Winter '18 / '19 - Sudden Stratospheric Warming: Watch #1

Polar vortex (PV) displacement event appears to be in the cards come Christmas.

Full flow reversal + warming ==> major sudden stratosphere warming (SSW) event ...

BLUE:  into the board ==> east wind (-U)
ORANGE:  out of the board ==> west wind (U)

"A major SSW occurs when the 10 mb 60°N zonal mean zonal wind reverses from westerly to easterly and the 10 mb zonal mean temperature gradient increases poleward of 60°N." (.pdf)

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Last winter's SSW event crash-landed over the UK (weeks of late season snow + cold)

This year ... round and round she goes.
Where she stops ...
Nobody knows.

Winter '18 / '19 - VCP32: Winning the Lottery!

Winter '18 / '19 - November/s AO Predicts The State Of Winter/s AO

NOV/s Arctic Oscillation (AO) Index:  -1.116

Conventional meteorological wisdom holds the state of winter/s AO is next to impossible to forecast.

Some use analogs.  The analog forecasting methods seeks similarities between the AO state in the run-up to the coming winter with AO run-up states of winters past.  The NEWxSFC method ranks analog years by their sum of square errors (SSE) statistic.

Lower SSE errors ==> stronger analog

Constraining the number of analog winters for analysis to five is arbitrary.
See this year's analogs below.

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An alternative forecasting technique looks at the AO/s 'sign' (i.e., positive or negative) for any calendar-year's month preceding the pending winter as a potential leading indicator of the AO/s sign for upcoming 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 the 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 negative signs than positive.

True + ==> prediction is True
False + ==> prediction is False

Given NOV-18/s negative AO ... the 2x2 contingency table predicts a 73% likelihood (27/37) the three-month average AO (D-J-F) will also be negative this winter.  The results says nothing about the magnitude of the winter/s AO or which months will be negative ... only the sign of its average.

During a +ENSO ... this bodes well for a colder than average winter over southern portions and snowier than average winter over just about everywhere across the NEWxSFC forecast area.

Read more »

Winter '18 / '19 - 18th Annual 'Season-total' Snowfall Forecast Contest - The Forecasts!

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

Two first-time forecasters
Welcome bdougherty and The Snowman

A lot of familiar faces ... too.  Many with 17 years experience.
Welcome back!

Forecaster table ranked by STP

BLUE - <= 25th percentile
RED - >= 75th percentile
ORANGE - Chief forecaster (1st Place - 17th Annual 'Season-total' Forecast Contest)
P-O-R-N - period of record normal
CONSENSUS - average station forecasts

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Station forecasts:  550 (including P-O-R-N & CONSENSUS)
Stations forecasts for ...
BELOW average snowfall - 84 (15%)
AVERAGE snowfall - 25 (5%)
ABOVE average snowfall - 441 (80%)

Confidence (at least 67% of forecasts) for stations with ...
BELOW average snowfall @ NONE
ABOVE average snowfall @ all stations except ACY
All forecasters expect above average season-total snowfall @ BGR & BDR

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

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NEWxSFC/s regular season 'snow storm' forecasting contest began 16-NOV.
'Call for Forecasts' for subsequent snow storms are issued at NEWxSFC/s web site and blog (you are here) ... via e-mail ... and Facebook.

Web site:  http://www.newx-forecasts.com/index.htm
Facebook:  https://www.facebook.com/newxsfc/

Winter '18 / '19 - 18th Annual 'Season-total' Snowfall Forecast Contest - Call for Forecasts!

NEWxSFC Meteorologist-in-Charge
Seasonal Forecasts

Here comes winter with its oscillating Arctic and North Atlantic indexes ... suddenly warming stratosphere ... and an endless parade of coastal teasers.

NE.Wx/s 18th 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 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!

Deadline: FRI ... 30-NOV-18 @ 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.'

1st place prize (delivered post-paid right to your front door):
"The Snow Booklet" by Nolan J. Doesken and Arthur Judson (paperback) and
"Snow in America" by Bernard Mergan (hardcover)

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As always ... NO cost ... NO fees ... NO advertising ... NO annoying requests for personal information to enter the contest.  NEWxSFC is just a fun exercise for winter wx enthusiasts to see who can make the best season-total snowfall forecast.

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Forecast element: sum-total season snowfall @ each station
Forecast period: 01-DEC-18 through 31-MAR-19

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

Read more »

Winter '18 / '19 - ENSO ... Arctic Oscillation ... & Season-total Snowfall @NEWxSFC Stations (Wonkish)

Roosting snow crows rooting for bonus snows thanks to expected weak-to-moderate El Niño conditions.

Typical analysis ignores influence of other controlling factors ... such as the Arctic Oscillation (AO).

BLUF:  ENSO state does not provide robust guidance for season-total snowfall (STP) outcomes @NEWxSFC stations unless AO is considered.

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Analysis period:  '66 / '67 to '17 / '18 (D-J-F-M)
n = 52

For all winter ENSO states ... if AVG D-J-F-M AO < 0 … then STP @NEWxSFC stations > AVG
Weak correlation:  R = -0.311

Correlation (R) >= +/- 0.6 considered generally to have useful predictive power

ONI = Oceanic Niño Index

Read more »

Winter '18 / '19 - Snow Storm #1: FINAL Results

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

1st - donsutherland1
SUMSQ:	38
SUMSQ Z:	-1.400
STP:	7.1	(1)
TAE:	18.9	(1)
AAE:	0.95	(1)
2nd - Brad Yehl
SUMSQ:	54
SUMSQ Z:	-1.215
STP:	9.2	(2)
TAE:	21.2	(2)
AAE:	1.06	(2)
3rd - WeatherT
SUMSQ:	85
SUMSQ Z:	-0.860
STP:	16.2	(4)
TAE:	33.4	(5)
AAE:	1.52	(3)
HM - Donald Rosenfeld
SUMSQ:	113
SUMSQ Z:	-0.541
STP:	20.3	(8)
TAE:	33.0	(3)
AAE:	1.57	(4)

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 #1: Preliminary STP Verification

Table of preliminary storm-total snowfall by station for THU and FRI from CDUS41 (CLI) ... CXUS51 (CF6) and ... SAUS41 (METAR) bulletins.

Exceptions:
BDR - daily snowfall reports missing.
STP estimated from METAR 6/nnnn group @ SLR 10:1

SLR not reported for some stations with measurable snowfall b/c liquid and / or freezing precipitation also occurred during the verification period.

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Stations observing at least Trace - 20 (74%)

Given a forecast station observed measurable snowfall ... stations observing at least:
4" - 10 (50%)
6" - 5 (30%)
8" - 3 (15%)
10" - 0

Max snow melt-water
CAR - 0.70"
BTV - 0.62"
CON - 0.60"
JFK - 0.91"

BGM SLR 6:1 (no liquid precipitation reported)

Max precipitation:  ACY - 1.73"

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New daily records:
15-NOV-18 (1)
ORH - 7.8" (5.7"; 1967)

Eleven daily records set this day -- some held since 1906; however ... snow fell on ten stations before the deadline; therefore  ... they are not included.

16-NOV-18 (4)
CAR - 9.3" (5.4"; 1973)
BGM - 4" (1.8"; 1987, 1999)
ABE - 0.7" (0.05"; 1995)
MDT - 0.5" (0.05"; 1985)


SFC analysis:  00z ... 16-NOV-18

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Please report errors in Comments along with a link to the correct data.
FINAL Results post expected SUN evening ... 18-NOV-18

Winter '18 / '19 - Snow Storm #1: The Forecasts

Forecaster class
Rookie 2
Journey 1
Senior 9
TOT 12

- Brad Yelh is NEWxSFC/s reigning 'Chief Forecaster' for 2019 ... having placed 1st in last year's 'Regular' season contest.

- Welcome and Good Luck to our Rookie forecasters NJWeather & Weather Wizard!

- No entry for ER NWS WSOs b/c of snowfall forecasts for many of their stations occurred before the verification period started.

All forecasts posted to the Contest/s web site. (direct link)

CORR:  quagmireweathercentral return to the fray for his third season warrants promotion to 'Journeyman' status. 

Forecast table ranked MIN-to-MAX by their verification period storm-total precipitation (STP).
BLUE = 25th percentile
RED >= 75th percentile
White / Grey- STP and 4cast cells range between the 25th and 75th percentile

Heaviest snowfall (>= 6") consensus expected along and to the right of a line from CAR - CON - ORH - ALB - BGM - BTV - CAR.  Lollipop @ BGM.

Flat PNA ... POS NAO ... Bi-polar AO.

Another NEWxSFC contest-worthy snow storm defies conventional teleconnection wisdom.

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Challenging verifications ahead given some lower latitude forecast stations observed much of their storm-total snowfall prior to the deadline.

Look for the forecast station's  preliminary verifying STPs NLT tomorrow (SAT) evening.

Winter '18 / '19 - Snow Storm #1: RAW Forecasts

Here