CONTEST STATUS - Updated: SAT ... 11-APR-20 @ 8:30 PM EST

Winter '19 / '20 - Snowfall Forecast Contests
21st Annual 'Snow Storm' Snowfall Forecast Contest
Season ended as quickly as it started.
No winner this go'round ... too few storms (minimum of three required)

Snow Storm #1 (01-DEC-19)
FINAL Results here

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19th Annual 'Season-total' Snowfall Forecast Contest
FINAL Results here

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Winter '18 / '19 - Snowfall Forecast Contests
20th Annual 'Snow Storm' Snowfall Forecast Contest
FINAL Results here

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18th Annual 'Season-total' Snowfall Forecast Contest
FINAL Results here
Forecaster verification table here

Sunday, December 15, 2019

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

Wednesday, December 11, 2019

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

Tuesday, December 10, 2019

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

Thursday, December 5, 2019

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

Wednesday, December 4, 2019

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.

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

Tuesday, December 3, 2019

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 $

Monday, December 2, 2019

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

Sunday, December 1, 2019

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

Friday, November 29, 2019

Winter '19 / '20 - Snow Storm #1: Call for Forecasts!

Haverhill ... MA
14-DEC-1890

Robust remnants of the last weekend/s powerhouse PAC NW storm is muscling its way east across the Central Plains ... Upper Midwest ... and taking aim on the northern M-A and SNE.

Progs pointing to an initial period of over-running snows followed by Miller 'B' re-development off the Jersey Shore ... the parent LOW/s subsequent capture ... and a long-duration event.

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Forecast element: each station/s storm-total snowfall

Deadline for entries: 10:00 PM EST ... SAT ... 30-NOV-19

Forecast verification period
Begins: 12:01 AM EST ... SUN ... 01-DEC-19
Ends: 11:59 PM EST when the flakes stop flyin'.

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Enter your forecast at the NEWxSFC/s home page HERE.
Follow the top-of-page link from 'Enter Storm Forecast' or in the 'Call for Forecasts!' section.

See how well your forecast stacks up against other winter wx enthusiasts and NWS Eastern Region Weather Forecast Offices (turns out the ER WFOs are fairly easy to beat).

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The forecasting contest for Snow Storm #1 may be cancelled prior to the deadline if at least six-to-eight stations are unlikely to observe at least a 4" storm-total snowfall.

Thursday, November 28, 2019

Winter '19 / '20 - Snow Storm #1: Outlook

Today/s prog courtesy AWS shows the surface LOW in prime position over the Benchmark (40°W / 70°W).

A cold overland HIGH NW of the LOW is the missing element.  Pinpointing the liquid / freezing / frozen transition zone will be challenging.

NWP model guidance suggests more than nuisance snows for at least six forecast stations qualify the season's inaugral storm as contest-worthy.

Likely 'Call for Forecasts': FRI ... 29-NOV-19
Deadline for entries would be SAT ... 30-NOV-19 @ 10 PM EST.

Sunday, November 24, 2019

Winter '19 / '20 - 19th Annual 'Season-total' Snowfall Forecast Contest: Call for Forecasts!

NEWxSFC/s Resident 'Season-total' Snowfall Forecaster

Here comes winter with its oscillating Arctic and North Atlantic indexes ... suddenly warming stratosphere ... so-so ENSO ... and if we/re lucky .... an endless parade of 'Miller A' LOWs raking the eastern seaboard.

NE.Wx/s 19th annual ‘Season-total' Snowfall Forecast Contest is the absolute best ... biggest ... and probably ONLY chance to be honored for your long-range forecasting acumen ;/

And it's s-o-o easy.
Cool prizes ... too!

All you have to do is issue the best forecast for the 'season-total' snowfall at 25 east coast stations between RDU and CAR!

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Forecast element: season-total snowfall @ each station
Forecast period: 01-DEC-19 through 31-MAR-20

Error statistic: total absolute error [Σ abs(forecast - observed)]
Verification: NWS preliminary climate reports (CLM or CF6)

Low score wins.

Deadline: SAT ... 30-NOV-19 @ 11:59 PM EST (01-DEC-19 @ 4:59 UTC)

Visit the Contest's website to enter your forecast.
Follow the link at the top of the page to 'Enter Season-total Forecast.'

Update your forecast as often as you want prior to the deadline.
Only your last entry gets verified.

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1st place prize (delivered post-paid right to your front door):
"Snow in America" by Bernard Mergan (hardcover) and
"The Snow Booklet" by Nolan J. Doesken and Arthur Judson (paperback) and
... the august title 'Chief Season-total Snowfall Forecaster' for Winter '20 / '21 and
... a well-deserved place of honor with past winners.

2nd place prize (delivered post-paid right to your front door):
"New England Weather, New England Climate" by Greg Zielinski and Barry Keim (paperback)

3rd place prize (delivered post-paid right to your front door):
"The Snow Booklet" by Nolan J. Doesken and Arthur Judson (paperback)

Thursday, November 21, 2019

Winter '19 / '20 - Multivariate ENSO Index (MEI) - Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

Multivariate ENSO Index (MEI) composites of 500 mb (5H) geopotential height anomalies (GPHa) and 2-meter air temperature anomalies (2mTa) for analog winters '53 / '54 ... '59 / '60 ... '69 / '70 ... '80 / '81 ... '90 / '91.

5H GPHa composite
- Ridge-W / Trof-E
- Negative 5H GPHa INVOF Aleutian Is. & positive 5H GPHa INVOF Hawaii ==> EPO  > 0
- Azores-like positive 5H GPHa ==> NAO > 0
- Negative 5H GPHa / lo-latitude trof axis ==> active sub-tropical jet (STJ)

5H GPHa weighted-composite

2mTa weighted-composite

Wednesday, November 20, 2019

Winter '19 / '20 - Outlooks

Thread updated periodically as new outlooks and forecasts become available from a variety of credible sources.

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CPC ...



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From WCVB Boston...
"More cold outbreaks. More opportunities for snowstorms here along the East Coast. This could be a very active winter" said Dr. Judah Cohen (AER)

"Cohen thinks this winter may get off to a slow start but make up for lost time later in the winter. A disturbance of the polar vortex sometime in December could make for a very cold January and February.

"Boston could receive about 59 inches of snow ..." said Cohen.

Tuesday, November 19, 2019

Winter '19 / '20 - Severe Weather Europe: FINAL November Model Forecast for the Upcoming Winter

"Most forecasts are showing certain lower pressure in the North Atlantic, and higher pressure over Europe and USA, which means generally  milder winter. The forecasts are on the same trend since September, which is very rare.

"Across the Atlantic, models generally agree on potential northerly flows over NW and NE USA and E Canada, while central USA currently has lower chances for winter weather overall.

"We still have the stratosphere as a major factor. Long-range forecasts are generally not as good at forecasting stratospheric dynamics in detail, which means they tend to underestimate any potential sudden stratospheric warming events (SSW’s) since the final forecast is made out of many individual calculations, which have different ideas about the stratospheric development.

"An SSW event can have a major impact on the circulation and can cause major pattern changes in the Northern Hemisphere. So a potential SSW event is an important factor that can change the course of winter in either way across the North Hemisphere."

Monday, November 18, 2019

Winter '19 / '20 - Pacific Decadal Oscillation (PDO): Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

Pacific Decadal Oscillation (PDO) composites of 500 mb (5H) geopotential height anomalies (GPHa) and 2-meter air temperature anomalies (2m Ta) for analog winters '66 / '67 ... '68 / '69 ... '90 / '91 ... '04 / '05 ... '17 / '18

5H GPHa composite
 - Trof-W / Ridge-E
- High GPHa INVOF Aleutian Is. & low GPHa INVOF Hawaii ==> EPO < 0
- Azores HIGH ==> NAO > 0
- High GPHa dipole Azores & Aleutian Is. ==> AO > 0

5H GPHa weighted-composite

2m Ta weighted-composite

Tuesday, November 12, 2019

Winter '19 / '20 - Quasi-Biennial Oscillation (QBO): Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

Quasi-Biennial Oscillation (QBO) composites of 500 mb (5H) geopotential height anomalies (GPHa) and 2-meter air temperature anomalies (2m Ta) for analog winters '78 / '79 ... '85 / '86 ... '95 / '96 ... '99 / '00 ... '02 / '03.

5H GPHa composite
- Ridge-W / Trof-E
- Hi-latitude blocking over Greenland ==> NAO < 0

5H GPHa weighted-composite

2m Ta weighted-composite

Sunday, November 10, 2019

Winter '19 / '20 - Arctic Oscillation (AO): Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

Arctic Oscillation (AO) composites of 500 mb (5H) geopotential height anomalies (GPHa) and 2-meter air temperature anomalies (2m Ta) for analog winters '53 / '54 ... '54 / '55 ... '59 / '60 ... '97 / '98 ... '14 / '15.

5H GPHa composite

- 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) effectively displace the Hudson LOW from its climatologically favored location.

5H GPHa weighted-composite

2m Ta weighted-composite

Saturday, November 9, 2019

Winter '19 / '20 - 500 mb Geopotential Heights and 2m T Anomaly Composites: La Nada Years


La Nada or neutral ENSO comes in two flavors -
Cool (-0.5 < Region 3.4 SSTa < 0)
Warm (0 < Region 3.4 SSTa < 0.5)

Current consensus expects 'warm' La Nada for Winter '19 / '20.

Recent La Nada years by decade:
1967
1979
1981 ... 1982 ... 1986 ... 1990
1991 ... 1993 ... 1994 ... 1997
2002 ... 2004
2013 ... 2014 ... 2017

5H GPHa composite - all La Nada years (n = 15)

Prevailing feature common to cool and warm La Nadas ...
- Positive 5H GPHa INVOF Aleutian Is. & negative 5H GPHa INVOF Hawaii = EPO < 0 ==> Arctic outbreaks into central CONUS

Thursday, November 7, 2019

Winter '19 / '20 - Eurasia Snow Cover: OCT

Eurasia/s areal snow cover for OCT-19: ~ 12,800,000 SQ-KM
24% above 52-year P-O-R-N (~10,300,000 SQ-KM)
27% above 52-year median (~10,100,000 SQ-KM)

Rank: 7th
3rd highest past 10 years
4 of past 20 years below median ('05 ... '07 ... '08 ... '11)
OCT-18:  ~10,400,000 SQ-KM
OCT-19: 23% greater than OCT-18


Ranked analog years 500 mb anomaly height composite for Winter '19 / '20
('15 / '16 ... '16 / '17 ... '09 / '10 ... '01 / '02 ... '14 / '15)

- High 500 mb geopotential heights at hi-latitude ==> NAO & AO < 0
- EPO > 0 ==> fast zonal flow over CONUS & mild PAC air masses
-weak evidence of trof over coastal M-A & NE CONUS


CORRECTION:  '15 / '16 & '09 / '10 ENSO should be 'W+'

Key
ENSO:  nada- (-0.5 < Region 3.4 SSTa <  0); C- (weak La Nina); W- (weak El Niño)
NAO:  sign of D-J-F average
AO:  sign of D-J-F average
PDO:  sign of O-N-D-J-F-M average
QBO:  + ==> west; - ==> east