The Retro Heat Ridge

Today/s D+10 ECMWF and GooFuS progs have kissed and made up following their recent spate of dissonant solns regarding the evolution of a La Nina-style heat-ridge parked over the SW ATL Ocean. Also note the hi-latitude block indicative of a strong negative phase of the Arctic Oscillation.


Should be good and chilly in the E and with the full latitude trof...good baroclinicity and opportunities for coastal storms.



There/s been talk of late in some 'well respected' quarters about a mid-month return to warmth -- as in 'abnormally warm' warmth -- when the full fx of La Nina become firmly established. It/s hard to see where that/s indicated or even remotely suggested if the D+10 and D+15 GFS ensemble means are to be believed.

Folklore - December

A green Christmas; a white Easter.

If there's thunder during Christmas week...
The Winter will be anything but meek.

The nearer the New Moon to Christmas Day...the harder the Winter.

If Christmas day be bright and clear
There’ll be two winters in the year.

Thunder in December presages fine weather.

Like in December like all the year long.

Winter '07 / '08 - What Is It About Week One?

Is there something special about the first week in December or is it merely a case of undue importance being placed on more recent events that makes it seem that way?

Questions about Week One/s seemingly 'stormy nature' have been raised b/c GooFuS LR solutions...as they/re wont to do now that winter grand entrance is waiting in the wings...have again begun dangling shiny objects before our eyes.

The first week of DEC has been a good period for snow storms in the NE the past half-decade. The table shows the number of contest stations reporting snow by year and day of week.

The only other period since 1948 where the first week of DEC was that active - defined as number of stations affected - was between 1954 and 1958.

CAR and BGM have the best chance (20 - 30%) of a measurable snowfall on any day during Week One. BGR has a 20% probability on three of the seven days.

As November 21st...so the winter

If that/s the case...then this winter will hew closely to the CW for 'above normal' temperatures...especially in SNE and the M-A.

A few stations in the NE were below normal yesterday. BGR - PWM - BOS - BDL - CON had departures from -1 to -3°F...due in large part to low overcast and light rain.

Elsewhere...
+1 to +4°F: CAR - BTV - PVD - BDR - ISP - JFK - EWR
+7 to +10°F: ALB - ABE - MDT - PHL
+12 to +20°: ACY - SBY - RIC - RDU - IAD - DCA - BWI

IAD took top honors at +20°F.

ECHAM/s October Outlook - Verification

Appears to be a miss grande.

In the ECHAM image...red (blue) indicates negative (positive) pressure anomalies.

Cooler (warmer) colors in the PSD image are negative (positive) pressure anomalies.

Trends in NHEMI Snow Cover

Plot of CPC/s NH snow area data...as of the end of SEP.

The black line near the chart/s center is the yearly average from the start of the period-of-record.

In 1977...the 5-year moving average snow area was 25.3 x 10^6 km^2. In 2006...the 5-year moving average snow area was 24.1 x 10^6 km^2...a change of ~1.2 million square kilometers.

The data generally show modest year-to-year variability...the exception being OCT...which has slowly increased by 6.7 million square kilometers since 1988.

WSI/s Foundering Winter '07 / '08 Forecast

"Typically, in the eastern U.S., La Nina means a warm October and a cold
December," Crawford said in the press release. But ocean temperatures in
the northern Pacific indicate a colder October in the Northeast, he said."

WSI got off to a slow start with its winter LR forecast issued in SEP calling for a 'below normal' OCT in the Northeast. OCT temperatures in the NE and mid-Atlantic came in 7 - 9°F above normal. Crawford went on to predict 'above normal' temperatures in NOV...but that call is going up in flames...as well.

WSI stuck to its 'warmer than normal' NOV forecast in its late OCT update...which also called for DEC to be 'below normal' and JAN 'above normal.'

The latest WSI forecast...issued a week ago...continues to expect DEC to be 'below normal' and JAN 'above normal.' The FEB forecast...appearing for the first time...is 'above normal.'

Beating CLIMO demonstrates forecast skill. The shorter the lead time the better chance there is to getting it right. So far this year...these guys got nothing.

Swiss Alps - Biggest Snowfall in 55 Years

Starved of snow the past few years...the Swiss Alps are making up for lost time this month. Up to 120 cm (~4') have been observed during the past ten days...with 62 cm (~2') falling in one 24-hour period in eastern Switzerland (elev. 1,560 m...~5200').

More...

Snowstorm Contest Season

The season starts when the storms start and continues until it/s obvious winter is over. The season runs normally from early December through the middle of March; however, IIRC, the earliest contest storm occurred in late November and the latest storm was in April. Most years there have been ten contest storms.

Not every snowstorm that affects the forecast area will trigger a contest. The criteria used to decide whether a storm is contest-worthy are loosely defined as one that/s expected to:

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

Visit the website for more information about how to enter a forecast and how forecasts are verified and scored.

Base Leg...Turning Final - Part II

In addition to the 500 mb time-series of 'MEI-preferred' La Nina years presented in a previous post...these examples also generally depict much different flow regimes than are presently observed...altho '75 is ballpark-ish.

1950...1955...1973...1975
500 mb time-series for early NOV from prior La Nina years.

Will have to look into the winter of '75 / '76 to see how the forecast area was treated.

Bump: Winter '07 / '08 Season-total Snowfall Forecast Contest

Visit NEWxSFC/s web site to enter. Follow the link to 'Enter Season-total Forecast.'

Deadline: 30 November 2007 @ 11:59 PM EST

Details

Base Leg...Turning Final

Climo...2007...1988...1970
Time series of SLP CLIMO...current wx...and 'preferred' MEI-analog Novembers.

First half of NOV 2007 SLPs mimic CLIMO/s low pressure signature over E-PAC. Both 'preferred' MEI-based 'La Nina' analog years are similar but they show a lower correlation with 2007...although '70 leans a bit more toward current conditions at end of period over E-PAC.

Current SLP time-series raises a measure of doubt about this year/s developing consensus for the "warm 'n dry" version of Nina-style winters.

Even stronger evidence of how useless analog forecasting can be...can be seen at 500 mb...


500 mb Climo...2007...1988...1970

Early winter at least...lookin/ more-n-more normal as December approaches.

Heresy in Harrisburg

"...colder than average and snowier than average..."

CBS-affiliate WHP-21/s wx heretic Tom Russell jumps into the winter forecast fray with both boots by taking the contrarian view.

His is the perennial favorite...'cold 'n snowy.' What/s not to like about that?

Bastardi Bold

"...(F)orecaster Joe Bastardi of AccuWeather on Tuesday reiterated his forecast for a warm winter in the Northeast, although the weather has been running colder than normal since Nov. 1. In an interview with MarketWatch, he said it will stay cold until the middle of December and then run about four degrees above normal in the northeastern U.S."

Rather BOLD prediction given December/s temperature departures during past -ENSO events. Much of NE has been one-half to one standard deviation below normal...the same being true for large portions of the M-A.

Nieves de La Nina

Take your pick.



D-J-F snowfall maps for seven La Nina Years Selected by Climate Predition Center using ocean criteria (1942-43...1950-51...1955-56...1970-71...1973-74...1975-76...1988-89)

Make your own.

November/s ENSO Anomaly Forecast

Latest consensus ensemble mean forecast for ENSO Region 3.4 this MET winter (D-J-F) is ~-1.8°C...indicating 'strong' La Nina conditions are expected. Five of the six latest model runs are less than or equal to the forecast ensemble mean. Forecast values have delined each month since May (-0.6°C). Last month/s forecast was -1.6°C.