Coastal Teaser - #2

Precious few flakes for folks south of northern New England the past several weeks. Mid-FEB is prime-time for many stations across the forecast area...so if not now...then when?

Hard to get too excited @ this point. None of the LR / MR models have performed very well this winter. All the best storms are just ten days away! Even so...it/s hard to ignore today/s D+6 prog from the ECMWF. Coastal cyclogenesis INVOF Hatteras and a buckling PAC jet.

One consistent antecedent element forecast by the LR models has been a strong arctic anticyclone flooding the eastern CONUS early next week...putting an end to the abominable warmth that has plagued the much of the area since the last week of JAN.

Reverse Engines

The polar vortex has been votexing fast and furious in recent weeks...evidenced by a painfully positive AO index and mild temperatures in the East.

All that may be about to change should the ECMWF forecast come to pass.



Note the negative values in blue above the Arctic Circle in the D+8 forecast indicating a zonal wind change from west to east. This is likely a depiction of the arctic jet...given the relative strongly negative values.

A strong polar vortex keeps arctic air bottled up over the pole; however...when if it weakens as forecast...the arctic air mass can escape to lower latitudes.

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"