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

VT - Stowe
(Marion Post Wolcott - 1940)

MAR-21 snowfall summary by forecast station.
Rank-ordered descending by percent of monthly period-of-record-normal (%MAR).

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

---
MAR Forecast Station Highlights
Stations at or above normal monthly snowfall:  none

Biggest Losers
BDR .. MDT ...PHL ... ACY ...BWI ... DCA ... SBY ... RDU (not even a Trace)

---
Season-Total-to-Date

MAR P-O-R-N contributes 184" (20%) toward the season-total snowfall (D-J-F-M) of 929"
MAR-21 observed snowfall:  19" (90% below P-O-R-N; 2% of season-total snowfall)
Image courtesy NOHRSC @ http://www.nohrsc.noaa.gov/nsa/

Teleconnections

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

---
DEC totals
https://newxsfc.blogspot.com/2021/01/winter-20-21-season-total-snowfall.html
JAN totals
https://newxsfc.blogspot.com/2021/02/winter-20-21-season-total-snowfall.html
FEB totals
https://newxsfc.blogspot.com/2021/03/winter-20-21-season-total-snowfall.html

Explosive origins of 'secondary' ice and snow

"... "rime splintering" isn't nearly the whole story.
 
"The new results from the Arctic show ... larger supercooled water droplets, classified as drizzle, play a much more important role in producing secondary ice particles than commonly thought.

" "When an ice particle hits one of those drizzle drops, it triggers freezing, which first forms a solid ice shell around the drop," explained Fan Yang, a co-author on the paper. "Then, as the freezing moves inward, the pressure starts to build because water expands as it freezes. That pressure causes the drizzle drop to shatter, generating more ice particles."

"... drizzle freezing fragmentation can enhance ice particle concentrations in clouds by 10 to 100 times -- and even 1,000 on occasion!"

More ...

 

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

BWI
St. Paul St.looking N from Read St. (MAR-42)

FEB-21 snowfall summary by forecast station.
Rank-ordered descending by percent of monthly period-of-record-normal (%FEB).

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

---
FEB Forecast Station Highlights
16 stations at or above normal monthly snowfall
ABE
29.7" (400%) above FEB normal
BDR
21.7" (341%) above FEB normal
EWR
21.5" (336%) above FEB normal
NYC
17.1" (292%) above FEB normal
MDT
10.4" (212%) above FEB normal

Biggest Losers
ORF ... RDU (4% and 2% of FEB P-O-R-N)

---
Season-Total-to-Date 

FEB P-O-R-N contributes 262" (28%) toward the season-total snowfall (D-J-F-M) of 929"

FEB-21 observed snowfall:  429" (64% above P-O-R-N; 46% of season-total snowfall)

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

---
Teleconnections

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

---
DEC totals
https://newxsfc.blogspot.com/2021/01/winter-20-21-season-total-snowfall.html
JAN totals
https://newxsfc.blogspot.com/2021/02/winter-20-21-season-total-snowfall.html

Winter '20 / '21 - Snow Storm Contest: Interim Standings #2

 After FOUR contest-worthy snow storms ... under the ‘two-thirds’ rule … forecasters who have entered at least THREE forecasts are included in Interim standings #2.

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

---
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.

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.

---
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.

Read more »

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.

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

---
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"

Read more »

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----

Read more »