Friday, April 10, 2020

Thursday, April 09, 2020

Winter '19 / '20 - 19th Annual 'Season-total' Snowfall Forecast Contest: Preliminary STP Verification

Preliminary sum-total season snowfalls for the verification period 01-DEC-19 though 31-MAR-20 collected from monthly climate bulletins (CLMxxx; CXUS51 ... CXUS52).


One forecast station (4% 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 SAT evening.

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Winter '19 / '20 monthly snow totals
DEC:  Winter '19 / '20 - Season-total Snowfall Forecast Contest: DEC Totals
JAN:  Winter '19 / '20 - Season-total Snowfall Forecast Contest: JAN Totals
FEB:  Winter '19 / '20 - Season-total Snowfall Forecast Contest: FEB Totals
MAR:  Winter '19 / '20 - Season-total Snowfall Forecast Contest: MAR Totals

Wednesday, April 08, 2020

Winter '19 / '20 - 'Season-total' Snowfall Forecast Contest: MAR Totals

MAR-20 snowfall summary by 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

Obs reported as 0.05" implies Trace

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MAR Forecast Station Highlights
No station observed more than 100% of its monthly normal snowfall.

Biggest losers (0")
PHL
BWI
ACY
DCA
RIC
SBY
RDU
ORF

P-O-R-N v. Observed (less than 15%)
PVD:  (6.8'' v. 0.4'')
IAD:  (3.5'' v. 0.05'')
NYC:  (4.9'' v. 0.05'')
EWR:  (5.1'' v. 0.05'')
BDR:  (5.5'' v. 0.05'')
ABE:  (6'' v. 0.05'')
MDT:  (6.5'' v. 0.05'')
BOS:  (8'' v. 0.05'')

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Season-total

MAR P-O-R-N contributes 184" (20%) toward the season-total snowfall (D-J-F-M) of 929".
MAR-20 observed snowfall:  66" (36% of P-O-R-N; 7% of season-total snowfall)

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Teleconnections
No contest-worthy storms in MAR.

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Winter '19 / '20 - Season-total Snowfall Forecast Contest: DEC Totals
Winter '19 / '20 - Season-total Snowfall Forecast Contest: JAN Totals
Winter '19 / '20 - Season-total Snowfall Forecast Contest: FEB Totals

Tuesday, March 10, 2020

Winter '19 / '20 - 'Season-total' Snowfall Forecast Contest: FEB Totals

FEB-20 snowfall summary by 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

Obs reported as 0.05" implies Trace

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FEB Forecast Station Highlights
CAR
- The observed 33" snowfall is 146% of its monthly P-O-R-N of 22.6".
- about one-third its season-total normal

BGM
- The observed 25.2" snowfall is 140% of its monthly P-O-R-N of 18".
- about one-third its season-total normal

BTV
- The observed 21.4" snowfall is 123% of its monthly P-O-R-N of 17.4".
- about one-third its season-total normal

RDU
- The observed 2.5" snowfall is 109% of its monthly P-O-R-N of 2.3".
- 38% its season-total normal

Biggest losers
DCA:  0"

Observed v P-O-R-N (less than 15%)
ORH:  (2.5'' v 17.8'')
RIC:  (0.5'' v 3.9'')
BOS:  (0.5'' v 12.6'')
BDL:  (0.4'' v 12.9'')
SBY:  (T v 3.4'')
ACY:  (T v 6.3'')
BWI:  (T v 6.8'')
IAD:  (T v 7.2'')
PHL:  (T v 7.4'')
NYC:  (T v 8.9'')
BDR:  (T v 9'')
EWR:  (T v 9.1'')
MDT:  (T v 9.3'')
ABE:  (T v 9.9'')
PVD:  (T v 10.2'')
DCA:  (0'' v 5.4'')

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Season-to-Date

FEB P-O-R-N contributes 262" (28%) toward the season-total snowfall (D-J-F-M) of 929".
FEB-20 observed snowfall:  124.2" (47% of P-O-R-N; 13% of season-total snowfall)

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Teleconnections

No contest-worthy storms in FEB.

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Winter '19 / '20 - Season-total Snowfall Forecast Contest: DEC Totals
Winter '19 / '20 - Season-total Snowfall Forecast Contest: JAN Totals

Tuesday, February 04, 2020

Winter '19 / '20 - 'Season-total' Snowfall Forecast Contest: JAN Totals

JAN-20 snowfall summary by forecast station.
Rank ordered descending by percent of monthly period-of-record-normal (P-O-R-N).


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Green ==> 75th - 100th percentile
White ==> less than 75th and greater than 25th percentile (inter-quartile range)
Red ==> 0 - 25th percentile

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JAN Forecast Station Highlights
CAR
- JAN/s 31.5" 131% of its monthly P-O-R-N of 24.1".
- about one-third its season-total normal

Biggest losers (again)
SBY ... ORF (0")

Observed v P-O-R-N (less than 15%)
BWI:  (0.2" v 5.9")
PHL:  (0.2" v 7.1")
RDU:  (T v 2.5")
RIC:  (T v 5")
ACY:  (T v 6")

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Season-to-Date

JAN P-O-R-N contributes 279" (30%) toward the season-total snowfall (D-J-F-M) of 929".
JAN-20 observed snowfall:  136.2" (49% of P-O-R-N; 15% of season-total snowfall)

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Teleconnections

Winter '19 / '20 - Season-total Snowfall Forecast Contest: DEC Totals

Thursday, January 16, 2020

Winter '19 / '20 - Snow Storm #2: Outlook


UPDATE: 16-JAN-20 @ 7 PM EST
Progs trending away from a contest-worthy event.

Outside chance the evening runs will proffer a better solution.  Otherwise ... we/re back to waiting.

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Original post (15-JAN-20 @ 2:55 PM EST)
Third time's a charm ... three on a match ... ménage à trois ... three to get ready ... or whatever; another chance for this winter/s second and long-awaited contest-worthy snow storm appears in the offing over the upcoming weekend.

Latest progs from national and international numerical weather prediction models covering the medium range distribute more than nuisance snowfalls over two-thirds of the forecast area.

Mixed precipitation associated with over-running  / isentropic ascent and the possibility for development of a secondary surface LOW in the nearshore waters along the Gulf of Maine will present forecasters with multiple precipitation-type challenges.

Should short range model guidance continue the currently favorable medium-range scenario ...

Call for Forecasts would be issued on THU ... 16-JAN-20.
Deadline for entries would be 10:00 PM EST ... FRI ... 17-JAN-20
Verification would begin: 12:01 AM EST ... SAT ... 18-JAN-20

Image courtesy pivotaleweather
NEWxSFC web site here

Sunday, January 05, 2020

Winter '19 / '20 - 'Season-total' Snowfall Forecast Contest: DEC Totals

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

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Green ==> 75th - 100th percentile
White ==> less than 75th and greater than 25th percentile (inter-quartile range)
Red ==> 0 - 25th percentile

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DEC Forecast Station Highlights
BDL
- DEC/s 22" was 224% above its monthly P-O-R-N of 9.8"
- almost half its season-total normal

ORH
- DEC/s 27.6" was 223% above its monthly P-O-R-N of 14.4"
- 46% of its season-total normal

ALB
- DEC/s 27.9" was 205% above its monthly P-O-R-N of 13.6"
- half its season-total normal

Biggest losers
ORF & RDU:  0"

Observed v P-O-R-N (less than 15%)
PHL:  0.1" v 3.6"
SBY:  0.05" v 1.6"
MDT:  0.2" v 5.6"
RIC:  0.1" v 1.9"
BWI:  0.3" v 3.1"
DCA:  0.4" v 2.7"

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Season-to-Date

DEC P-O-R-N contributes 203.3" (22%) toward the season-total snowfall (D-J-F-M) of 929".
DEC-19 observed snowfall:  224.6" (10% above P-O-R-N; 24% of season-total snowfall)

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Teleconnections

Wednesday, December 18, 2019

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