Another Look at Isaac-Related Rainfall

The Hydrometeorological Prediction Center’s latest precipitation forecast really tells the story of where Isaac’s downpours will be heaviest! As the storm slowly tracks north through Friday and then gradually turns northeast over the weekend, the best chance of heavy rain (and severe weather) will be well west of the Tennessee Valley:

While that map is pretty with nice, smooth lines, the weather really never works on smooth contours! This is a picture of the latest NAM precipitation outlook through Saturday evening. It may be a little more realistic for North Alabama and Southern Tennessee because of the “spotty” look to the areas of heavier and lighter rain around here.

There will be enough tropical moisture and instability for a good scattering of showers and storms on both Thursday and Friday; fewer storms are likely Saturday.

The scattered nature of the storms means that some of us will get more than an inch (possibly up to 2 inches of rain) over the next 5 days. Most communities will not see more than 0.75″ through early next week, and unfortunately, some spots may barely get enough to settle the dust.

If Isaac had moved north faster, we would have been in a more favorable area for a good, solid soaking rain across the entire region. On the flip side of that, if he had been closer, we would have also had a threat of more severe storms. There’s good and bad to be seen in every weather situation. By the way, if you’re wondering how much rain we need, here’s some more info:

Year-to-Date Rainfall Deficits

• Huntsville: -2.17″
• Muscle Shoals: -7.83″
• Chattanooga: -3.92
• Birmingham: -4.17″
• Tuscaloosa: -6.02″

About 44% of Alabama’s land area is considered to be in some level of drought. Tennessee’s drought covers about 46% of the Volunteer State. Around the Tennessee Valley region, we need around 3″ to 6″ of rain to totally get out of the drought. That won’t be likely unless Isaac has another trick or two up his sleeve that we haven’t seen yet.

-Jason
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