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Those “scattered” thunderstorms and CoCoRaHS - The Galveston County Daily News : Weather Watch

March 27, 2015

Those “scattered” thunderstorms and CoCoRaHS

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Posted: Wednesday, August 13, 2014 11:35 am

Sunday, I was on the extreme East End of Galveston. A thunderstorm rumbled off to the southwest, but only a few drops of rain fell at that location. Later as I traveled towards the central part of the city, the streets were flooded in some areas to curb level and a CoCoRaHS observer (a volunteer precipitation observation network) in that area reported 0.96” of rain. Meanwhile, just a couple of miles further west, the official reporting station at Scholes Field monitored but a trace of rain from the same event.

Rainfall amounts usually reflect two general varieties of precipitation. The general rains, where most locales in a region receive reasonably similar amounts of precipitation in any given event and scattered rains, where rainfall totals can vary widely even within a few blocks.

Most rains along the upper-Texas coast during the summer months tend to be of the scattered variety. It usually takes a tropical event, a deep upper-level disturbance or a rare frontal boundary to produce the more generalized rains.  Summer rains over inland areas of the County often come from the influence of the sea breeze boundary and reflects the impact of afternoon heating. At the coast, many summer rains occur during the morning as deep moisture results in an unstable layer of air over the northwest Gulf of Mexico. Because of this, rainfall can be wildly erratic and vary considerably from locale to locale and from year to year.

For example, precipitation in Galveston this summer at Scholes Field has totaled only 1.36” from July 1 to August 11. Meanwhile, the location in central Galveston mentioned above, has received 4.83” during this same period of time. This is a significant difference for this time of year, when heat is already stressing vegetation. On the mainland, the National Weather Service Office has seen rain totals of 5.58” since July 1. A site just southwest of Friendswood has reported a similar amount with 6.01”. Meanwhile, an observer near Kemah has measured only 2.31” since the beginning of July.

Needless to say, summer rains can be either feast or famine, depending on your location and the “luck of the draw” so to speak.

By the way, I am including a link to the CoCoRaHS site, for those of you who might like to participate in providing more complete rainfall reports for Galveston County: Anyone who is willing to obtain the proper rain gauge and submit reports is welcome to participate. As a bonus, you get to keep your records on line and can check them for any period of time desired.

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