An influx of deep moisture from the Gulf of Mexico (partly residual moisture from former Tropical Depression #4) and an upper-level low just north of the Yucatan will keep a good chance of showers or thunderstorms in our picture through early next week.

The National Weather Service is calling for P.W. (Precipitable Water) values of around 2 inches locally, which indicates a deep pool of moisture. Basically, P.W. shows the amount of moisture above a given locale. Often rain amounts can exceed the total P.W, value as water vapor flowing in from the surrounding area can increase rain potential. However there is a general correlation between P.W. values and precipitation amounts.

The waxing and waning of P.W. over certain areas can be tracked. This loop shows a loop of current P.W. amounts. You can see a surge of deep moisture passing through the Bahamas, and then Florida and now moving into the eastern and central Gulf: http://tropic.ssec.wisc.edu/real-time/mimic-tpw/natl/main.html.

The moisture flow can also be tracked on a water vapor loop, which also shows the upper-level low off the Yucatan.

At any rate, expect rain to hang around awhile longer with a 40-50% chance for thunderstorms through the weekend.

Rainfall amounts should be fairly modest, though totals in excess of 1 inch may be common over inland parts of Galveston County as afternoon heating enhances atmospheric instability.

Here is a link for those wanting to know about precipitable water: http://www.theweatherprediction.com/habyhints3/899/

Stan Blazyk is a life-long weather enthusiast, long-time Galveston resident and author of "A Century of Galveston Weather." He has written the weather blog for the Galveston County Daily News for more than a decade.

(1) comment

mark niles

Nice counter-clockwise flow above Yucatan with the upper-level low. Not too much moisture associated with that however. Interesting video clip,

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