Winter '10 / '11 - Snow Storm #6 - Raw Forecasts

Raw forecasts at ne_wx GoogleGroup here.

Winter '10 / '11 - Snow Storm #6 - Game On!

WOW-ZER!

Winter '10 / '11 - Snow Storm #6 - Call for Forecasts

Boston...MA
02-FEB-61
NESIS:  7.06 (crippling)

Potent winter storm heading east today from the central plains is packed to the gills with dynamic and thermo-dynamic forcing elements.

Models advertising coupled upper-level jet streaks...100+ kt speed-max at 5H...tight thermal gradient bent into an 'S-shape' at 85H indicating strong WAA on 60 kt winds loaded with 1"+ PWs from the GOM.

The intensity of initial wave crossing the forecast area this evening looks to be a contest-worthy event; however...it was not well-modeled with enough lead time to issue a 'call for forecasts.'

The contest may be canceled prior to the deadline if NWP indicates a fizzling event.

---
Deadline for entries: 10:30 PM EST TUE...01-FEB-11
Forecast element: storm-total snowfall

Verification period begins: 12:01 AM WED...02-FEB-11
Verification period ends: 11:59 PM WED...02-FEB-11

Enter your forecast at the Contest's home page here.
Follow the link from 'Enter Storm Forecast.'

---
As always...there/s no cost...or fee...or advertising...or annoying requests for personal information to enter a forecast. It's just a fun exercise among winter wx enthusiasts to see who can make the best synoptic-scale snowfall forecast.

If you are issuing your first forecast this winter...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).

Want to be notified via e-mail when a 'Call for Forecasts' is issued?
Send your request to newx at newx-forecasts dot com.

Winter '65 / '66 - On This Day in NESIS History

A MAJOR (NESIS 5.05 5.93) snowstorm affected the northeast between January 29 and 31...1966. This storm ranks 12th out of 66 since 1948.

Originating in the GOM on 29-JAN...the storm marched up the coast to a position off the Delmarva Peninsula on the 30th where a 930-ish central pressure was observed.  The strong cyclonic circulation threw high PW air into an arctic air mass where dew points were in the single digits.  Little doubt there was a coastal front involved...altho it/s not shown in the SFC analysis.  The 7 AM temperature in Birmingham...AL was 1°F and 3°F in Atlanta...GA.

Snowfall records were established that still stand today at...
ABE - 9.6"
BDL - 6.2"
BDR - 5"
BGM - 14.5" (1.01" liquid)
BOS - 5.7"
EWR - 5.6"
JFK - 5.2"
ORH - 8.5" (1.4" liquid)
PHL - 5.6"
PVD - 5.2"

NAO for D-3...D-2...D-1...and storm day

-1.654

-1.739

-1.622

-1.402

AO

-3.510

-2.929

-2.853

-3.053

PNA

0.002

-0.034

0.250

0.565

Daily Wx Map
(click to enlarge)

The Northeast Snowstorm Impact Scale (.pdf) was developed by Paul Kocin and Dr. Louie Uccellini in 2004 to "...convey a measure of the impact of heavy snowfall in the Northeast urban corridor, a region that extends from southern Virginia to New England.

"The NESIS differs from the Fujita tornado scale and the Saffir–Simpson hurricane scale in that NESIS focuses on the amount of snow that falls, mapped onto the population density that experiences the snow, rather than focusing on wind as the major impact agent."

Winter '10 / '11 - Interim Standings - #3

After five snow storms...



Under the 'two-thirds' rule...the best 'two out of three' z-scores are used to compute the interim standings. After Snow Storm #4 5...your top four z-scores were used to calculate these standings. Data used to compute the standings are posted at the Contest web site here.

Z-scores are used to standardize / normalize forecast errors for each snow storm so at the end of the season...the 'equalized' scores can be averaged.

An expanded data table with higher resolution graphics and additional measures of forecaster skill at the Contest's home page.

Winter '10 / '11 - Forecaster Master Database

The forecaster master database through Snow Storm #5 has been updated here.

The database (.html) has each forecast verification element by forecaster...such as Sum of Square Errors (SUMSQ)...Total Absolute Error (TAE)...Average Absolute Error (AAE)...and the Coefficient of Determination (RSQ). These 'measures of skill' are described at the Contest's web site here as part of the interim 'regular season' standings (scroll down).

Winter '10 / '11 - Snow Storm #5 - Final Results

1st - nnjwxguy78
SUMSQ: 327.44
SUMSQ Z: -1.369
STP: 5.00 (1)
TAE: 70.70 (2)
AAE: 2.83 (4)

2nd - Mitchel Volk
SUMSQ: 377.41
SUMSQ Z: -1.086
STP: 38.40 (5)
TAE: 73.00 (4)
AAE: 2.70 (2)

3rd - donsutherland1
SUMSQ: 436.72
SUMSQ Z: -0.750
STP: 45.65 (8)
TAE: 70.15 (1)
AAE: 2.70 (1)

Honorable mention - ejbauers
SUMSQ: 448.55
SUMSQ Z: -0.683
STP: 55.55 (9)
TAE: 71.65 (3)
AAE: 2.76 (3)

SUMSQ: sum of square errors
STP: storm-total precipitation error
TAE: total absolute error
AAE: average absolute error
(rank)

---
Full forecast verification and summary at the Contest/s home page.

Winter '10 / '11 - Snow Storm #5 - Preliminary Verification

Preliminary storm-total snowfalls for Wednesday and Thursday from CDUS41...CXUS51...and PNS...as of noon Friday.

No updated snowfall report was carried in the NWS PNSBOX bulletin for HYA. Verifying storm-total snowfall of 3.5" was estimated from vicinity reports.

SBY/s Daily Climate Bulletin did not carry a snowfall report.  Verifiying storm-total snowfall came from PNSAKQ.

PHL/s record-setting snowfall on Wednesday piled-up over the course of six hours!

Many stations in the data table do not have SN:H2O reported b/c their totals included mixed precipitation.
---
Fourteen new daily records!

Wednesday...26-JAN-11
PHL - 14.2" (4.4"; 1963)
ABE - 11.3" (5.3"; 1994)
EWR - 11" (5.8"; 1994)
BWI - 7.8" (6.9"; 1966)
MDT - 6.4" (6.1"; 1904)
BDR - 6" (3.6"; 1949)
JFK - 6" (3.3"; 1994)

Thursday...27-JAN-11
ORH - 11" (6.1"; 1963)
ISP - 9.6" (1.1"; 2004)
BDL - 9.1" (5.2"; 1963)
BOS - 8.8" (8"; 1894)
BDR - 7" (3.8"; 1963)
PVD - 6.7" (3"; 1963)
JFK - 4.3" (2.7"; 2004)

---
Please report any errors and drop a link to the correct data in Comments.
Final results and storm summary Saturday evening.

Winter '10 / '11 - Snow Storm #5 - Snow Gun

(Updated below)

Tonight's 00z rawindsonde flight launched from OKX observed some major-league instability atop deep low-level moisture.

- Note the strong deep-layer iso-thermal WAA through ~600 mb beneath a layer of CAA near 500mb.
- Snow is indicated b/c the entire column is below zero.
- Specific gravity peaks close to 5g/kg near 750 mb.
- Baroclinic instability indicated with strong increase in wind speed with height.

More importantly is the observed instability AOA 700 mb as indicated by the theta-E plot shown below.  Strong instability is indicated when the trace goes straight up as it does ~700 mb and in the layer between 650 and 500 mb.

Snowfall rates at IAD earlier this evening were quite intense...where less instability was observed.  If I'm the duty forecaster at OKX this evening...I'd be preparing for snowfall rates in excess of 2"/HR over my CWA.

Sounding images courtesy SPC.

UPDATE:

METAR KISP 270656Z 02025KT 1/4SM R06/1800V2200FT +SN BLSN BKN003 OVC008 M01/M03 A2950 RMK AO2 SLP988 SNINCR 5/019

5" / hour!

Winter '10 / '11 - Snow Storm #5 - TSSN

SPECI KIAD 262021Z 34007KT 1SM -TSSN BR BKN004 OVC010CB 01/M01

METAR KFDK 262051Z AUTO 35010KT 1SM -TSSN OVC009 01/01

METAR KBWI 270154Z 34009KT 3/4SM R10/3500V4500FT -TSSN BR OVC003 01/00