britain.

GEM has a shallower low, at 985mb, out in the mid Atlantic and only light to moderate southerlies.

T+120 (to Wednesday 3rd May)

GFS has a strong 970mb low off W Scotland, with strong south-westerlies over Britain, and a 1010mb weak high over Europe.

The UKMO has the main low much shallower, at 985mb, and Britain in southerly winds- the hot continental air flooding in, rather than being swept away by the south-westerlies.

ECMWF seems to agree more with GFS, with a 965mb low off W Scotland and strong cyclonic SSW winds for Britain, the hot continental air out to the east.

NOGAPS has a 965mb low out in the mid Atlantic and cyclonic SSW winds over Britain, the hot continental air out to the east.

JMA has a similar scenario to GFS/ECMWF with a 975mb low off W Scotland and SSW winds.

GEM has a 975mb mid-Atlantic low and a long drag of southerlies sucking up hot continental air.

So, we have the GFS/ECMWF/NOGAPS/JMA going for an Atlantic dominated outlook with SSW winds and low pressure, but UKMO and GEM go for a long draw of tropical continental southerlies.

T+144 (to Thursday 4th May)

GFS has a 980mb Icelandic Low, and keeps Britain in south-westerlies, the continental southerlies continuing to be kept out to the east.

UKMO has a draw of SSE winds, with a strong 1035mb Scandinavian High and low pressure to the west, with a likelihood of storms being imported from the continent.

ECMWF has a tussle between a 980mb Icelandic Low and 1035mb Scandinavian High, with the hot continental plume extending westwards, and Britain in a long drag of southerlies.

NOGAPS sticks with a 970mb low south-west of Iceland and cyclonic SSW winds, but even here, the continental air is closer than at T+120, extending into the SE.

JMA has a 990mb low west of Iceland and southerlies, the continental southerly plume extending into eastern Britain and the low's influence retreating W.

GEM has a 995mb low in the mid Atlantic and a strong 1040mb Scandinavian High and SE winds.

28 April's models show the continental southerlies and high temperatures extending towards us at T+144. UKMO and GEM have the Atlantic never making it against the block, while NOGAPS and GFS have the Atlantic prominent at all three timeframes. ECMWF and JMA have the Atlantic initially pushing in, but the block pushing the Atlantic influences back westwards with hot southerlies streaming in.

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Model Comparisons for T+144, T+120 and T+96 on 29 April 2006.

T+96 (to Wednesday 3rd May

GFS has a strong 970mb low to the west of Scotland and Atlantic SSW winds for the west, but a long drag of hot continental southerlies for the east, assisted by a 1030mb Russian High.

UKMO has the low at 980mb, with a pronounced SSW flow for most, but a 1035mb high lurking over Russia.

ECMWF has the low at 970mb and over Iceland, with SSW winds only in the far west, and a SSE flow from the hot continent affecting the eastern two-third of Britain.

NOGAPS has a 975mb Icelandic Low and a long continental drag of southerlies for all of Britain.

JMA has the low at 965mb over Iceland, and a SSW flow for most, but lighter SSE winds in the far east.

GEM has the low at 980mb and just off W Scotland and SSW winds for all, but hot continental southerlies just to the east.

T+120 (to Thursday 4th May)

GFS has a 985mb low just west of Iceland. High pressure at 1030mb has extended to Scandinavia, and Britain is in a long drag of southerlies, with hot weather and thunderstorms.

UKMO has a 995mb low just west of Iceland and a 1040mb Scandinavian High. The outcome is a flow of hot SSE winds and probable thunderstorms.

ECMWF has the low at 975mb over Iceland and a 1035mb Scandinavian High. The flow is southerly over Britain but has a more Mediterranean source than the Spanish source of the UKMO and GFS's southerlies; nonetheless I guess that the resulting weather type would be the same.

NOGAPS is unavailable at T+120.

JMA has a 975mb low over Iceland and a 1035mb Scandinavian High, and a long draw of southerlies for Britain.

GEM has a 990mb low west of Iceland and 1035mb Scandinavian High. There is a long drag of south/south-easterly winds covering the British Isles.

The models are pretty unanimous in their T+120 outlook.

T+144 (to Friday 5th May)

GFS has the low west of Iceland weakening, at only 1010mb, with a 1040mb Scandinavian High. We maintain hot southerlies and a high likelihood of thunderstorms.

UKMO has a 1000mb low west of Iceland, a 1010mb secondary low over Ireland and 1040mb Scandinavian High. It remains hot with southerlies, and likely associated thunderstorms, over Britain.

ECMWF has a 1010mb slack low to the west, 1040mb Scandinavian High, and the southerly flow continuing, but again with a more easterly source than on GFS and UKMO. Overall, tremendous agreement out to T+144 from the "big three".

NOGAPS is available at T+144 and has us in more of an easterly flow, propelled by that 1040mb Scandinavian High, with lowest pressure at 1000mb to the SW.

JMA has a 995mb low west of Iceland and Atlantic systems pushing against the 1035mb Scandinavian High. Winds are cyclonic and southerly in the east, WSW'ly in the west.

GEM has a 1015mb slack low to the south, 1040mb Scandinavian High, and easterlies over Britain.

There is near-unanimous agreement on the models out to T+120. Wednesday is projected to be warm, damp and muggy with rain and strong SSW winds, though ECMWF in particular seems to have the rain band affecting only western areas. Thursday looks distinctly interesting, with an early taste of summer heat and thunderstorms in the offing. At T+144 (Friday) there is some disagreement, with GFS, UKMO and ECMWF keeping southerlies, heat and thunderstorms, the JMA having Atlantic systems push in, and the GEM and NOGAPS having easterlies push in and probably bring cooler cloudier weather particularly to north-eastern districts.

Given that ECMWF, followed by GFS and UKMO, have the best track record, heat and thunder looks to be a distinctly likely outcome at this stage.