The January 18-25, 2008 Cold Period: Initial Thoughts

[donsutherland1]

For several days, even as eastern North America experienced a historic bout of extreme warmth and then a surge of another shot of unseasonable warmth, the ensemble guidance has been suggesting the possibility of a period of below to much below normal readings over a large portion of North America. At the same time, the guidance has grown increasingly aggressive with the development of a negative EPO around that timeframe.

EPO Forecast:


The forecast 500 mb height anomalies and 850 mb temperatures match up quite well with a composite analog centered from 1/18/1957, 1/18/1959, 1/17/1982, and 1/23/2004.

1/11/2008 0z NCEP Ensemble Mean 500 mb Height Anomalies at 216 hours:


Composite Analog 500 mb Height Anomalies:


1/11/2008 0z NCEP Ensemble Mean 850 mb Temperature Anomalies at 216 hours:


Composite Analog 850 mb Temperature Anomalies:


Although the pattern depicted on the NCEP ensemble suite is not the classic setup for extreme cold with a big PNA+ ridge, it is still similar to some past patterns that saw noticeable cold. In my opinion, there is a good possibility that much of the Mid-Atlantic region, Northeast, and southern Canada could experience their coldest readings so far this winter during the 1/18-25 timeframe.

Coldest Readings for Select Cities during Winter 2007-08:
Boston: 7°, 1/3
Burlington: -8°, 1/3
New York City: 12°, 1/3
Ottawa: -12° (-24.5°C), 1/3
Philadelphia: 18°, 1/3-4
Toronto: 0° (-17.7°C), 1/3
Washington, DC (DCA): 21°, 1/4

Given the reasonable consistency of the NCEP ensembles and analog set for similar 500 mb patterns, I believe Boston could see its coldest temperature reach 5° or below; New York City and Philadelphia should have at least one reading of 12° or colder with a single-digit reading possible in either city; Washington, DC (DCA) should bottom out at 16° or colder. Farther north, Toronto should see its coldest reading fall to -4° (-20.0°C) or colder; Burlington should reach -8° or lower and a -10° low temperature is possible; Ottawa should see its coldest reading fall to -13° (-25.0°C or colder).

[JonathanBelles]

I know you dont specialize in the SE, how cool do you think the SE states will get?

[donsutherland1]

Fact789,

The brunt of the cold will likely stay farther north this time around. Whereas Tampa saw a low of 29° and St. Petersburg a low of 34° on 1/3, I believe this time around Tampa will probably see its coldest temperature around 38° +/- a few degrees and St. Petersburg will probably bottom out in the lower 40°-45° range.

[Extremeweatherguy]

Don,

Any thoughts on what the Atlanta region may see during the January 18th - 21st time period? I will be there at that time, and any input on what I could possibly expect would be greatly appreciated.