Large fire threatens Los Alamos nuclear lab; 95L headed for Mexico

The dangerous Los Conchas wildfire has burned to a spot one mile southwest of Los Alamos, New Mexico, forcing the nuclear laboratory there to close, and the evacuation of 8,000 people. The fire was fanned yesterday by winds that reached sustained speeds of 21 mph, gusting to 30 mph, along with temperatures in the low 80s and humidities as low as 14%. The fire was 0% contained as of Monday night, and had consumed 176 square miles. Today, winds will be out of the south at 10 - 20 mph, which will tend to force the fire towards the laboratory. According to the NOAA Storm Prediction Center, these will not be critical fire conditions, and critical fire conditions are not expected to return to the area until Wednesday or Thursday. Smoke from the fire has blown over 1,000 miles downwind, and is causing air pollution problems in downwind regions of New Mexico.



Figure 1. New Mexico's Los Conchas fire (marked by the cluster of red squares on the left) sends smoke across a large swath of southern Kansas in this image taken at 1:40pm EDT June 27, 2011. Image credit: NASA.

Tropical disturbance 95L headed towards Mexico
Heavy thunderstorm activity is increasing over the Gulf of Mexico's Bay of Campeche due to a tropical wave (Invest 95L), moving west-northwest at 5 - 10 mph towards the coast of Northeast Mexico. Satellite loops show that the thunderstorms are currently poorly organized, and there is no sign of a surface circulation. Mexican radar out of Alvarado also shows little organization and no spiral banding. Wind shear has fallen by 5 knots to 20 - 25 knots over the past day, and is predicted to continue to fall over the next two days. This should allow 95L to continue to organize, and the Hurricane Hunters are scheduled to visit the storm Wednesday afternoon to see if a tropical depression is forming. Several reliable computer models are predicting that 95L could become a tropical depression or weak tropical storm before making landfall. Landfall will probably occur on Mexico's Bay of Campeche coast several hundred miles south of the Texas border on Wednesday night. NHC is giving the system a 50% chance of developing into a tropical depression by Thursday. Development will be hindered by a large region of dry air to the west, associated with the great 2011 Texas-Mexico drought. However, the topography surrounding the Bay of Campeche tends to boost counter-clockwise air flow, enabling systems there to spin up faster than any other portion of the Atlantic.

There is a strong ridge of high pressure over the Gulf, which should act to keep 95L moving west-northwest or west, with impacts limited to Mexico and perhaps extreme South Texas. Rainfall amounts of 1 - 2 inches are possible over Brownsville, Texas on Wednesday. The main danger from the storm for Mexico is likely to be heavy rains of 4 - 8 inches, but the rain is likely to be more a blessing than a danger. Mexico is experiencing its worst drought in 70 years over 40% of the country, and wild fires have burned 500,000 acres in northern regions near the U.S. border.


Figure 2. Morning satellite image of Invest 95L.

All-time dry air record set at Las Vegas
On Monday, Las Vegas, Nevada reported its driest air in recorded history, when the temperature hit 107° and the dewpoint reached -22° at 4:32pm MDT. This gave the city a dewpoint depression of 129 degrees, and a relative humidity of just 0.6%. The dew point depression is defined as the difference between the air temperature and the dew point temperature. The previous all-time record dew point depression for Las Vegas was 120 degrees set on July 2nd 2007. Not surprisingly, this record dry air is creating dangerous fire conditions, and much of the Southwest U.S. including Las Vegas is under a Red Flag Warning for critical fire conditions today.

Jeff Masters