Blessed Weather

Agreed gentlemen. But also, another clue as to what the daily figure represents can be gleaned from the "Calculation Parameters" box just below the headline Index at the top of the OPI webpage. It clearly states the date of the GFS run the calculation is based on, and it clearly states the "OPI Calculate at..(date)" which is 10 days out from the current run. Hence my take that it is a running Index based on actual charts to date plus 10 forecast charts.

Well knock me down with a feather!! I quite agree with neige57's comment. EDIT: And Steve's excellent comments above. If you look at the GFS 12z Nth Hemisphere chart all the way out at 26th Oct there is still a large high pressure dominating the Pole. So a puzzle why the big drop in the Index between the 06z and 12z today. I guess we need to study the link that Interitus posted earlier and better understand the way the OPI is calculated. And if Steve's earlier comment is right about human intervention "modifying" the output, why?? Today's GFS 12z for 26th Oct:

Well that’s a third of October under our belt and it being the 10th of the month, today could also be considered a small milestone along the way as the OPI calculation will consist of the same number of “actual†days (i.e. 10) as the number of forecast days. From here on in the Index will increasingly contain more “actuals†than forecasts. Here's a simple table I've knocked together showing this: So today’s calculation takes GFS’s forecast out to 20th Oct and it’s very encouraging to see the 06z Nth Hemisphere forecast for the 20th still showing high pressure dominant across the Pole. And today’s ECM/GFS H500 8 – 10 Day Height Anomalies remains supportive. GFS for 20th Oct: ECM/GFS 8-10 Day Hgt Anomalies: We continue to look in great shape for the OPI to remain well south of any positive value!!

I know, I shouldn't watch each run for FI developments! But it is interesting to see this afternoon's GFS12z dismiss the idea of the PV muscling the high pressure away from the Pole on the Oct 22nd (see my earlier post). Tonight's 12z output continues with the cross-Pole high pressure right until the end of it's run on Oct 24th. Below, the comparison of 06z and 12z N. Hemisphere H500 charts for 24th Oct. This is looking a very interesting month indeed! 06z 12z

Whilst acknowledging there is more to Riccardo's OPI model than a simplistic look at Northern Hemisphere patterns, a look at today’s NWP model output gives reasons to be cautiously optimistic that the current negative index won’t be suffering a major reversal in the near term. Today’s GFS N. Hemisphere H500 output shows the PV still disorganised with plenty of high pressure where it might normally be expected to rule the roost at this time of year. And bearing in mind the OPI calculation today will be using GFS forecasts out to the 18th Oct, looking at the H500 chart for that date shows high pressure stretching right across the pole, from the Aleutians over to the Euro high, with the PV pushed into Siberia. This scenario is supported by ECM H500 chart for the 18th Oct, and today’s ECM/GFS Mean H500 8 – 10 day Anomaly chart adds weight. GFS ECM 8-10 day anomaly According to GFS it’s not until around the 22nd of October that the PV finally muscles the high pressure residing over the pole out of the way. By then we would have 22 days actual and 9 days forecast to month end. A long way to go, but reasons to be cheerful!

Exactly mulzy. I for one am now a little confused (easily achieved nowadays!) as to what the “Daily Value†of the OPI shown on Riccardo’s web link actually represents. In my post (above) I assumed the value shown each day was the running monthly average up to that day, based on the model taking all previous daily “actuals†for the month and adding 10 forecast days. My assumption being based on what Riccardo posted at the start of the thread: “The software analyzes the previous consolidated daily charts plus 10 forecast charts as given by the GFS model. For example on the 15th of October, the software calculates the OPI index based on the 15 consolidated daily charts (1-15 October) adding 10 forecast charts as given by the GFS model (16-25 October).†Additionally, if you look below the headline Index value at the box called “Calculation Parameters†it says “OPI Calculate at 16/10/14†which looks like it supports the above methodology (i.e. 6 actual days plus 10 forecast days = 16h). Steve (above) does not appear to have interpreted the “Daily Value†in the same way and has taken each days Index and worked out the average himself. It would be good if someone (Riccardo himself?) could clarify this please. Many thanks.

Very interesting situation at the moment karyo. The OPI modelling has taken the first 5 days of October (actual readings) and added on the forecast for the next 10 days. With the index dropping as it has today, my take is that it suggests the GFS model doesn't see the PV getting its act together in any significant way in the next 10 days. Can't wait for Steve Murr's winter forecast if this keeps up! But a word of caution... we mustn't forget there's 26 days of Oct left!!

Report published on the BBC News website today 5th Oct 2014: The deeper half of the ocean did not get measurably warmer in the last decade, but surface layers have been warming faster than we thought since the 1970s, two new studies suggest. Because the sea absorbs 90% of the heat caused by human activity, its warmth is a central concern in climate science. .....Dr Zika added that the heat content of shallow layers is a particular concern, as that warmth is more likely to return to the atmosphere. "If it were getting really deep down, then we might think that it's basically stuck there," he said. Full story: http://www.bbc.co.uk/news/science-environment-29474646

This year North America is certainly demonstrating it has a wide variety of weather in September as it moves from summer to winter. This year from early month cold to record breaking heat in the plains on 25th/26th September and finally the start of winter cold descending on the Rockies at the end of the month. Here's a wonderful photo of Vail on 30th Sept 2014 showing the colours of Autumn and early season snowfall:

Sorry to use the P word before winter proper has started, but it’s struck me that the PV might be struggling to get its act together this October. Using today’s GFS 12z N. Hemisphere H500 output for 6th and 10th October and comparing it with the same dates in 2010, 2011, 2012 and 2013, it indicates that this year the PV is somewhat scattered around and not an organised entity as in the previous years. Is this of any significance? It seems to fit with the fact that the “October Pattern Index†is negative at the moment and hopefully bodes for a weak PV over the coming months. Any views guys? Or of no significance at this stage? Below I've compared today’s GFS output with 2012 and 2013 as illustration: For 6th Oct: 2014 2013 2012 For 10th Oct: 2014 2013 2012

The Languedoc region of Southern France has seen some extreme weather this September 2014. Extracts from the blogs I follow on Weather Underground: Incredible Rainstorm in Southern France Torrential rainfall Tuesday through Thursday morning (September 16-18) in the Languedoc Region of southern France has resulted in flooding that has killed at least four people with two others still missing. The rainfall rates during the storm were phenomenal. A possible new all-time 2-hour rainfall record for France of 180 mm (7.09â€) was measured at Saint-Gervais-sur-Mare (Herault District) between 10 p.m. and midnight on September 16th, surpassing the previous record rainfall for a two-hour period of 178.4 mm (7.02â€) at Solenzara on October 26, 1979. Full story: http://www.wunderground.com/blog/weatherhistorian/comment.html?entrynum=305 Another Record Rainfall in Southern France It is hard to believe that another rainstorm of equal intensity to that which I blogged about just 11 days ago has again struck the Languedoc Region of Southern France. This time the focus of the storm was centered over the city of Montpellier, Herault District, near the Mediterranean Coast. Montpellier, a city of some 240,000, was deluged with an all-time 24-hour record 299 mm (11.77â€) of rainfall between 8 a.m September 29th and 8 a.m. (local time) September 30th. This is the equivalent of almost four times the average monthly precipitation for September in the city. Full story: http://www.wunderground.com/blog/weatherhistorian/comment.html?entrynum=308#commenttop Note: If the links above land you half way down the page at "Readers Comments", just scroll to the top of the page for the story.

It’s been a month since I posted the UK SST’s and SST anomalies for the 31st August. At that time the UK had just experienced a very cool and unsettled August and not surprisingly the sea temperatures had been pulled down over the month from an above average start figure to more in line with the long term average. One month on and the UK has just experienced a notably warm and settled September. Not surprisingly the UK SST’s for the 30th September reflect this, with temperatures around Scotland’s coastline holding steady at 13C (close to the long term average), whilst temps around Southern England have actually crept up a degree from 17C to 18C (typically +2C above the long term average). In the SW approaches temps have climbed from 17C to 19C (+3C above long term average). UK SST’s 30th Sept 2014: Anomaly against long term average:

After the very cold spell in early September, there's been some record breaking heat in the Northern US and Canadian High plains in the last week of September. Extracts below from Weather Underground posted Sept 26th: Record Fall Heat in the U.S. and Canadian High Plains Temperatures on Thursday and Friday, September 25-26, soared to record levels for this time of the year in Montana, Wyoming, western North Dakota, and the south-central Canadian Plains. ....The hottest reading observed was 98°F (36.7°C) at Terry, Montana and also at Wasta, South Dakota..... their hottest temperatures ever observed during the fall (post September 22nd) and for so late in the year. ....In Canada, Esteven, Saskatchewan hit 34.3°C (93.7°F) and Brandon, Manitoba 34.0°C (93.2°F). Both sites are near 50°N latitude so it goes without saying that these were the warmest temperatures ever observed for so late in the year at those sites. ....The 90°F (32.2°C) isotherm pushed as far north as Swan River, Manitoba (52° 07’ N) where on Friday, September 26th 35.1° (95.2°F) was observed. This may be the hottest temperature ever measured so far north so late in the year on the North American continent. Full blog here: http://www.wunderground.com/blog/weatherhistorian/comment.html?entrynum=307#commenttop Edit: If this link lands you half way down the page at "readers comments", just scroll up to top of page for the article.

Something that caught my eye from the ECM and GFS model outputs this morning was the possible build of cold air in Russia starting at the end of next week. The 850 hPa output from both models for 1st Oct shows a plunge of -5 uppers coming down into Russia on the eastern flank of the Scandinavian High. ECM: GFS: By the 6th Oct both models are still broadly in agreement that the resultant cold pool is still there and indeed has crept West, by then knocking on the door of Poland. ECM: GFS: Very much FI but should this happen it will certainly accelerate the cooling of continental Europe during early October.

Global Analysis Report for August 2014 issued by NOAA states: .....the August global sea surface temperature was 0.65°C (1.17°F) above the 20th century average of 16.4°C (61.4°F). This record high departure from average not only beats the previous August record set in 2005 by 0.08°C (0.14°F), but also beats the previous all-time record set just two months ago in June 2014 by 0.03°C (0.05°F). http://www.ncdc.noaa.gov/sotc/global/2014/8

Blog posted by Dr. Jeff Masters' at Weather Underground today, 18 Sept 2014: Earth has Warmest Summer and August on Record. August 2014 and the summer of 2014 were Earth's warmest since records began in 1880, said NOAA's National Climatic Data Center today. NASA also rated August 2014 as the warmest August on record. August is the third time NOAA has ranked a 2014 month as the warmest on record; May and June 2014 were the warmest May and June on record. Global ocean temperatures during August 2014 were the warmest on record, and the 0.65°C (1.17°F) ocean temperature anomaly was the highest ever measured, beating the record set just two months previously in June 2014. http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2803&cm_ven=tw-jm

Well spotted Knocker. Thanks to this model thread and posts such as yours I've enjoyed the learning experience of how these tropical storms impact the UK weather. We had ex-Bertha parking itself to the NE of the UK and being largely responsible for bringing us a disappointing August. ex-Cristobal ran further north and arguably helped usher in the settled weather we've been enjoying of late. And now the models are suggesting that (in FI) another ex-tropical storm will maybe be the catalyst that allows the Atlantic to finally break through with a vengeance. Here's some charts showing how this might happen. First today's Atlantic chart from the US NHC showing the fledgling storm and in their view with a >50% chance of developing into a tropical cyclone over the next 5 days. Today's GFS 12z picks up the storm and shows it entering stage left on Saturday 20th Sept. Finally by Wed 24th Sept a direct hit on the UK. A long way to go and with the fickle nature of tropical storms, it will no doubt end up differently. But an interesting one to watch.

The sea surface temps around the UK are pretty much in line with where they should be for the time of year. Little change around Scotland's coast from the charts I posted 2 weeks ago, temps holding at 13c to 14c, but down a degree or two around southern Britain's coast at 16c to 17c. Actual SST's 31/08/14: Anomaly against long term average

ECM has just provided a master class in the perils of posting FI charts. Last night's 12z run 850hPa chart for Mon 8th Sept "cold incoming from the north".... This mornings 0z run for Tues 9th Sept "maybe not... heat incoming from the south now"....

In my view the ECM is a disappointing backtrack tonight on the warmth promised from runs over the last few days. Tonight the +10c isotherm on the 850 hPa charts only briefly touches the UK right through the run. Yes it's still a settled week (after ex-hurricane Cristobal's straggling front clears the UK on Monday) and pleasant enough with decent temps in the low 20c's but not quite what recent runs had promised. As posts above suggest, at the end of the run ECM taunts us with the prospect of a rather cool blast of polar air running down from a high forming to the east of Greenland. Cold lovers would indeed be cheering if it was January!! ECM 850hPa chart tonight for Monday 8th Sept:

After the negative impact of hurricane Bertha, it’s nice to have cross-model agreement that Cristobal should have a positive impact on the UK. As the vigorous low resulting from Cristobal tracks NW close to Iceland, the warm air advection brings us a welcome rise in temperatures and allows high pressure to build in from the SW. In fairness to the ECM it was showing this evolution several days back whilst other models struggled somewhat. Latest Cristobal forecast track from the US NHC for today until Sun 31st Aug: ECM and GFS 850 hPa charts for Sun 31st Aug in agreement:

^ Yes Anyweather and I'm dreaming of. Big differences in how the models handle ex tropical storm 96L. Whilst this morning’s ECM 0z shows a similar track and evolution as described in my post yesterday, in the space of 24 hours it has delayed matters by 48 hours. Meanwhile the GFS 0z is having none of it, showing ex-96L fizzling in the Atlantic, whilst GEM, as I'm dreaming of describes, “barrels it into the northern half of the UKâ€. ECM 0z (the low to the south of Greenland) and GFS 0z (the low in mid Atlantic) 850 hPa charts for 3rd Sept:

Whilst agreeing with your sensible words of caution Knocker, it's interesting how this morning's ECM has tropical storm 96L as eventually (in F1) having a beneficial impact on the UK. I've selected three charts to show the progress of the storm across the Atlantic and marked the charts with arrows showing direction. First, the ECM N. Hemisphere HGT500 chart shows 96L leaving the Eastern seaboard on Thurs 28th Aug and heading into the Atlantic: Then switching to the ECM T850 we see 96L on 31st Aug as a vigorous low in mid Atlantic. Shortly after this 96L combines with the low to it's north: Finally, by 1st Sept the ECM T850 shows the low steaming towards Iceland, but with the favourable impact of WAA about to waft over the UK as the Azores High nudges in from the SW. So yes, it's FI, but here's hoping!

As anticipated, the unseasonal weather (cool with brisk N to N/W winds) over the last week has reduced the SSTs around the UK. Evening Thunder's post above giving the likely explanation. Typically temps are down by 2c in the seas to the North and East of the UK, although the impact in waters to the S and SW of the UK is less marked. SSTs now range from 18c off Southern coasts, to 13c to 14c around Scotland. I've decided to use the charts suggested by Mike Meehan at the start of this thread as I prefer the graphics over the charts produced by the Met Office/National Centre for Ocean Forecasting (NCOF). The charts are from surf-forecast.com (owned by meteo365.com, the same crowd behind snow-forecast.com). I've checked them against the NCOF and the SSTs are the same, just the graphical presentation differs. Actual SSTs 19/8/14 SST Anomaly 19/8/14 Edit: I meant to mention the excellent and long standing thread "Sea Surface Temperatures" started by Bornfromthevoid some while back but still going. Full of great posts including causes and effects of SSTs. I guess that thread is more a global view whilst this thread is UK focussed?

Whoops! You're absolutely right Yarmy. I never was very good at maths! I guess it might need the temperature to be pulled down temporarily during heavy showers!