Tuesday, October 11, 2022
Friday, July 22, 2022
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 ...
Sunday, February 21, 2021
An Overview of Thundersnow
"The purpose of this article is to summarize our current understanding about this unusual wintertime event.
"This article describes where and when thundersnow happens, the ingredients needed to make thundersnow, and new efforts at understanding and forecasting the occurrence of thundersnow."
http://www.newx-forecasts.com/reference/An%20overview%20of%20thundersnow.PDF
Tuesday, November 03, 2020
Winter '20 / '21 - Eurasia Snow Cover: OCT
~ 11,000,000 SQ-KM
Under-performing all year ...
6% above P-O-RN (~10,320,000 SQ-KM)
9% above median (~10,080,000 SQ-KM)
Period-of-Record: 53 years
Rank: 19th
2nd lowest past 10 years
16 of past 20 years above P-O-R-N
OCT-19: ~12,700,000 SQ-KM
OCT-20: 14% less than last year
Eurasia snow analog years offer little if any guidance given this winter should have cool ENSO / PDO and QBO-W.
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P-O-RN ==> period-of-record normal
Data courtesy Rutgers University Global Snow Lab
http://climate.rutgers.edu/snowcover/index.php
Monday, December 02, 2019
Winter '19 / '20 - Snow Storm #1: Six Daily Snowfall Records Set - Storm Day 1
Station - New Record (Old Record; Year)
ALB - 13.3" (3.7"; 1969)
ORH - 8.9" (4.2"; 1917)
BDL - 4.6" (1.9"; 1925)
BOS - 1.2" (1"; 1940)
PVD - 1.6" (0.5"; 1907)
BDR - 0.7" (T; 2012)
ALB/s heaviest period of snow occurred SUN evening between 7 and 11 PM EST where up to ~2" / hr snowfall rate was reported.
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KALB 020351Z 01006KT 1/4SM R01/4500V6000FT +SN FZFG VV006 M03/M05 A2972 RMK AO2 SLP069 SNINCR 1/12 P0015 T10281050
KALB 020251Z COR 36007KT 1/4SM R01/2800V3500FT +SN VV005 M03/M06 A2973 RMK AO2 SLP072 SNINCR 1/11 P0024 60052 T10281056 56027
KALB 020159Z 01007KT 1/4SM R01/5500VP6000FT +SN VV008 M03/M06 A2974 RMK AO2 P0010 T10331061
KALB 020151Z 02008KT 1/8SM R01/5500VP6000FT +SN VV007 M03/M06 A2975 RMK AO2 SFC VIS 1/4 SLP077 SNINCR 2/10 P0008 T10331061
KALB 020051Z 02007KT 1/8SM R01/3000V5000FT +SN FZFG VV005 M04/M06 A2979 RMK AO2 SFC VIS 1/4 SLP092 SNINCR 2/8 P0020 T10391061
KALB 012351Z COR 02007KT 1/4SM R01/3500V5500FT +SN VV006 M04/M07 A2981 RMK AO2 SLP099 SNINCR 1/6 4/006 P0008 60051 T10391067 11039 21056 58015
Friday, November 01, 2019
Winter '19 / '20 - Eurasia/s OCT Snow Advancement
UPDATE (31-OCT-19)
Dr. Cohen via Tweeter ..."... the snow cover advance index came in at +0.6.
"This does suggest a negative winter Arctic Oscillation and upcoming #PolarVortex disruption."
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UPDATE (29-OCT-19)
Dr. Cohen via Tweeter ... "October SCE will likely be more than one standard deviation above normal.
"My research shows this favors colder winter temperatures across the N Hemisphere mid-latitudes including East US (sic)"
Saturday, January 26, 2019
Winter '18 / '19 - We're the Heckawi
- High amplitude ridge to the West.
- Full latitude trof in the East.
- Sub-tropical jet in a split flow
- Split stratospheric polar vortex with the stronger daughter vortice over eastern North America to boot.
So WTF?
If times be so good ... then bro ... where's my fookin' snow?
Us snow crows nesting here in the eastern half of the mid-Atlantic will most often get our winter wx fix when ...
1) LOW pressure spawns over the Gulf of Mexico & proceeds to crawl slowly up the east coast and
2) A strong Arctic HIGH (1040-ish mb; 30.70" Hg) parks herself over Maine and
3) The wavelength between the Ridge-West / Trof-East pattern contracts i.e., becomes shorter. As the wavelength shortens ... storms spin-up (intensify) the same way ice skaters spin-up when when they draw their arms inward (see Conservation of Angular Momentum)
Wicked winter wx 'round here has always been a tricky combination of having a deep layer of Arctic / Polar air in place ... ready to interact with moisture surging from the south.
The current long wave flow regime is certainly delivering in spades with the cold air component; however ... it's coming on too strong ... in effect suppressing moisture from coming north.
FWIW ... the world-wide federation of numerical weather prediction (NWP) models have been tilting toward an adjustment to the long wave pattern in mid-range; a shuffling of the deck so to speak (more like re-setting the tumblers in a one-armed bandit).
Climatologically for snow crows ... FEB is our time 'round here ... especially the period either side of mid-month. Whether the coming pattern change produces the weather we be waiting for is anyone's guess.
Even though long-range NWP offers us nothing more than possible outcomes ... outcomes more often fantasy than fact ... it's one of those j'ne sais WTF reasons why we all be Weather Weenies.
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Sunday, November 11, 2018
Winter '18 / '19 - Eurasia Snow Cover: OCT
Last year: ~12,052,000 km2
1% above 53-year P-O-R-N (~10,260,000 km2)
Rank: 22nd
Lowest in eight years
Seven of the last ten years above normal
Analog years for winter '18 / '19
Rank Winter ENSO
1 82-83 W+
2 00-01 C-
3 69-70 W-
4 01-02 nada-
5 84-85 C
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Data courtesy Rutgers University Global Snow Lab
http://climate.rutgers.edu/snowcover/index.php
Saturday, November 10, 2018
Winter '18 / '19 - Gains and Losses: 10-NOV-18
Minor snow event over extreme northern portions of the forecast area today forced by a lifting 5H LOW centered @12z over SE Canada and 2ndry SFC LOW occluding INVOF the Gulf of ME.
Gains: Blue
Losses: Reds
Saturday, April 07, 2018
Winter '17 / '18 - 'Season-total' Snowfall Forecast Contest: Month of MAX Snowfall
![]() |
BOS Red Sox Opening Day 14-APR-53 |
DEC - 0
JAN - 7 (CAR ... PVD ... ACY ... SBY ... RIC ... ORF ... RDU)
FEB - 0
MAR - 18 (all the rest)
Leaving aside for the moment the fact FEB has 28 days and all other snow-season months have 31 ... 72% of our forecast stations observed their highest monthly snowfall total in MAR -- yes MAR -- this season.
Climo finds most of the contest/s forecast stations (14) observe their MAX monthly snowfall in JAN. MAX monthly snowfall happens in FEB at 10 of the remaining 11 stations with only BDL having its greatest monthly climo snowfall in DEC.
No station/s monthly snowfall climo reached its maxim in MAR which makes the winter '17 / '18 all the more remarkable.
Wednesday, March 14, 2018
Sunday, November 05, 2017
Winter '17 / '18 - Eurasia Snow Cover - OCT - Snow Advance Index (SAI)
Snow Crow suicide watch now in effect.
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AER reports a statistically significant correlation between their 'winter severity index' and how quickly Eurasian snow cover advances during OCT.
They define the 'winter severity index' by the state of the North Atlantic Oscillation / Arctic Oscillation (N/AO) and interpret it as an indicator of 'high latitude' blocking potential during D-J-F.
More blocking.
More winter.
More better.
Here's the model ...
"When snow cover advances rapidly (slowly) across Eurasia in October, this is an indication that the upcoming winter will be more severe (milder) for the Eastern US [sic], Europe and East Asia.
Study period seems surprisingly short seeing how contiguous monthly Eurasian snow cover data begins in 1970. How well does the SAI correlate with the N/AO index prior to 1988?
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Snow Advance Index (SAI) backgrounder from AER here.
Earlier Eurasia snow cover posts here.
Sunday, October 29, 2017
Winter '17 / '18 - Eurasia Snow Cover - OCT Preview
Cohen projecting above normal Eurasia snow cover for OCT ahead of an expected weak La Nina winter (D-J-F).
Nine previous weak La Nina winters ... including the famed 1995 - 1996 season ... have been observed during the Eurasia snow cover period of record (1967 - 2016). Only two NEWxSFC forecast stations -- BGM and ALB -- have a statistically significant correlation between season-total snowfall and above normal Eurasia snow cover.
Related:
Winter '17 / '18 - Correlation of Eurasia's OCT Snow Cover and Season-total Snowfall in NE and M-A Regions
Winter '17 / '18 - First Contact
Boone ... NC (3146' MSL)
KTNB 291615Z AUTO 30013G25KT 4SM -SN SCT008 BKN014 BKN020 02/01
Richlands ... VA (2653' MSL)
KJFZ 291555Z AUTO 32004KT 3SM -SN SCT004 BKN007 OVC014 00/00 A2972 RMK AO2 T00011001
Wise county ... VA (2684' MSL)
KLNP 291555Z AUTO 31004KT 1 1/2SM -SN OVC003 00/00
Hot Springs ... VA (3793' MSL)
KHSP 291555Z AUTO 29014KT M1/4SM -SN OVC003 02/02
Bluefield ... WV (2856' MSL)
KBLF 291552Z AUTO 31008KT 1 3/4SM -SN BR BKN006 OVC012 00/M01
Bedford county ... PA (1161' MSL)
KHMZ 291555Z AUTO 32006KT 5SM -SN OVC010 07/06
Thursday, January 12, 2017
Winter '16 / '17 - Snow Storm #2 - Another NWP and Public Forecast Failure
![]() |
NYC |
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
---
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.
Friday, December 30, 2016
Winter '16 / '17 - Snow Storm #1: New Daily Record Snowfall @ KCON
SFC: 00Z FRI ... 30-DEC-16 |
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
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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
Saturday, December 24, 2016
Winter '66 / '67 - White Christmas Eve
Classic Miller 'A'
Lived this one in SNJ :)
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23-DEC
- Cyclogenesis ovr LA
- Rapid movement east along stalled Arctic boundary INVOF GOM states
- Full latitude trof just east of MS river
SFC: 23-DEC-66 |
24 - DEC
- LOW on the SC coast
- Light pre-dawn snow begins over southern mid-Atlantic
+TSSN (thunder snow) @ PHL and ILG between 4 and 8 PM
SFC: 24-DEC-66 |
LOW occludes ovr Cape Cod
Select mid-Atlantic storm-total snowfall
PHL: 12.6" (1.09 liquid; 11.5:1 SLR)
ACY: 6.5"
BWI: 8.4"
ILG: 12.4"
SFC: 25-DEC-66 |
5H: 23-DEC-66 |
5H: 25-DEC-66 |