How Much for Philly? - Scourge of Conventional Wisdom

A question for the ages.

John Bolaris...meteorologist for PHL/s FOX-TV affillite...issued his Winter '08 / '09 outlook today.

"...December...expect below normal temperatures with above normal snowfall.
...January...above normal temperatures with below normal snowfall.
February and March could be vicious, with below normal temperatures with (sic) above normal snowfall."

Bottom line: group think.

What is it with these TV-WX guys (gals) anyway? Begs the question about needing so many 'forecasters' when they all essentially parrot the same narrative.

Of particular note...JB/s unsupported claim that "(a) negative NAO means more snow; a positive NAO means less snow."

An analysis of PHL/s daily snowfall events since 1950 - a shortened period-of-record necessitated by data availability for AO...NAO...and PNA - finds there/s a greater probability for any amount of snow when NAO is positive and AO is negative.

The only time -NAO is the preferred mode over +NAO is for events that produce 6" to almost 9" snowfalls.

There are equal chances that a +NAO or -NAO drops at least 9" but less than a foot.

By a 2:1 margin...+NAO and AO of either sign is the favored mode for snowfalls of 12" or more.

It/s pretty obvious someone didn/t get the memo about NAO/s effect of snowfall in Philly.

Snowfall data courtesy Utah University Climate Center.

WSI - NOV Update - Winter '08 / '09

From PRWEB...

"WSI expects the upcoming three-month period to average colder than normal across the northern and western US, with above-normal temperatures confined to the Southeast.

In the NE...
DEC: colder than normal

"The WSI December forecast indicates colder-than-normal temperatures in key Northeast and North Central regions; much colder-than-normal temperatures are expected in New York, New England, and eastern portions of PJM.

JAN: warmer than normal
FEB: colder than normal

"According to WSI seasonal forecaster Dr. Todd Crawford, "The current cold pattern in the northeastern US should persist through at least the first half of December. A temporary transition to a mild pattern should occur from January into early February, before the pattern reverts back to a much colder regime during the last weeks of winter. The current configuration of the very cold North Pacific ocean temperatures and wind patterns in the tropical Pacific should result in a cold winter in the Northwest and a warm winter in the Southeast. The Northeast will likely experience more subseasonal variability than other regions this winter.""

WSI/s OCT outlook here.

How Often is Frequently?

Out of necessity...weather observations and forecasts apply a degree of smoothing to the chaos known as the atmosphere in order convey a sense of the 'prevailing' conditions at any one time.

The answer to tonight/s musical question is informed less by the definition of 'frequently' than by its antonyms....

Never
Rarely
Seldom
Occasionally
Uncommonly

...and by its usage in axioms such as "more often than not."

"Nearly"..."several times"...and "almost" just don/t measure up. Scientific phenomena...such as hurricanes...severe wx...and blizzards...are described and categorized according to a well-defined classification scheme.

Nobody ever said this was horseshoes.

Blizzard Defined

"A blizzard means that the following conditions are expected to prevail for a period of 3 hours or longer.

(1) Sustained wind or frequent gusts to 35 miles an hour or greater;

and
(2) considerable falling and/or blowing snow (i.e., reducing visibility frequently to less than 1/4 mile).

Although there is no set temperature requirement for blizzard conditions, the life-threatening nature of the low temperatures in combination with the other hazardous conditions of wind, snow, and poor visibility increases dramatically when the temperature falls below 20°F. "

WSOM

Let/s be careful out there this winter. Heavy snowfall does not a blizzard make. Blizzards are meso-beta scale (20 - 200 km) severe winter wx wind storms where visibility is restricted for at least three (3) hours.

La Nina is Back

So sayeth EBerry...

"...tropical forcing does have a MJO component to it, projecting ~1.5 sigma in octant 5...~2 sigma in octant 4 with the interannual component left in. There has been eastward propagation of ~5-6 m/s along the equator for the past couple of weeks."
[...]
"Global relative AAM (plots updated through 20 November) is ~1 standard deviation (1 AMU) above the R1 data climatology, working with ~ plus 40 Hadley positive global tendency."
[...]
"At times, during the last several weeks, there have been well defined projections onto a positive phase of the Branstator (2002) circumglobal teleconnection (anomalous midlatitude ridges)."

Who among us could argue anything but?

Cold Start to December

1052 HIGH coming into CONUS from Siberia for first week of meteorological winter as the AO experiences a bit of its version of the China Syndrome...free-falling to six (6) standard deviations below its mean.

Arctic Oscillation Market Collapse

Unless there/s been a big mistake in reporting the data...the AO took a steep...67% nose-dive today...as the index fell 1.456 points.

Yesterday/s AO index value had soared to 2.187.... creeping toward outlier territory.

Today...there must have been a strong 'sell' signal in the global teleconnection markets...b/c the index lost 2/3 of its value as it crashed-landed @ 0.730!

Positive AO values trend to keep Arctic air bottled up at hi-latitudes. When the AO lurks below zero...the cold air often escapes into the Lower 48.

By the looks of it...AO is heading downtown for an extended stay.

CPC Outlook - Update - Winter '08 / '09

CPC/s latest 90-day outlook for NEWxSFC/s forecast area this coming meteorological winter (D-J-F) continues with its 'equal chances' theme from last month/s outlook.

Equal chances? Is that the best they can do?

In other words...the odds are 50 / 50. The same odds you have when flipping a fair coin. For this we pay how much?

Probability theory considers 50% as a 'good' chance of getting a desired outcome...so there/s no reason...yet...to abandon all hope for a memorable season.

The Climate Prediction Center...located in the World Weather Building...SE of Washington...DC...uses many tools to develop the 90-day outlook. CPC forecasters...or maybe they/re known as 'outlookers' inside the WWB...consider ENSO...climatological departures from persistence trends in 10-year temperature and 15-year precipitation periods...Madden-Julian Oscillation voodoo(MJO)...teleconnection indexes such as the North Atlantic Oscillation (NAO)...Pacific-North American (PNA)...and Pacific Decadal Oscillation (PDO)...along with current soil moisture anomalies...razz-ma-tazz statistical tools...and last but not least...the dynamic Climate Forecast System (CFS) model.

ENSO is seen currently as neutral by CPC and it/s expected to remain that way throughout the upcoming winter...even though...NCEP/s own SST forecasts maintain slightly negative anomalies in Nino 3.4.

A much more detailed forecast discussion from the CPC is here.

AO and NAO - NHEMI Air Temperature Variability

Winter Northern Hemisphere surface air temperature variability
associated with the Arctic Oscillation and North Atlantic Oscillation

"The paper shows that the NAO and the AO have different impacts on winter NH (surafce air temperature) SAT. The variability of other atmospheric variables related to the AO and the NAO is discussed."

A bit wonkish...but a still a good read.

GEOPHYSICAL RESEARCH LETTERS, VOL. 32
Dongxiao Wang,1 Chunzai Wang,2 Xiaoyi Yang,1 and Jian Lu3
Published 20 August 2005.

AER - Winter Outlook '08 / '09

sCAST modeler Judah Cohen of AER expects 'warm' temperatures in the east this winter. Cohen mentions the below normal snow cover in Siberia as a contributing factor in this year/s forecast.

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