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Jack’s

Some Long-Term Forecast Ideas

Posted on: 3:53 pm, July 4, 2012, by

Occasionally we like to go a little beyond the simple Seven Day Forecast and look at some of our longer-range ideas.

The over-all weather pattern is going to through a little bit of change in the next two weeks, and considering how hot and dry it’s been, most folks have told me that any change is good!

As of today’s climate report, Huntsville had a rainfall deficit of 7.03″ on the year; Muscle Shoals’ deficit of 9.53″ is one of the largest in the state. From June 23rd to today, Huntsville’s average high temperature is 101º F. That average is 103º F for Muscle Shoals in that same period.

Next week’s weather map will look much different than this week’s. The big ridges that have kept it hot and dry here since mid-June will not be as big a factor; in fact, one large ridge over the Central and East will split this weekend. Two smaller, weaker ridges will emerge as that happens; one slips west over the Rockies, and the other moves out over the Atlantic. Between now and then, the ridge will be the biggest factor deciding who gets rain and who doesn’t. Note the rain-free area in the middle of the country in the picture below; more rain is likely with numerous scattered storms on the edges of the hot, dry air called the “Ring of Fire” (not the same one you’re thinking about in plate tectonics):

With less ridging over this region, a weak cool front will slide down into the Tennessee Valley early next week. Here’s the forecast surface map for 7 AM Tuesday (via HPC):

A cold front in the area means a better chance of showers and thunderstorms and at least a little bit of a cool-down. The average high temperature is around 90 to 91 degrees in this area next week, and thanks to the cool front’s presence, we will be a lot closer to that mark for daytime highs! Our probability of rain creeps up to about 50% on Tuesday and Wednesday as this weak front meanders around Alabama, Mississippi and Georgia through the middle of next week; by the end of the week, it will move all the way down to the Gulf Coast leaving us hot and dry again as it passes.

After the brief break from the excessive heat, there’s some more bad news. While we could get some beneficial rain in this break, it won’t be enough to get us out of drought conditions, and there is a good chance the heat could come roaring back for mid-July (12th to 19th). This is the Canadian GEMS forecast of temperature anomaly (departure from normal) probability for that time period, and this is usually a very good indicator of longer-term temperature trends:

That big red spot over Alabama and Tennessee makes me believe it’s going back to the 97 to 102 range at least by the end of next week and into next weekend. There’s some room for adjustments, but look for more hot, humid weather after this brief break that is upcoming!

-Jason
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