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

Eurasia/s areal snow cover for SEP-19: ~1,570,000 SQ-KM

3% below 48-year P-O-R-N (~1,629,000 SQ-KM)
1% below 48-year Median (~1,588,000 SQ-KM)

Rank: 26th
4th lowest past 10 years
11 of past 20 years below median
SEP-18:  ~1,300,000 SQ-KM
SEP-19 21% greater than SEP-18

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

Read more »

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

Analog 5H composite ('53/'54 ... '54/'55 ...'59/'60 ... '97/'98 ... '14/'15) ... as of SEP-19

 

- Overall North American pattern mimics Tropic/Northern Hemisphere's (TNH) negative phase often associated with +ENSO.

- Positive height anomaly over eastern Canada displaces climatologically favored position of Hudson Bay trof limiting high-latitude cold air supply to the Lower 48.

- TNH associated with stronger than normal Pacific jet farther south of its normal axis and well above normal temperatures in eastern North America.

CORRECTION:  '53 / '54 ENSO should be 'W-'

KEY
ENSO:  nada- (-0.5 < SSTa <  0); C- (weak La Nina); W- (weak El Niño); W (moderate El Niño); W+ (strong El Niño)
NAO:  sign of D-J-F average
PDO:  sign of O-N-D-J-F-M average
QBO:  + ==> west; - ==> east; +/- flipped west to east

Read more »

Winter '19 / '20 - North Atlantic Oscillation (NAO): Leading Analogs' 500 mb Anomaly Height Composite... as of AUG-19

UPDATE:  SEP/s NAO did not change the analog years other than to shuffle the 4th and 5th ranks.

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Analog 5H composite ('50/'51 ... '08/'09 ... '12/'13 ... '16/17 ... '17/'18) ... as of AUG-19

- Another round of Trof West - Ridge East

- EPO-like ridge offset slightly to the west of preferred position for a 'Trof-East' regime

- Azores HIGH suggests NAO > 0

- Negative height anomaly over south-central Canada favors primary storm track through the Upper Plains and across the Great Lakes in line with current soil moisture axis.

Winter '19 / '20 NAO analog analysis here.

Winter '19 / '20 - Eurasian Snow Cover: AUG

Eurasia/s areal snow cover for AUG-19:  ~158,300 km2

-61% below 48-year P-O-R-N (~403,000 km2)
-46% below 48-year Median (~294,000 km2)
Rank: 39th

7th highest past 10 years
19 of past 20 years below median
 Last year:  ~140,800 km2

Analog years for winter '19 / '20

CORRECTION:  Second instance of 15/16 should be 16/17
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Snow cover data courtesy Rutgers University Global Snow Lab
http://climate.rutgers.edu/snowcover/index.php

Winter '19 / '20 - Arctic Oscillation (AO): AUG

AUG AO:  -.722
Leading analog contenders ... as of AUG-19.

Consensus Outlook:  Winter '19 / '20 AO < 0

KEY
ENSO:  nada- (-0.5 < SSTa <  0); C- (weak La Nina); W- (weak El Niño); W (moderate El Niño); W+ (strong El Niño)
NAO:  sign of D-J-F average
PDO:  sign of O-N-D-J-F-M average
QBO:  + ==> west; - ==> east; +/- flipped west to east

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Present state
ENSO: 0 < ONI < 0.5 trending lower
NAO < 0 past 5 months
QBO > 0 past 10 months.  Peaked JUN-19; trending lower.  Possible flip during upcoming winter
PDO (MAR-18 to OCT-19) < 0 No trend.

Winter '19 / '20 - North Atlantic Oscillation (NAO): AUG

AUG NAO:  -1.17
Leading analog contenders ... as of AUG-19.

Consensus Outlook:  Winter '19 / '20 NAO > 0

CORRECTION:  '50 / '51 ENSO should be 'C-'

KEY
ENSO:  nada- (-0.5 < SSTa <  0); C- (weak La Nina); C (moderate La Nina)
AO:  sign of D-J-F average
PDO:  sign of O-N-D-J-F-M average
QBO:  + ==> west; - ==> east

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Present state
ENSO: 0 < ONI < 0.5 trending lower
QBO > 0 past 10 months.  Peaked JUN-19; trending lower.  Possible flip during upcoming winter
PDO (MAR-18 to OCT-19) < 0 No trend.

Winter '18 / '19 - North Atlantic Oscillation (NAO) Analog Verification

The analog forecasting technique seeks similarities to the NAO state in the run-up to the coming winter with NAO run-up states of winters past.  Presented here is the verification of NAO analogs for the '18 /'19 winter.

The NEWxSFC method ranks analog years by their the sum of square errors (SSE) statistic.
Lower SSE errors ==> stronger analog

Constraining the number of analog winters for analysis to five is arbitrary.

North Atlantic Oscillation (NAO) Index Analog Forecast Verification

In the run-up to Winter '18 / '19 ... '84 / '85 was the leading analog followed by '72 / '73 ... '59 / '60 ... '89 / '90 ... and '91 / '92.  Winter '18 / '19 NAO started weakly positive ... approached zero at meteorological winter's end ... then climbed above 1 in MAR.

A qualitative assessment of the analog forecast's accuracy would rate the analogs #2 or #5 as 'best' with #1 ... 3 ... and 4 'poor.'

A quantitative assessment of the other '72 / '73 and '91 / '92 teleconnections ... not so much.

Read more »

Winter '18 / '19 - Arctic Oscillation (AO) Analog Verification

The analog forecasting technique seeks associations to the AO state in the run-up to the coming winter with AO run-up states of past winters.  Presented here is the verification of AO analogs for the '18 /'19 winter.

The NEWxSFC method ranks analog years by their the sum of square errors (SSE) statistic.
Lower SSE errors ==> stronger analog

Constraining the number of analog winters for analysis to five is arbitrary.

In the run-up to Winter '18 / '19 ... '55 / '56 was the leading analog followed by '64 / '65 ... '84 / '85 ... '99 / '00 ... and '91 / '92.  Observed AO values for Winter '18 / '19 began neutral in DEC ... turned weakly negative in JAN ... then surged positive at meteorological winter/s end and into MAR.

A qualitative assessment of the analog forecast/s accuracy rates '84 / '85 as best.

A quantitative assessment of the other '84 / '85 teleconnections ... not so much.

Read more »

Winter '19 / '20 - NCDC Issues Updated Period-of Record Snowfall Climatology

Here

It's only been four years since the last update.

More NCDC climo data here

Winter '18 / '19 - 20th Annual 'Regular Season' Snowfall Forecast Contest: FINAL Results

After five snow storm forecasting contests ... under the ‘two-thirds’ rule … forecasters who entered at least FOUR forecasts are included in this season's FINAL standings.

Full table with all other error statistics at the Contest/s web site here (direct link).
Individual forecaster's storm statistics here (direct link).

Read more »

Winter '18 / '19 - 18th Annual 'Season-total' Snowfall Forecast Contest: FINAL Results

UPDATE (08-APR-19)
Forecaster verification table at the Contest web site (direct link)
Season-total snowfall v period-or-record normal trend chart

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Original post:  (07-APR-19 @ 8:30 PM EDT)

Congratulations to Donald Rosenfeld for his 1st Place finish.
Donald also placed first in '05 / '06 and '12 / '13.

Forecasters ranked by their total absolute error.

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Season-total snowfall from all stations (784") came in 14% below the period-of-record normal (914").
Winter '18 / '19 ranks 11th among other Contest years since winter '04 / '05 ... the season when BGR and BGM were added to the station list.

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Apologies for the abbreviated recap.
Will add to the pile a little at a time this week including each forecaster's station-by-station verification.

Winter '18 / '19 - Season-total Snowfall Forecast Contest: Preliminary STP Verification

UPDATE (08-APR-19 @ 11:55 AM EDT)
Added links to monthly snowfall totals

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Original post (06-APR-19 @ 6:42 PM EDT)

Preliminary sum-total season snowfalls for the verification period 01-DEC-18 though 31-MAR-19 collected from monthly climate bulletins (CLMxxx; CXUS51 ... CXUS52).

Seven forecast stations (28% of all stations) with bonus season-total snowfalls [more than Period-Of-Record-Normal (P-O-R-N)].

Rank ordered descending by percent of P-O-R-N.

Green ==> 75th percentile
White ==> Interquartile range (< 75th & > 25th percentiles)
Red ==> 25th percentile

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

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Winter '18 / '19 monthly snow totals
DEC:  http://newxsfc.blogspot.com/2019/01/winter-18-19-season-total-snowfall.html
JAN:  http://newxsfc.blogspot.com/2019/02/winter-18-19-season-total-snowfall.html
FEB:  http://newxsfc.blogspot.com/2019/03/winter-18-19-season-total-snowfall.html
MAR:  http://newxsfc.blogspot.com/2019/04/winter-18-19-season-total-snowfall.html

Winter '18 / '19 - Season-total Snowfall Forecast Contest: MAR Totals

MAR-19 snowfall summary by Contest forecast station.
Rank ordered descending by percent of monthly period-of-record-normal (P-O-R-N).

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Green ==> 75th percentile
White ==> Interquartile range (< 75th & > 25th percentiles)
Red ==> 25th percentile

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MAR Forecast Station Highlights
Eleven stations above P-O-R-N
MA: 5
NE:  6

BDR ... NYC ... ABE ... MDT
At least 200% of monthly P-O-R-N

Biggest losers
Observed v P-O-R-N (% P-O-R-N)
RDU:  0" v 1.0"
ORH:  0" v 0.9"
RIC:  0" v 2.2"
SBY:  T v 1.8" (3%)
DCA:  0.3" v 2.1" (14%)

Winter '18 / '19 - Regular Season: Status

Philly

Winter '18 / '19 getting long in the tooth for another contest-worthy snow storm; although ... it/s happened four times previously in April ('02 ... '03 ... '07 ... and '11) which works out to a five-year 'return period' so maybe we get lucky.

Winter '18 / '19 - Regular Season Interim Standings: #3

CORRECTED (09-MAR-19)
Don Sutherland had been identified incorrectly as the Chief 'Regular Season' forecaster when that honor belongs to Brad Yehl.  We regret the error and thank Don Sutherland for bringing it to our attention.

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After five snow storm forecasting contests ... under the ‘two-thirds’ rule … forecasters who have entered at least FOUR forecasts are included in interim standings #3.

Complete interim statistics table and chart at the Contest/s web site HERE (direct link)
Forecaster statistics for Winter '18 / '19 contest snow storms HERE (direct link)

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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.

Winter '18 / '19 - Snow Storm #5: FINAL Results

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

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
Dotted blue line below (above) solid red line ==> under (over) forecast

Station by Station Comparison of Top Forecasters

Winter '18 / '19 - Snow Storm #5: Preliminary STP Verification

Preliminary storm-total snowfalls for SUN and MON from CDUS41 (CLI) ... CXUS51 (CF6) ... METARs ... and PNS bulletins.  Good coverage and reporting.

Exceptions
CON
No daily snowfall reported in CF6 or CLI bulletins for 03-MAR-19.
PNSGYX carried 5.8" ASOS
STP may be amended if official data reported prior to posting of FINAL results.

HYA
STP estimated by inverse distance weighting of Barnstable county vicinity reports within 10 miles of the station carried in PNSBOX.

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Stations observing >= Trace - 22 (81%)
Given stations with measurable snowfall ... stations observing at least:
4" - 14 (64%)
6" - 8 (36%)
8" - 3 (14%)
10" - 1 (5%)

Max snow melt-water (minimum SLR 10:1)
BOS:  1.06"
ORH - 0.88"
BDL - 0.65"

Max precipitation (frozen + freezing + liquid):
HYA:  1.53"
PVD - 1.20"
BDR - 1.08"

New daily record(s)
04-MAR-19
BDR - 6" (1.5"; 1971)
ISP - 0.5" (0.05"; 1971, 2010)

Image courtesy NOHRSC

SFC analysis:  06z ... 04-MAR-19
Image courtesy NWS / NCEP /WPC

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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 '18 / '19 - Season-total Snowfall Forecast Contest: FEB Totals

FEB-19 snowfall summary by Contest forecast station.
Rank ordered descending by percent of monthly period-of-record-normal (P-O-R-N).

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Green ==> 75th percentile
White ==> less than 75th and greater than 25th percentile (inter-quartile range)
Red ==> 25th percentile

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FEB Forecast Station Highlights
CAR
56% > monthly P-O-R-N

Biggest losers
Observed v P-O-R-N (% P-O-R-N)
RDU:  T v 2.4"
ORH:  T v 2.9"
RIC:  0.1" v 4" (3%)
NYC:  2.6" v 8.9" (29%)
SBY:  1" v 3.4" (29%)

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Season-to-Date
On average ... FEB contributes 257" (28%) toward the average season-total snowfall (D-J-F-M) of 914".

FEB-19 observed snowfall:  220" (24% of season-total snowfall)

Bonus snows in the M-A may seem like a distant memory; however ... five of the seven forecast stations with at least 95% of the annual average snowfall are in the M-A at this point in the season.

Winter '18 / '19 - Snow Storm #5: The Forecasts

Rookie      -
Intern      -
Journey  1
Senior      11
GOVT      1
PWSP      -
TOT      13

Forecaster table ranked ascending by storm-total precipitation (STP)

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

Heaviest snowfall (+6") consensus along and to the right of BGR - PWM - BOS - BDL - ORH - CON - BGR.  Lollypop expected at ORH.

Teleconnections still on vacay.

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

Winter '18 / '19 - Snow Storm #5: RAW Forecasts

HERE

Winter '18 / '19 - Snow Storm #5: Call for Forecasts! Take 2

Boston Commons
MAR-33

Snow Storm #5 ... a late season nor'easter ... takes aim at most of the forecast area to open the season/s final quarter.

Rapid deepening of the mid-latitude cyclone during its approach and transit near 'Teh Benchmark' (40N/70W) typically produces bonus snows over SNE/s I-95 corridor.  Lack of Arctic air anchored north of the LOW could play a important role defining the RN / SN transition zone.

NOTE:  Any snowfall observed over extreme northern forecast stations (e.g., CAR ... BGR ... etc.) from the exiting storm during the first few hours of SUN should not be included in your forecast.

The forecasting contest for Snow Storm #5 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.

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Forecast element: each station/s storm-total snowfall

Deadline for entries: 10:00 PM EST ... SAT ... 02-MAR-19
Verification begins: 12:01 AM EST ... SUN ... 03-MAR-19
Verification ends: 11:59 PM EST ... MON ... 04-MAR-19

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Enter your forecast at the NEWxSFC/s home page HERE. (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.

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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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 '18 / '19 - VCP32: Too Far Apart

Winter '18 / '19 - Regular Season Interim Standings: 2

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 '18 / '19 contest snow storms here (direct link)

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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.

Winter '18 / '19 - Snow Storm #5: Call for Forecasts!

Norfolk ... CT
17-FEB-69

UPDATE:
Call for Forecasts - CANCELLED

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Two separate snow-producing storm systems expected to affect two separate portions of the forecast area over the course of two days.

Each system taken by itself would not qualify as a 'contest-worthy' snow storm but when we cobble them together ... we get just enough stations likely to observe more than a nuisance snowfall to issue a Call for Forecasts.

The forecasting contest for Snow Storm #5 may be cancelled prior to the deadline if fewer than six stations are likely to observe at least a 4" storm-total snowfall.

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Forecast element: each station/s storm-total snowfall
Deadline for entries: 10:00 PM EST ... TUE ... 19-FEB-19
Verification begins: 12:01 AM EST ... WED ... 20-FEB-19
Verification ends: 11:59 PM EST ... THU ... 21-FEB-19

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Enter your forecast at the NEWxSFC/s home page here.
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.

You also get the chance to see how well your forecast stacks up against NWS Eastern Region Weather Forecast Offices (turns out they/ve pretty easy to beat!)

---
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 '18 / '19 - Season-total Snowfall: Departures-from-Normal

Images courtesy NOHRSC

Winter '18 / '19 - Season-total Snowfall: Accumulations

Images courtesy NOHRSC

Winter '18 / '19 - Snow Storm #4: FINAL Results

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

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 Best Forecasts
Dotted blue line below (above) solid red line ==> under (over) forecast

Station by Station Comparison of Best Forecasts