how 'bout this?
from
www.capitalweather.com"Winter is finally near, and the outlook is finally here. We'll start with the caveat. Long range seasonal forecasting is still in its infancy. Although great strides are being made, there is still a lot of uncertainty and therefore bust potential in these outlooks. We believe we can provide more value and accuracy than a mere coin flip, but the ideas presented should be viewed as general guidance and themes. The more specific we get, the more chance there is to err. This is especially true for snow amounts, as 1 or 2 storms or lack thereof can make or break snow totals. As always, we will grade the outlook both during and after the winter.
Outlook Factors
The following factors were considered in preparation of this outlook. For more detail, links and explanation refer to the whole version of the outlook here.
- El Nino event: We are currently in a weak to moderate El Nino state that is expected to strengthen slightly and persist throughout winter.
- Temperature/Precipitation Pattern: The summer of 2006 was very warm for the entire US, with the core of the warmth centered in the upper Plains region. After a normal and extremely wet June with flooding rains, DC had a very warm July and August with an extended heat wave. September and October have seen a turn to much cooler conditions across the majority of the country including DC. Additionally both months had above average rain and precipitation is running well above normal for the year, despite long stretches of dry conditions.
-
North Atlantic Oscillation(NAO): The NAO has been very negative over the past 3 months. Climatology/Statistics indicate a return to neutral/positive for the winter average, while sea surface anomalies in the North Atlantic suggest otherwise.
- Hurricane Season: We saw an average to below average Hurricane season with very little US activity and multiple storm recurvatures well out in the Atlantic.
- Other Indices Considered:
Quasi-Biennial Oscillation(QBO), Pacific Decadal Oscillation(PDO),
North Pacific Index(NP).
- Miscellaneous Factors:
- Persistent High Latitude Blocking over the last several months.
- Below normal September and October with cold outbreaks longer and stronger than forecast.
- Sea Surface Temps(SST's) in the North Atlantic that favor colder conditions, and SST's in the North Pacific that give a mixed signal.
- Expansive snowcover over Canada and points north.
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The Forecast
This winter will be colder and stormier than normal with above average snowfall. We will see both extended cold outbreaks and thaws, but as has been the case this fall, the cold will overwhelm the warmth and thus will be more commonplace and long lasting. The core of winter will be colder with respect to normal than the beginning and end, and I expect the January/February timeframe to also be the stormiest. The higher level of storminess also means we will see more mixed events then normal. I expect a number of events will not be all snow, but rather snow to rain, rain to snow, sleet, freezing rain, or a combination of all. Overall, I expect the coldest winter since 03-04 and possibly colder, and the snowiest since 2002-03, although not as snowy.
The temperatures below will be measured against the official readings at National Airport(DCA), and snowfall measured against the airports as indicated.
Overall Temperatures for December through March: -1.25 below normal
December: -1 to +1, leaning very slightly above normal
January: -2 to -4
February: Normal to -2
March: Normal to -2
Snowfall: 20-30% above normal
National Airport(DCA): 20" (versus average of 16")
BWI: 24" (versus average of 20")
Dulles(IAD): 27" (versus average of 22")
Arlington/Alexandria/DC: 19-25"
Fairfax Co.: 22-28"
Loudoun Co.: 26-33"
Mo Co: 23-29"
PG: 17-23"
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Analog Years:
No two winters are alike, and this winter will be no exception. Analogs are used as general guidance only.
Primary Analogs: 1899-1900, 1904-05, 1939-40
Secondary Analogs: 1876-77, 1896-97, 1902-03, 1994-95
Other Analogs: 1887-88, 1888-89, 1911-12, 1914-15, 1923-24, 1940-41, 1969-70, 1986-87
What can go wrong:
- The El Nino becomes much stronger than predicted, thus warmer conditions with less snow. Chances: 15%
- The El Nino weakens much more quickly than forecast. This could signal warmer and less stormy conditions and an earlier end to winter. Chances: 10%
- The NAO is very positive for much of the winter. This would likely lead to warmer conditions and would also lead to many events being rain or snow to freezing rain/rain, thus less snow. Chances: 25%
- We never see a real pattern change/positive NAO emerge as we head through November, and December ends up much colder than forecast. Chances: 25%"
All that said... no matter how much you science it out, the winter '06 - '07 is a crap-shoot.