Thursday, July 04, 2013

" Extreme Jet Stream Bringing U.S. Record Heat, Record Cold, and Flash Flooding"

Here is the Midwest - we are having quite the pleasant summer - unusually so. Relatively cool, low humid, rather rainy - good for the gardens, good for having the windows open.

By Dr. Jeff Masters - From the WeatherUnderground:

"The jet steam is exhibiting unusual behavior over the U.S., a pattern we've seen become increasingly common in summertime over the past decade. There's a sharp trough of low pressure over the Central U.S., and equally sharp ridges of high pressure over the Western U.S. and East Coast. Since the jet acts as the boundary between cool, Canadian air to the north and warm, subtropical air to the south, this means that hot extremes are penetrating unusually far to the north under the ridges of high pressure, and cold extremes are extending unusually far to the south under the trough of low pressure." 

"The ridge over the Western U.S., though slowly weakening, is still exceptionally intense. This ridge, which on Sunday brought Earth its highest temperatures in a century (129°F or 54°C in Death Valley, California), was responsible for more record-breaking heat on Tuesday. July 2. Most notably, Redding, California hit 116°, just 2° short of their all-time record. Death Valley had a low of 104°, the second hottest night on record since 1920 (the hottest was just last summer!) Numerous daily high temperature records were set in Arizona, California, Nevada, Utah, Montana, Oregon, and Washington. It was the opposite story in the Central U.S., where the southwards-plunging jet stream allowed record cold air to invade Texas. Waco, Texas, hit 58°F this morning (July 3), the coldest temperature ever measured in July in the city. Numerous airports in Texas, Nebraska, Arkansas, Louisiana, Kansas, and Missouri set new daily record low temperatures this morning. And over the Eastern U.S., the northward-pointing branch of the jet stream is creating a potentially dangerous flooding situation, by pulling a moisture-laden flow of tropical air from the Gulf of Mexico over the Florida Panhandle north-northeastward into the Appalachians. Up to five inches of rain is expected over this region over the next few days, and wunderground's severe weather map is showing flash flood warnings for locations in Florida, Georgia, South Carolina, and North Carolina."

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