Sunday, November 7, 2021

Winter '21 / '22 - Pacific Decadal Oscillation (PDO): OCT-21

 -3.06 (~2.25-sigma below the monthly mean)

PDO/s cool phase continues apace.  22 continuous months with an index value < 0 (JAN-20 - present).

Leading analog years
Winter / ENSO (MEI) / QBO
99-00 / C / W
08-09 / C- / W
62-63 / C- / E
75-76 / C / W
55-56 / C / -

All PDO analog years happened during a La Nina; however ... only one winter ('62 / '63) had QBO-E (D-J-F AVG:  ~ -16).

Winter '62 / '63
D-J-F Index Averages
NAO: -1.467
AO:  -1.914

Select season-total snowfalls  / P-O-R-N (inches)
RIC - 16.9 / 12.5
RNK - 29.7 / 19.5
DCA - 21.4 / 15.6
PHL - 20.5 / 22.1
NYC - 16.3 / 28.7
BGM - 95.3 / 83.7
BTV - 72.6 / 80.8
BOS - 30.9 / 43.7
CAR - 147.5 / 115.6

PDO < 0 (cool water along NOAM/s west coast) is associated with a longwave trof over NOAM/s west coast + above normal 500 mb geopotential heights over the SE CONUS + mild eastern U.S. winters.  La Nina is also associated with 500 mb ridging over SE CONUS.

These conditions more often than not mean a warmer than normal winter with below normal snowfall over at least the southern half of the forecast area but there have been notable exceptions to those rules.


Friday, November 5, 2021

Winter '21 / '22 - Quasi-Biennial Oscillation (QBO): OCT-21

-19.14 (just inside 1-sigma from the mean)

OCT is now the 5th month with a QBO index below zero having flipped in JUN following its 14 month run in positive territory.  The 30mb flow over the Equator oscillates from east to west every 14 months; therefore ... the current easterly state of the QBO is expected to last throughout Winter '21 / '22.

Leading analog years
Winter / ENSO (MEI)
72-73 / W+
00-01 / C-
09-10 / W
91-92 / W+
58-59 / W-

With La Nina temperature anomalies in ENSO Region 3.4 expected to persist through at least late winter ... all QBO analog years are rejected except Winter 00/01.

- Winter '00 / '01
The sum-total of the season-total snowfall for all Contest forecast stations was 1,312".  (~21% above the 1968 - 2021 period-of-record average 1,085".

Eurasia/s OCT areal snow cover slightly below normal.

D-J-F Index Averages
AO:  -1.312
NAO:  +0.040

"The QBO determines the character of the early winter, leading to a colder and more stable polar vortex in December and January during the west phase of the QBO and a more disturbed and warmer Arctic during the east phase of the QBO." [1]

In years with low solar activity (solar cycle 25 is just beginning) ... the polar winter vortex tends to be disturbed and weak when the QBO is easterly.  Positive geopotential height anomalies over high latitudes ... i.e., blocking ... are also correlated with QBO-E and solar minimums.
 
Antecedent odds currently favor a weak and disturbed stratospheric polar vortex and SSW (sudden stratospheric warming) leading to a long-lasting negative Arctic Oscillation (AO) and well-below normal temperatures periodically in eastern North America ... northern Europe ... or eastern Asia.


Tuesday, November 2, 2021

Winter '21 / '22 - Eurasia Snow Cover: OCT-21

Observed:  10,671,792 km^2
Average:  10,310,000 km^2
Median:  10,130,000 km^2

3.5% (5.3%) above normal (median)
Rank:  19 (n = 54)

Above average snow cover observed in 10 of the past 10 OCTs.
At least 1 standard deviation above normal snow cover in 5 of the last 10 OCTs.

Top Analog Winters (weight) / ENSO state / QBO state
1 - 2009/10 (2x) / W / E
2 - 2001/02 (2x) / nada- / W
3 - 2020/21 (1x) / C / W
4 - 2019/20 (1x) / nada+ / E
5 - 2015/16 (1x) / W+ / W

These analog winters have questionable predictive value b/c a moderate La Nina (C) and QBO-E are expected to prevail during Winter '21 / '22.

Blue markers located between the inner and outer circle have a weak yet statistically significant (p <= 0.05) positive correlation between Eurasia/s OCT areal snow cover and a forecast station/s season-total snowfall.  Strongest correlations found in New England where correlations range between 0.269 (BTV) and 0.376 (ORH).

A paultry ~16% of the variability (R2 = 0.158) in combined season-total snowfall from all forecast stations is explained by Eurasia/s OCT areal snow cover. 

---
Period-of-Record:  1967 - 2021 (1969:  no data)
Data courtesy Rutgers Global Snow Lab

Previous posts about Eurasia's OCT areal snow cover here

Sunday, October 31, 2021

Winter '21 / '22 - 21st Annual 'Season-total' Snowfall Forecast Contest: Call for Forecasts!

NEWxSFC/s Director of Season-total Snowfall Forecasting
Here comes winter with its oscillating Arctic and North Atlantic indexes ... sudden stratosphere warmings ... so-so ENSO ... and if we get lucky ... a seemingly endless parade of 'Miller A' LOWs raking the eastern seaboard.

NE.Wx/s 21st Annual ‘Season-total' Snowfall Forecast Contest is the absolute best ... biggest ... and possibly ONLY chance to be recognized for your astute 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!

---
Forecast element:
season-total snowfall @ each station

Forecast period:
01-DEC-21 through 31-MAR-22

Error statistic: total absolute error
[Σ abs(forecast - observed)]

Verification:
NWS climate reports (CLM or CF6)

Low. Score. Wins.

Deadline for entries: TUE ... 30-NOV-21 @ 11:59 PM EST (01-DEC-21 @ 4:59 UTC)

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

Update your forecast as often as you want prior to the deadline.
Only the last entry gets verified.

---
1st place prize (delivered post-paid right to your front door):
... choice of a book from NEWxSFC library
... the august and coveted title 'Chief Season-total Snowfall Forecaster' for Winter '22 / '23 and
... a well-deserved place of high esteem and honor with past winners.

2nd place prize (delivered post-paid right to your front door):
... choice of a book from NEWxSFC library

3rd place prize (delivered post-paid right to your front door):
... choice of a book from NEWxSFC library

---
The reigning NE.Wx ‘Season-Total’ Snowfall Forecasting Champ-een is MillVillWx
Last winter's 'Season-total' forecast summary ... verification ... and final results at our website here.

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

The Contest is open to all including amateur and professional forecasters; broadcasters with or without trained Seals; any and all weather-biz types and / or wanna-bees; wish-casters ... astrologers ... along with any other universally recognized classes of dreamers; Pollyannas or Cassandras ... registered Nostradamuses ... non-violent megalomaniacs ... woolly-bear caterpillars or their agents ... pest detectives ... ne.weather USENET veterans and lurkers ... riders on the StormVista ... refugees from AmericanWx ... US Weather survivors ... including self-imposed exiles from Eastern Wx ... and of course ... meteorologists.

In honor of USENET/s ne.weather patron saint Mr. Joseph Bartlo's final request (RIP); trolls ... goats ... hat3-lsiters ... and psests need not apply.

Thursday, October 28, 2021

Contest Status

Winter '21 / '22 - Snowfall Forecast Contests
23rd Annual 'Snow Storm' Snowfall Forecast Contest
Contest kicks-off when flakes start a'flyin'
Deadlines typically ~24 hours before a contest-worthy snowfall is expected to begin at a forecast station.

21st Annual 'Season-total' Snowfall Forecast Contest
Forecast window opens 01-NOV-21 
Deadline for entries:  30-NOV-21 @ 11:59 PM EST (01-DEC-21 ... 04:59 UTC )
Enter forecast at the Contest/s web site here.

---
Winter '20 / '21 - Snowfall Forecast Contests
22nd Annual 'Snow Storm' Snowfall Forecast Contest
FINAL results here

20th Annual 'Season-total' Snowfall Forecast Contest
FINAL results here

Saturday, April 17, 2021

Winter '20 / '21 - 22nd Annual 'Regular Season' Snowfall Forecast Contest: FINAL Results

DC (30-JAN-66)

After FOUR snow storm forecasting contests ... under the ‘two-thirds’ rule … forecasters who entered at least THREE forecasts are included in this season's FINAL standings.

Full table with all other error statistics at the Contest/s web site here (direct link).
Individual forecaster's storm statistics here (direct link).

Best Forecasts by Storm (lowest SUMSQ Error Z-Scores)

Top 10 Forecasts (Error statistic:  SUMSQ Z)

 

SUMSQ Error Z is the primary measure of forecaster skill (lower the better).
Accounts for the magnitude and distribution of the storm-total snowfall for all stations.

Top 10 Forecasts (Error statistic:  Total Absolute Error Z - TAE)

 

TAE Error Z is the secondary measure of forecaster skill (lower the better).
Accounts for the magnitude of snowfall forecast errors at each station.

Top 10 Forecasts (Error statistic:  RSQ Z) 


RSQ is a measure of the how well the 'forecast' snowfall captured the variability of the 'observed' snowfall (higher the better).

---
28 unique forecasters submitted a total of 2,036 station forecasts.
14 forecasters entered all 4 contests.
5 forecasters entered 3 contests.
8 forecasters entered 1 contest.

---
Hope to see y'all again next winter!

Tuesday, April 13, 2021

Snow chaos in Europe caused by melting sea-ice in the Arctic

"A 50% reduction in Arctic sea-ice cover has increased open-water and winter evaporation to fuel more extreme snowfall further [sic] south across Europe.

"When analyzing the long-term trends from 1979 onwards [sic], researchers found that [sic] for every square meter of winter sea-ice lost from the Barents Sea, there was a corresponding 70 kg increase in the evaporation, moisture, and snow falling over Europe."

Science Daily ... 

Monday, April 12, 2021

Winter '20 / '21 - 20th Annual 'Season-total' Snowfall Forecast Contest: FINAL Results

BOSOX Opening Day
(14-APR-53)

Congratulations to MillVilleWx for issuing the top forecast among forecasters in the 'Season-total' Snowfall Forecast Contest.

Climatology (Period-of-Record-Normal) followed by Consensus verified 1st and 2nd for the first time in the Contest's 20 year history.

Forecasters ranked descending by their Total Absolute Error (TAE)

RED ==> 4th Quartile
WHITE ==>  Interquartile range
BLUE ==> 1st Quartile 

The '%MPRV over PORN' metric indicates how well the forecast improved over climatology.
Skillful forecasts beat climatology.

---
Forecasters' stations having the lowest absolute error


---

Season-total snowfall from all stations (895") came in 4% below the Period-Of-Record Normal (929").

Winter '20 / '21 ranks 11th among the 17 Contest years since winter '04 / '05 ... the season when BGR and BGM were added to the station list.

---


Climo ... Observed ... Departure ... and Percent of Normal Snowfall
...
Forecaster verification table at the Contest web site (direct link)

http://www.newx-forecasts.com/
http://www.newx-forecasts.com/NEWxSFC_22/season-total/season_total_verification_2021.htm

 ---
Teleconnections


---
PRIZES
1st place prize (delivered post-paid right to MillVilleWx/s front door):
... pick of the litter from NEWxSFC/s library of meteorology and weather publications
... the august title 'Chief Season-total Snowfall Forecaster' for Winter '21 / '22
... a well-deserved place of honor with past Contest winners

2nd place prize (delivered post-paid right to kc2dux/s front door):
... second pick at NEWxSFC/s library of meteorology and weather publications

3rd place prize (delivered post-paid right to Shillelagh/s front door):
... third pick at NEWxSFC/s library of meteorology and weather publications

---
Prizes winners: please contact (newxsfc [at] comcast [dot] net) with a USPS address.

Sunday, April 11, 2021

Winter '20 / '21 - 'Season-total' Snowfall Forecast Contest: MAR Totals

VT - Stowe
(Marion Post Wolcott - 1940)

MAR-21 snowfall summary by forecast station.
Rank-ordered descending by percent of monthly period-of-record-normal (%MAR).

Green ==> 4th quartile
White ==> Inter-quartile range
Red ==> 1st quartile

---
MAR Forecast Station Highlights
Stations at or above normal monthly snowfall:  none

Biggest Losers
BDR .. MDT ...PHL ... ACY ...BWI ... DCA ... SBY ... RDU (not even a Trace)

---
Season-Total-to-Date
MAR P-O-R-N contributes 184" (20%) toward the season-total snowfall (D-J-F-M) of 929"
MAR-21 observed snowfall:  19" (90% below P-O-R-N; 2% of season-total snowfall)
Image courtesy NOHRSC @ http://www.nohrsc.noaa.gov/nsa/

Teleconnections
AO / NAO / PNA data
https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/daily.index.ascii

---
DEC totals
https://newxsfc.blogspot.com/2021/01/winter-20-21-season-total-snowfall.html
JAN totals
https://newxsfc.blogspot.com/2021/02/winter-20-21-season-total-snowfall.html
FEB totals
https://newxsfc.blogspot.com/2021/03/winter-20-21-season-total-snowfall.html

Tuesday, March 23, 2021

Explosive origins of 'secondary' ice and snow

"... "rime splintering" isn't nearly the whole story.
 
"The new results from the Arctic show ... larger supercooled water droplets, classified as drizzle, play a much more important role in producing secondary ice particles than commonly thought.

" "When an ice particle hits one of those drizzle drops, it triggers freezing, which first forms a solid ice shell around the drop," explained Fan Yang, a co-author on the paper. "Then, as the freezing moves inward, the pressure starts to build because water expands as it freezes. That pressure causes the drizzle drop to shatter, generating more ice particles."

"... drizzle freezing fragmentation can enhance ice particle concentrations in clouds by 10 to 100 times -- and even 1,000 on occasion!"

More ...