Right Forecast - Wrong Reason

Newsweek blogger Sharon Begley has posted a mid-season review of Dr. Judah Cohen/s (AER...Inc.) long-range '07 / '08 winter forecast.

Cohen/s "...forecast calls for a cold start to December in the East and a mild early January, followed by a possible return to the deep freeze around Martin Luther King's birthday" (emphasis added).

He attributes these events to "...extensive snow cover in Siberia (which) sets in motion a train of meteorological events, with energy waves propagating to the stratosphere, where they weaken the vortex of winds over the North Pole."

Begley gives Cohen/s forecast high marks. "Don’t say we didn’t warn you. Anyone, especially in the northeast and Midwest, who is surprised by the arctic express that moved in over the weekend and is still gripping most of us today wasn’t paying attention last month.."

Cohen thinks he done good..too. "To predict swings in the weather almost to the day two months in advance should be impossible based on accepted climate theory," he said.

There/s room to argue whether these events have unfolded as forecast; however...the room b/comes quite small about whether Cohen/s physical reasoning was correct. Weakening the "vortex of winds over the North Pole" is a clear reference to the Arctic Oscillation going negative...which as a driver for the cold wx regime in the East...has clearly not been the case.

Right forecast - wrong reason.

State of the Cryosphere

Hard to tell...what with all the warm air afoot along the East Coast in recent days...but the NHEMI cryosphere continues to run a surplus.



In fact...NHEMI is enjoying its best boreal snow cover over the past ten years.



Graphics courtesy Bob Hart @ FSU

Contest # 6?

Today/s 12z GooFuS presents a potentially 'contest-worthy' snowstorm for FRI. The forecast storm track and frozen precipitation signature have a look similar to the snowstorms of DEC.

Biggest concern ATTM is the depiction of vigorous lo-lvl WAA which could push the 0°C isotherm north of too many stations.

Baby...It/s Warm Outside

Typically the coldest part of winter...January/s temperature departures are running a surplus.

Time to sell.

Coming Attractions

Various analyses and LR forecasts for early FEB abound the Internets. Most have a decidedly warm flavor yet today/s 12z GooFuS may be the first indication those outlooks wil turn on their collective heads.

LR progs over the past several days have shown a triad of low latitude storms rising from the Gulf 'o Mexico with plus-size warm sectors full of moist air assaulting the Northeast and mid-Atlantic regions. The storm tracks offered little hope for 'contest-worthy' snows over the forecast area through the end of Week2.

Not to put to fine a point on any numerical forecast past D+3...but today/s D+10 and beyond progs showed a notable shift from the previous storm tracks during the same time. Storms have taken on an ENE trajectory with arctic air positioned to their north instead of a rapid increase in latitude toward the NNE coming out of the GOM.

One model run does not a trend make. No way to tell whether this change is a one hit wonder or is the beginning of real shift in the forecast.

Contest # 6 - CANCELLED

Last night/s progs leaned the wrong way and continued to do so with today/s 12z runs.

Too few stations will be affected and with nuisance amounts expected decided to cancel Contest #6.

Ignore-o-sphere Warming

Important signs point toward a sudden warming of the ignore-o-sphere in the coming weeks.

Wind reversal over the Pole...



Temperature reversal...



Warming of constant pressure surfaces from ~100 mb and up occur with a lowering of geo-potential heights. This phenomenon oft times leads to a dramatically colder troposphere...and eventually...a strongly negative AO. Not an unexpected event given the state of this winter/s QBO...which is depicted in the zonal wind chart above as the negative values (i.e., east wind) between 30 and 50 mb over the Equator.

In general...it takes about three weeks for the strat/s warming to work its way down to the near-sfc...all of which suggests a weak...unstable polar vortex...very cold temperatures...and storminess come early FEB.

Jim Hughes...posting @ StormVista...has be tracking the development of this impending event for several weeks and appears to have made a skillful LR forecast for it back in DEC.

Who Knew?

More than a nuisance snowfall over portions of the mid-Atlantic region today as a weak Miller-B 'snowstorm' interacted with a weak arctic wedge lodged against the Appalachians when it climbed out of the GOM/s loins and laid a swath of heavy...wet snow from northern GA to northern NJ.

Click Image to Animate

A few notable totals in the forecast area...

WFO LWX: 5.3"
DT-land: ~4.5"
CHO: 4.3"
IAD: 4"
BWI: 2.3"
ABE: 2.1"
DCA: 1.3"
PHL: 1"
WFO PHL: 1"
PTB: 0.5"

Contest # 6 - Call for Forecasts

So as not to miss out on what could turn out to be a good coastal snow storm...going with the aggressive 12Z GFS / NAM progs for SAT/s event. If subsequent SR runs hew toward the ECMWF 'out-to-sea' scenario...Contest #6 will be cancelled before FRI/s deadline.

Deadline: 10:30 PM EST FRI…18 JAN 2008
Forecast verification begins: 12:01 AM EST SAT…19 JAN 2008

Enter your forecast via the Contest/s web site
Follow the link to 'Enter Storm Forecast.'

Please enter 0.05 for trace amounts instead of a 'T.'

The Contest Administrator will post all forecasts to the NE_Wx Google Group within 30 minutes after the deadline and to the Contest web site the following day.

Contest subject to cancellation before the deadline…if forecast conditions warrant.

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Forecasters need to register once before entering…even if they were registered last year.

Registration is simple…requiring only a username and password. If you provide a valid e-mail address…a copy of your forecast will be sent to you. Please ensure your browser is enabled to accept first-party cookies.

Each contest must have a minimum of seven (7) forecasters for the results to be included in the end-of-season standings.

The NE.Wx Snowfall Forecast Contest (NEWxSFC) is a multi-month event that continues into late March or early April. In general…contests are held whenever a decent…synoptic-scale storm rears its head and threatens at least a half-dozen forecast stations with more than nuisance snowfall amounts. Forecasters are called to post their 'storm total' snowfall predictions…on deadline…for 27 NWS / FAA observing stations scattered about New England and the Mid-Atlantic regions. The Contest Administrator determines the deadlines for entries…verifies all forecasts…and publishes the final results to the Contest/s web site.

Please be sure to read the rules before entering the contest b/c your entry constitutes agreement to abide by them.

You can find the Contest Rules and additional information about error scoring…current monthly snowfall climatology from NCDC…daily CPC teleconnection indices…daily NESDIS N-Hemi snow cover…and NWS Daily Climate Bulletins (CDUS41) by pointing your browser here.
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Interim Standings

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

Click to enlarge
Donsutherland1 re-claims 1st place after five snowstorms with a 'best 4 out of 5' average SUMSQ Z-Score of -1.134.
Shanabe (-0.982) dropped one click to second.
TQ (-0.589) holds on to 3rd place.
Raven (-0.514) on the strength of winning Contest # 5...jumped from sixth to fourth.

Data table @ the Contest web site.

The forecasters listed below have issued three forecasts to date. They will be included in the next interim summary if they enter a forecast for Contest #6.

bruced39
dmcguriman
ilibov
Mitchel Volk
pjc368

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 their 'best two-thirds' forecasts are used to calculate interim and final standings. Same idea as dropping the lowest quiz score before the final grade is computed.