Winter '20 / '21 - Snow Storm # 1: RAW Forecasts

here ...

Winter '20 / '21 - Snow Storm #1: Call for Forecasts!

NYC
19-DEC-45

Rousing start to NEWx/s 22nd Annual 'Snow Storm' Forecasting Contest!

Rapidly deepening coastal LOW ... cold air damming ... and a potent fast-moving mid-level short wave combine mid-week for a rare 'contest-worthy' event in DEC.

Everyone is welcome to enter a forecast.

You also get the chance to see how well your forecast stacks up against NWS Eastern Region Weather Forecast Offices.  Turns out they/ve been fairly easy to beat!

Forecast element: each station/s storm-total snowfall

Deadline for entries: 10:00 PM EST ... TUE ... 15-DEC-20
Verification begins: 12:01 AM EST ... WED ... 16-DEC-20
Verification ends: 11:59 PM EST on the day when accumulating flakes stop flyin'.
---
Enter your forecast at the NEWxSFC/s home page at http://www.newx-forecasts.com/
Follow the top-of-page link from 'Enter Storm Forecast.'

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).

The snowfall forecasting contest for Snow Storm #1 may be cancelled prior to the deadline if at least six-to-eight stations are unlikely to observe at least a 4" storm-total snowfall.

---
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.

Winter '20 / '21 - North Atlantic Oscillation (NAO): Analog Composites of 500 mb Height and 2-meter Temperature Anomalies ... as of NOV-20

 NOV:  +2.54 🔥🔥🔥
Only two other NOVs had a higher index ('78 +3.04; '93 +2.56)

TL;DR  This winter/s average NAO index expected to be positive ( >0 ).

---
Analogs and weights for composites:
'03 / '04 (1)
'99 / '00 (1)
'91 / '92 (1)
'93 / '94 (1)
'15 / '16 (1)

Each analog's average NAO for D-J-F was > 0.

NAO/s analog winters are assessed against the upcoming winter/s expected states of:
- ENSO (MEI moderate - trending weak La Nina)
- QBO-W < 10
- PDO (cool)

We removed '03 / '04 ... '91 / '92 ... and '15 / '16 from further consideration b/c they were +ENSO winters.  Winter '93 / '94 had QBO-E so it too drops out.

Winter '99 / '00 survives with its weak La Nina --- QBO-W < 10 ... and a cool PDO.

Read more »

Winter '20 / '21 - Snow Storm #1: Contest-worthy or What?

The winter/s first nor'easter has moved into the Canadian Maritimes but not before laying down an impressive stripe of early season snowfall across northern portions of the forecast area.

On occasion the prestorm NWP output and expert guidance suggest a snowstorm will not be contest-worthy only to turn out to have been a contender.

Did NEWxSFC miss the call on this one?

Not every snowstorm expected to affect the forecast area will trigger a contest. The criteria applied to decide whether a storm is contest-worthy are loosely defined as one expected to:

- Affect at least six to eight forecast stations ...
- Produce more than a nuisance snowfall (>= 4") ...
- Be well progged by NWP ~36 to 48 hours before snow is observed at any one station.

So ... did the weekend storm rise to the occasion or fall short as expected?

Read more »

Winter '20 / '21 - 20th Annual 'Season-total' Snowfall Forecasting Contest: The Forecasts!

Forecasters:  22

Forecasters also compete against the Period-of-Record-Normal (P-O-R-N) and Consensus.
Forecaster table ranked by season-total snowfall

BLUE - <= 25th percentile
RED - >= 75th percentile
ORANGE - Chief 'Season-total' Forecaster
P-O-R-N - period of record normal
CONSENSUS - median station forecasts

Some forecasts have decimal values and are recorded for verification purposes as such; however ... rounding was applied for display purposes only.

Read more »

Winter '20 / '21 - 20th 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/re lucky .... an endless parade of 'Miller A' LOWs raking the eastern seaboard.

NE.Wx/s 20th 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-20 through 31-MAR-21

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

Verification:
NWS climate reports (CLM or CF6)

Low. Score. Wins.

Deadline for entries: MON ... 30-NOV-20 @ 11:59 PM EST (01-DEC-20 @ 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 your last entry gets verified.

Read more »

Winter '20 / '21 - Temperature and Precipitation Characteristics for CONUS During La Niña Winters Since 1950

No surprise ... all cool ENSO winters are not created equal.
Some are weak or moderate or strong.
Some associated with QBO-East and some with QBO-West.

During the analysis period between 1950 and 2012 ... most La Niña winters occurred with QBO-E.
Of the winters depicted below ... 15 of the 21 (~71%) were QBO-E.

QBO for winter '20 / '21 will be west.
Probably a moderate La Niña through mid-winter.

 

Read more »

Winter '20 / '21 - Season-total Snowfall Anomalies During La Nina Winters

 Taken at face value M-A snow crows suffer the most ...

The NOAA analysis of Rutgers' Global Snow Lab data does not account for the different categories of La Nina episodes (weak ... moderate ... strong) and it has an end date of 12 years ago.  Since then ... there have been three La Nina winters - '10 / '11 ... '11 / '12 ... and '17 / '18.

Relative to season-total snowfall at 28 NEWxSFC stations ...
'10 / '11 - well above average (moderate La Nina)
'11 / '12 - well  below average (weak La Nina)
'17 / '18 - above average (weak La Nina)

 Image courtesy NOAA Climate

Winter '20 / '21 - Outlooks

Thread updated periodically as new outlooks and forecasts become available from a variety of credible sources.

---

CDC - NOV ...

Read more »

Winter '20 / '21 - Multivariate ENSO Index (MEI): Analog Composites of 500 mb Height and 2-meter Temperature Anomalies ... as of SEP / OCT-20

 Analogs and weights for composites:
'70 / '71 (24)
'07 / '08 (5)
'88 / '89 (1)
'95 / '96 (1)
'64 / '65 (1)

 We assess the MEI analog winters with the upcoming winter/s expected states of ENSO (moderate-to-strong La Nina) ... QBO-W ... and (cool) PDO.

Seeing how statistical and dynamic models predict a moderate La Nina this winter ... '64 / '65 and '95 / '96 don/t match the expectation which leaves '70 / '71 ... '07 / '08 ... and '88 / '89 as problem children.

Two concerns about the utility of winters '70 / '71 ... '07 / '08 ... and '88 / '89 ...
Two analogs depict a late winter La Nina intensification (vice expected fade) ... all three had QBO - E contrary to this winter's QBO-W ... and sadly no composites nor forecast guidance. 

MEI analog data table (unranked)
Analog statistic (not shown):  sum of squared errors

The MEI is based on five variables:
Sea level pressure (SLP)
Sea surface temperature (SST)
Surface zonal winds (U)
Surface meridional winds (V)
Outgoing Longwave Radiation (OLR)