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Thursday, June 30, 2011

Jeff Masters: Hottest day on record in Texas panhandle

Hottest day on record in Texas Panhandle
by Jeff Masters, wunderblog, June 27, 2011
The hottest temperatures in recorded history scorched large portions of the Texas Panhandle, Oklahoma Panhandle, and southwestern Kansas on Sunday. Amarillo hit 111 °F, breaking its hottest day-ever record of 109 °F (set just two days previously, on June 24). Borger, Texas, hit 113 °F, smashing the previous hottest day-ever record set on June 24, 2011, of 108 °F. Dalhart, Texas, had its hottest day on record, 110 °F, beating the 108 °F on June 24, 2011. Dodge City, Kansas, tied its all-time record with 110 °F (last seen on June 29, 1998). Dodge City has temperature records back to 1874. Yesterday saw the hottest temperatures of the month for Texas with 116.2 °F at Childress, Northfield, and Memphis (all in the panhandle region). These readings are not far from the state record of 120 °F set at Monahas on June 28, 1994, and at Seymore on August 12, 1936.

A cold front moved through the region overnight, bringing northerly winds and cooler temperatures to the region. However, a new ridge of high pressure will gradually build in this week and temperatures are expected to reach near-record levels again by Thursday, with 102 °F expected in Amarillo, which is their all-time record for the date. The record-breaking temperatures in Texas are being caused, in part, by the record drought. Under normal conditions, the sun's heat expends part of its energy evaporating water from the soil and from vegetation. This energy is stored as "latent heat" in the water evaporated, and is not available to heat the air up. However, when a severe drought dries up the soil and kills the vegetation, there is much more heat available to go directly into heating up the air, since there is little moisture to evaporate. The increased temperatures help to strengthen the high pressure system dominating the drought region, making it even more difficult for rain-bearing low pressure systems to bring drought-busting rains. This positive feedback effect is a key reason why we expect more intense droughts and heat waves in a warmer climate.

Wunderground's weather historian Christopher C. Burt has many more details on the great Texas drought of 2011 in his latest post, updated Sunday night. He reports that Pecos, Texas has had no precipitation since September 23, 2010 -- one of the longest rain-free periods for a U.S. city in recorded history, outside of the desert regions of Arizona and California.

Figure 1. Latest weekly drought conditions for Texas, as compiled by the U.S. Drought Monitor. West Texas is experiencing its worst drought in recorded history.

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