April 22, 2001 Dust Episode

20% worst for three sites in West Texas and Mid South Region

Worst day for Bext at GUMO

20% best day for several sites in UT, CO, NM and AZ

GUMO

SACR

WIMO

Just after the Asian dust episode

Synoptic ConditionsNWS: “Intense upper low and associated surface cyclone pulling away from the area the evening of April 22nd in this map. Expect winds to decouple fairly quickly this evening across all but the ECNTL/NE where a wind advisory will be in effect until 03Z.”

Surface Conditions: AM

Dryline

coldfront

Surface Conditions: PM

coldfront

Surface Conditions: El Paso

The El Paso airport reported blowing dust afternoon and evening of April 21st. Winds gusting between 24 and 36 knots on April 22nd.

Low dewpoints-dry air

Surface Conditions: El PasoNEXRAD reports no rain at the West Texas sites by the morning of April 22nd.

Flagstaff, Farmington and Front Range stations report light snow in the morning. Forecasted snow at Northern NM upper elevations.

Probably snow

5 day West Texas backtrajectoriesImply Southern NM and West Texas “local” sources and potential transport from Northern Mexico

12z 12z

Large regional dust sourcesThere are more sources to the east in NM and west Texas not shown on this map

GICL

GUMO

SACR

5 day Oklahoma backtrajectories

12z 18z

23z 03z

Site in Moist Gulf air east of dryline Dryline moving eastward

Dryline at lower levels only: red is 10m trajectory, warm dry air is aloft to transport air from the west

Causes of haze during the event

DustSource

CM transported from West Texas wind aloft; Sulfates at WIMO from Ohio Valley and sea salt; organics may be from Ohio Valley and low level transport from central Texas

CM and FS at GUMP and SACR from sources in NM, TX and Mexico

WIMO