Winter 2011-12

8/3/2019 Winter 2011-12

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It is October 13, 2011 and it is time to post my long range forecast for the 2011-12 winter.

La Niña is back with us for yet another winter, this is only the 4 th time a back to back La Niña hasoccurred since 1950.

La Niña is a natural phenomenon that occurs when sea surface temperatures across the equatorial

central and eastern Pacific are below normal.

The upcoming winter at this point appears to be very similar to last winter with a few exceptions:

First; The La Niña pattern we are currently in is of a moderate intensity at best, this is typically thecase when a back to back El Niño or a La Niña occur which happens about 50% of the time.

Second; The El Niño Southern-Oscillation(ENSO) is trending more toward a positive phase then thispoint a year ago, again typical when a back to back cycle occurs. What does this equate to, a slightlywarmer Eastern Pacific and a weaker La Niña, this will have an impact on the size and strength of thehigh pressure ridge the forms over the Aleutians during a La Niña winter and therefore I anticipate thePolar Jet Stream to trend a little more toward a zonal flow (east-west) instead of the large trough thatformed over the eastern US last winter. I am anticipating the storm track this winter to be a little bitfurther west, through the Northern Plains, the Midwest, The Ohio Valley, and the Appalachians, unlikelast year where the storms tended to track through the Great Lakes, Ohio and Tennessee Valley, andalong the I-95 Corridor. The timing of when, where, and the intensity of this ridge in the Aleutianswill be key to pinning down the storm tracks for the season. I will make addendums to this forecastover the next 4-6 weeks. There GFS and European models both are in agreement with each other. A

preliminary run of the models was generated last week, a final run will be on October 27.

Third; A slightly later formation of the Aleutian ridge, this will translate to a stormier and colderDecember and early January for the eastern half of the country, where as last winter late November andDecember and by New Year's the east half of the country was experiencing a January thaw.

Here is a sea surface temperature graphic from October 12, focus on the area circled and you will notethat temperatures are about 2-3 degrees below average.

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This is warmer than last year when we saw temperatures as much as 5-8 degrees below average. Againboth were moderate La Niña's. Sea surface temperatures in this region warmed slightly in the last 30days, but certainly not enough to say the La Niña is weakening, these are just normal fluctuations.

The following is a graphic that shows the relationship between a La Niña and the jet stream pattern

over the United States, note the high pressure ridge over the Aleutian chain.

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Here are 2 graphics I created depicting what the winter will look like for the US based on currentENSO conditions, historical data and the recent computer models runs:

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As typical during a La Niña winter the northern half of the country experiences cold stormy weatherand the southern half is mild and dry, I don't see much deviation from this for 2011-12 except for midDecember to mid January where the potential for large temperature swings is there for much of the eastincluding the southeast and several nor'easters along the east coast. The Pacific northwest will see

frequent storms throughout the winter.

The risk for severe weather and tornadic outbreaks across the south during the spring months is veryhigh, due in part to the expected breakdown of the Aleutian ridge which will allow the storm tracks tobecome more erratic and allow storms to slide further south, the La Niña will likely be phasing out bylate spring, some computer models are hinting a return to El Niño over the 2012 summer, some aretrending a return to neutral conditions, I tend to agree with the latter, however we are talking aboutsomething 8-10 months down the road so it's way to early to speculate, stay tuned. At any rate we willbe talking about something other than La Niña as there has never been a triple play on either La Niñaor El Niño since the discovery of the phenomenon.

Forecast by Region:

The West;

Expect large swings in temperature and precipitation, November and December will likely be very mildand dry across much of southwest the exception to this will be the Pacific Northwest where frequentstorms are expected all winter and heavy snows at the higher elevations.

The second half of the winter could bring a return the “Pineapple Express", a phenomenon that occurswhen a strong, persistent flow of tropical moisture sets up from the Hawaiian Islands to the West Coastof the U.S. Winter storms will dip further south in January and February bringing much needed rains

to California and snow to the Rockies.

Southwest/Texas;

Unfortunately it looks to be more of the same for drought stricken Texas and the southwestern states.The projected jet stream pattern and storm track will keep few if any storms from making it into thatpart of the country, warm temperatures will be dominant as well. Relief may come in the spring asstorms will be prevalent across the southern third of the country. Frequent cold shots will likely occurin December-January across northern Texas, mild weather will prevail the rest of the winter.

Southeast/Florida;

Winter across the southeast will generally be mild especially in Florida with the exception of midDecember- mid January when the best chances for frost and freezes will occur. During this time willbe the best chances for winter storms to form along the Gulf Coast and track up the eastern seaboardalong with the chances for snow and ice events in the Carolinas and Georgia.

Winter will be mostly dry except for precipitation from the few storms that are likely to occur inDecember and early January.

There is a significant risk for severe storms starting in late February. Tornadic outbreaks are very

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likely.

Mid Atlantic/Northeast;

Overall winter will not be as extreme as last winter, however there will be the potential shaping up for afew significant nor'easters especially in December and early January along the I-95 corridor. Most of

the winter will average out colder than normal. A January thaw will be likely possibly extending intoearly February before winter like conditions return. March will be volatile with the likelihood of asignificant nor' easter occurring early in the month.

The Appalachian chain will likely see large snowfall accumulations, western Pennsylvania and NewYork will be the target of the “lake effect machine” this season.

Plains/Midwest/Great Lakes;

This area will be the bulls eye for the worst winter has to offer this season. Expect frequent blizzardsalong with severe cold waves will prevail from early December extending into early April.

Chicago, Minneapolis, and Detroit are in the line of fire for significant snowfall accumulations.

Watch for the potential for severe storms and flooding in April.

Lastly since we are going into another La Niña pattern, the potential is there for another activehurricane season in 2012. This year has been pretty close to predicted with 16 named storms so far 19were forecasted. That will be in another blog.

I will be posting updates over the next few month along with periodic blogs.

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Winter 2011-12