All-time record low temperature in Oklahoma — and a Tehuano wind event

February 10th, 2011
GOES-13 10.7 µm IR images (click image to play animation)

GOES-13 10.7 µm IR images (click image to play animation)

Following a record-setting 27 inches of snowfall in a 24-hour period on the previous day, new all-time record low temperature was set for the state of Oklahoma when Nowata dropped to -31º F (Tulsa OK Public Information Statement) on the morning of 10 February 2011. AWIPS images of 4-km resolution GOES-13 10.7 µm IR data (above; click image to play animation) showed a large region with very cold surface IR brightness temperatures (darker blue color enhancement) over the snow-covered portions of Kansas and Oklahoma. The GOES-13 IR imagery also showed a few thin bands of cirrus cloud moving eastward across the region — one could speculate as to whether these cirrus clouds may have had a small effect on briefly slowing the surface radiational cooling as they passed overhead, possibly preventing the surface air temperatures from dropping any further?

A 1-km resolution MODIS 11.0 µm IR image at 08:16 UTC (below) gave a more detailed view of the cold surface IR brightness temperatures, which were as cold as -38º C over northern Oklahoma at that time.

MODIS 11.0 µm IR image

MODIS 11.0 µm IR image

Looking farther to the south, the 12:00 UTC surface analysis (cyan) overlaid on a GOES IR image (below) suggested that the leading edge of the cold frontal boundary associated with this outbreak of arctic air was approaching the Pacific coast of southern Mexico. About 3 hours later,  14:58 UTC  ASCAT scatterometer surface winds  (green wind vectors) indicated that the cold air had already crossed the high terrain of Mexico and and emerged as a well-defined “Tehuano wind event“ over the Gulf of Tehuantepec along the Pacific coast (hence the name “Tehuantepecer“ given to this type of strong wind event). This region was outlined as one of a “Developing Gale” on the surface analysis.

GOES IR image + ASCAT scatterometer surface winds + surface analysis

GOES IR image + ASCAT scatterometer surface winds + surface analysis

A closer view (below) showed a number of ASCAT wind vectors of 30-33 knots out over the near-shore waters of the Gulf of Tehuantepec — confirming that the cold frontal boundary had indeed emerged into the Pacific Ocean. Northerly surface winds at Ixtepec (station identifier MMIT) gusted to 45 knots later in the day.

GOES IR image + ASCAT scatterometer surface winds + surface METAR reports

GOES IR image + ASCAT scatterometer surface winds + surface METAR reports

McIDAS images of GOES-13 0.63 µm visible channel data (below; click image to play animation) showed the formation of distinct cloud lines that marked the edges of the emerging gap flow winds. In addition, the slightly hazy signal of blowing dust being carried offshore could be seen.

GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 0.63 µm visible channel images (click image to play animation)

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