Aug 082010
 

I’d like to say that July was very unique. For many reasons it was.

It was the month where the global surface station system data came under suspicion again. When the monthly temperatures were reported to be the hottest ever, it did jive with the satellite data which showed near normal temperatures. It is expected that this will be repeated for July. But, how did we do in Flagstaff.

The big news was the 4th largest rainfall amount for Flagstaff for July at 5.94 inches. Obviously, the wet month was especially tough for those who have been faced with the run-off from the Schultz Fire Burn Area. The regular flooding to the east of the San Francisco Peaks. Interestingly, while many parts of Northern Arizona had similar heavy rainfall results, Prescott did not. They were about an inch and a half below normal. The last weekend of the month was, simply put, very wet!

So, what about temperatures. Compared to the last few years, we saw a continuation of the moderate to cooling trend in July and June.

Departure from average monthly mean temperatures January 2004 - July 2010

Departure from average monthly mean temperatures January 2004 - July 2010

As you can see from this grapg going back to 2004, June was below the monthly average. July was 0.57 degrees above this short-term average, but not outside of 1 standard deviation. Our airport is in a remarkably stable environment for a suburban location. So, I don’t think Urban Heat Island (UHI) effect is very strong, unlike many of the other surface stations on the planet.

The warm July was driven by two factors. First, relatively late start to the month allowed a beautiful, sunshine filled start to the month which boosted high temperatures. Second, when the monsoonal flow did begin, we had many nights with thick cloud cover that acted like a blanket and cushioned our low temperatures. Still, it was cooler when compared to last summer’s high and mean temperatures. Here is a great graphic that summarizes the last week of July.

Last week of July 2010 precipitation anomaly summary

Last week of July 2010 precipitation anomaly summary (US Climate Data Center)

Last week of July 2010 temperature anomaly summary

Last week of July 2010 temperature anomaly summary (US Climate Data Center)

So, what lies ahead? Many have started to ask me about this coming winter already. More on that later. Currently, I am concerned that the building La Nina could alter monsoon pattern. Will it bring an early end by ushering a dry spell, or will it allow more tropical flow from the Caribbean to the southwest?

Stu

 Posted by at 7:56 am

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