Winter '09 / '10 - Snow Storm #1 - ECMWF Verification

Outstanding NWP performance!
ECMWF/s 96-HR (4-day) Forecast

Miller-hybrid 996 mb surface LOW south of HSE.
Open 5H trof over OH river valley
Occluding 2ndary surface LOW over NE OH

Observed

Miller' A' 989 mb surface LOW due E HSE.

Closed 5H LOW over OH river valley

2ndary surface LOW over southern OH / NE KY

GooFuS didn/t have a clue...projecting the storm off-shore near the VA Capes...then out to sea.

Winter '09 / '10 - Snow Storm #1 - Blizzard Conditions

Blizzard conditions were observed at Islip...NY between 10:30 PM EST...19-DEC-09 through almost 2 AM EST...20-DEC-09.

Three conditions are needed for a blizzard:

1 - Visibility frequently less than 1/4 SM (< 1320')...

2 - Sustained wind speed or frequent gusts of 30 KTs (35 MPH) or higher...and

3 - Restricted visibility and high-wind conditions observed for at least three hours.

Note the METAR reports of SNINCR 3/xx (three inches-per-hour followed by the amount on the ground...rounded to closest whole number) in the 0456z...0556z...and 0656z observations (Sunday midnight - 3 AM EST)

SPECI KISP 200328Z 36017G27KT 1/8SM +SN BLSN FZFG VV001 M04/M07 A2955 RMK AO2 PK WND 01030/0300 P0001 $

METAR KISP 200356Z 36020G30KT 1/8SM +SN BLSN FZFG VV001 M04/M07 A2952 RMK AO2 PK WND 36031/0330 SLP998 SNINCR 1/7 P0001 T10441067 $

METAR KISP 200456Z 36019G30KT 1/16SM +SN BLSN FZFG VV001 M04/M07 A2949 RMK AO2 PK WND 01034/0441 SLP987 SNINCR 3/10 P0003 T10441067 410111050 $

METAR KISP 200556Z 36020G35KT 1/8SM +SN BLSN FZFG VV001 M04/M07 A2948 RMK AO2 PK WND 35035/0554 SLP985 931114 4/013 SNINCR 3/13 P0002 60013 T10441067 11039 21050 56023 $

METAR KISP 200656Z 35021G32KT 1/8SM +SN BLSN FZFG VV001 M04/M07 A2950 RMK AO2 PK WND 36032/0649 SLP989 SNINCR 3/15 P0003 T10441067 $

METAR KISP 200756Z 35016G22KT 1/4SM +SN FZFG BLSN VV002 M04/M07 A2953 RMK AO2 PK WND 36030/0717 SLP999 SNINCR 2/17 P0003 T10441067 $
 
Blizzards are wind storms where visibility is restricted by falling or blowing snow.
 
Blizzards defined here and here.

Winter '09 / '10 - Snow Storm #1 - Snow Cover

Snow cover as of 20-DEC-09 at 12z.  Heavy snow axis 18 - 21" runs through ROA - DCA - BWI - DOV - southern NJ - eastern LI.

Image courtesy NOHRSC

Winter '09 / '10 - Snow Storm #1 - The Forecasts

26 forecasters...including 10 rookies...issued 550 stations forecasts for this season/s inaugural snow storm.  Forecasts are ranked by storm total precipitation (STP) in ascending order.  Blue (red) values are in the 25th (75th) percentile.

Forecasts here.

Consensus heavy snowfall axis from IAD - DCA - BWI - PHL - EWR - JFK - ISP -ACY - IAD.

Amplifying flow regime evidenced by rising PNA and cold air source indicated by strongly negative values for NAO and AO.  Oscillations come on the heels of a minor stratospheric warming event that slowed and split the PV.  Arctic region surface pressure rose as the one piece of the PV moved from eHEMI to wHEMI...where opposing flow between the two circulations created weak ridging near the pole.

986 surface LOW over HSE SAT 19-DEC-09 at 12z crawls to a position abeam the southern end of Delmarva peninsula 12 hours later laying down a wide swath of heavy snow from VA to MD on its way to SNE.

Verification period ends 11:59 PM EST...SUN 20-DEC-09.  Preliminary storm-total snowfall totals will be posted the evening of MON 21-DEC-09.

Winter '09 / '10 - Early Snow...Cold Snap Hits NW Europe

"The iconic Eiffel Tower was closed to visitors, and train and bus services were delayed in many areas, as daytime temperatures dropped below zero for the first time in the year and black ice coated northern roads.

"Snow also fell in Britain, Germany, Belgium and the Netherlands and weather experts forecast worse to come, with disruption especially in Scotland and northern England.

"The northern Netherlands experienced the worst falls in four years, with snow up to 25 centimetres deep in places..."

More...

Winter '09 / '10 - Snow Storm #1 - Call for Forecasts

Today's PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION from HPC:

"THE 12-18Z NAM NOW SHOW SNOW OF HISTORIC PROPORTIONS IN THE CORRIDOR FROM SOUTHWEST VA TO WASHINGTON DC AND BALTIMORE."

Snow may begin falling late FRI evening over southern forecast stations.  Any snow that accumulates before the verification period begins will not be included in the amount of storm-total snowfall for those stations.

Deadline: 10:30 PM EST FRI...18-DEC-09

Forecast element:  storm-total snowfall

Verification begins: 12:01 AM EST SAT...19-DEC-09
Verification ends: 11:59 PM EST SUN...20-DEC-09

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

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:  NYC 1917

Winter '09 / '10 - Coastal Teaser #2

The European starting showing signs of life in the eastern Gulf of Mexico and offshore from Georgia the last few runs.  Today...GooFuS came on board after several days of sending the storm out to sea.

Prospects for a Miller 'A' storm coming up the coast now looms in the medium range. 

Extension of the parent arctic air mass... centered south of Hudson Bay...will be over land as far south as CHS on Saturday... providing an excellent baroclinic zone along the SE coast for cyclogenesis as short-wave dives into base of trof on NW flow aloft.

Progressive westerlies currently progged suggest storm will skirt the M-A coast and not affect SNE.  More energy entering into the trof from the NW than forecast may cause a more northerly trajectory of the surface LOW.

Winter '09 / '10 - WSI - December Update

WSI Energycast Outlook Calls for Colder-Than-Normal Period in US, Especially in Northern States

Dr. Todd Crawford - WSI seasonal forecaster:

"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."

In February:

Northeast - Colder than normal

In March:
Northeast - Colder than normal

More...

Is -NAO Over-valued as an Antecedent Condition for Significant NE Snowfall?

Introducing another round of posts in a series of posts... challenging the conventional wisdom about the relationship between a negative North Atlantic Oscillation (NAO) and north-eastern US snowfall.

The analysis will use data from a paper by Paul Kocin and Dr. Louie Uccellini published in the Bulletin of the American Meteorological Society (BAMS - 2004).

The Northeast Snowfall Importance Scale (NESIS) categorizes and ranks snowstorms affecting the NE CONUS by snowfall and population distribution.

More about NESIS here and here.

Data for the analysis comes from Table 6 in the BAMS article.  Storm-day NAO values...as well as NAO values for the three days preceding the event will be examined to determine their correlation to notable snowfalls.  Contributions from the Arctic Oscillation (AO) and the Pacific-North  American (PNA) index will also be assessed.

Previous analysis on the subject have shown a weak...yet statistically significant relationship... between increased snowfall @ stations in the NE and mid-Atlantic regions during winters (D-J-F) where the average NAO is negative but no statistically significant relationship between -NAO and individual snowfalls of any amount.

Forecasters and wx enthusiasts often pine for the westerlies to align is such a way for the NAO to b/come negative in the mistaken belief this pre-condition is an essential requirement for decent snows over NE CONUS.

NAO values leading up to and those observed during the so-called 'Storm of the (20th) Century) stands this idea on its head.

VCP32 - No Surprise to Me