Winter '17 / '18 - Snow Storm #1: FINAL Results

Forecasters' station verifications and the storm summary at NEWxSFC/s home page.
http://www.newx-forecasts.com/

	1st - JessicaCain
	SUMSQ:	17
	SUMSQ Z:	-0.991
	STP:	4.3	(4)
	TAE:	12.0	(1)
	AAE:	0.63	(1)
	2nd - TQ
	SUMSQ:	24
	SUMSQ Z:	-0.858
	STP:	4.7	(5)
	TAE:	14.3	(2)
	AAE:	0.75	(2)
	3rd - Shillelagh
	SUMSQ:	25
	SUMSQ Z:	-0.847
	STP:	3.6	(3)
	TAE:	14.4	(3)
	AAE:	0.76	(3)
	HM - WeatherT
	SUMSQ:	33
	SUMSQ Z:	-0.685
	STP:	0.4	(2)
	TAE:	17.4	(5)
	AAE:	0.92	(5)

SUMSQ:  sum of square errors (")

STP:  storm total precipitation (")

TAE:  total absolute error (")
AAE:  average absolute error (")

(#): rank

Forecast by Observed Snowfall Scatter Plots of Top Forecasters 

 

Station Verification Comparison of Top Forecasters

 

Snowfall Distribution and Magnitude by Station (Power Map - Excel 2013)

 

 

Winter '17 / '18 - Snow Storm #1: Preliminary STP Verification

Table of preliminary storm-total snowfalls by station for MON from CDUS41 and CXUS51 bulletins.

Exceptions:
PWM and CON
25-DEC/s daily CLI and CF6 bulletins carry 'MM' as daily snowfall at post-time. 
Preliminary verification STP from latest PNSGYX and METARs.
Values subject to change pending updates to CDUS41 ... CXUS51 ... or PNS bulletins.

HYA
Storm-total snowfall report based on METARs

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Stations observing at least:
Trace - 19
4" - 6
6" - 1
8" - 1
10" - 0

Max melt-water at BGR (0.46")
Snow-Liquid Ratios (SLR) for areas with mixed precipitation ... such as BDR and BOS ... are not reported.

12z 12-25-17

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Please report any errors in Comments along with a link to the correct data.
Final results expected NLT WED evening.

Winter '17 / '18 - Snow Storm #1: The Forecasts!

Rookie 0
Intern 1
Journey 0
Senior 11
TOT 12 (+ 1 for GOVT / NWS)

Forecasts at the Contest/s web site.
Direct link:  http://www.newx-forecasts.com/NEWxSFC_19/storms/storm1_forecasts_25Dec17.htm

Forecasts are ranked by their storm-total precipitation (STP).

BLUE ==> 25th percentile

RED ==> 75th percentile
White STP and 4cast cells range between the 25th and 75th percentile

NWS forecasts derived from current issuances at the deadline.

 

Heaviest snowfall (>= 6") consensus along and the right of CAR - BGR - PWM - CON - CAR.

Lollypop expected at CAR.

 

 

AO/s dead-cat bounce cushioned by NAO and PNA bank shot.

Winter '17 / '18 - Snow Storm #1: RAW FORECASTS

Here

Winter '17 / '18 - Ignorosphere Tonight

Polar vortex centered over Barents Sea.
Anticyclonic circulation over NOAM

10 mb circulation

The HIGH made a strong attempt to displace the PV but will lose out shortly.

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Image courtesy Earth

Winter '17 / '18 - Snow Storm #1: Call for Forecasts Redux

Court St. Keene ... NH
c.1870
 

Sharp short wave diving into the base of a high-amplitude long wave trof centered nicely near 85W progged to spawn a meek area of LOW pressure over the OH river valley then transfer its energy to the SNE coast.

Bare minimum number of stations appear candidates for more than nuisance snowfall for this season/s inaugural event.  Contest may be cancelled before deadline if storm appears not to be contest-worthy.

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Forecast element: station total snowfall

Deadline:  SUN ... 24-DEC-2017 @10:30 PM EST
Verification begins:  MON ... 25-DEC-2017 @ 12:01 AM EST
Verification ends:  MON ... 25-DEC-2017 @ 11:59 PM EST

Enter your forecast at the NEWxSFC/s home page @ http://www.newx-forecasts.com/
Follow the top-of-page link from 'Enter Storm Forecast.'
Contest rules.

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

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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.

Winter '17 / '18 - Snow Storm #1: White Christmas

Time Square - NYC
26-DEC-47

Today/s American NWP output continued their collective tease for a potentially contest-worthy snow storm over northern portions of the forecast area on Christmas day.

Little comfort in store for true believers in sacred tele-connections for NE / M-A snows ... such as -AO ... -NAO ... +PNA ... despite plenty of evidence the conventional wisdom is largely unsupported empirically ... but I digress.

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Should the stars finally align for this winter/s inaugural snowfall forecasting contest ... the 'Call for Forecasts' will be issued late tomorrow (SAT) afternoon / early evening with the deadline for entries NLT 10:30 PM EST on SUN.

Winter '17 / '18 - VCP 32: Anything Yet?

Winter '17 / '18 - Snow Storm #1: Call for Forecasts!

Broadway - NYC
19-DEC-32

CANCELLED CANCELLED CANCELLED
Areal snowfall coverage not expected to meet minimum standards for a contest-worthy event.

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Promising Clipper system swings into the northern forecast area TUE deepening nicely over the Lakes before slowly exiting on WED.

Forecast element: station total snowfall

Deadline:  MON ... 11-DEC-2017 @10:30 PM EST
Verification begins:  TUE ... 12-DEC-2017 @ 12:01 AM EST
Verification ends:  when snow stops accumulating over the forecast area

Enter your forecast at the NEWxSFC/s home page @ http://www.newx-forecasts.com/

Follow the top-of-page link from 'Enter Storm Forecast.'

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

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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.

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Contest may be cancelled before deadline if storm appears to fizzle.

Winter '17 / '18 - Snow Storm #1: Close Call

Valley Forge ... PA
16-DEC-70

Some winter storms ... like the one affecting a large swath of the M-A and SNE coastal plain this weekend ... have a sneaky way of not playing its 'snow card' until it's too late to issue a 'Call for Forecasts' and a contest-worthy storm ends up slipping through the cracks.

This has been especially true over the years for primarily rain events featuring a ribbon of accumulating snows along the NW edge of the precipitation shield.

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Call it a failure of numerical weather prediction.
Call it a failure of operational weather forecasters.
Call it Banana-Bana ... BO-Bana ... FE-FI ... FO-fanna ...

Either way ... the 19th Annual NEWxSFC awaits its inaugural event for Winter '17 / '18.

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But did anyone ... anywhere ... get it right three days out?

Why ... yes.  'Someone' did get it right.
The 06/12z NAM ... of all things ... kinda nailed it (GFS was all along ... all in on all liquid).


Image courtesy MeteoCentre

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Logistically ... the deadline for this storm would have been FRI evening given snow was expected to begin over the forecast area by early SAT AM.  With a FRI deadline ... the 'Call for Forecasts' would have been issued THU evening.  The NCEP forecast at that time called for 10% chance for at least 4" over interior VA stations and a 10% chance for at least 4" along the coasts of NJ continuing into SNE.

As outlined in this post from 2016 ... issuing a 'Call for Forecasts' is not a trivial matter.

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Had this been the Day3 NCEP prog ... there would have been more than enough lead time to issue the call and the season would be up and running.

Instead ... the call ended up being too close.

Winter '17 / '18 - Arctic Oscillation - NOV

NOV/s Arctic Oscillation (AO) Index:  -0.078

Given NOV-17/s negative AO ... the 2x2 contingency table predicts a 72% likelihood the three-month average AO will be negative this winter.  The results says nothing about the magnitude of the winter/s AO or which months will be negative ... only its sign.

NOTE:
True + ==> correct prediction
False + ==> incorrect prediction


Scatterplot of the 67-year AO period of record (1950 - 2016)

Lower left quad:  NOV -AO and DJF -AO
Lower right quad:  NOV +AO and DJF -AO

Upper left quad:  NOV -AO and DJF +AO
Upper right quad:  NOV +AO and DJF +AO

Related posts by NEWxSFC ...
Winter '17 / '18 - NOV/s Arctic Oscillation: Winter/s Leading Indicator
http://newxsfc.blogspot.com/search?q=arctic+oscillation

Winter '17 / '18 - 17th Annual 'Season-total' Snowfall Forecast Contest - The Forecasts!

17 forecasters + P-O-R-N + CONSENSUS

Two first-time forecasters
Welcome Any.wx and 33andrain

475 station forecasts
Entries ranked by STP

BLUE - <= 25th percentile
RED - >= 75th percentile
ORANGE - Winter '16 / '17 Top 'Season-total' forecaster
P-O-R-N - period of record normal
CONSENSUS - average of individual forecasts by station

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Station forecasts for ...
BELOW average snowfall - 189 (40%)
AVERAGE snowfall - 26 (5%)
ABOVE average snowfall - 260 (55%)

NOTE:  Label should read '17 / '18

Consensus (at least 67% of forecasts) for stations with ...
BELOW average snowfall @ ACY ... IAD ... RIC ... ORF ... RDU
ABOVE average snowfall @ CAR ... BGR ... CON ... BTV ... PWM ... ORH ... PVD ... BDL ... BGM ... BDR
Forecasters are all in for above average snows @ BDR

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See all forecasters' entries at the Contest/s web site here.

The regular 'snow storm' forecasting contests begin when the flakes start a-flyin'.
'Call for Forecasts' are issued at NEWxSFC/s web site and blog (you are here) ... via e-mail ... and Facebook.