Winter / Autumn 2009-10 Part 4

[Thundery wintry showers]

The 8th and 9th of February 2007 at Cleadon both featured some interesting temperature fluctuations. Temperatures fell to -2.1C overnight 7th/8th but jumped to 0.7C as a hail shower moved in off the North Sea, covering the ground in about an inch of hail. A wind picked up off the North Sea causing the temperature to shoot up to 4C, initiating a thaw.

Overnight 8th/9th the onshore wind eased and the temperature dropped, falling as low as -1.8C. There was a brief hiccup when a graupel shower moved in off the sea, the temperature shot up to 1.3C, and a dusting of graupel resulted. The temperature then fell back to -1C. But at 9am, as another shower moved in off the sea, the temperature suddenly shot up to 1.7C, and sleet resulted. Then it went up to between 3 and 5C for the rest of the day, resulting in rain and sleet showers.

[Snowyowl9]

If we`re to look back at one El nino winters take 1997/98 for instance,there were still a few cold easterlies and NE-lys even in December,and even a greenland high modern chart it`s not.

http://www.wetterzentrale.de/archive/ra/1997/Rrea00119971202.gif

And why is it only a 3 year gap since the last(2 years since la nina I meant follows following year,when sometimes it`s 5 years or more.

I think it`ll die away and we`ll have a more S-ly tracking jet to normal anyway,who knows.

Edited November 16, 2009 by Snowyowl9

[Don]

I will be putting it up tomorrow- it definitely needs one as the proposed cold third week with continental air isn't going to happen.

OK

[osmposm]

And why is it only a 3 year gap since the last(2 years since la nina I meant follows following year,when sometimes it`s 5 years or more.

Snowy, maybe I'm being dense, but after several attempts I simply can't make head or tail of that sentence. I'm always interested in your thoughts, but sometimes you don't make it easy, mate!

Punctuation (and a bit of care writing a post) are not just silly things pompous old idiots go on about for no reason - they help people understand what you're saying.

Ossie

Edited November 16, 2009 by osmposm

[Iceberg]

A quick update today from the Aussie BOM, re SOI, MJO and ENSO activity.

http://www.bom.gov.au/climate/tropnote/tropnote.shtml

"El Nino-Southern Oscillation Update

The 30-day Southern Oscillation Index [sOI] to November the 14th was -15. Contributing pressure anomalies were +0.7 hPa at Darwin and -1.7 hPa at Tahiti. The monthly SOI for October was -15, and its 5-month running mean [centred on August] was -3. After many months near neutral, the SOI fell rapidly in October, and has remained strongly negative over the past few weeks. This is in-line with what is expected during an El Nino event.

Sea surface temperatures [sST] remain greater than normal across almost the entire equatorial Pacific Ocean, with anomalies greater than 2.0 C evident in the equatorial Pacific east of the dateline. Sub-surface temperatures along the central equatorial Pacific Ocean have warmed in October and November, with weekly anomalies exceeding 4.0C above average in an area between 150W and 110W. SSTs across northern Australia and the Maritime Continent are mixed but generally close to normal. Equatorial easterly winds have strengthened in the western Pacific ahead of the approaching Madden-Julian Oscillation [MJO], whilst remaining close to the long-term mean elsewhere. El Nino and Southern Oscillation [ENSO] predictors suggest that the current El Nino conditions are likely to persist into early 2010. See the Bureau's "ENSO Wrap-Up" at www.bom.gov.au/climate/enso/ which includes a compilation of ENSO computer model predictions.

Intra-Seasonal Patterns

During the northern hemisphere summer, the MJO was generally weak and inconsistent.

Towards the end of October and start of November we saw enhanced convection in the western and central Indian Ocean. Convection is now progressing eastward into the Maritime Continent region, indicative of the MJO moving into this area. This convective signal appears to be weakening as it moves into the Indonesian region however. Generally, forecast models predict the MJO signal will continue to deteriorate over the coming week as it progresses east across the Maritime continent, however there is still a chance of increased shower and thunderstorm activity over this region in the latter half of November.

Although an active MJO pulse increases the likelihood of tropical cyclogenesis and monsoon activity in the Australian region, it is considered a low probability for the end of November."

I've also updated the ENSO thread

ENSO:

The figures are as follows

4 1.5,

3.4 1.7,

3 1.2,

1+2 0.5.

4-weekly Index 1.5 (strong)

12 weekly Index 1.15 (moderate)

SOI is back into the negative after spending a few days positive, the average is still very negative though as shown by BOM above.

What does it all mean ?, GP and others can advise better, but IMO more atmospheric/ENSO coupling, which means less HP, but potentially some cold cyclonic weather, which GFS is hinting at.

Also according Washington the PDO is still positive and has been since August.

[Glacier Point]

The MJO may fire up again in phases 6,7 and 8 during December but the trade wind surge is still persisting. Total angular momentum is nearly -2SD, mainly from negative contributions across the tropics and the east QBO which has strengthend to -15m/s values.

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltotaam.sig.90day.gif

Consequently, the GWO is indicative of a low angular momentum base state.

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

Based on the weakening of the MJO and convection, allied to the east QBO and SST fields reflecting a neutral negative PDO, we look to have the low angular momentum - El Nino combination locked in place for the first part of the winter. Cue comparisons of the winters of 1965/6, 1972/3, 1986/7, 1979/80.

[Iceberg]

Thanks GP, I would agree with that.

The following CET's are below.

65/66 4.7 2.9 5.7 avg 4.43

72/73 5.8 4.5 4.3 avg 4.86

86/87 6.2 0.8 3.6 avg 4.13

79/80 5.6 2.3 5.7 avg 4.53

So going from that a winter CET of around 4.5 seems accurate.

Then it's upto people whether they want to add in a "even larger teapot factor"/GW, less sea ice, positive amo etc.

I think a winter of 4.5 to 5 looks quite reasonable, with very little chance of a cold December, maybe a 20-40% chance of a cold Jan and maybe 20% of a cold Feb.

All off the cuff and only my figures..

[karyo]

Thanks GP, I would agree with that.

The following CET's are below.

65/66 4.7 2.9 5.7 avg 4.43

72/73 5.8 4.5 4.3 avg 4.86

86/87 6.2 0.8 3.6 avg 4.13

79/80 5.6 2.3 5.7 avg 4.53

So going from that a winter CET of around 4.5 seems accurate.

That's rather disappointing! Mild winters with the exception of the odd cold month (small chance)! December looks very underwelming according to those years and considering the consistently above average autumn we are enduring...

Karyo

[Methuselah]

For some reason, I don't take 'analogues' very seriously??? Weren't they (in the guise of pattern-matching) the bases of the ill-fated MetO 30-day forecasts of the 1960s, '70s and early '80s??

Maybe JH could clarify??? :blink:

[Glacier Point]

Pattern matching and composites (using carefully selected analogues) are two different things Pete.

Reanalysis of composites can give us valuable clues as to how the atmosphere and general circulation will respond given forcing from oceanic or atmospheric signals. It's really starkly apparent that despite all of the clutter and white noise of the atmosphere, certain variables shared across years can result in a strong composite anomaly. The key is how these are put together within an overall forecast. Analogue-based composites are used on a daily basis by the CPC as a tool for their 8-14 day outlooks alongside the GFS and GEM Ensemble Means.

I would agree though that predicting a monthly temperature on the back of this is not the way to go as variables such as SSTA and inter-seasonal factors will be much more influential.

Edited November 17, 2009 by Glacier Point

[johnholmes]

For some reason, I don't take 'analogues' very seriously??? Weren't they (in the guise of pattern-matching) the bases of the ill-fated MetO 30-day forecasts of the 1960s, '70s and early '80s??

Maybe JH could clarify???

to an extent they were Pete but back then we/they had far less idea about many of the variables we are starting to take for granted now-also read what Stewart (GP) has just posted re the differences between the two things.

Edited November 17, 2009 by johnholmes

[Methuselah]

Thanks guys...I'll do that. :blink:

[geoffw]

so when is bftp's winter forecast going to be issued? also can we expect a cold, average or mild winter given the current signals?

[kippure]

so when is bftp's winter forecast going to be issued? also can we expect a cold, average or mild winter given the current signals?

Some time this evening i,d say.

[Backtrack]

so when is bftp's winter forecast going to be issued? also can we expect a cold, average or mild winter given the current signals?

Given the current conditions, with an El Nino dominating, we are set for a mild, unsettled winter until February. Obviously a few cold spells can be expected but a much more mild winter than last winter is on the cards unfortanately.

Edited November 17, 2009 by Backtrack

[johnholmes]

I suspect you may be a touch out with that lad but who knows you might be right.

[Snowstorm1]

I suspect you may be a touch out with that lad but who knows you might be right.

So whats your thoughts then :blink:

[johnholmes]

So whats your thoughts then

nothing beyond early December chum-I'm not in the 3 month lrf game-but for what its worth I would punt for not much above average if at all temperature wise over the whole winter-but I don't profess to be an expert in this length of lrf.

[fear sneachta]

Given the current conditions, with an El Nino dominating, we are set for a mild, unsettled winter until February. Obviously a few cold spells can be expected but a much more mild winter than last winter is on the cards unfortanately.

I agree. It'll be a generally mild winter, at least until early January.

http://www.independent.ie/farming/kiwi-weather-expert-forecasts--a-watery-end-to-dreadful-2009-1886289.html

[LomondSnowstorm]

Given the current conditions, with an El Nino dominating, we are set for a mild, unsettled winter until February. Obviously a few cold spells can be expected but a much more mild winter than last winter is on the cards unfortanately.

That's a fair prediction but from what I've seen on the forum the atmospheric conditions seem to be more like a la nina than a strong el nino so there is still the distinct posibility of a colder than average end to winter with the El Nino perhaps weakening somewhat. I doubt the period between late November and early February will be as cold as last year but factoring in the mild final two weeks of last February we may come out with something similar overall if we're lucky! I still think we could get a memorable cold snap at some point this winter even if it isn't as cold as last year.

[Backtrack]

I agree. It'll be a generally mild winter, at least until early January.

http://www.independe...09-1886289.html

Early December is actually looking cold with Easterly/Northerly winds dominating bringing wintry weather to the UK!

[LomondSnowstorm]

I agree. It'll be a generally mild winter, at least until early January.

http://www.independe...09-1886289.html

But then so was 1946/47!

[Backtrack]

That's a fair prediction but from what I've seen on the forum the atmospheric conditions seem to be more like a la nina than a strong el nino so there is still the distinct posibility of a colder than average end to winter with the El Nino perhaps weakening somewhat. I doubt the period between late November and early February will be as cold as last year but factoring in the mild final two weeks of last February we may come out with something similar overall if we're lucky! I still think we could get a memorable cold snap at some point this winter even if it isn't as cold as last year.

I hope you are right. As I say, a cold start to December is on the cards!

I agree. It'll be a generally mild winter, at least until early January.

http://www.independe...09-1886289.html

Take no notice of the forecast, he's doing a summer forecast there too which is obserd! He's also giving exact dates to snow events. What a load of crap.

[LomondSnowstorm]

I hope you are right. As I say, a cold start to December is on the cards!

Take no notice of the forecast, he's doing a summer forecast there too which is obserd! He's also giving exact dates to snow events. What a load of crap.

It is certainly looking cooler than at present into next week and an early December cold snap seems quite reasonable!

It does seem a little bit rich for the Irish Independent to call him a 'weather expert' just for roughly prediciting one summer slightly better than the met office!

His overall forecast though doesn't seem that far off though, considering it's for Ireland, although he does go a bit far in predicting the dates of snowfall events!!

We'll just have to wait and see, I guess.

CW

[Ben_Cambs]

Yes, the medium range model charts are showing colder conditions in early December, but at the end of October they showed cold conditions for around this week, so they are not entirely accurate and there is still two weeks until Decembe, so anything can change! But im certainly hoping for a cold snap soon with snow!

Edited November 17, 2009 by Snowman0697