The October 15-20, 2007 Warm Spell: Quick Thoughts

[donsutherland1]

During the October 15-20 timeframe, exceptional warmth is likely to roll across parts of Alberta, Saskatchewan, Manitoba, and the Northern Plains. The latest mean 500 mb height anomalies are forecast to be 240 meters or more above normal by 168 hours:



That synoptic setup is reasonably similar to those that occurred in the October 15-31 timeframe during 1952, 1953, 1963, and 1977. The composite 500 mb anomalies for those periods follows:



The following were the highest temperatures for select cities during the four outbreaks of exceptional warmth noted in the composite height anomalies:

October 20-23, 1952:
Bismarck: 79°
Calgary: 73° (22.8°C)
Regina: 68° (20.0°C)
Winnipeg: 73° (22.8°C)

October 16-21, 1953:
Bismarck: 84°
Calgary: 69° (20.6°C)
Regina: 75° (23.9°C)
Winnipeg: 78° (25.6°C)

October 15-18, 1963:
Bismarck: 78°
Calgary: 78° (25.6°C)
Regina: 79° (26.1°C)
Winnipeg: 79° (26.1°C)

October 23-25, 1977:
Bismarck: 78°
Calgary: 70° (21.0°C)
Regina: 70° (20.9°C)
Winnipeg: 74° (23.3°C)

Conclusion:
Given that the size of the above normal 500 mb height anomalies is progged to be somewhat less expansive than those in the composite, the warmth to the south of where those anomalies are centered could be somewhat less extreme than occurred in some of the historic examples.

Nonetheless, given the combination of model and ensemble data coupled with the historic examples cited above, I believe Bismarck will likely see its temperature peak at 73° or above during the referenced timeframe. Calgary, Regina, and Winnipeg should all experience a high temperature of 70° (20.9°C) or above. At Regina and Winnipeg, the temperature could reach or exceed 75° (23.9°C).

[dtrain44]

Don, that's some interesting analysis. How long do you expect that sort of heat to persist?

[HurricaneBill]

Don, could these warm spells have an influence on severe weather during November?

BTW, Don, I thought you were excellent in "M*A*S*H" and "Ordinary People".

[JonathanBelles]

Is that blue blue blotch over Fl a negative anomaly or cooler weather?

[donsutherland1]

Fact789,

Those were slightly negative 500 mb anomalies. However, the historic pattern saw somewhat below normal readings over parts of the Florida peninsula. Interestingly enough, the ensembles are also suggesting somewhat below normal to near normal readings for the most part during the 10/15-20 timeframe.

[donsutherland1]

HurricaneBill,

If one kept seeing episodes of exceptional warmth breaking out, there would be the possibility of perhaps an outbreak of severe weather given the contrasting air masses. However, at this time, my very early thinking is that one might see the Mid-Atlantic/Southeast come out close to normal in November with the Northeast westward across the Great Lakes region and Northern Plains come out warmer than normal, though I'm not committing to such an idea yet. If that works out, the contrast between air masses, in general, might be less than normal.

[RL3AO]

CPC agrees.

[CrazyC83]

HurricaneBill,

If one kept seeing episodes of exceptional warmth breaking out, there would be the possibility of perhaps an outbreak of severe weather given the contrasting air masses. However, at this time, my very early thinking is that one might see the Mid-Atlantic/Southeast come out close to normal in November with the Northeast westward across the Great Lakes region and Northern Plains come out warmer than normal, though I'm not committing to such an idea yet. If that works out, the contrast between air masses, in general, might be less than normal.

If this holds up, expect a major severe weather outbreak around October 21-23.

[Extremeweatherguy]

It looks like Alaska will be getting pretty chilly during this period!

[RL3AO]

Instead of starting a new thread I just wanted to mention that it looks like an extended cool spell in the eastern 2/3rds of the U.S. Maybe Don can do more of his great analysis.

[JonathanBelles]

I had the hint to a cool down in my October forecast, however I was two weeks off . It just seemed not quite right to have a warm winter. I'd love to see an analysis from a promet.

[JonathanBelles]

I know this is accuweather and I know this is 7+ days out but WOW!!! Hi:71 and Low 59 on wed oct 24th!! I almost have to say that can no way in hell be right...have a look : http://www.accuweather.com/forecast-15d ... 1&metric=0