Winter '21 / '22 - Coastal Teaser #3

DC
24-JAN-1940

Persistent Ridge-West / Trof East mid-level flow regime looking to cough up another contest-worthy snow storm this coming weekend.

Progs pointing to a Miller 'A' type storm beginning its long climb up the east coast on FRI then exploding into a meteorological 'bomb' (and no ... not a so-called 'bomb cyclone'; a made-up term never used by Sanders and Gyakum 1980) during SAT.

A 'Call for Forecasts' expected WED ... 26-JAN-22.

All else equal ... deadline for entries would be 10 PM EST ... THU ... 27-JAN-22.

Winter '21 / '22 - Coastal Teaser #2

 

Worst kept secret evah ...

Snow Storm #2 all but certain to affect most if not all forecast stations SUN into MON.  NWP models tease for a yuge event of mixed precipitation types makes for a challenging forecast.

Call for Forecasts likely FRI.

Deadline for entries would be 10 PM EST ... SAT ... 15-JAN-22

Winter '21 / '22 - Coastal Teaser #1

Hot on the heels of the 03-JAN snow storm comes the chance for a contest-worthy nor'easter and the first snowfall forecasting contest of the '21 / '22 winter.

Progs currently advertising cyclogenesis along the trailing end of an arctic cold frontal boundary draped across the central Gulf coast states attended by a negatively-tilted trough aligned along the MS river valley THU AM with snow beginning over the forecast area early FRI AM.

A 'Call for Forecast' would be issued WED evening with a deadline for entries @ 10 PM EST ... THU ... 06-DEC-22 should current model trends continue.

Winter '20 / '21 - Coastal Teaser #3

UPDATE:  05-FEB-21 @ 9:45 AM EST 

No consensus among the overnight NWP model runs whether enough stations are in play to warrant a contest-worthy snow storm.

Will continue to evaluate through the 00z run this evening.

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Originally posted 04-FEB-21 @ 6:49 PM EST

Hot on the heels of this week's heavy snowfall event looms a full-latitude ... mid-level trof poised to excite a Miller 'A' nor'easter and the threat of a contest-worthy snow storm over the forecast area.

Latest NWP guidance points toward accumulating snow beginning over southern portions of the forecast area early SUN AM and continuing into MON as the storm scrapes along the coast. Without a closed LOW at 5H this go'round ... a long duration event is not expected.

Should events unfold as advertised currently ...
Call for Forecasts:  FRI ... 05-FEB-21
Deadline for entries:  10 PM EST ... SAT ... 06-FEB-21
Verification beginning:  12:01 AM EST ... SUN ... 07-FEB-21
Verification ending: 11:59 PM EST the day when flakes stop accumulating

Snow Storm #3 comes about seven days after Snow Storm #2.  In its wake ... the progs rocket the AO toward neutral and give the PNA a pump.  Should the cycle continue ... what's in store for Presidents Day 2021? 🤔

Winter '20 / '21 - Coastal Teaser #2

Long-duration and ginormous Miller 'B' storm complex beginning to loom large in the window as an otherwise disappointing JAN comes to a close.

Contest-worthy nor'easters have been in short supply of late so this is a welcome development.

Latest NWP guidance points toward snow beginning to accumulate over southern portions of the forecast area early SUN AM and continuing through the first few days of FEB over northern stations.

Should events unfold as advertised currently ...
Call for Forecasts:  FRI ... 29-JAN-21
Deadline for entries:  10 PM EST ... SAT ... 30-JAN-21
Verification beginning:  12:01 AM EST ... SUN 31-JAN-21
Verification ending: 11:59 PM EST the day when flakes stop accumulating 

Could be the start of an hyper-active period as heights progged to rise over the Pole and PNA region while AO remains below zero and the displaced PV drifts toward Greenland ...

Winter '20 / '21 - Coastal Teaser #1

UPDATE:  02-JAN-21 @ 9 AM EST
Not happenin' ...

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UPDATE:  01-JAN-21 @ 6:41 PM EST

Today/s 12z / 18z progs suggest too few stations in play for a contest-worthy snow storm.

Will evaluate 00z / 06z runs just in case ...

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Originally posted:  31-DEC-20 @ 6:41 PM EST

Cyclogenesis progged early this weekend in the Gulf of Mexico on the trailing end of a cold front attending FRI/s storm moving NE through the Mid-West ... Great Lakes ... and New England may turn into a long duration contest-worthy snow storm for the northern half of the forecast area come SUN.

Should the present trend in NWP output continue ...

Call for Forecasts:  FRI ... 01-JAN-21
Deadline for entries:  10 PM EST ... SAT ... 02-JAN-21
Verification period:  12:01 AM EST ... SUN ... 03-JAN-21 till flakes stop accumulating

Watch this space ...

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

Winter '18 / '19 - Sudden Stratospheric Warming: Watch #1 - UPDATE 3

 From Judah Cohen's (AER) blog ...

"I have been arguing for at least a decade now that the winter season is shifting ahead in time so that it starts later and ends later.  The fall months are warming across the NH (with one notable exception in Siberia) and that warming extends into December.  However surprisingly the next three months, January through March are cooling across the NH mid-latitudes.
[...]
"The frequency of severe winter weather is increased following an SSW across the NH mid-latitudes including more Arctic outbreaks and heavy snowfalls.  Therefore, temperatures are cooling for late winter starting in January and extending into March.
[...]
" ... if you are anticipating severe winter weather or a winter weather enthusiast the mild bland weather is necessary for a period of elevated risk of severe winter weather.  Sure, there has been nothing memorable (at least for me; not true if you live in the Carolinas or Virginia) about December but the non-first half of winter is not independent of what I anticipate is a more active second half of winter.
[...]
"So, if you are a winter weather enthusiast, at least in my opinion the lack of winter so far is a necessary condition for cold and snow to follow.  And if you like your winters mild then if the winter turns harsher in the near future it also was the cost for the benign winter so far.
[...]
" If the stratosphere and troposphere fail to couple, then I see no reason why the relatively benign winter weather can’t continue right up to spring.
[...]
"After the PV split the lowest heights and coldest temperatures are predicted to be in three regions in the stratosphere in Western Asia/Eastern Europe, the North Pacific and Southeastern Canada/Northeastern US.  The models all agree that in the troposphere the lowest geopotential height anomalies will also be in Western Asia/Eastern Europe and the North Pacific with the models only disagreeing in Southeastern Canada/Northeastern US.

"But for the biggest impact the Arctic in the troposphere needs to warm up in my opinion and that has not happened.  Also, the only region that is experiencing significant below normal sea ice extent is the Barents-Kara Seas.  If the positive temperature anomalies remain confined to this region this is supportive of cold in Asia but not eastern North America.[...] In fact, low sea ice in the Barents-Kara Seas favor warm temperatures in the Eastern US based on this plot alone."

Winter '18 / '19 - Sudden Stratospheric Warming: Watch #1 - UPDATE 2

Brief ... less dramatic stratospheric warming at 30 mb on 20-DEC-18 has faded only to be replaced by a much larger  ... stronger ... and very well modeled event with its sprawling center over the northern Asia continent.

Figure 1.  10 hPa temperature change in a week in the Northern Hemisphere
Contour interval:  5 °C.
PINK and light BLUE shadings indicate warming and cooling, respectively.
RED shading denotes warming for values higher than 25 °C.

Image courtesy:  Tokyo Climate Center, Climate Prediction Division

Figure 2.  10 mb Zonal Mean Temperature for 2017 & 2018
Note the sharp on-going increase in temperature (far right) and the previous SSW events during FEB-18 (center) and FEB-17 and again in MAR-17 (far left).

Image courtesy:  CPC Stratosphere's Global Temperature Time Series 

Figure 3.  Latitude-height cross section of zonal mean temperature
Note the descending bulge of warm temperatures in bottom row as the current SSW event unfolds

Image courtesy:  Tokyo Climate Center, Climate Prediction Division
 

Figure 4.  Latitude-height cross section of zonal mean wind
Note the descending blue region in last panel as the easterly wind (negative values flow into the board) begins to disrupt the polar vortex.

Image courtesy:  Tokyo Climate Center, Climate Prediction Division
 

Figure 5.  240-hr 10 mb zonal wind forecast
Note the PV split (sister vortices) over NE Europe and NE North America

Once the circulations work their way to the surface ... they're expected to bleed a mother lode of numbing Arctic air into the Upper Midwest and ooze its way deep into the southern tier of states.  Arctic boundary likely to drape along the eastern seaboard providing favorable baroclinic conditions for coastal cyclogenesis.

Image courtesy:  Freie Universität Berlin Institute for Meteorology - Stratospheric Diagnostics

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 '17 / '18 - Coastal Teaser: #2

Snow Storm #6 may be in the cards mid-week at the start of NEWxSFC/s fourth quarter.

Upper LOW currently over the PAC NW ejects to the east ... then deepens as its progression b/comes retarded by high-latitude blocking.  Miller 'B' cyclogenesis progged off the VA Capes followed by a slow crawl up the coast suggesting a long duration event.

Should the present trend in NWP output continue ...
Call for Forecasts:  MON ... 05-MAR-18
Deadline for entries:  10:30 PM EST ... TUE ... 06-MAR-18
Verification period:  12:01 AM EST ... WED ... 07-MAR-18 till TBD

NEWxSFC/s email client has been off-line for over a week with no estimated return-to-service date.

Watch this space.

Winter '17 / '18 - Coastal Teaser #1

Snow Storm #2 may be in the cards later this week as an Arctic air mass in a high amplitude flow regime excites cyclogenesis along the SE coast where SST are anomalously warm.

Latest progs suggest nuisance snow amounts may begin accumulating over extreme southern forecast stations around sundown on WED ... several hours before the deadline.

Don't see any reason to set the deadline for entries TUE evening to ensure these stations are in the mix when this system/s main event will likely play out farther north on THU.

Should the present trend in NWP output continue ...
Call for Forecasts:  TUE ... 02-JAN-18
Deadline for entries:  10:30 PM EST ... WED ... 03-JAN-18
Verification period begins:  12:01 AM EST ... THU ... 04-JAN-18
Verification period ends:  11:59 PM EST ... FRI ... 05-JAN-18

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 '15 / '16 - Coastal Teaser #3

Decent inter - and intra-run-to-run consistency suggesting this season's first contest-worthy snow storm may be in the offing toward week's end.

Timing the on-set of precipitation remains a moving target.  18-JAN / 00z GFS pointing toward FRI AM over southern portions of the forecast area.

'Call for Forecasts' possible WED evening (20-JAN).

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There have been five previous winters without a contest-worthy storm in DEC ('99-'00, '06-'07, '11-'12, and '14-'15).

The first storms those winters were:
1/20/00
2/14/07
1/21/12
1/26/15

Total snowfall forecasting contests those winters:
'99-'00:  5
'06-'07:  5
'11-'12:  2
'14-'15:  6

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Hang in there forecasters.
All is (probably) not lost.

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NWP image courtesy meteocentre.com

Winter '15 / '16 - Coastal Teaser #2

A little past the halfway point of meteorological winter ... another coastal teaser lurks on the horizon.

Should be noted the ECMWF didn't get the memo.
 

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NWP image courtesy meteocentre.com

Winter '15 / '16 - Coastal Teaser #1

Maybe DEC 2015 won't go into the record books as not having a single contest-worthy snow storm.

Progs depict weak cyclogenesis this weekend over southern TX and a track to the NE well west of the Appalachian mountains with half-hearted secondary development off the Delmarva a few days later.

Retreating and weakening Arctic HIGH over SE CN would support a layer a slop along the coast with plowable snows inland.

NWP image courtesy meteocentre.com

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NEWxSFC's historian reports four of 16 DECs without a contest-worthy storm (winters ending:  '00, '07, '12, '15).



Season-total snowfall totals ... P-O-R-N ... and PCT of P-O-R-N
'99 - '00 (unavailable - no season-total contest)
'06 - '07   617" / 926" (67%)
'11 - '12   393" / 934" (42%)
'14 - '15  1,336" / 934" (143%)

Not a good sign but too soon to abandon all hope.

Winter '15 / '16 - Sudden Stratospheric Warming: Watch #1 UPDATE 1

ECMWF continues to signal PV weakening near month's end.

Initial panel (right) @ 80 m/s (155 knot; 179 mph).

D+10  @ 60 m/s (117 knot;134 mph).Also note the weakening +QBO feature INVOF 30 mb.

00 mb D+10 prog (bottom) signals the start of a splitting PV with circulation centers over the Laptev Sea (west of Barents Sea) and extreme northern Canada ... as well as the leading edge of a sharp wave over the Prime Meridian.

Takes a few weeks for a propagating wave to reach 10 mb then work its way to the surface.

Winter '14 / '15 - Sudden Stratospheric Warming: Watch #2 - Update 4

Incoming!

 

Deep layer Easter easterlies.

 

 

PV displacement

 

Split vortices.

 

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Major SSW event has begun!

 

 

Winter '14 / '15 - Sudden Stratospheric Warming: Watch #2 - Update 3

ECMWF continues its forecast for a SSW event in the near-term.

Winter '14 / '15 - Sudden Stratospheric Warming: Watch #2 - Update 2

Complete break down of the Polar vortex at month's end.

Deep ... deep layer wind reversal (easterlies up and down the Polar atmosphere) 

 

Prediction:  cold spring in the east.