Winter '19 / '20 - VCP32: Winning the Lottery

Winter '19 / '20 - North Atlantic Oscillation (NAO): Leading Analogs' 5H and 2mT Composite Anomalies ... as of NOV-19

NOV-19 NAO:  +0.28

Same analog years as those associated with NAO/s OCT-19 analysis but with a shuffled ranking.
Winter / AVG NAO
80-81 / 0.487
08-09 / 0.077
12-13 / 0.227
14-15 / 1.197
16-17 / 1.113


Weighted NAO Analogs for Winter '19 / '20:  5H GPHa (l) & 2mTa (r)

- Positive 5H GPHa over west CONUS & negative 5H GPHa over eastern third of CONUS ==> Ridge-W / Trof-E flow regime
- Positive 5H GPHa INVOF Azores ==> NAO > 0
- Negative 5H GPHa over North Pole ==> AO > 0
- Negative 5H GPHa INVOF Great Lakes and along East Coast ==> Miller B-type storms
- Negative 2mTa along East Coast and most of New England

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At the 95% confidence level ... the Chi-square 'Test of Independence' shows the state of NOV/s NAO and the average NAO state for the ensuing D-J-F period are not independent.  They are related and have predictive value.

Over the NAO/s 69 year period-of-record ... the data show when NOV/s NAO is positive  ... there's a 73% chance the winter/s average NAO will be also positive.

The present analog years add weight to the Chi-square analysis suggesting NAO/s average state this winter will be positive.  An important caveat:  four of the five NAO analogs years occurred during 'cold' ENSO winters.  Winter 14 / '15 was the exception with a weak El Nino (SSTa 0.6°C).  All forecast stations ... in total ... measured 50% above normal snowfall that winter.

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Key
5H - 500 mb
2mTa - 2 meter temperature anomaly
GPHa - geopotential height anomaly
CONUS - continental United States
INVOF - in the vicinity of
ENSO - El Nino Southern Oscillation
SSTa -  sea surface temperature anomalies

Winter '19 / '20 - Arctic Oscillation (AO): Leading Analogs' 5H and 2mT Composite Anomalies ... as of NOV-19

NOV-19 AO:  -1.193
Same analog years as those associated with AO/s OCT-19 analysis but with a shuffled ranking.

Winter / AVG AO
97-98 / -0.778
58-59 / -1.579
14-15 / 0.849
54-55 / -0.717
53-54 / 0.082

Weighted AO Analogs for Winter '19 / '20:  5H GPHa (l) & 2mTa (r)
- Negative 5H GPHa over Gulf of Alaska & Positive 5H GPHa INVOF Hawaii ==> EPO > 0
- Overall North American pattern mimics Tropic/Northern Hemisphere's (TNH) negative phase often associated with +ENSO.
- Negative TNH ==> 1)  stronger than normal Pacific jet farther south of its normal axis and 2) well above normal temperatures in eastern North America.
- Active sub-tropical jet
- Positive GPHa over eastern Canada would 1) advect cP flow from hi-latitude snow fields into the eastern U.S. and 2) weaken the Hudson LOW.

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At the 95% confidence level ... the Chi-square 'Test of Independence' shows the negative state of NOV/s AO and the average AO state for the ensuing D-J-F period are not independent.  They are related and have predictive value.

Over the AO/s 69 year period-of-record ... the data show when NOV/s AO is negative ... there's a 71% chance the winter/s average AO will be also negative.

The present analog years add weight to the Chi-square analysis indicating AO/s average state this winter will be negative.

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Key
5H - 500 mb
2mTa - 2 meter temperature anomaly
GPHa - geopotential height anomaly
EPO - Eastern Pacific oscillation
cP - continental Polar air mass
INVOF - in the vicinity of

Winter '19 / '20 - Leading Analog: Winter '04 / '05

Through a careful multi-variate analysis of key teleconnection indices and the process of elimination ... we/ve settled on the '04 / '05 winter as this winter/s leading analog for the Contest/s forecast area.

Bottom line up front:
- Temperature:  near normal except below normal over far northern stations
- Snowfall:
Above normal - northern half of forecast area
Normal to below normal - southern half of forecast area

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Consensus of dynamic and statistical model outlooks
ENSO:  La Nada+ (0.5°C < ENSO Region 3.4 SSTa < 0.5°C)

Current PDO state (OCT-to-MAR) < 0

2019 trend analysis
QBO:  W (+) going E (-)

2x2 contingency table (Chi-SQ Test for Independence) AO NAO
If NOV AO < 0 then 71% probability D-J-F average AO < 0
If NOV NAO > 0 then 73% probability D-J-F average NAO > 0

The analog winter/s key features follow:
ENSO:  +0.5°C (lowest threshold of weak El Niño)
MEI:  La Nada+
QBO:  W (+) going E (-)
PDO < 0
AO < 0
NAO > 0
EPO < 0
Contest stations' cumulative season-total snowfall:  1,446" (AVG:  1,095")

Winter '04 / '05 - 5H GPHa (l) & 2mTa (r)
Negative 5H GPHa - W & Negative 5H GPHa - E  ==> Trof-W / Trof-E
Neutral 2mTa over east coast; negative 2mTa over New England

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Winter '04 / '05 monthly anomalies (D-J-F)
 
DEC '04 - 5H GPHa (l) & 2mTa (r)
Positive 5H GPHa - W & Negative 5H GPHa - E  ==> Ridge-W / Trof-E
Negative 5H GPHa INVOF Greenland ==> NAO > 0
Positive 5H GPHa INVOF Gulf of Alaska & Positive 5H GPHa eastern ATL ocean ==> AO > 0
Positive 5H GPHa INVOF Gulf of Alaska & negative 5H GPHa INVOF Hawaii ==> EPO < 0
Negative 2mTa over SE and Gulf Coast


JAN '05 - 5H GPHa (l) & 2mTa (r)
Negative 5H GPHa - W & Positive 5H GPHa - E  ==> Trof-W / Ridge-E
Negative 5H GPHa INVOF Greenland ==> NAO > 0
Positive 5H GPHa INVOF Gulf of Alaska & Positive 5H GPHa eastern ATL ocean ==> AO > 0
Positive 5H GPHa INVOF Gulf of Alaska & negative 5H GPHa INVOF Hawaii ==> EPO < 0
Positive 2mTa over SE and Gulf Coast; negative 2mTa over NE CONUS

FEB '05 - 5H GPHa (l) & 2mTa (r)
Negative 5H GPHa - W & Negative 5H GPHa - E  ==> Trof-W / Trof-E
Positive 5H GPHa INVOF Greenland ==> NAO < 0
Negative 5H GPHa INVOF Gulf of Alaska & Negative 5H GPHa eastern ATL ocean ==> AO < 0

Neutral 2mTa over east coast; positive 2mTa over NE CONUS

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Key
5H - 500 mb
2mT - 2 meter temperature
2mTa - 2 meter temperature anomaly
GPHa - geopotential height anomaly
ENSO - El Nino Southern Oscillation
MEI - Multivariate ENSO Index
AO - Arctic oscillation
NAO - North Atlantic oscillation
EPO - Eastern Pacific oscillation
PDO - Pacific Decadal oscillation
CONUS - continental United States
INVOF - in the vicinity of

Winter '19 / '20 - Snow Storm #1: FINAL Results

Forecaster verifications 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
Snowfall forecast's dotted blue line below (above) Observed snowfall solid red line ==> under (over) forecast

Station by Station Comparison of Top Forecasters

Winter '19 / '20 - Snow Storm #1: Preliminary STP Verification

AVG SN:H2O is quantity-weighted

UPDATE 2 (09-DEC-19 @ 6:50 PM EST):  For the Record - CON STP changed from 6.9" to 7.1" per CF6 bulletin.

Revised STP did not change rank ordering of forecasts; however ... the minor changes in Z-Scores will be applied to season-end calculations.

UPDATE (04-DEC-19 @ 9:50 PM EST):  corrected BOS STP

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Preliminary verification of storm-total snowfalls for SUN through TUE from CDUS41 (CLI) ... CXUS51 (CF6) ... METARs ... and PNS bulletins.  Good coverage and reporting with exceptions at CON.

Exceptions
CON
No daily snowfall reported in CF6 or CLI bulletins for 02-DEC-19.
PNSGYX carried 5.2" from ASOS
SUN-TUE CLI bulletins carried 3.5" ... MM ... 1.9" = 5.4" (0.69" liquid)

CON METARs did not report mixed-precipitation
PWM SLR 10:1 (no mixed precipitation)
ORH SLR 10.7 (0.02" freezing precipitation removed)
CON verification STP:  6.9" (estimated at 10:1 SLR for 0.69 liquid precipitation)
STP may be amended if official data reported prior to posting of FINAL results.

HYA
STP estimated by applying 10:1 SLR to 0.12" liquid reported in METARs during period of frozen precipitation

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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.

Read more »

Winter '19 / '20 - Snow Storm #1: Three Daily Snowfall Records Set - Storm Day 3

Three forecast stations along the eastern edge of the forecast area set new daily snowfall records on the third and final day of Snow Storm #1.

Station - New Record (Old Record; Year)
BOS - 4.8" (4"; 1893)
PVD - 3.4" (3.3"; 1963)
JFK - 0.2" (T"; 1989)

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CORRECTED to include BOS

Winter '19 / '20 - Snow Storm #1: Three Daily Snowfall Records Set - Storm Day 2

Three forecast stations in the central portion of the forecast area set new daily snowfall records on the second day of Snow Storm #1.  Two daily records had stood since 1949.

Station - New Record (Old Record; Year)
BGM - 9.6" (4.6"; 2005)
BDL - 8.8" (6"; 1949)
ALB - 6.8" (6.2"; 1949)

ALB and BDL also set new daily records on Storm Day 1.

Several hours of heavy snow -- ~2" / hr  -- observed late Monday evening at Bradley Field (BDL).

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KBDL 030451Z 35014G21KT 1/2SM R06/P6000FT -SN BR OVC011 M02/M03 A2952 RMK AO2 SFC VIS 1 1/4 SLP998 SNINCR 2/13 P0008 T10171033 400171022 $

KBDL 030351Z 36013G23KT 1/4SM R06/2200V3500FT +SN FZFG VV005 M02/M03 A2955 RMK AO2 TWR VIS 1/2 SLP007 SNINCR 1/11 P0011 T10221033 $

KBDL 030251Z 01017G28KT 1/4SM R06/4000V6000FT -SN BR VV009 M02/M03 A2955 RMK AO2 PK WND 01028/0243 SFC VIS 3/4 SLP006 SNINCR 2/10 P0007 60021 T10221033 56010 $

KBDL 030151Z 36016G25KT 1/4SM R06/1800V2400FT +SN FZFG VV004 M02/M03 A2955 RMK AO2 SLP008 SNINCR 2/8 P0011 T10171033 $

Winter '19 / '20 - 19th Annual 'Season-total' Snowfall Forecasting Contest: The Forecasts!

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

Forecaster table ranked by STP

BLUE - <= 25th percentile
RED - >= 75th percentile
P-O-R-N - period of record normal
CONSENSUS - average station forecasts

Some forecasts have decimal values and were recorded as such; however ... rounding was applied for display purposes only.

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Total station forecasts:  475 (including P-O-R-N & CONSENSUS)
Total station forecasts for ...
BELOW average snowfall - 175 (37%)
AVERAGE snowfall - 26 (5%)
ABOVE average snowfall - 274 (58%)

Confidence -- at least 67% of forecasts -- for stations with ...
- ABOVE average snowfall:  10
CAR ... BGR ... PWM ... CON ... BTV ... BDR ... BDL ... ALB ... BGM ... ABE

- AVERAGE snowfall:  1
ACY

- BELOW average snowfall:  14
BOS ... ORH ... PVD ... NYC ... MDT ... PHL ... EWR ... BWI ... DCA ... IAD ... SBY ... RIC ... ORF ... RDU

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All forecaster entries at the Contest/s web site here (direct link to forecasts here).

Winter '19 / '20 - Snow Storm #1: Six Daily Snowfall Records Set - Storm Day 1

Six forecast stations in the northeast portion of the forecast area set new daily snowfall records on the first day of Snow Storm #1.  Two daily records had stood for over 100 years.

Station - New Record (Old Record; Year)
ALB - 13.3" (3.7"; 1969)
ORH - 8.9" (4.2"; 1917)
BDL - 4.6" (1.9"; 1925)
BOS - 1.2" (1"; 1940)
PVD - 1.6" (0.5"; 1907)
BDR - 0.7" (T; 2012)

ALB/s heaviest period of snow occurred SUN evening between 7 and 11 PM EST where up to ~2" / hr snowfall rate was reported.

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KALB 020351Z 01006KT 1/4SM R01/4500V6000FT +SN FZFG VV006 M03/M05 A2972 RMK AO2 SLP069 SNINCR 1/12 P0015 T10281050

KALB 020251Z COR 36007KT 1/4SM R01/2800V3500FT +SN VV005 M03/M06 A2973 RMK AO2 SLP072 SNINCR 1/11 P0024 60052 T10281056 56027

KALB 020159Z 01007KT 1/4SM R01/5500VP6000FT +SN VV008 M03/M06 A2974 RMK AO2 P0010 T10331061

KALB 020151Z 02008KT 1/8SM R01/5500VP6000FT +SN VV007 M03/M06 A2975 RMK AO2 SFC VIS 1/4 SLP077 SNINCR 2/10 P0008 T10331061

KALB 020051Z 02007KT 1/8SM R01/3000V5000FT +SN FZFG VV005 M04/M06 A2979 RMK AO2 SFC VIS 1/4 SLP092 SNINCR 2/8 P0020 T10391061

KALB 012351Z COR 02007KT 1/4SM R01/3500V5500FT +SN VV006 M04/M07 A2981 RMK AO2 SLP099 SNINCR 1/6 4/006 P0008 60051 T10391067 11039 21056 58015

Winter '19 / '20 - Snow Storm #1: The Forecasts

Forecasters
Rookie      1
Intern      -
Journey      -
Senior      13
GOVT      1
PWSP      -
TOT      15

NEWxSFC welcomes Rookie Forecaster Karmageddon and our returning veterans.
Congratulations to JessicaCain and VWN Quags for achieving SENIOR Forecaster status this year.

Don Sutherland is our Chief Forecaster this winter having won last year/s 'snow storm' contest.

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Table ranked by ascending storm-total precipitation (STP)

BLUE ==> 25th percentile.
RED ==> 75th percentile.
WHITE and GREY STP cells range between the 25th and 75th percentile.

 

Heaviest snowfall (+10") consensus along and to the right of CON - ORH - BGM - ALB - CON.  Lollypop expected at ALB.
 

At season/s start ... teleconnections abiding by their assigned roles.

Everyone/s station-by-station forecast at the Contest/s web site.
Direct link to the forecast table HERE