Sep 042010
 

Well, La Nina isn’t looking like it will back-off in time for winter. The typical La Nina effects for Northern Arizona are slightly warmer than normal (near normal) temperatures with substantially below average precipitation.

La Nina Precipitation Effects - Winter

La Nina Precipitation Effects - Winter

La Nina Temperature Effects - Winter

La Nina Temperature Effects - Winter

1998 continues to look like a reasonable analog year. Both ENSO (El Nino Southern Oscillation) and the PDO (Pacific Decadal Oscillation) moved strongly to the cool side. They are forecast to stay cool for the winter. However, I think the move this year happened a little earlier than 1998. This gives some concern about the onset of the changes as a result.

The tropical storm season in the Atlantic got off to an earlier start this year than in 1998. Still, the number of storms could be very similar. In both years we have strong clusters of storms forming in early September. The early start makes me wonder about the precipitation in the fall in Arizona. Hurricanes and tropical storms can limit the flow of moisture to the region. At this point it looks like the Monsoon Season is over and the typical fall and winter weather pattern has begun. This pattern has storm fronts sweeping through and past Arizona.

1998 Hurricane Season - Wikipedia

1998 Hurricane Season - Wikipedia

2010 Hurricane Season - Wikipedia

2010 Hurricane Season - Wikipedia

September and October had above average and near average precipitation amounts in 1998. Right now, it doesn’t look like we will see anything for a couple weeks. I still think there is a good chance for near normal precipitation in September and October. However, the earlier transition from El Nino to La Nina could mean we will see an earlier chance to dry conditions. Temperatures in these months should be pretty close to normal, I think.

So, where does that leave us for the winter? Sorry folks. As of the start of September, it appears this winter will be near climitological normals for temperature. Now, the global outlook is for a colder than normal winter. This may cause Northern Arizona to be colder than normal. I’m just not sure. I doubt it will be warmer. This cooling trend is being driven by a very weak solar cycle among other things.

On the precipitation side, we will be dry. Probably very dry. December – February may see precipitation totals of less than 1.5 inches. I won’t be buying a season pass at Snowbowl. Then again, I never buy one. I just don’t get up there enough.

Is there a chance for change? Can I be out to lunch? Sure. Rapid changes in the sea states linked to ENSO and PDO are possible. Last year at this time, most thought El Nino would fade before winter. It didn’t, and we had a wet winter.

postscript: I installed a heated sidewalk this summer. This almost guarantees a dry winter, right?

Stu

 Posted by at 6:48 am

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