Sudden Stratospheric Warming - Full On

Full-blown SSW underway with a reversal of the 10 mb wind extending below 60°N.

Broke through 50 and 70 mb...heading for 100.

Sudden Stratospheric Warming - Close @ Hand

Defined as a complete disruption / reversal of the polar vortex @ 60°N... a well-forecast MAJOR stratospheric warming appears close-at-hand.

The vortex has bifrucated @ 10 mb on JAN 24...30 mb on JAN 27...and is poised to reach 50 mb level in a few days.

The event gets a quick mention in WSI/s latest winter update...

""An incipient stratospheric warming event, which appears to be historic in magnitude, may continue to favor more Arctic air masses in mid-latitudes and increases confidence in the widespread cold forecast of the US these upcoming few months.""

Upper air plots courtesy Univeristy of Wyoming/s Department of Atmospheric Science





Wowzer!

Snow Storm #7: The Forecasts

14 forecasters...including 3 rookies...for the season/s seventh storm. Forecasters in the table above are ranked in ascending order by expected storm-total snowfall.

Station forecasts here.



Mid-Atlantic region gets a bone tossed its way. Best snows expected over northern stations...a season-long trend.



Teleconnections celebrating Opposite Day.



LOW pressure over Mississippi River on tonight/s surface chart expected to morph into...

Snow Storm #7: Raw Forecasts

Here.

13 entries...including 11 veterans and 2 rookies.

Formatted forecasts will be available at the Contest web site early tomorrow evening.

Overview and some summary charts will go up on the web blog around the same time...too.

WSI - JAN Update - Winter '08 / '09

NE...
Feb - colder than normal
March - colder than normal
April - colder than normal

""The general pattern of cold-north and warm-south observed during the winter so far will generally continue into early spring. The warmest temperatures, relative to normal, will be in the south-central and southeastern states while the coldest temperatures will continue to be observed in the north-central states.

"The cold Pacific Ocean suggests that the upcoming aggregate three-month period will be relatively cold nationwide, relative to normal, especially in March and April.

"An incipient stratospheric warming event, which appears to be historic in magnitude, may continue to favor more Arctic air masses in mid-latitudes and increases confidence in the widespread cold forecast of the US these upcoming few months.""

(updated to include full forecast discussion)

Full press release here.

Snow Storm #7: Call for Forecasts

Large-scale...two-day event expected over the forecast area on Tuesday and Wednesday as the long-wave trof currently over the west coast comes east.

HPC discounted today/s 12z solutions for widespread heavy snow from GooFuS as an outlier; however...long-range NWP models have been flip-flopping for days on the evolution of the western trof...so here/s hoping they/ve missed the boat.

Deadline: 10:30 PM EST Monday...26 January 2009

Forecast element: storm-total snowfall
Verification begins: 12:01 AM EST Tuesday...27 January 2009
Verification ends: 11:59 PM EST Wednesday...28 January 2009

Enter your forecast here.
Follow the link from 'Enter Storm Forecast.'

Make the best forecast and you/ll win one month of FREE access to StormVista GOLD.
Details here.

More prizes will be awarded at the end of winter for the best over-all forecaster.
Details here.

As always...there/s no cost...or fee...or annoying requests for personal information to enter.

If you are making your first forecast this year or you entered the 'season-total' forecast contest...you/ll need to create an account (user name / password / valid e-mail...if you want a copy of your forecast sent to your Inbox) before entering a forecast.

Image: Niagra Falls 2/9/1908

VCP 32 - What/s Wrong With Your Snowman?

Sudden Stratospheric Warming

Welcome to our visitors from The Wx Outlook - TWO Community Wx Forum...NetWx...and UKWxWorld. Good discussions and information about this unusual event.

(updated below)

240-hr ECMWF: complete disruption / reversal of the polar vortex ==> MAJOR stratospheric warming.



Major winter stratospheric warmings preferentially occur during the easterly phase of the QBO (Holton and Tan (1980))...so this event is notable since QBO is currently west ~10 m/sec...as seen on the latitide-height x-section in the 30 - 50 mb layer over the Equator.



As would be expected...AO tanks...too.



All a consequence of the huge mid-month +PNA / Rossby wave propagating into the ignore-o-sphere?



Sig wx ahead?

UPDATE

Chart below shows just how unusual SSW is during QBO-west and solar minima.



(h/t TWO Community Weather Forum from across the pond)

Tropospheric after-effects of SSW lag by ~4 weeks and can last for many weeks afterward. A warm stratosphere means the tropopause has lowered which in turn means lower heights in the troposphere and low trope heights mean cold conditions at the surface.

"Pronounced weakenings of the NH wintertime stratospheric polar vortex tend to be followed by episodes of anomalously low surface air temperatures and increased frequency of occurrence of extreme cold events throughout densely populated regions such as eastern North America, northern Europe, and eastern Asia that persist for ~2 months." (Thompson et. al. - 2002)

EDIT: corrected reference to present QBO phase.

Interim Standings

Plenty-o-new faces in the latest Interim Summary with four more forecasters eligible for ranking.

After six snow storms... donsutherland1 retains his lead... anthony appears out of nowhere into second...a mere 0.0004 points ahead of shanabe...who slips to third.

Under the ‘two-thirds’ rule…forecasters who have entered at least four forecasts are included in this interim summary.

Full interim forecaster error statistics table and charts here.

Forecaster storm summary data here.

SUMSQ errors for each contest snow storm are normalized with a 'Z-score'...then averaged to compute the standings. Forecasters who have entered at least 2/3 of all snow storm contests are included in the standings.

If a forecaster has participated in more than two-thirds of all snow storm contests...then Z-scores from two-thirds of their best forecasts are used to calculate Interim and Final standings. Same idea as dropping the lowest quiz score before the final grade is computed.

Previous Interim summary here.

Snow Storm #6: Results

Senior forecaster Donald Rosenfeld made the best synoptic-scale forecast for NEWxSFC/s sixth snow storm. His 24 station forecasts verified with 84 SUMSQ error points (Z-Score = -1.285)...which was a 54% improvement over the average error of 183".

He placed first in all other forecast skill categories...as well.
Total Absolute Error: 32.15" (27% better than average)
Average Absolute Error: 1.34" (31% better than average)
STP: 14.35" (54% better than average)
R-SQ: 78% (24% better than average)

Donald Rosenfeld/s forecast had the lowest station errors @ CAR ISP SBY ORF.

Congratulations Donald Rosenfeld!

Donald Rosenfeld wins one FREE month of StormVista GOLD for his forecasting acumen.

2nd Place: Raven (117.9"; -0.846)
3rd Place: Newa (122.2"; -0.791)
Honorable Mention: Mitchel Volk (123.4"; -0.774)

Full forecast verification and results summary here.