HARD Winter Follows HOT August

Apparently...if it/s unusually warm the first week of August...a hard winter/s a/comin/.

"If the first week in August is unusually warm,
The coming Winter will be snowy and long."

Must have missed class the day that old chestnut was presented!

How can an 'unusually warm' first week of August be quantified? NWS field manuals of old described 'mild' temperatures as departures 5-10 °F above normal. 'Hot' was a departure of 10 or more.

'Hot' seems to lend itself more to 'unusually warm' than does 'mild.' If that/s the case...then a station would need a total anomaly of 70°F to qualify as 'unusually warm.'

So...what/s in store this winter according to folklore for NE and the M-A regions? The bar chart shows 7-day total temperature anomalies for NEWxSFC stations.


The 'rule' cannot be expressly applied b/c there were no stations where the 7-day anomaly total was 70°F or higher. IAD and BWI were most 'unusually warm' with 49 and 44°F anomalies... respectively.

The average station temperature anomaly was ~31 °F. The 90th percentile station temperature anomaly came in @ 41°F...which includes IAD...BWI...ACY...and RIC.

So...there it is. If indeed...a hot August ==> long, snowy winter...then this year/s action center will be found in a tightly constricted corridor along the M-A/s coastal plain.

ENSO Anomaly Forecast - Winter '07 - '08

Latest CFS forecast for ENSO Region 3.4 SST anomaly of ~-1.1°C continues trend from previous model runs for La Nina conditions to be well established this winter.


Previous DJF forecast values (°C)
April -0.6
May -0.6
June -0.8
July -0.9

Monthly temperature and precipitation anomalies reflect the model/s La Nina forecast for warm and dry in the SE.

Farmers/ Almanac 07-08 Winter Outlook - Atlantic Corridor

"Winter will be about a degree milder than normal, on average. Precipitation will be a bit above normal across southern New England and eastern Long Island and below normal elsewhere. Snowfall will be near to slightly below normal, with the snowiest periods in mid-December, mid- to late January, and mid-February. The coldest temperatures will occur in early and late December, mid-January, and early and mid-February."

More...

sCAST Money Shot

Note the negative correlation (increased snow cover associated with decreased temperature) between Siberia and the cold signal across the OH / TN River Valleys and ern GL regions of the upper M-W.

sCAST Launched

News about this LR winter forecast method has dribbled out once and a while over the past few years. Appears the model is ready for prime-time. The sCAST developers have a paper about their model in the current Journal of Climate.

Improved Skill of Northern Hemisphere Winter Surface Temperature Predictions
based on Land-Atmosphere Fall Anomalies.

Abstract
A statistical forecast model, referred to as the sCAST model, has been developed using observed October mean snow cover and sea level pressure anomalies to predict upcoming winter land surface temperatures for the extra-tropical Northern Hemisphere. In operational forecasts since 1999, snow cover has been used for seven winters and sea level pressure anomalies for three winters. Presented are skill scores for these seven real-time forecasts and also for thirty-three winter hindcasts (1972/73-2004/05). The model demonstrates positive skill over much of the eastern United States and Northern Eurasia; regions that have eluded skillful predictions among the existing major seasonal forecast centers. Comparison with three leading dynamical forecast systems shows that the statistical model produces superior skill for the same regions. Despite the increasing complexity of the dynamical models, they continue to derive their forecast skill predominantly from tropical atmosphere-ocean coupling, in particular from ENSO. Therefore, in the Northern Hemisphere extratropics, away from the influence of ENSO, the sCAST model is expected to outperform the dynamical models into the foreseeable future.



From TerraDaily...
"(Dr. Judah) Cohen and colleagues outline the link between October snow cover in Siberia and the Northern Hemisphere's winter temperatures, and snowfall.

"October is the month when snow begins to pile up across Siberia. October is also the month that the Siberian high, one of three dominant weather centers across the Northern Hemisphere, forms.

"In years when Siberian snow cover is above normal, a strengthened Siberian high and colder surface temperatures across Northern Eurasia develop in the fall.

""The result is a warming in Earth's stratosphere that occurs in January," said Cohen. "This eventually descends from the stratosphere to Earth's surface over a week or two in January, making for a warmer winter in Northern Hemisphere high latitudes.

"However, in mid-latitudes it turns colder, so winters in the northeastern U.S. and eastern Europe are likely to be colder and snowier than normal."

Summer Cancel - Snow Observed in North Finland

Several inches fell near Lapland on the last day of August. Locals report the last time that happened was back in '86.


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