Winter '17 / '18 - Snow Storm #1: FINAL Results

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

	1st - JessicaCain
	SUMSQ:	17
	SUMSQ Z:	-0.991
	STP:	4.3	(4)
	TAE:	12.0	(1)
	AAE:	0.63	(1)
	2nd - TQ
	SUMSQ:	24
	SUMSQ Z:	-0.858
	STP:	4.7	(5)
	TAE:	14.3	(2)
	AAE:	0.75	(2)
	3rd - Shillelagh
	SUMSQ:	25
	SUMSQ Z:	-0.847
	STP:	3.6	(3)
	TAE:	14.4	(3)
	AAE:	0.76	(3)
	HM - WeatherT
	SUMSQ:	33
	SUMSQ Z:	-0.685
	STP:	0.4	(2)
	TAE:	17.4	(5)
	AAE:	0.92	(5)

SUMSQ:  sum of square errors (")

STP:  storm total precipitation (")

TAE:  total absolute error (")
AAE:  average absolute error (")

(#): rank

Forecast by Observed Snowfall Scatter Plots of Top Forecasters 

 

Station Verification Comparison of Top Forecasters

 

Snowfall Distribution and Magnitude by Station (Power Map - Excel 2013)

 

 

Winter '17 / '18 - Snow Storm #1: Preliminary STP Verification

Table of preliminary storm-total snowfalls by station for MON from CDUS41 and CXUS51 bulletins.

Exceptions:
PWM and CON
25-DEC/s daily CLI and CF6 bulletins carry 'MM' as daily snowfall at post-time. 
Preliminary verification STP from latest PNSGYX and METARs.
Values subject to change pending updates to CDUS41 ... CXUS51 ... or PNS bulletins.

HYA
Storm-total snowfall report based on METARs

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Stations observing at least:
Trace - 19
4" - 6
6" - 1
8" - 1
10" - 0

Max melt-water at BGR (0.46")
Snow-Liquid Ratios (SLR) for areas with mixed precipitation ... such as BDR and BOS ... are not reported.

12z 12-25-17

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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 '17 / '18 - Snow Storm #1: The Forecasts!

Rookie 0
Intern 1
Journey 0
Senior 11
TOT 12 (+ 1 for GOVT / NWS)

Forecasts at the Contest/s web site.
Direct link:  http://www.newx-forecasts.com/NEWxSFC_19/storms/storm1_forecasts_25Dec17.htm

Forecasts are ranked by their storm-total precipitation (STP).

BLUE ==> 25th percentile

RED ==> 75th percentile
White STP and 4cast cells range between the 25th and 75th percentile

NWS forecasts derived from current issuances at the deadline.

 

Heaviest snowfall (>= 6") consensus along and the right of CAR - BGR - PWM - CON - CAR.

Lollypop expected at CAR.

 

 

AO/s dead-cat bounce cushioned by NAO and PNA bank shot.

Winter '17 / '18 - Snow Storm #1: RAW FORECASTS

Here

Winter '17 / '18 - Ignorosphere Tonight

Polar vortex centered over Barents Sea.
Anticyclonic circulation over NOAM

10 mb circulation

The HIGH made a strong attempt to displace the PV but will lose out shortly.

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Image courtesy Earth

Winter '17 / '18 - Snow Storm #1: Call for Forecasts Redux

Court St. Keene ... NH
c.1870
 

Sharp short wave diving into the base of a high-amplitude long wave trof centered nicely near 85W progged to spawn a meek area of LOW pressure over the OH river valley then transfer its energy to the SNE coast.

Bare minimum number of stations appear candidates for more than nuisance snowfall for this season/s inaugural event.  Contest may be cancelled before deadline if storm appears not to be contest-worthy.

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Forecast element: station total snowfall

Deadline:  SUN ... 24-DEC-2017 @10:30 PM EST
Verification begins:  MON ... 25-DEC-2017 @ 12:01 AM EST
Verification ends:  MON ... 25-DEC-2017 @ 11:59 PM EST

Enter your forecast at the NEWxSFC/s home page @ http://www.newx-forecasts.com/
Follow the top-of-page link from 'Enter Storm Forecast.'
Contest rules.

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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.

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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 '17 / '18 - Snow Storm #1: White Christmas

Time Square - NYC
26-DEC-47

Today/s American NWP output continued their collective tease for a potentially contest-worthy snow storm over northern portions of the forecast area on Christmas day.

Little comfort in store for true believers in sacred tele-connections for NE / M-A snows ... such as -AO ... -NAO ... +PNA ... despite plenty of evidence the conventional wisdom is largely unsupported empirically ... but I digress.

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Should the stars finally align for this winter/s inaugural snowfall forecasting contest ... the 'Call for Forecasts' will be issued late tomorrow (SAT) afternoon / early evening with the deadline for entries NLT 10:30 PM EST on SUN.

Winter '17 / '18 - VCP 32: Anything Yet?

Winter '17 / '18 - Snow Storm #1: Call for Forecasts!

Broadway - NYC
19-DEC-32

CANCELLED CANCELLED CANCELLED
Areal snowfall coverage not expected to meet minimum standards for a contest-worthy event.

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Promising Clipper system swings into the northern forecast area TUE deepening nicely over the Lakes before slowly exiting on WED.

Forecast element: station total snowfall

Deadline:  MON ... 11-DEC-2017 @10:30 PM EST
Verification begins:  TUE ... 12-DEC-2017 @ 12:01 AM EST
Verification ends:  when snow stops accumulating over the forecast area

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

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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.

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Contest may be cancelled before deadline if storm appears to fizzle.

Winter '17 / '18 - Snow Storm #1: Close Call

Valley Forge ... PA
16-DEC-70

Some winter storms ... like the one affecting a large swath of the M-A and SNE coastal plain this weekend ... have a sneaky way of not playing its 'snow card' until it's too late to issue a 'Call for Forecasts' and a contest-worthy storm ends up slipping through the cracks.

This has been especially true over the years for primarily rain events featuring a ribbon of accumulating snows along the NW edge of the precipitation shield.

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Call it a failure of numerical weather prediction.
Call it a failure of operational weather forecasters.
Call it Banana-Bana ... BO-Bana ... FE-FI ... FO-fanna ...

Either way ... the 19th Annual NEWxSFC awaits its inaugural event for Winter '17 / '18.

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But did anyone ... anywhere ... get it right three days out?

Why ... yes.  'Someone' did get it right.
The 06/12z NAM ... of all things ... kinda nailed it (GFS was all along ... all in on all liquid).


Image courtesy MeteoCentre

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Logistically ... the deadline for this storm would have been FRI evening given snow was expected to begin over the forecast area by early SAT AM.  With a FRI deadline ... the 'Call for Forecasts' would have been issued THU evening.  The NCEP forecast at that time called for 10% chance for at least 4" over interior VA stations and a 10% chance for at least 4" along the coasts of NJ continuing into SNE.

As outlined in this post from 2016 ... issuing a 'Call for Forecasts' is not a trivial matter.

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Had this been the Day3 NCEP prog ... there would have been more than enough lead time to issue the call and the season would be up and running.

Instead ... the call ended up being too close.

Winter '17 / '18 - Arctic Oscillation - NOV

NOV/s Arctic Oscillation (AO) Index:  -0.078

Given NOV-17/s negative AO ... the 2x2 contingency table predicts a 72% likelihood the three-month average AO will be negative this winter.  The results says nothing about the magnitude of the winter/s AO or which months will be negative ... only its sign.

NOTE:
True + ==> correct prediction
False + ==> incorrect prediction


Scatterplot of the 67-year AO period of record (1950 - 2016)

Lower left quad:  NOV -AO and DJF -AO
Lower right quad:  NOV +AO and DJF -AO

Upper left quad:  NOV -AO and DJF +AO
Upper right quad:  NOV +AO and DJF +AO

Related posts by NEWxSFC ...
Winter '17 / '18 - NOV/s Arctic Oscillation: Winter/s Leading Indicator
http://newxsfc.blogspot.com/search?q=arctic+oscillation

Winter '17 / '18 - 17th Annual 'Season-total' Snowfall Forecast Contest - The Forecasts!

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

Two first-time forecasters
Welcome Any.wx and 33andrain

475 station forecasts
Entries ranked by STP

BLUE - <= 25th percentile
RED - >= 75th percentile
ORANGE - Winter '16 / '17 Top 'Season-total' forecaster
P-O-R-N - period of record normal
CONSENSUS - average of individual forecasts by station

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Station forecasts for ...
BELOW average snowfall - 189 (40%)
AVERAGE snowfall - 26 (5%)
ABOVE average snowfall - 260 (55%)

NOTE:  Label should read '17 / '18

Consensus (at least 67% of forecasts) for stations with ...
BELOW average snowfall @ ACY ... IAD ... RIC ... ORF ... RDU
ABOVE average snowfall @ CAR ... BGR ... CON ... BTV ... PWM ... ORH ... PVD ... BDL ... BGM ... BDR
Forecasters are all in for above average snows @ BDR

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See all forecasters' entries at the Contest/s web site here.

The regular 'snow storm' forecasting contests begin when the flakes start a-flyin'.
'Call for Forecasts' are issued at NEWxSFC/s web site and blog (you are here) ... via e-mail ... and Facebook.

Winter '17 / '18 - 17th Annual 'Season-total' Snowfall Forecast Contest - Call for Forecasts!

NEWxSFC Meteorologist-in-Charge
Seasonal Forecasts

NE.Wx/s 17th annual ‘Season-total' Snowfall Forecast Contest is the absolute best ... biggest ... and probably ONLY chance to be recognized for your long-range forecasting acumen ;/

And it's easy.

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

Deadline: THU ... 30-NOV-17 @ 11:59 PM EST

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

Read more »

Winter '17 / '18 - North Atlantic Oscillation Analog Years

To date ... 1990 is the leading analog year for the North Atlantic Oscillation (NAO) in the run-up to the coming winter.

The average NAO for Winter '17 / '18 would turn out positive should this come to pass.  The analog forecast reaches winter's NAO/s minimum in DEC and its maximum in FEB before declining at the start of meteorological spring.

One problem.
Winter '90 / '91 ENSO/s signal was warm La Nada (+0.4°C ENSO Region 3.4 temperature anomaly) yet a weak La Nina appears in the cards for this year and unlike this year ... the corresponding PDO analog year was negative (this year it's positive; trending negative) and QBO was west-positive (this year it's east-negative and trending same).

And herein lies the problem with analogs.
Analog years don't exist in a vacuum.
'94 / '95 moderate El Nino; cool PDO trending warmer; QBO east trending west [REJECTED]
'54 / '55  moderate La Nina; cool PDO trending cooler; QBO east trending west [REJECTED]
'04 / '05 weak El Nino; PDO cool trending warmer;  QBO west trending west [REJECTED]
/73 / '74 strong La Nina; cool PDO, QBO west [REJECTED]

Other teleconnection indexes frequently confound the potential predictive value of a particular index.

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Other correlation-type analysis techniques can also provide insight into the likely state of important winter teleconnection indexes.

Analysis of the North Atlantic Oscillation (NAO) index's period-of-record reveals a statistically significant association (Chi-square Test for Independence; alpha = 0.05) between its sign for the month of NOV and the sign of the average NAO index during a subsequent meteorological winter (D-J-F).

Period-of-record correlation analysis finds if NOV/s NAO is positive (negative) ... then there's a 73% (54%) probability the winter's average NAO/s sign will also be positive (negative).  The analysis false alarm rate is 27% (46%).

Winter '17 / '18 - Fans of cold and snow in the U.S. will love this new winter outlook

Or so reads the headline from Mashable which comes with these nuggets of questionable conventional wisdom:

"Along the East Coast of the U.S., for example, major snowstorms tend to take place when a blocking pattern
is in place over Greenland." which more than explains why the AO index for 16 of the KU 66 storms rated '3' or higher was greater than zero including the Storm of the Century (1996).  The AO was positive for 42 storms in the landmark study.

The claim "When the Arctic Oscillation is negative, cold and snowy conditions are favored (though not guaranteed) in the eastern U.S." is unsupported by the data but why let pesky facts get in the way of a quality click-bait headline.


Don't know why the FB text field doesn't render.  Displays OK in Blogger's editor.
Here's the text ...

"Laying to rest the claim season-total snowfall in the NE and M-A is associated with winter's average Arctic Oscillation index.

"A mere 13% of the variability in NE and M-A season-total snowfall is explained by variability in the D-J-F average Arctic Oscillation."

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What's not to love?

Winter '17 / '18 - What about snow during La Niña winters?

From the ENSO blog at Climate.gov

"This La Niña footprint is pretty intuitive.

"Given the northward shift of the storm track, relatively cold and wet conditions are favored over the northern Rockies and northern Plains, resulting in the enhancement of snowfall.

"Warmer and drier winters are more likely during La Niña over more southern states, and this is exactly where seasonal snowfall tends to be reduced (4).

"The more vigorous storm track and slight tilt toward colder temperatures over the northern tier of U.S. during La Niña modestly increases the chance of a relatively snowy winter.

"We can break up the snow pattern further and look at the weakest and strongest La Niña events.  Splitting La Niña events into strength reveals some interesting differences worth investigating further.

"In this preliminary analysis below, there is a suggestion that weaker events are snowier over the Northeast and northern and central Plains on average."

More ...

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NOTE:  the data period ends '09 / '10.  Since then ... there have been two El Ninos (one quite strong) ... two La Ninas ... and three cool La Nadas.

Winter '17 / '18 - Arctic Oscillation Analog Years

 

To date ... 1973 is the leading analog year for the Arctic Oscillation (AO) in the run-up to the coming winter.

The average AO for Winter '17 / '18 would turn out negative should this come to pass.  The analog forecast has winter's AO/s minimum extent in FEB then continues its decline into meteorological spring and suggests a late-winter stratospheric warming event.

One problem.
Winter '73 / '74 ENSO/s signal was strong La Nina (-1.8°C temperature anomaly) yet a weak La Nina appears in the cards for this year and unlike this year ... the corresponding PDO analog year was negative (this year it's positive; trending negative) and QBO was west-positive (this year it's east-negative and trending same).

And herein lies the problem with analogs.
Analog years don't exist in a vacuum.
'08 / '09 weak La Nina; cool PDO trending warmer; QBO west [REJECTED]
'54 / '55 weak La Nina; cool PDO trending cooling; QBO east trending west [REJECTED]
'95 / '96  weak La Nina; warm PDO trending cooler; QBO west trending east [BEST MATCH]
'94 / '95 moderate El Nino; warm trending cooler;  QBO east trending west [REJECTED]

Other teleconnection indexes frequently confound the potential predictive value of a particular index.

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Other correlation-type analysis techniques can also provide insight into the likely state of important winter teleconnection indexes.

Analysis of the Arctic Oscillation (AO) index's period-of-record reveals a statistically significant association (Chi-square Test for Independence; alpha = 0.05) between its sign for the month of NOV and the sign of the average AO index during a subsequent meteorological winter (D-J-F).

Period-of-record correlation analysis finds if NOV/s AO is negative (positive) ... then there's a 72% (52%) probability the winter's average AO/s sign will also be negative (positive).  The analysis false alarm rate is 28% (48%).

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Historical note:  this is NEWxSFC web log's 1000th post!

Winter '17 / '18 - Outlooks

Thread updated periodically as new outlooks and forecasts are issued from a variety of credible sources.

 

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Judah Cohen (AER) via National Science Foundation

"The combination of cold and wet could result in an above normal snow season for parts of the northern U.S., including the large population centers of the northeastern U.S.

 

"... indicators suggest ... the polar vortex will break down later this winter, potentially unleashing an extended period of severe winter weather." (ED:  not necessarily over the Western Hemisphere)

 

 

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International Research Institute for Climate and Society

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Cohen (AER):  DCA 17"; BOS 64"; all large cities in the NE and M-A above normal

Bastardi (WxBell Analytics):  PHL 30"; DCA near normal

Crawford (Wx Co.):  DCA 17"

Rogers (Commodity Wx Group):  DCA below normal

Tolleris (WxRisk):  DCA near normal

Capital Wx Gang:  DCA 11"; IAD 16"; BWI 16"

Accu-Wx:  I-95 corridor near normal; NYC/BOS >=6" above normal

NECN:  New England near normal 

 

Read more »

Winter '17 / '18 - NOV/s Arctic Oscillation: Winter/s Leading Indicator

The sign of NOV/s Arctic Oscillation (AO) index has a statistically significant (Chi-square Test for Independence; p <= 0.05) association with the sign of the average AO index during meteorological winter (D-J-F).

AO Contingency Table
p = 0.046	Nov +	Nov -	Total
D-J-F +	16	10	26
D-J-F -	15	26	41
Total	31	36	67
True +	52%	28%	False -
False -	48%	72%	True +

'True + (-)' indicates a true (false) prediction.

IOW ... if NOV/s AO is negative ... then there's a 72% chance the winter's average AO/s sign will also be negative ...

...and the association between the AO/s negative sign for NOV and D-J-F has a 28% 'false alarm rate' (FAR).

The relationship is nowhere near as strong when NOV/s AO is positive (48% FAR).

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Interesting ... albeit different ... relationship between NOV/s North Atlantic Oscillation (NAO).

Winter '17 / '18 - Eurasia Snow Cover - OCT

12,052,000 km2
18% above 52-year P-O-R-N (10,225,000 km2)

Rank: 11th
Lowest in five years

Eight of the last nine October above period-of-record-normal
Analog years for winter '17 / '18

Rank Winter ENSO
1 06-07 W-
2 69-70 W-
3 77-78 W-
4 00-01 C-
5 98-99 C+

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Data courtesy Rutgers University Global Snow Lab
http://climate.rutgers.edu/snowcover/index.php

Winter '17 / '18 - Eurasia Snow Cover - OCT - Snow Advance Index (SAI)

OCT-17's snow advance index is negative.
Snow Crow suicide watch now in effect.

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AER reports a statistically significant correlation between their 'winter severity index' and how quickly Eurasian snow cover advances during OCT.

They define the 'winter severity index' by the state of the North Atlantic Oscillation / Arctic Oscillation (N/AO) and interpret it as an indicator of 'high latitude' blocking potential during D-J-F.

More blocking.
More winter.
More better.

Here's the model ...
"When snow cover advances rapidly (slowly) across Eurasia in October, this is an indication that the upcoming winter will be more severe (milder) for the Eastern US [sic], Europe and East Asia.

Study period seems surprisingly short seeing how contiguous monthly Eurasian snow cover data begins in 1970.  How well does the SAI correlate with the N/AO index prior to 1988?

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Snow Advance Index (SAI) backgrounder from AER here.
Earlier Eurasia snow cover posts here.

Winter '17 / '18 - Eurasia Snow Cover - OCT Preview

Cohen projecting above normal Eurasia snow cover for OCT ahead of an expected weak La Nina winter (D-J-F).

Nine previous weak La Nina winters ... including the famed 1995 - 1996 season ... have been observed during the Eurasia snow cover period of record (1967 - 2016). Only two NEWxSFC forecast stations -- BGM and ALB -- have a statistically significant correlation between season-total snowfall and above normal Eurasia snow cover.


Related:
Winter '17 / '18 - Correlation of Eurasia's OCT Snow Cover and Season-total Snowfall in NE and M-A Regions 

Winter '17 / '18 - First Contact

Post-frontal ... elevation snows INVOF UVM associated with SFC LOWs

Boone ... NC (3146' MSL)
KTNB 291615Z AUTO 30013G25KT 4SM -SN SCT008 BKN014 BKN020 02/01

Richlands ... VA (2653' MSL)
KJFZ 291555Z AUTO 32004KT 3SM -SN SCT004 BKN007 OVC014 00/00 A2972 RMK AO2 T00011001

Wise county ... VA (2684' MSL)
KLNP 291555Z AUTO 31004KT 1 1/2SM -SN OVC003 00/00

Hot Springs ... VA (3793' MSL)
KHSP 291555Z AUTO 29014KT M1/4SM -SN OVC003 02/02

Bluefield ... WV (2856' MSL)
KBLF 291552Z AUTO 31008KT 1 3/4SM -SN BR BKN006 OVC012 00/M01

Bedford county ... PA (1161' MSL)
KHMZ 291555Z AUTO 32006KT 5SM -SN OVC010 07/06

Winter '17 / '18 - La Nina Teleconnections and Flavors

Image courtesy The International Research Institute for Climate and Society (IRI)

The Flaw of Averages ... not all La Ninas are created equal.

 

 

 Images courtesy NOAA Climate.gov - ENSO Blog

Winter '16 / '17 - Arctic Oscillation (AO) Analog Verification

The analog forecasting technique seeks similarities to the AO state during the multi-month run-up to the coming winter with same AO run-ups of winters past.

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

Arctic Oscillation (AO) Index Analog Forecast Verification

In the run-up to Winter '16 / '17 ... the leading analog was '12 / '13 followed by '73 / '74 ... '02 / '03 ... '74 / '75 ... and '88 / '89.  A qualitative assessment of the forecast's accuracy would rate the top three analogs as 'poor' ... IOW ... useless.

Winter '12 / '13 NAO oscillated weak negative to strong negative; whereas ... Winter '16 / '17 was essentially a mirror opposite.  The closest analogs ... on the basis of the AO remaining positive throughout the three-month forecast period ... were ranked last ('88 / '89) and next to last ('75 / '76).

Conclusion:  The top three Winter '16 / '17 AO analogs showed little ... if any ... skill.

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An alternative forecasting technique looks at the AO's sign for any calendar-year's month preceding the pending winter as a potential leading indicator of the AO's sign for D-J-F period.

Results from a chi-square 'test for independence' infers a statistically significant relationship ... at the 95% confidence level and a p-value < 0.05 ... between NOV's AO sign and AO's sign of the upcoming D-J-F period.  IOW ... if NOV's AO is negative (positive) ... then average AO state during the upcoming winter will also be negative (positive); although the classification model is stronger ... i.e., lower false alarm rate ... for the predictor's month with a negative sign than positive.

Conclusion:  If NOV's AO is negative ... chances are good the AO state will average negative during D-J-F period.

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Period-of-record AO data here.