Winter '09 / '10 - Snow Storm #2 - Preliminary Verification

Preliminary storm-total snowfalls for Saturday and Sunday from CDUS41...PNS...and CF6 bulletins.

No specific report for HYA.  Interpolated between Chatham (5") and Marston Mills (3.5") from BOX PNS bulletin.

Six new daily records.

SAT...02-JAN-10
CAR - 8.5" (5.8"; 1972)
BGR - 12.1" (9.1"; 1995)
BTV - 19" (7.5"; 1947)
ISP - 3" (1"; 1987)

SUN...03-JAN-10
BTV - 16.4" (7.7"; 1996)
ISP - 2.1" (0.9"; 1988)

Please report errors and a link to the correct data in Comments.

Final results and storm summary Tuesday evening.

Winter '09 / '10 - Snow Storm #2 - The Forecasts

17 entries...including four Rookies...two Interns...one Journeyman...and 10 Senior  forecasters issued 239 station forecasts for this winter/s second contest snow storm.

Forecasts are ranked by storm total precipitation (STP) in ascending order. Blue (red) values are in the 25th (75th) percentile.

Forecasts at the Contest web site.

Consensus for a northern New England event.

Northern annular modes still well below zero providing well-chilled air masses for dendrite production.  Not the typical NE CONUS snow storm morphology where westerlies amplify and long-wave length shortens...evidenced by flat PNA.

Surface LOW forecast to retro-grade and stall in the Gulf of Maine during next 24 hours...which will likely create a tight baroclinic zone and strong forcing from coastal frontogenesis.

Verification period ends 11:59 PM EST SUN 03-JAN-10.
Preliminary storm-total snowfall totals will be posted the evening of MON 04-JAN-10.

Winter '09 / '10 - Snow Storm #2 - RAW FORECASTS

RAW FORECASTS here

 

All forecasts at the Contest web site and summary statistics at the web log will be posted NLT SAT evening.

Winter '09 / '10 - Snow Storm #2 - Call for Forecasts

Two weeks to the day since the last contest-worthy snow storm. Latest NWP forecasts indicate this event will affect mainly northern forecast stations over a two-day period as the surface LOW meanders around the Gulf of Maine.

This storm won/t spawn from the typical winter wx regime where the mid-upper level westerlies amplify...the wavelength shortens...and a nor-easter gains latitude as it comes up the east coast. If anything...the long-wave pattern is de-amplifying...evidenced by decreasing PNA index values. This weekend/s storm is a child of a down-stream Rex block formed by a strong...closed anti-cyclone over Greenland. HPC mentions 'phasing' a few times in HPC/s afternoon 'Heavy Snowfall Discussion' (HSD)...so...a call goes out for forecasts.

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Deadline: 10:30 PM EST FRI...01-JAN-10

Forecast element: storm-total snowfall

Verification begins: 12:01 AM EST SAT...02-JAN-10
Verification ends: 11:59 PM EST SUN...03-JAN-10

Enter your forecast at the Contest web site here.
Follow the link from 'Enter Storm Forecast.'

As always...there/s no cost...or fee...or annoying requests for personal information to enter.  Just a fun exercise to see who can make the best synoptic-scale snowfall forecast.

If you are issuing 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 submitting your entry.

Image:  Millville...NJ

Winter '09 / '10 - ECMWF/s 'Happy New Year' Xmas Present or Coastal Teaser?

Arctic air everywhere.  Happy New Year!



Center of upper LOW progging farther S+W w/time ==> surface development @lower latitude.
Trof appears to take on a negative-tilt.

Fits the pattern.
Don't want it looking too good this far out.

Winter '09 / '10 - White Xmas

Winter '09 / '10 - WSI - December Update 2

Dr. Todd Crawford - WSI seasonal forecaster:

""The combination of the current El Niño event, cold north Pacific, and weakened stratospheric vortex are favorable for a continuation of widespread below-normal temperatures across the US for the upcoming season"...

""There may be a relaxation of the current cold pattern in the Northeast during January, followed by a return to more consistent cold in February and March."

"In January, WSI predicts regional temperature anomalies as follows:
Northeast - Warmer than normal, except PA/NJ/DE

"In February, WSI sees the monthly breakdown as:
Northeast - Colder than normal

"In March, WSI forecasts:
Northeast - Colder than normal"

More...

The stratospheric vortex began to weaken and split late last month continuing into early DEC; however...the two PV circulations have since merged and the upper level anticyclone has dissipated.  The effects of the weakened PV took about three weeks to reach the bottom of the troposphere...as evidenced by near-record low AO index.

Today/s 10 mb geo-potential height / air temperature analysis (courtesy U of WY) shows a strong... consolidated PV centered near the pole.

Winter '09 / '10 - Snow Storm #1 - Final Results

NEWxSFC Chief forecaster donsutherland1 picked up where he left off last winter with another top-ranked synoptic-scale snowfall forecast.

His 27 station forecasts verified with 344.2 SUMSQ error points (Z-Score = -0.915)...a 67% improvement over the average error of 1056".  The 220" storm-total precipitation (STP) forecast for all stations came within 5% of the observed 213.4" snowfall.

Donsutherland1/s issued perfect forecasts @ BOS and BGM.

Congratulations donsutherland1!

2nd Place:  Donald Rosenfeld (SUMSQ error: 372.9"; Z-score:  -0.878)

3rd Place:  Newa2010 (379.16"; -0.870)
Honorable Mention:  Herb @ MAWS (383.2; -0.865)

Full forecast verification and results summary here.

Winter '09 / '10 - Arctic Oscillation

The Arctic Oscillation (AO) was headed toward near-record levels during the past weekend while an historic storm buried many locations in the mid-Atlantic and southern New England with record snowfalls. 

A minor stratospheric warming event preceded the east coast snow storm by three-to-four weeks. The polar vortex (PV) weakened after splitting in two during late NOV and early DEC...as reported on the NEWxSFC web log here...here...and here.

The PV/s stronger half shifted from the eHEMI to wHEMI...where opposing flow between the two circulations created weak ridging near the pole.  With time...the ridging aloft made its way to the surface where an arctic anti-cyclone pushed the AO to levels seldom seen.

The last time the AO was less than or equal to 21-DEC-09/s -5.668 value was over 20 years ago on 01-JAN-85.

The AO has been this low...or lower...on just 15 days since modern record-keeping began in 1950  (NOV-59, JUN-64, JUL-64, MAR-70, JAN-77, JAN-85).  The odds of an AO index value at or below -5.668 are 1 in 1460 (0.07%).

The record negative value of -7.433 was set 15-JAN-77 during a borderline +ENSO (MEI = 0.484)... strong +PDO (1.65)...and an east QBO (-14.91).

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

Preliminary storm-total snowfalls for Saturday and Sunday from CDUS41...PNS...and CF6 bulletins.

Nine new daily records.

SAT...19-DEC-09
ISP - 9.6" (5.6"; 1995)
PHL - 22.5" (9.2"; 1945)
ACY - 11.4" (4.5"; 1979)
DCA - 15" (7"; 1945)

SUN...20-DEC-09
BOS - 10" (7.7"; 1995)
PVD - 14.3" (6.3; 1995)
ISP - 14.3" (4.2"; 1995)
JFK - 4.7" (3.8"; 1995)
EWR - 4.3" (3.2"; 1964)

Please report errors in Comments.

Final results and storm summary Tuesday evening.

Surface analysis:  19-DEC-1945.
Daily snowfall records last set in 1945...fell at PHL and DCA during Storm Day 1.  The 1945 Miller 'A' nor'easter originated in Galveston Bay...TX...then tracked NE to a position near HSE.

Surface analysis:  20-DEC-1995
Daily snowfall records set in 1995 at ISP...JFK...BOS...and PVD during Storm Day 2.  The 1995 MIller 'B' nor'easter formed near HSE...passing just south of the 'benchmark' at 40/70.