Saturday, September 17, 2011

Much Needed Rain Falls on Parts of Drought Stricken Texas, Surrounding Areas; More On the Way...

...but before you get too excited about the 2nd part of the headline - I don't see a major "drought buster" in the cards at this time, unfortunately (although we'll certainly take every drop of rain that we can get)...

Much needed rain fell yesterday across the high plains of West Texas and eastern New Mexico.  The above image shows a maximum of 3-5 inches of rain across the far Southeast corner of New Mexico as the extreme, with fairly widespread amounts of  0.25 to 0.75 inches across much of the remainder of the region.  The image does not reflect locally heavy rains that took place across the DFW Metroplex region yesterday evening, were isolated amounts up to 2.5 inches were reported.

The rains fell across mainly the Western and Northern sections of the regions that are in "extreme" to "exceptional" drought, as indicated by the latest update on the U.S. Drought Monitor below:

While certainly welcome, along with cooler temperatures via the additional cloud cover to much of the region, unfortunately the latest rain event didn't even begin to make a dent in the extreme conditions that continue across the region.

The overall pattern across the region will remain unstable for the next 5-7 days, giving several opportunities for additional rainfall across the same area, as well as areas futher to the Southeast as well.

Below is the latest GFS computer model forecast of total rainfall for the period today through next Sunday, September 25th.  The first image is the raw data, and the 2nd is the same with my annotations of particular rainfall amounts that are forecast across the drought stricken region we're focusing on:

As you can see, the model is forecasting widespread 0.5 to 1 inch rains across much of the region (with the exception of much of eastern New Mexico).  A large area of 1-2 inch rains are indicated within the blue shaded areas on the image, along with localized amounts of 2-4 inches in the red and orange shaded areas.

This isn't meant to imply that it is going to rain constantly from now through a week from Sunday (although that would certainly be fine by me).  There will be opportunities for scattered showers and thunderstorms each day, mainly coinciding with afternoon heating as several weak surface boundaries interact with unstable air and an increasing amount of upper-level energy flowing into the region.

There are a few opportunities coming into view where we can pinpoint the greatest chance for the most widespread and significant rainfall during the period.  The first will come tomorrow afternoon and evening along a weak cool front, with the main concentration of widespread activity across Oklahoma and adjacent portions of Missouri, northwest Arkansas and northwest Texas (see GFS computer model forecast image, valid 7pm CDT Sunday evening, 9-18):

This boundary is also likely to result in a more widespread coverage of scattered activity across central and south Texas.  If you're lucky enough to get underneath one of these scattered storms, you may pick up a quick quarter to half inch of rain!

The front will progress Southward on Monday, giving a better chance for more widespread rain (though generally less than one half inch) across a large part of central and eastern Texas (see GFS forecast model image below, valid 7pm CDT Monday, 9-19):

The front is then forecast to become very ill defined and basically lounge around central or southeast Texas Tuesday and Wednesday of next week.  The boundary will generate scattered thunderstorm activity during the heat of the day each afternoon.  If you're lucky enough to get underneath one of the storms, you might pick up an additional quarter to one-half inch of rain.

The next chance of significant rain across the region will come toward the end of the week, ahead of a much stronger surface front and upper-level weather disturbance.  The latest GFS computer forecast image below is valid 7am CDT on Thursday, 9-22, and shows widespread rain along and ahead of the front across much of Oklahoma and northwest Texas:

...which will progress further Southeast across Texas Thursday night and Friday morning.  Rainfall potential with this round will average one-half inch, with localized amounts of 1 inch in heavier showers and storms near the front, particularly on Thursday afternoon or evening.

With the above in mind, here is how the daily GFS computer model rainfall forecasts look for each day of the coming week (click to enlarge - note rainfall scale in inches on left hand side of each image):

Valid 1am Saturday to 1am Sunday

 Valid 1am Sunday to 1am Monday

 Valid 1am Monday to 1am Tuesday

 Valid 1am Tuesday to 1am Wednesday

 Valid 1am Wednesday to 1am Thursday

Valid 1am Thursday to 1am Friday

While certainly not a "drought buster" event this coming week, we obviously have to be thankful for every opportunity we have, and this is certainly looking like the best chance that we've seen in a very long time for daily rainfall opportunities across much of the region...

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