The National Weather Service hasn’t published their review for the month of September, yet. But, I think it’s a pretty easy month to summarize. Here is the monthly climate graph from Weather Underground.
There were two stormy times, from September 6-9 and September 22-23. These provided us with significantly cooler temperatures for several days. The rest of the month was absolutely beautiful. It was the best month this year to get outdoors and enjoy. As you can see the last week of the month was well above normal for temperatures and drove us firmly into an above average temperature month. Overall, according to the National Weather Service, we were 2.4deg F above normal with precipitation coming in at a meager 0.79 inches, 1.33 inches below normal. This shift in temperature represents a strong move in the departure from normal temperatures since 2004.
Temperatures have been mostly below normal since the fall of 2009.
September 1998 doesn’t match September 2010. I think this is due to the timing and rapidity of the shift from El Nino to La Nina, and the accompanied change from a warm Pacific Decadal Oscillation Index to a cool one. I think this has led to a faster return of dry, and possibly warmer conditions. Notice the large cool body of water in the Equatorial Pacific.
Also note the warm North Atlantic Ocean. As an aside, there are a couple cooler patches of water in the North Atlantic. One from the coast of Africa stretching north of the Caribbean towards the East Coast of United States. The other from the coast of Nova Scotia to the east. These are under the tracks of Hurricanes Earl and Danielle, and Tropical Storms Colin and Fiona. Tropical storms provide this cooling.
The warm Atlantic and the cool Pacific are going to be the drivers for our upcoming dry winter.