Winter '17 / '18 - Sudden Stratospheric Warming: Watch #1

Something worth keeping an eye on ...

 

D+10/s polar vortex splits in two with action centers over northern Canada along ~90W and ~45E INVOF the Black Sea.

 

Deep layer ... high latitude flow reversal (negative / blue values into the board i.e., east wind / anticyclonic circulation) would provide highly favorable conditions for a negative Arctic Oscillation index over an extended period toward meteorological winter's end.

Winter '17 / '18 - Season-total Snowfall Forecast Contest: DEC totals

Station snowfall summary for DEC-17.
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:  -0.059⇧
NAO:  0.88⇧
PDO:  0.50⇧
QBO:  -18.12⇩
SOI:  -1.4⇩

Winter '17 / '18 - Regular Season Interim Standings: 1

Under the ‘two-thirds’ rule … forecasters who have entered at least TWO forecasts are included in the interim standings.

Complete interim statistics table and charts at the Contest/s web site here. (fixed)
Forecaster statistics for Winter '17 / '18 contest snow storms here.

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SUMSQ errors for each contest snow storm are normalized 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.

Same idea as dropping the lowest quiz score before computing the final grade.

Winter '17 / '18 - Snow Storm #3: FINAL Results

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

	1st - donsutherland1
	SUMSQ:	28
	SUMSQ Z:	-1.085
	STP:	5.9	(4)
	TAE:	22.5	(1)
	AAE:	0.83	(1)
	2nd - TQ
	SUMSQ:	37
	SUMSQ Z:	-0.841
	STP:	2.3	(3)
	TAE:	23.0	(3)
	AAE:	0.85	(3)
	3rd - Herb @MAWS
	SUMSQ:	39
	SUMSQ Z:	-0.803
	STP:	0.8	(1)
	TAE:	25.1	(4)
	AAE:	0.93	(4)
	HM - Brad Yehl
	SUMSQ:	41
	SUMSQ Z:	-0.739
	STP:	6.9	(6)
	TAE:	23.0	(2)
	AAE:	0.85	(2)

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

Forecast by Observed Snowfall Scatter Plots for Top Forecasts
Dotted blue line below (above) solid red line ==> under (over) forecast

Station Verification Comparison of Top Forecasters

Winter '17 / '18 - Snow Storm #3: Preliminary STP Verifications

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

Exceptions:
SBY
17-JAN CLI and CF6 bulletins carried 'MM' as daily snowfall at post-time.  Intermittent light snow reported during the day between 1029 and 1527 ... twice reducing VSBY briefly to 2 1/2 SM for a total of 34 minutes.  Tipping bucket data unhelpful.  STP entered as Trace.

HYA
Estimated storm-total snowfall based on inverse distance weighting technique using vicinity STP reports from Barnstable county carried in PNSBOX.

BOS
All frozen precipitation.  Low SLR due likely to 2M temperatures > 0°C.

PWM and CON
17-JAN CLI and CF6 bulletins carried 'MM' as daily snowfall at post-time.  STPs from PNSGYX.

UPDATE 19-JAN-18 @ 3:15 PM EST
PWM/CON CLI and CF6 carry 5.9" and 2.5" ... respectively.

UPDATE 19-JAN-18 @ 10:15 PM EST
CON
The 17-JAN CLI snowfall report issued by GYX for CON is clearly in error given VCNTY PNSGYX
reports.

Inverse distance weighting using all VCNTY PNSGYX reports from Merrimack county in NH results in
a derived two-day STP of 4.3". The closest public report of 4.2" came from CoCoRaHS 1.7 MI SE of
CON.

The derived two-day STP of 4.3" was reduced for verification to 3.5" after applying an SLR of 13.6 to the 0.06"
liquid reported by ASOS prior to contest deadline.  CON/s SLR was derived by inverse distance
weighting of SLRs from 'neighboring' NEWxSFC forecast stations (ORH [12.7] and PWM [14.6]).

Bottom line:  Changing CON/s preliminary STP (5.6") to the verifying STP (3.5") flipped
forecaster rankings in the 4th / 5th and 8th / 9th slots along with changes to all Z-scores
(some better; some worse).

CON ... along with SBY ... have long been a troublesome stations.

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Stations observing at least:
Trace - 27
4" - 5 (19%)
6" - 1 (4%)
8" - 0

Max melt-water at RDU (0.49")
PWM - 0.41"
BGR - 0.37"

New daily records:  2
RDU - 5.9" (4"; 1946)
ORF - 2.5" (1.8"; 1911) [corrected station ID:  h/t Roger Smith / Peter O'Donnell in Comments]

Surface analysis:  15z ... 17-JAN-18
 
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Please report any errors in Comments along with a link to the correct data.
Final results for Snow Storm #3 delayed one day (conducting fermentation experiment FRI evening)
Expected post time: NLT SAT evening.

Winter '17 / '18 - Snow Storm #3: The Forecasts

Rookie -
Intern 1
Journey -
Senior 10
GOVT 1
PWSP 1
TOT 13

All forecasts posted to the Contest/s web site.
Direct link:  http://www.newx-forecasts.com/NEWxSFC_19/storms/storm3_forecasts_17Jan18.htm
Forecasts ranked by their verification period storm-total precipitation (STP).



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

NWS ER WFOs (GOVT)  and PWSP (Private Weather Service Provider) forecasts derived from public issuances current at the deadline.  Adjustments were made by NEWxSFC to account for snowfall measured on 16-JAN-18.

Heaviest snowfall (>= 4") consensus along and to the right of BGR - PWM - ORH - BDL - ALB - CON - BGR.  Snow cone expected at CON.  All forecast stations get a share of the wealth from this barely contest-worthy storm.

Upside down tele-connections indexes prove once again their lack of importance for observing more than nuisance amounts of frozen precipitation at first-order observing stations in the M-A and NE.

Median station forecasts (Excel 2013 - Power Map)

Winter '17 / '18 - Snow Storm #3: RAW FORECASTS

Here

Winter '17 / '18 - Snow Storm #3: Call for Forecasts

Windsor County ... NH

Fast moving storm in a progressive flow regime and marginal low-level temperature profiles are not the best set-up for a contest-worthy storm; however ... NWP sometimes doesn't catch on until the last minute so we/ll hope for the best.

Contest for Snow Storm #3 may be cancelled prior to the deadline if fewer than six stations are likely to observe at least a 4" snowfall.

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Forecast element:  each station's verification period snowfall
Deadline for entries:  10:30 PM EST ... TUE ... 16-JAN-18
Verification begins:  12:01 AM EST ... WED ... 17-JAN-18
Verification ends:  11:59 PM EST ... WED ... 17-JAN-18

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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.  See how well your forecast stacks up against NWS Eastern Region Weather Forecast Offices.

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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). sent to your Inbox.

Winter '17 / '18 - Snow Storm #2: FINAL Results

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

	1st - Brad Yehl
	SUMSQ:	107
	SUMSQ Z:	-1.566
	STP:	19.9	(3)
	TAE:	42.8	(1)
	AAE:	1.58	(1)
	2nd - WeatherT
	SUMSQ:	156
	SUMSQ Z:	-1.220
	STP:	23.1	(4)
	TAE:	46.1	(2)
	AAE:	1.71	(2)
	3rd - Shillelagh
	SUMSQ:	190
	SUMSQ Z:	-0.977
	STP:	23.2	(5)
	TAE:	56.6	(3)
	AAE:	2.10	(3)
	HM - donsutherland1
	SUMSQ:	215
	SUMSQ Z:	-0.799
	STP:	42.9	(11)
	TAE:	56.7	(4)
	AAE:	2.10	(4)

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


Forecast by Observed Snowfall Scatter Plots of Top Forecasters
Dotted blue line below (above) solid red line ==> under (over) forecast


Station Verification Comparison of Top Forecasters

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


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

Winter '17 / '18 - Snow Storm #2: Preliminary STP Verifications

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

Exceptions:
SBY
04-JAN and 05-JAN CLI and CF6 bulletins carried 'MM' as daily snowfall at post-time.  Tipping bucket data unhelpful.

Estimated storm-total snowfall based on inverse distance weighting technique using the four closest STP reports carried in AKQPNS.  STP value subject to change pending updates to CDUS41 ... CXUS51 ... or PNS bulletins.

HYA
Estimated storm-total snowfall based on METARs @ 10:1 SLR.

Suspect SLRs at ORH ...PVD ... and BGM ... a likely consequence of the storm's high-wind conditions.  Looks like BDR applied 10:1 to derive melt-water given hinky 6- and 7-group data.

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Stations observing at least:
Trace - 27 (100% - something for everyone.  RDU 0.9" fell during pre-deadline hours)
4" - 18 (67%)
6" - 14 (52%)
8" - 14 (52%)
10" - 10 (37%)
12" - 9 (33%)
14" - 5 (19%)
16" - 4 (15%)
18" - 2 (17%)
20" - 0

Max melt-water at ISP (1.53")
CAR - 1.36"
BDR / ACY - 0.80"
BGR - 0.79"

New daily records:  13
BGR - 18.3" (8.5"; 2003)
ISP - 16" (3.8"; 1988)
PVD - 14.1" (5.7"; 1988)
BOS - 13.4" (7.9"; 1994)
ACY - 13.2" (2.5"; 1905)
CAR - 13" (10.5"; 1988)
BDL - 10.2" (8.1"; 1923)
SBY - 8.5" (0.9"; 1952)
EWR - 8.4" (4"; 1988)
BDR - 8" (5.3"; 1988)
JFK - 8" (4.9"; 1988)
ORF - 5.1" (1.2"; 1905)
RIC - 2.4" (1.6"; 1980)

Surface analysis:  18z ... 04-JAN-18

Central pressure:  950 mb
 

 Daily weather map for 04-JAN-88.
 

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