Winter '20 / '21 - Forecaster Statistics

Lincoln Memorial Reflecting Pool
and Washington Monument (c.1930)

For each contest-worthy snow storm ... the forecasts are verified against the observations of storm-total snowfall.

Statistics are calculated to determine how well each forecast captured the magnitude and distribution of the storm's snowfall.

Individual forecaster statistics for the first four snowstorms here.

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Statistics include:
The average normalized ‘SUMSQ error’ is the Contest/s primary measure of forecaster performance.

This metric measures how well the forecaster/s expected snowfall 'distribution and magnitude' for _all_ forecast stations captured the 'distribution and magnitude' of _all_ observed snowfall amounts.

A forecaster with a lower average SUMSQ Z Score has made more skillful forecasts than a forecaster with higher average SUMSQ Z Score.

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Winter '20 / '21 - Snow Storm #4: FINAL Results and Storm Summary

Complete forecaster verification table and the FINAL Results / Storm Summary available at NEWxSFC/s home page.

SUMSQ:  sum of square error (")
SUMSQ Z:  Z-score
STP:  storm total precipitation error (")
TAE:  total absolute error (")
AAE:  average absolute error (")
(#):  category rank

Forecast by Observed Snowfall Scatterplots for Top Forecasts
Forecast/s dotted blue line below (above) the Observed snowfall/s solid red line ==> under (over) forecast error.

Station by Station Comparison of Top Forecasters

An Overview of Thundersnow

"The purpose of this article is to summarize our current understanding about this unusual wintertime event.

"This article describes where and when thundersnow happens, the ingredients needed to make thundersnow, and new efforts at understanding and forecasting the occurrence of thundersnow."

http://www.newx-forecasts.com/reference/An%20overview%20of%20thundersnow.PDF

Winter '20 / '21 - Snow Storm #4: Preliminary STP Verification

Accumulation-weighted SN:H20 (SLR)

Preliminary verification of storm-total snowfalls for THU (18-FEB-21) through SAT (20-FEB-21) from CDUS41 (CLI) ... CXUS51 (CF6) ... METARs ... and PNS bulletins.  Spotty coverage and reporting.

HYA STP estimated from a vicinity report within 2.5 SM of the station carried by the BOXPNS bulletin.  H2O value derived from METAR precipitation groups 7nnnn (24 hour) ... 6nnnn (6 hour) ... and Pnnnn (1 hour).

SBY STP estimated based on METAR 6-hour precipitation report of '60006' and 10:1 SLR.

CON/s Daily Climate Bulletin on THU reported 0.01" liquid but no snowfall total.  Estimated snowfall of 0.1" by applying 10:1 SLR.

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SLR not reported for some stations with measurable snowfall b/c significant liquid and / or freezing precipitation also occurred during the verification period.

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Stations observing at least 0.1":  23 (85%)

Given a station had measurable snowfall; stations observing at least ...
4" - 12 (44%)
6" - 2 (7%)
MAX:  7.6"

MAX snow melt-water (minimum SLR 8:1)
ABE:  0.55"
BDR:  0.51"
HYA:  0.36"

MAX precipitation (frozen + freezing + liquid):
ORF:  1.50"
RDU:  1.20"
RIC:  0.91"

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Winter '20 / '21 - Snow Storm #4: The Forecasts!

Barton ... VT
Main train summit (1886)

Rookie      3
Intern      -
Journey      -
Senior      11
GOVT      1
PWSP      1
TOT      16

We welcome Rookie petenotpetrock who's issuing his first NEWxSFC forecast.

Forecasters rank-ordered by ascending storm-total precipitation (STP)
BLUE ==> 1st quartile
RED ==> 4th quartile
WHITE STP cells fall between the 1st and 4th quartiles

Heaviest snowfall (+5") consensus along and to the right of BDL - ORH - BOS - PVD - ISP - JFK - EWR - MDT - ABE - BDL.

Lollypop expected at ABE (7")

All three teleconnections were photographed getting onto a plane destined for Cancún ... Mexico.

Forecasters' station-by-station forecasts posted to the Contest/s web site ...
http://www.newx-forecasts.com/

Direct link to the table of forecasts ...
http://www.newx-forecasts.com/NEWxSFC_22/storms/storm4_forecasts_18FEB21.htm

Winter '20 / '21 - Snow Storm #4: RAW forecasts

Portland ... ME
28-JAN-1886

Entry No. 1785
Forecaster = petenotpetrock
Time = 2/17/2021 6:57:51 AM
CAR = 3
BGR = 4
PWM = 6
CON = 6
BTV = 5
BOS = 4
HYA = 3
ORH = 7
PVD = 4
BDR = 5
BDL = 6
ALB = 6
BGM = 7
ISP = 3
JFK = 3
ABE = 8
MDT = 8
PHL = 2
ACY = 2
EWR = 6
BWI = 2
IAD = 3
DCA = 1
SBY = 1
RIC = 2
ORF = 1
RDU = 0
Comments =
----End of Entry----

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Winter '20 / '21 - Snow Storm #4: Call for Forecasts! - Take 2

Boston Public Garden
25-FEB-62

Too few stations stayed in play after Storm #4/s first Call for Forecasts on SUN.

This storm shows much more promise to have more than enough forecast stations in play to be contest-worthy.

One thing remains unchanged from - the parade of winter storms affecting the M-A and the NE with messy p-types.

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

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

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Forecast element: each station/s storm-total snowfall

Deadline for entries: 10 PM EST ... WED ... 17-FEB-21
Verification begins: 12:01 AM EST ... THU ... 18-FEB-21
Verification ends: 11:59 PM EST the day when snow stops accumulating

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Winter '20 / '21 - Snow Storm #4: Call for Forecasts!

BWI
Columbia Ave.  (13-FEB-1899)

UPDATE 4:30 PM EST ... MON ...15-FEB-21

Not happenin' ...

UPDATE 10:45 AM EST ... MON ...15-FEB-21
Trend not being very friendly ... 

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Original post (5:13 PM EST ... SUN ...14-FEB-21)

Contest-worthy snows expected along the NW edge of the precipitation shield as the next in a parade of winter storm slides east across the northern M-A then off the SNE coast.  Messy p-type forecasts downstate.

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

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

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Forecast element: each station/s storm-total snowfall

Deadline for entries: 10 PM EST ... MON ... 15-FEB-21
Verification begins: 12:01 AM EST ... TUE ... 16-FEB-21
Verification ends: 11:59 PM EST ... TUE ... 16-FEB-21

You also get the chance to see how well your forecast stacks up against NWS Eastern Region Weather Forecast Offices. Turns out they/ve been fairly easy to beat!

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Winter '20 / '21 - 'Season-total' Snowfall Forecast Contest: JAN Totals

Mass General Hospital (06-FEB-61)

UPDATE 14-FEB-21 4 PM EST:  corrected JAN total for EWR ... NYC ... BDR and JAN Forecast Station Highlights section.

h/t Roger Smith

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JAN-21 snowfall summary by forecast station.

Rank-ordered descending by percent of monthly period-of-record-normal
(%JAN)

Green ==> 4th quartile
White ==> Inter-quartile range
Red ==> 1st quartile

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JAN Forecast Station Highlights
3 stations with above normal monthly snowfall

BTV
4.1" (21%) above JAN normal

ORF
0.2" (6%) above JAN normal

SBY
0.2" (6%) above JAN normal

Biggest Losers
PWM ... CON (less than 35% JAN P-O-R-N)

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Season-Total-to-Date

JAN P-O-R-N contributes 279" (30%) toward the season-total snowfall (D-J-F-M) of 929".

JAN-21 observed snowfall:  212" (-44% below P-O-R-N; 17% of season-total snowfall)

Image courtesy NOHRSC @ http://www.nohrsc.noaa.gov/nsa/

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Teleconnections

AO / NAO / PNA data
https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/daily.index.ascii

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DEC Totals
https://newxsfc.blogspot.com/2021/01/winter-20-21-season-total-snowfall.html

Winter '20 / '21 - Snow Storm Contest: Interim Standings #1

After three snow storm forecasting contests ... under the ‘two-thirds’ rule … forecasters who have entered at least TWO forecasts are included in interim standings #1.

Complete interim statistics table and chart at the Contest/s web site HERE (direct link)
Forecaster statistics for Winter '20 / '21 contest snow storms HERE (direct link)

Don Sutherland has been identified incorrectly as the Chief 'Regular Season' forecaster for the '20 / '21 season when that honor belongs to Brad Yehl.  We regret the error and apologize to Brad for the oversight.

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SUMSQ errors for each contest snow storm are normalized (i.e., standardized) with a 'Z-score' ... then averaged to compute the standings. If a forecaster has issued forecasts for more than two-thirds of all snow storm contests ... then Z-scores from their 'best two-thirds' forecasts are used to calculate the Interim and Final standings.  Similar idea as dropping the lowest test score before computing the final grade.