Friday, March 30, 2018

A Bullseye of Dry

The past winter season (December-February) was a little on the weird side. The west coast, which normally experiences it's wet season in the winter, was pretty dry. It was cold across the Plains and Midwest, but snowfall was way below average in many areas. Winter had a late surge in the northeast in late February and March. However, one aspect of the last five to six months that has been interesting to watch is the fairly rapid development of severe to exceptional drought in the panhandle region of Texas and Oklahoma and adjacent portions of Colorado, Kansas and New Mexico.

Here is the U.S. Drought Monitor as of today, showing parts of this area in Extreme Drought, compared to the Drought Monitor in early October.

Dryness expanded and intensified through November and December, and by early January the first depictions of Extreme drought were showing up on the U.S. Drought Monitor. 

By early March an area from the Four Corners region to the panhandles was painted with Extreme Drought, with a small area of Exceptional Drought in northern Oklahoma. That small area has doubled in size in the past two weeks.

The precipitation map for the past 6 months depicts the seriousness of the precipitation deficit.

This map from the Oklahoma Mesonet demonstrates the incredible precipitation gradient across Oklahoma the past four months, ranging from only an inch in the panhandle to more than 25 inches in the southeastern part of the state.

Then there was this note included in the Area Forecast Discussion by the NWS Amarillo office on March 28.

We have some dedicated CoCoRaHS observers that have been submitting daily observations, mostly zeros, throughout the development of this drought. Here is a list of CoCoRaHS rainfall totals under one inch from Texas, Oklahoma, Colorado, New Mexico and Kansas October 1 through March 28 for all stations which had observations for at least 90 percent (161) of the days in this period.
Station Number Station Name Total Precip Total Snow
 CO-BA-27  Stonington 8.6 SE 0.28 1.3
 CO-LA-16  Kim 8.8 SSE 0.58 2.7
 KS-HM-3  Syracuse 14 SSE 0.59 0.0
 TX-LK-24  Ransom Canyon 0.4 ENE 0.64 0.2
 NM-SC-26  Lemitar 0.7 NNE 0.67 0.0
 KS-SV-18  Hugoton 0.6 NNW 0.69 0.0
 NM-SN-39  Rio Rancho 3.3 ENE 0.73 0.0
 NM-SN-62  Rio Rancho 3.0 WSW 0.75 0.0
 KS-WH-9  Leoti 6.8 NNW 0.78 7.4
 TX-LK-14  Lubbock 5.3 SSW 0.79 0.4
 NM-SN-43  Rio Rancho 3.5 W 0.80 0.3
 CO-OT-25 La Junta 1.0 S 0.82 1.8
 NM-SJ-19  Farmington 3.4 WSW 0.83 0.0
 NM-BR-205  Albuquerque 8.9 NW 0.83 0.0
 NM-BR-36  Albuquerque 5.9 WNW 0.86 0.0
 TX-LK-59  Wolfforth 4.6 S 0.86 0.5
 TX-LK-7  Lubbock 6.7 SW 0.87 0.3
 NM-BR-7  Albuquerque 7.1 SW 0.88 0.0
 TX-LK-77  Lubbock 6.4 NW 0.89 0.0
 CO-BN-8 Las Animas 8.1 NE 0.92 3.4
 NM-BR-152  Albuquerque 2.9 W 0.92 0.0
 CO-OT-28 La Junta 1.6 SW 0.93 1.5
 NM-SJ-32  Kirtland 21.7 S 0.95 0.2
 NM-TR-1  Mountainair 1.0 S 0.96 1.0
 TX-LK-81  Lubbock 3.0 S 0.96 0.0
 NM-BR-215  Albuquerque 5.3 W 0.96 0.0
 KS-HM-19  Syracuse 3.1 NNE 0.96 0.0
 KS-FO-23  Dodge City 12.7 S 0.98 1.2

The winds aloft, particularly in December and January, were west-northwest on average in this part of the country. Any moisture heading toward the Texas and Oklahoma panhandle region would get wrung out of the atmosphere as the air was forced up on the west side of the Rockies. Any low pressure systems that developed tended to be steered east before they started to develop. What the drought-affected area needed, and didn't get, were some strong low pressure system developing on the lee side of the Rockies that could tap into moisture from the Gulf of Mexico to produce precipitation.
These maps depict the average 500 millibar height pattern (~20,00 ft) for the months of December, January and February. Winds at this level blow parallel to the contour lines. The arrows show the general direction of the wind at this level.

Although this region did get a little rain this week, the operative word is "little". The latest forecasts keep the drought area dry for at least the next week or so.

1 comment:

  1. They really need rain bad. We are right on the line between those who got a lot of rain & those that got almost none. I sure hope they get something before summer sets in.