Tehuano wind event

April 8th, 2014
GOES-13 0.63 µm visible channel images (click to play animation)

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

As we have seen a number of times during the Winter 2013/2014 season, another strong Tehuano wind event occurred on 08 April 2014. McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed distinct arc clouds marking the leading edge of 2 pulses of gap winds emerging southward over the Gulf of Tehuantepec. The second (later) pulse of gap winds appeared to be stronger, and transported plumes of blowing dust to the south.

A timely overpass of a Metop polar-orbiting satellite provided ASCAT surface scaterometer winds which showed the fanning out of the Tehuano flow at 16:20 UTC (below). An advisory for the development of Storm Force winds had been issued by the NOAA Ocean Prediction Center for the Gulf of Tehuantepec.

GOES-13 10.7 µm IR image with Metop ASCAT surface scatterometer winds

GOES-13 10.7 µm IR image with Metop ASCAT surface scatterometer winds

MADIS 1-hour interval satellite winds (below; click image to play animation) tracked the velocity of the arc cloud and dust plumes during the day, which were moving at speeds up to 30 knots.

GOES-13 10.7 µm IR images with MADIS 1-hour satellite winds (click to play animation)

GOES-13 10.7 µm IR images with MADIS 1-hour satellite winds (click to play animation)

Past cases of well-defined Tehuano wind events can be found here.

Widespread blowing dust across the south-central US

March 18th, 2014
GOES-13 0.63 µm visible channel images (click to play animation)

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

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed two very large blowing dust features during the afternoon hours on 18 March 2014: one moving southward out of southeastern Colorado, and another moving eastward out of New Mexico across Texas and Oklahoma. Winds gusted to 75 mph in southeastern Colorado, and 60 mph in the Texas Panhandle; surface visibilities were reduced to near zero at times at some locations. As a result, some highways were closed in southeastern Colorado. Another significant blowing dust event had impacted much of this same region one week earlier.

GOES-13 0.63 µm visible channel images with METAR surface reports (click to play animation)

GOES-13 0.63 µm visible channel images with METAR surface reports (click to play animation)

Taking a closer look at the large southward-moving dust plume with AWIPS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) and GOES-13 3.9 µm shortwave IR channel data (below; click image to play animation), it can be seen that a large wildfire began to burn around 19:15 UTC (2:15 PM local time) near the Texas/Oklahoma border as the strong winds associated with the leading edge of the dust storm moved through. The hot fire (yellow to red to black pixels on the shortwave IR images) produced pyrocumulus clouds and a smoke plume that rose above the top of the dust layer, high enough to cast a shadow due to the low sun angle at the end of the day. Note from the distance scale on the lower left portion of the visible images that this “wall of dust” was at least 300 miles wide.

GOES-13 3.9 µm shortwave IR images with METAR surface reports (click to play animation)

GOES-13 3.9 µm shortwave IR images with METAR surface reports (click to play animation)

The CLAVR-x POES AVHRR Cloud Top Height product (below) indicated that the top of the southward-moving dust layer was generally 1-2 km above ground level (cyan to light green color enhancement).

POES AVHRR Cloud Top Height product

POES AVHRR Cloud Top Height product

Terra and Aqua MODIS true-color Red/Green/Blue (RGB) images visualized using the SSEC RealEarth web map server (below) revealed that the composition of the dust from the 2 source regions took on a different appearance, indicating that the nature and composition of the aerosols were different.

Terra and Aqua MODIS true-color RGB images

Terra and Aqua MODIS true-color RGB images

AWIPS images of the Terra and Aqua MODIS “reverse absorption” 11-12 µm IR brightness temperature difference product (below) offered another method of identifying the areas where the airborne dust was the most dense.

Terra and Aqua MODIS 12.0-11.0 µm IR brightness temperature difference product

Terra and Aqua MODIS 12.0-11.0 µm IR brightness temperature difference product

Additional satellite images from this event can be found on the Wide World of SPoRT and RAMMB: GOES-R Proving Ground Blog sites.

===== 19 March Update =====

IDEA-I forecast aerosol trajectories (click to play animation)

IDEA-I forecast aerosol trajectories (click to play animation)

The IDEA-I MODIS Aerosol Optical Depth product indicated that much of the airborne dust remained over southern and eastern Texas on 19 March. Forecast forward trajectories (above; click image to play animation) suggested that some of this dust would get recirculated back northward across western Texas, and eventually move over Kansas in 24-48 hours.

Blowing dust from Baja California

March 16th, 2014
GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

McIDAS images of GOES-15 (GOES-West) 0.63 µm visible channel data (above; click image to play animation) revealed large plumes of blowing dust and sand, which were moving south/southwestward from the coast of Baja California and western Mexico on 16 March 2014. There were no surface observations in the immediate vicinity of the Baja California dust plume source regions, but farther to the southeast at Loreta (station identifier MMLT) winds gusted to 37 knots or 43 mph at 19 UTC (12 Noon local time), and surface visibility was reduced to 3 miles. Surface winds were likely channelled by the upstream mountainous terrain to reach higher speeds near the dust plume source regions.

A comparison of AWIPS images of Aqua MODIS 0.65 µm visible, 1.38 µm “cirrus detection”, 3.7 µm shortwave IR, 11.0 µm “IR window”, and 6.7 µm water vapor channel data at 21:40 UTC (below) showed the following: (1) the dust/sand plume could also be seen on the 1.38 µm “cirrus detection channel” image, since this channel can be used to identify any airborne particles that are effective scatterers of light (such as cirrus ice crystals, volcanic ash, haze, or dust/sand); (2) while there was no obvious dust/sand signal on the conventional IR window channel image, the much warmer (darker black) signature on the shortwave IR image was due to reflection of incoming solar radiation off the dust/sand particles; (3) on the water vapor image, an undular bore appeared to be developing near the leading edge of the dust/sand plume. According to 1-hour interval MADIS satellite-derived atmospheric motion vectors (green wind barbs), the plumes were moving toward the southwest at speeds as fast as 25 knots at the time.

Aqua MODIS 0.65 µm visible, 1.38 µm cirrus channel, 3.7 µm shortwave IR, 11.0 µm IR, and 6.7 µm water vapor channel images

Aqua MODIS 0.65 µm visible, 1.38 µm cirrus channel, 3.7 µm shortwave IR, 11.0 µm IR, and 6.7 µm water vapor channel images

Metop ASCAT surface scatterometer winds (cyan wind barbs) at 17:43 UTC (below) indicated that winds were northeasterly at speeds around 20 knots just off the western coast of Baja California; 18 UTC GOES-15 satellite-derived winds (green wind barbs) tracked the southwestward motion of the dust plumes at speeds of 20-31 knots.

GOES-15 0.63 µm visible image with GOES-15 satellite-derived winds and Metop ASCAT surface scatterometer winds

GOES-15 0.63 µm visible image with GOES-15 satellite-derived winds and Metop ASCAT surface scatterometer winds

A sequence of true-color Red/Green/Blue (RGB) images from Terra MODIS, Suomi NPP VIIRS, and Aqua MODIS viewed using the SSEC RealEarth web map server (below) showed the southwestward progression of the tan-colored dense plumes of airborne dust/sand from Baja California. In the initial Terra MODIS image, the source region of many of the plumes appeared to be near the El Vizcaíno Biosphere Reserve.

Terra MODIS, Suomi NPP VIIRS, and Aqua MODIS true-color RGB images

Terra MODIS, Suomi NPP VIIRS, and Aqua MODIS true-color RGB images

Dust storm over the central and southern High Plains region

March 11th, 2014
GOES-13 0.63 µm visible channel images (click to play animation)

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

AWIPS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) show the hazy signature of an intense dust storm (sometimes locally referred to as a “haboob”) created by strong winds in the wake of a southward-moving cold front on 11 March 2014. This blowing dust reduced surface visibility to zero in parts of southwestern Kansas (where there were wind gusts of 59 mph), causing several traffic accidents. At Amarillo, Texas (KAMA) the wind gusted to 60 mph, and visibility was reduced to 0.25 mile at times. A pilot report indicated that the top of the blowing dust was as high as 11,000 feet over the Oklahoma panhandle region.

A sequence of Terra/Aqua MODIS and Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images visualized using the SSEC RealEarth web map server (below) showed the southward advancement of the lighter tan colored areas of blowing dust.

Terra/Aqua MODIS and Suomi NPP VIIRS true-color RGB images

Terra/Aqua MODIS and Suomi NPP VIIRS true-color RGB images

A signal of the airborne dust (cyan color enhancement) was also seen on Terra/Aqua MODIS images of the 11-12 µm “reverse absorption” IR difference product (below).

MODIS 11-12 µm "reverse absorption" IR difference product

MODIS 11-12 µm “reverse absorption” IR difference product

GOES-13 6.5 µm water vapor channel images (below; click image to play animation) showed the development of a “cirrus bloom” over far northeastern New Mexico as the surface cold front and blowing dust moved through that region. It is interesting to note that there was a pilot report of severe turbulence at an altitude of 45,000 feet around that time (reportedly due to a mountain wave) — this raises the question as to whether a vertically-propagating wave generated by the strong cold front might have caused that high-altitude turbulence.

GOES-13 6.5 µm water vapor channel images, with pilot reports of turbulence (click to play animation)

GOES-13 6.5 µm water vapor channel images, with pilot reports of turbulence (click to play animation)

Additional satellite images of this event can be found on the Wide World of SPoRT blog.

===== 12 March Update =====

Suomi NPP VIIRS 0.7 µm Day/Night Band image, with surface observations and frontal analysis

Suomi NPP VIIRS 0.7 µm Day/Night Band image, with surface observations and frontal analysis

During the subsequent night-time hours, a Suomi NPP VIIRS 0.7 µm Day/Night Band image at 08:35 UTC or 2:35 AM local time (above) displayed a signature of the airborne dust over far southwestern Texas — the glow of the city lights below the dust layer was more diffuse than in dust-free areas farther to the east in central Texas. Also note that an undular bore had formed along the cold frontal boundary near the coast of southeast Texas.

A comparison of the VIIRS Day/Night Band image with a MODIS 11-12 µm image (below) confirmed the presence of airborne dust over southwestern Texas. As in the MODIS example above, the brighter cyan color enhancement was a signal of dust.

Suomi NPP VIIRS 0.7 µm Day/Night Band and MODIS 11-12 µm IR difference product images

Suomi NPP VIIRS 0.7 µm Day/Night Band and MODIS 11-12 µm IR difference product images