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Texas heat wave smashes more records; 93L more organized

By: Dr. Jeff Masters, 3:26 PM GMT on August 17, 2011

Texas' Texas-sized drought and heat wave is setting new records, as August temperatures regularly topping 100° continue to impact most of the state. The high temperature hit 102° at the Houston Intercontinental Airport yesterday, a record for the date, and the 16th consecutive day of 100°+ heat. The 16-day streak is a new record. The previous record was 14 straight days, ending on July 19, 1980.

The low temperature yesterday morning at Dallas/Fort Worth International was 86°--the all-time highest minimum temperature recorded there. This is the 4th time this summer Dallas has had an 86° minimum temperature, with the other dates being July 26, August 3, and August 4. Prior to this year, the hottest minimum temperature ever recorded in Dallas was 85° on September 1, 1939 (which they also matched this summer on July 25, August 7, and again this morning.) Thus Dallas has matched or exceeded their all-time hottest minimum temperature from previous years seven times this year. It's extremely rare for a station with a long observation history spanning more than fifty years to break an all-time record seven times in one year; if anyone can find an example of this in the past, I'd love to hear about it. The National Climatic Data Center records page is a good place to look. Dallas has had 40 days with a minimum temperature of 80° or higher this year, breaking the previous record of 39 days, set in 1998. Dallas had a streak of 40 straight days with a maximum temperature above 100° which ended August 10, good for 2nd place all-time, next to a 42-day streak in 1980.

Figure 1. The amount of rain needed to break the Texas drought is in excess of 15 inches (purple colors) over most of the state. This year's drought is officially Texas' worst one-year drought on record. Image credit: NOAA/NWS.

According to the National Climatic Data Center, twelve other major airports set or tied their all-time high minimum temperature two or more times this summer: San Angelo, TX (four times); Lake Charles, LA (three times); Bristol, TN; Indianapolis, IN; Trenton, NJ; Newark, NJ; West Palm Beach, FL; Shreveport, LA; Beckley, WV; Texarkana, AR; Lake Charles, LA; Lubbock, TX; plus, Fort Worth Meacham Field. This year's total of fourteen airports that broke their all-time high minimum temperature multiple times this summer is similar to last year's total of ten sites. Most notable last year was West Palm Beach, Florida, which tied it's all-time high minimum temperature of 83° five times in 2010.

Fifteen major airports have tied or broken their all-time highest temperature multiple times this summer: Tyler, TX (three times); Tallahassee, FL (three times); Fort Smith, AR; Harrison, AR; Tulsa, OK; McAlester, OK; Longview, TX; and Oklahoma City, OK, Ypsilanti, MI; Altoona, PA; Dubois, PA; Salisbury, MD; Raton, NM; Amarillo, TX; and Dalhart, TX. For comparison, only three stations broke their all-time maximum temperature record multiple times in 2010: Wilmington, DE; Norfolk, VA; and Richmond, VA.

Figure 2. Morning satellite image of Invest 93L.

Caribbean disturbance 93L
A westward-moving tropical wave in the Central Caribbean a few hundred miles south of Hispaniola, Invest 93L, has increased in organization overnight, building up a modest amount of heavy thunderstorms. Low-level spiral bands have begun to form on all sides of the storm this morning. There are currently no signs of a surface circulation, though there is plenty of large-scale rotation apparent on satellite imagery. Dry air surrounds 93L and has infiltrated the center of the disturbance, giving 93L a doughnut-like appearance. However, the disturbance is steadily moistening its environment and is under low wind shear of 5 - 10 knots, so this dry air should gradually mix out today and allow 93L to continue to organize. There is a hurricane hunter mission scheduled for this afternoon at 2pm EDT to see if a tropical depression is forming.

93L will bring heavy rain showers to southern Haiti this afternoon and to Jamaica tonight. By Thursday, 93L's forward motion will slow to 10 - 15 mph, and the storm will bring heavy rains to Northern Honduras and Northeast Nicaragua. These rains will spread to Belize and Mexico's Yucatan Peninsula by Saturday. The latest SHIPS model forecast shows wind shear remaining in the low range and the atmosphere steadily moistening as 93L enters the Western Caribbean on Thursday. All of the models agree that the ridge of high pressure steering 93L to the west will remain strong, forcing the storm into a landfall Friday in Northeast Nicaragua or Northeast Honduras. It is possible that 93L will have time to intensify into a Category 1 hurricane before then, though landfall as a tropical storm would be more likely, given the dry air that 93L needs to overcome. Regardless of development, the storm will bring very heavy rains of 4 - 8 inches or more to Nicaragua and Honduras. These rains are likely to cause dangerous flash flooding and mudslides. NHC gave 93L a 30% chance of developing into a tropical depression by Friday morning in their 8am outlook; I'd put these odds at 50% now, given the continued increase in organization seen on satellite images.

Figure 3. Morning satellite image of the tropical wave 500 miles west-southwest of the Cape Verde Islands.

Elsewhere in the tropics
A tropical wave near 14°N 34°W, about 500 miles west-southwest of the Cape Verde Islands off the coast of Africa, is moving westward near 15 - 20 mph. This wave has little heavy thunderstorm activity associated with it due to dry air, but an impressive amount of large-scale spin is obvious in visible satellite loops. This wave is expected to arrive in the Lesser Antilles Islands by Saturday. Three of our four reliable models for predicting tropical storm genesis predict that this wave could develop into a tropical depression sometime Friday through Sunday. A west-northwest track through the Northeast Caribbean bringing the storm near Puerto Rico by Sunday or Monday is favored by most of the models.

Jeff Masters
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The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.