By John Ruggiano

October 1, 2009

From December 1, 2009 Through March 31, 2010 (Dec, Jan, Feb, and Mar)

A Weak to Moderate El Nino Signal, along with an active STJ (Subtropical Jet), will bring stormy conditions across much of the Southern US, & a good part of the Eastern 1/3rd of the Nation.

This upcoming 2009-2010 winter season, will be quite a switch from the last 2 winter seasons. For the most part, during last year the heaviest snow and coldest temperatures were concentrated over the Northern 1/3 rd of the country. This was mainly due too, weak to moderate La Nina conditions. This year things will change, as the main storm track will likely be much further south, as weak to moderate El Nino conditions prevail. In addition, a more active subtropical jet can be expected.

The mean storm track for the 2009-2010 Winter Season will extend from the Southern Rockies, eastward to the SE States, and then mainly along and east of the Apps, through the M/A States and SE New England. Overrunning events will be quite common from the Tenn/Ohio Valley into the M/A States. This will also raise the flag for possible Moderate to Severe Ice Storms, from the Southern Plains into the interior SE, and lower M/A States. This is something to be aware of this winter season. I expect plenty of this for the month of January into mid February.

Clipper type systems and Strong cold fronts riding with the Polar Jet (P/J) and Arctic Jet (A/J) will be less common, than the last couple of years. Sure, we’ll still have a fair amount of activity with the Northern branch, but most of the energy this year will come from the STJ and effects of the ENSO El Nino, with more southern storm systems. Some of these Southern systems will get a chance to phase with the Northern branch energy, so I expect several good east coast storms, mainly in January and February !

This year I’m forecasting “Above Normal Snowfall” to be concentrated in two general areas: One area will be over the Southern Rockies into the Southern/Central Plains. The second area will be from the Tenn/Ohio Valley’s, The interior SE, all of the M/A States, and into SE New England. All other areas will be “Near Normal Snowfall”, with the exception of the NW PAC, The Northern Rockies, and Northern Plains, were I’m forecasting “Below Normal Snowfall”. (See Snowfall Map)

The NAO (North Atlantic Oscillation) And other key Teleconnections.

The NAO/AO couplet that I mentioned in my prelim winter forecast back in mid August, continue to flow in very similar wavelengths, and I expect this couplet to continue into the fall and winter months. During the Fall months, I expect both the NAO and AO to be mainly near neutral overall, then continue to maintain a near Neutral Index for much of the winter season. But at the specified times I’ve listed below, mainly during January and February, the NAO/AO couplet will go NEG. The best chance for a slightly POS NAO index will come in both December and March.

Click to enlarge:

This NAO/AO couplet will be one of the key players this winter for the Southern and Eastern US. Unlike the past several winter’s the NAO has been mainly in a Neutral to Positive state, with the exception of last year, being more Neutral to slightly NEG, as I forecasted this quite well last year. I’ve also commented there’s some strong indications that a long term switch to a Negative NAO decadal cycle, is starting to take place.

These factors I’ve mentioned, along with a more favorable ENSO State, will allow for “Above Normal Snowfall”, and “Near to Below Normal Temps” to occur for much of The M/A Region and the SE States. The only exception being, Northern New England, and Upper Midwest Region, where “Near to Slightly Above Normal Temps”, and “Near Normal Snowfall” can be expected.

Here’s my forecast for the NAO signal, with Monthly breakdowns.Dec, Jan, Feb, and Mar)

December: Neutral to Slightly POS.

January: Neutral to Slightly NEG.

February: Neutral to NEG.

March: Neutral to POS

During December I expect variable conditions with the signal being mainly neutral to slightly POS. Both January and February is where I’m forecasting the coldest and stormiest (snowiest) month’s to occur. Both months will be mainly Neutral to NEG. Overall, temps will be “Slightly Below Avg.” during January, and “Below Avg. during February, with a continued active pattern, producing both Rain and Snow, along with some big Ice threats in the areas I’ve outlined earlier. During March, a switch to a POS NAO signal will occur, and close out the 2009-2010 winter season, with Slightly Milder than normal temps, with a less active and drier pattern.

With a Weak to Moderate El Nino Signal, the PNA signal will likely be Neutral to POS for much of the winter. This will allow for more Ridging over the NW PAC States into the Northern Rockies and Plains states, so expect milder and drier conditions for much of the winter in these areas.

The AO (Arctic Oscillation) will be Neutral to at times NEG, this will allow for a rather active Northern and Arctic branch to evolve and nose into the Central and Eastern US, causing some phasing and overrunning to occur from the Mid section east to the M/A coast.

So, Will the Delaware Valley & The M/A States see a big snowstorm or two this winter ? I’ll have to say: YES

My best estimated time-frame for any Snowstorms of 6″ or greater, will be between January 5th and 15th, and an even better chance in late January and early February, between Jan 25th and February 15th. During both of these time frames, the NAO signal will be going into a NEG phase. With an active sub-tropical jet stream and a mean Southern storm track, It’s during these time-frames that Miller A, and East coast storms are most likely to develop.

So once again the best chance for a SECS/MECS, for the M/A and NE States, will be between Jan 5th-15th and also between Jan 25th-Feb 15th. In the M/A States, both December and March we’ll only see minor snow events for the I-95 Corridor from RIC to NYC, but The interior M/A States, SE New England and Boston, will see good snow events during December and March.


In this segment I’ve attached all my maps, to summarize my overall Winter Outlook. Please see the (4) maps below: Temperature, Precipitation, Snowfall, and Overall Storm Track’s. These maps best illustrate my outlook for the month’s of: December, January, February, and March.

These maps indicate the overall Anomalies for both “Temperatures” and “Precipitation” for the 4 month period.

In addition I have included a “Total Snowfall Map”, relative to normal and a “Mean Storm Tracks Map”, to show the type of pattern I‘m forecasting for the winter months.

TEMPERATURE MAP: (Click map to enlarge)

PRECIPITATION MAP: (Click map to enlarge)

SNOWFALL MAP: (Click map to enlarge)

MAIN STORM TRACK MAP: (Click map to enlarge)

My Forecast for Philadelphia, PA. (PHL)
(Including extreme SE PA, Interior Southern NJ, and Northern DE.)
Dec 1, 2008 – Mar 31, 2009 (Dec, Jan, Feb, and Mar)

Mean Temperature: -0.5 F
(Slightly Below Avg.)

Mean Temp Range: 0.0 to -2.0 F

(Near to Slightly Below Avg)

Total Snowfall Range: 26″ to 32″
(Above Normal)

Target Snowfall Prediction: 29″

Total Precipitation: Above Normal

The Monthly Breakdown for PHL (Philadelphia, PA:

December: + 1.0 F
Mean Temp Range: 0.0 to +2.0 (Near to Slightly Above Avg.)
Snowfall: 2″ to 4″ or (Near Avg.)

January: – 1.5 F
Mean Temp Range: -1.0 to -3.0 (Slightly Below Above)
Snowfall: 10″ to 12″ or (Above Avg.)

February: – 3.0 F
Mean Temp Range: -2.0 to -4.0 (Below Above)
Snowfall: 10″ to 12″ or (Above Avg.)

March: + 1.5 F
Mean Temp Range: +1.0 to +3.0 (Slightly Above Avg.)
Snowfall: 2″ to 4″ or (Near Avg.)

Selected I-95 Corridor Cities:
(Dec, Jan, Feb, and Mar)

BOS (Boston, MA)
Temps: 0.0 to -2.0 F (Near to Slightly Below Avg.)
Total Snowfall: 44″ to 50″ (Above Normal)
Overall Forecast: Temps: -0.7 F / Snowfall: 47″

NYC (New York City, NY)

Temps: 0.0 to -2.0 F (Near to Slightly Below Avg.)
Total Snowfall: 26″ to 32″ (Above Normal)
Overall Forecast: Temps: -0.5 F / Snowfall: 31″

BWI (Baltimore, MD)

Temps: 0.0 to -2.0 F (Near to Slightly Below Avg.)
Total Snowfall: 22″ to 28″ (Above Normal)
Overall Forecast: Temps: -1.0 F / Snowfall: 26″

DCA (Washington DC)

Temps: 0.0 to -2.0 F (Near to Slightly Below Avg.)
Total Snowfall: 18″ to 24″ (Above Normal)
Overall Forecast: Temps: -1.0 F / Snowfall: 21″

RIC (Richmond, VA)

Temps: -2.0 to -4.0 F (Below Avg.)
Total Snowfall: 14″ to 20″ (Above Normal)
Overall Forecast: Temps: -2.3 F / Snowfall: 17″

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Take Care,