Winter '16 / '17 - Sudden Stratospheric Warming: Watch #1 - UPDATE 2

The well forecast major warming 'displacement' event is well underway.
Major warming:  temperature increase >= 25°C over seven days.

 

Stratosphere Diagnostics courtesy Freie Universität Berlin / Department of Earth Sciences / Institute of Meteorology  

 

 

 

 

Stratosphere analysis courtesy Tokyo Climate Center, Climate Prediction Division Japan Meteorological Agency

 

Winter '16 / '17 - Sudden Stratospheric Warming: Watch #1 - UPDATE

Displacement event looms near month's end.

 

 

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QBO > 10 kt

Strong STJ (50 kt)

Weak PV (30 kt)

Flow reversals above 5 mb and below 300 mb

 

 

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Cold air mother lode sits over Hudson Bay with full-latitude trough attending.

 

 

 

Winter '16 / '17 - Sudden Stratospheric Warming: Watch #1

A sudden stratospheric warming (SSW) event may be in the works for the last week of the month.

After weeks and weeks of a high-speed rotation ... polar vortex (PV) forecasts suggest a significant slowing / weakening.  Slowing of PV suggests a deep layer of easterlies (light blue; lower right corner) over the Pole.

A maturing of this scenario would portend Arctic air drainage into the mid-latitudes.


Stratosphere Diagnostics courtesy Freie Universität Berlin / Department of Earth Sciences / Institute of Meteorology

Winter '16 / '17 - Snow Storm #2 - Another NWP and Public Forecast Failure

NYC

The season/s third contest-worthy snow storm out-performed not only the suite of numerical models but the professional meteorologists responsible for issuing the official forecasts.

As of Wednesday afternoon (04-JAN) ... the progs and public forecasts for the Friday/Saturday award-winning event (06-JAN thru 07-JAN) all indicated a low probability (40%) for a meager 4" snowfall across a narrow slice of SE VA and NE NC.

When all was said and done ... heavy snowfall was observed from SE VA (up to 12") ... the Delmarva (up to 13") ... LI (up to 7") ... and Cape Cod (where near-blizzard conditions were reported and up to 16").  Eleven contest stations measured at least 4".

Four new daily records:
PVD  10.7"
ISP  9.7"
RIC  7"
SBY   9"

SLRs where at least 4" of snow was observed ranged between ~12:1 and ~25:1

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Some have suggested a 'Call for Forecasts' be issued whenever a potential snow storm looms.
That way ... a contest-worthy storm would seldom be missed.

Sounds like a good idea and it would be if there wasn't four hours of work involved when issuing the call.

Hundreds of email 'invitations' have to been sent (50 at a time ... 30' apart so as not to be flagged as spam or blocked by my ISP).

The contest/s web site has to be updated.
The contest/s web log has to be updated.
The contest/s Facebook page has to be updated.

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Then it becomes a judgment call during the evening of the deadline ... deciding whether the storm will be contest-worthy (six to eight stations with more than nuisance storm-total snowfall i.e., >= 4").

Collecting surface ... upper air ... and remote sensing data used in the final analysis and storm summary reporting takes time while the event is unfolding. All for naught if the storm fizzles.

Believe you me ... no one is more disappointed than me when a good snow storm slips through the cracks.
Bottom line: a contest-worthy storm has to be reasonably well-predicted by the numerical weather prediction models and WPC 36-to-48 hours before the first flakes fall for a 'Call for Forecasts' to be issued.

Winter '16 / '17 - Season-total Snowfall Forecast Contest: DEC totals

Station snowfall summary for DEC-16.
Rank ordered by percent of monthly normal.

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Green ==> 75th percentile
White ==> Less than 75th and greater than 25th percentile
Red ==> 25th percentile

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Teleconnection indexes and month-over trend (updated as they become available)
AO:  1.786⇧
NAO:  0.48⇧
PDO:  1.17⇩
QBO:  15.09⇧
SOI:  2.6⇧

Winter '16 / '17 - Snow Storm #1: FINAL Results

Forecaster verifications and storm summary at NEWxSFC/s home page.
http://www.newx-forecasts.com/

	1st - shillelagh
	SUMSQ:	51
	SUMSQ Z:	-1.032
	STP:	0.6	(1)
	TAE:	19.4	(2)
	AAE:	0.92	(1)
	2nd - Herb @MAWS
	SUMSQ:	64
	SUMSQ Z:	-0.887
	STP:	9.7	(6)
	TAE:	17.7	(1)
	AAE:	0.99	(2)
	3rd - TQ
	SUMSQ:	79
	SUMSQ Z:	-0.721
	STP:	5.9	(4)
	TAE:	22.4	(3)
	AAE:	1.18	(3)
	HM - WeatherT
	SUMSQ:	96
	SUMSQ Z:	-0.537
	STP:	6.5	(5)
	TAE:	24.5	(5)
	AAE:	1.29	(5)

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 SUMSQ: sum of square errors (")
 STP: storm-total precipitation error (")
 TAE: total absolute error (")
 AAE: average absolute error (")
 (number): category rank

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Winter '16 / '17 - Snow Storm #1: Preliminary Verification

Preliminary storm-total snowfalls for THU and FRI from CDUS41 and CXUS51 bulletins.  Good overall coverage.

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One new daily record.
29-DEC-16
CON - 8.3" (7.1"; 1956)

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Snow Storm #1 underperformed slightly with five stations reporting more than nuisance snowfall (>= 4").  BGM just couldn/t make it over the finish line.

A dozen stations reported snowfall greater than Trace.

No Snow-Liquid ratios for mixed precipitation conditions ... such as PWM ... where 1.84" liquid was measured.

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Please report any errors in Comments along with a link to the correct data.

Final results NLT SUN evening.

Winter '16 / '17 - Snow Storm #1: New Daily Record Snowfall @ KCON

SFC:  00Z FRI ... 30-DEC-16

Concord ... NH (KCON) set a new daily snowfall record on 29-DEC-2016.

New record:  8.3" (12.2:1 SLR)
Old record:  7.1" (1956)

Light snow began falling over the station shortly before noon on the 29th ... turning heavy and increasing to an inch to an inch and one-half per hour between 5 and 8 PM EST.

Winter '16 / '17 - Snow Storm #1: TSSN

On-set of convection heralded the change from liquid to frozen precipitation.
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KBED 300112Z 32011G19KT 1SM R11/6000VP6000FT -TSSN BR VV004 01/M01 A2941
RMK AO2 LTG DSNT SE AND S TSB06 P0001 T00061011

KBOS 300119Z 31015G25KT 3SM -TSSNGS SCT006 OVC015 01/01 A2938
RMK AO2 PK WND 32028/0056 RAE07SNB01GSB13 TSB10 LTGICCC W TS W MOV E P0007 T00110006

KPWM 300251Z 33013KT 1/2SM +TSSN FEW004 OVC010 M02/M02 A2929
RMK AO2 WSHFT 0154 RAE17SNB17 TSB49 PRESFR SLP918 LTGIC P0024 60079 I1002 I3002

K1P1 300255Z AUTO 00000KT 2 1/2SM -VCTSSN M03/M03 A2936 RMK AO2 P0001 60003 T10281031

Winter '16 / '17 - Snow Storm #1: The Forecasts!

Rookie 0
Intern 0
Journey 0
Senior 8
Official 1
TOT 9
Included NWS 'official' forecasts ... as of the deadline.
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Forecasts are ranked by their storm-total precipitation (STP).

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

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Heaviest snowfall (>= 4") consensus along and the right of CAR - BGR - ORH - BGM - ALB - CON - CAR
Lollypop expected at CAR.

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Teleconnection headwinds

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Everyone/s station-by-station forecast post to NEWxSFC/s web site @ http://www.newx-forecasts.com/