Wednesday, April 17, 2013

April 17 - What a day along the border! Not just another dust storm but one that lasted more than 12 hours.

At 9 am: Winds are forecasted in Las Cruces area to be in the 31 to 41 mph range in the afternoon with gusts up to 55 mph. The time series plot below is based on the 13-km resolution Rapid Refresh model at a grid cell in Las Cruces for wind speed today. Winds should peak at 23 UTC.
 Below is a color shaded wind speed forecast for 22 UTC today.
As of 7pm, this dust storm is a whopper. I-10 has been close since noon and the winds and dust plumes have not let up. Below a NMDOT truck blocks the entrance to the frontage road that runs along I-10 near the Las Cruces Airport. A State Police cruiser blocked the entrance to I-10. I talked to the NMDOT worker who was directing traffic here and he said that there are locations down the road that have zero visibility. He also mentioned he exchanged words with some disgruntled travelers from 'back east' who didn't understand the dangers of driving along this stretch of highway. State Police had ultimate say on when the road will open up.
Hundreds of trucks and cars line both I-10 and side-roads as they wait for the interstate to open.
Below is another videocast of today's dust storm as seen from GOES, courtesy of NCAR RAP webpage.
Another look at the storm from the GOES sounder longwave difference product provides some more information. As I mention in the videocast, a distinct New Mexico hot spot is clear in the looping images.
Below is a view southwestward from the Las Cruces Airport at 5 pm. As I expected this area is not a likely source area for the dust. A few construction areas on the way to the airport were causing some localized dust but not a lot.
A quick look at surface particulate matter concentrations shows very high concentrations of PM10 in Deming in the afternoon. Peak hourly PM10 nearly hit 3000 ug/m3 at 1 pm and again at 4 pm .
Below are the PM10 concentrations measured at the Las Cruces West Mesa station today. Peak PM10 was nearly 3000 ug/m3 this afternoon.What is interesting is that the dust started to increase about the same time as in Deming, with Deming reaching the peak earlier.
We installed the CL31 ceilometer on top of the monitoring trailer so we'll be showing some products from that soon. I just received the unit on Monday after being used in a year-long project in Sparks, NV for investigating high PM2.5 exceedances. I glanced at the backscatter profiles at around 6:30 pm and it was showing most of the dust confined to a layer about 800 meters thick. As expected the highest levels were near the ground.

By the end of the day, particulate concentrations decreased to pre-storm levels. Below is a summary of hourly PM10 across the New Mexico monitoring stations. The Las Cruces Holman station recorded the highest hourly value of 3977 ug/m3. The 24-hour average PM10 at that location was 557 ug/m3, which is about 3.7 times the EPA standard.
Peak hourly PM2.5 were nearly 200 ug/m3 across all stations in southern NM.  Highest 24-hour averaged PM2.5 was at the Sunland Park Desert View Elementary School station with a 90 ug/m3 concentration.

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