Fires and blowing dust across western Texas

February 27th, 2011

 

MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth)

MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth)

 

High winds (gusting to 69 mph at Amarillo, Texas) downed power lines that ignited a number of grassland wildfires across western Texas on 27 February 2011 — according to media reports, these fires destroyed at least 60 homes, burned more than 140,000 acres, and caused an accident on Interstate 20 near Midland, Texas that killed a 5-year-old child. These high winds were also responsible for widespread areas of blowing dust, which reduced surface visibilities in a number of locations. Laredo, Texas recorded a daily high temperature of 103ºF (the first high temperature of 100º F or greater of the year in the US). A MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (above, viewed using Google Earth) showed the areas which were affected by blowing dust and smoke plumes from wildfires.

 

A comparison of AWIPS images of 4-km resolution GOES-13 3.9 µm shortwave IR data with the corresponding 1-km resolution MODIS 3.7 µm shortwave IR data (below) demonstrated the improved fire hot spot (red to yellow color enhancement) detection capability provided by higher spatial resolution. On the MODIS image, some of the fire pixels were so hot that they “wrapped around” on the color scale and appeared as white pixels.

MODIS 3.7 µm + GOES-13 3.9 µm shortwave IR images

MODIS 3.7 µm + GOES-13 3.9 µm shortwave IR images

 

An AWIPS comparison of the MODIS 0.65 µm visible channel and the corresponding MODIS 1.38 µm “cirrus detection channel” image (below) showed the utility of the near-IR cirrus detection channel for highlighting the areal coverage of the blowing dust (which showed up as the slightly brighter areas, since this MODIS channel is sensitive to any particles that are efficient scatters of light). At the time of the MODIS image, winds across this region were gusting as high as 46 knots at Pecos (station identifier KPEQ).

 

MODIS 0.65 µm visible image + MODIS 1.38 µm "cirrus detection" image

MODIS 0.65 µm visible image + MODIS 1.38 µm "cirrus detection" image

 

Farther to the north over the Texas Panhandle region, a similar comparison of the 4-km resolution GOES-13 3.9 µm shortwave IR data with the corresponding 1-km resolution MODIS 3.7 µm shortwave IR data (below) again demonstrated the improved fire hot spot (red to yellow color enhancement) detection capability provided by higher spatial resolution.

MODIS 3.7 µm + GOES-13 3.9 µm shortwave IR images

MODIS 3.7 µm + GOES-13 3.9 µm shortwave IR images

 

A similar AWIPS comparison of the MODIS 0.65 µm visible channel and the corresponding MODIS 1.38 µm “cirrus detection channel” image (below) again showed the utility of the near-IR cirrus detection channel for highlighting the areal coverage of the blowing dust. At the time of the MODIS image, winds across this region were gusting as high as 60 knots at Amarillo (station identifier KAMA), where surface visibility was restricted to 1.5 miles.

MODIS 0.65 µm visible image + MODIS 1.38 µm "cirrus detection" image

MODIS 0.65 µm visible image + MODIS 1.38 µm "cirrus detection" image

 

 

High winds and wildfire activity over the Mid-Atlantic region

February 19th, 2011
GOES-13 6.5 µm water vapor channel imagery (click image to play animation)

GOES-13 6.5 µm water vapor channel imagery (click image to play animation)

AWIPS images of 4-km resolution GOES-13 6.5 µm “water vapor channel” data (above; click image to play animation) revealed an extensive “mountain wave signature” across much of the Mid-Atlantic region of the US on 19 February 2011. Strong winds (gusting to 71 mph in Virginia and 63 mph in Maryland and Pennsylvania) in the wake of a cold frontal passage were interacting with the terrain of the Appalachian Mountains to create the widespread mountain waves — and some of the mountain waves were responsible for pilot reports of moderate to severe turbulence.

1-km resolution MODIS 6.7 µm water vapor images (below) offered a more detailed view of the mountain wave structure.

MODIS 6.7 µm water vapor images

MODIS 6.7 µm water vapor images

On occasion, these mountain waves appear in “clear air’ with no clouds present — this can be seen from Virginia to the Delmarva Peninsula in a comparison of a MODIS 0.65 µm visible image with the corresponding MODIS 6.5 µm water vapor image (below). Aircraft sometimes encounter “clear air turbulence” under such circumstances.

MODIS 0.65 µm visible image + MODIS 6.5 µm water vapor image

MODIS 0.65 µm visible image + MODIS 6.5 µm water vapor image

It is interesting to note that the MODIS 2.1 µm near-IR “snow/ice channel” image (below) displayed  a signature of what appeared to be the effect of atmospheric gravity waves over the adjacent offshore waters. A similar signature was discussed on the MODIS Image of the Day site off the coast of New Zealand on 21 December 2010.

MODIS near-IR 2.1 µm "snow/ice channel" image

MODIS near-IR 2.1 µm "snow/ice channel" image

The combination of strong winds and dry vegetation (MODIS Normalized Difference Vegetation Index) created an environment favorable for wildfire activity — and on this day there were more than 100 wildfires reported across the state of Virginia alone. The “hot spots” signatures (black to yellow to red color enhancement) from many of the larger fires could be seen on 4-km resolution GOES-13 3.9 µm imagery, with many more of the smaller fires exhibiting such signatures on the corresponding 1-km resolution POES AVHRR 3.7 µm shortwave IR image (below).

GOES-13 3.9 µm shortwave IR image + POES AVHRR 3.7 µm shortwave IR image

GOES-13 3.9 µm shortwave IR image + POES AVHRR 3.7 µm shortwave IR image

A MODIS “true color” Red/Green/Blue (RGB) image (below; displayed using Google Earth) showed a few of the longer smoke plumes that were emanating from the largest fires located from western Virginia to the Washington, DC area.

MODIS true color RGB image (displayed using Google Earth)

MODIS true color RGB image (displayed using Google Earth)

Gulf of Mexico “Loop Current” affecting cumulus cloud development

February 13th, 2011
GOES-13 0.63 µm visible channel imagery (click image to play animation)

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

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the development of a batch of cumulus clouds over the central Gulf of Mexico during the day on 13 February 2011. Other features of interest on the visible imagery include the rapidly-melting snow cover over the portions of the southern Plains, and a few small smoke plumes drifting northeastward due to fires burning in some of the Gulf Coast states.

A comparison of AWIPS images of the 1-km resolution MODIS 0.65 µm visible channel and the corresponding MODIS Sea Surface Temperature (SST) product (below) indicated that this area of cumulus development was occurring over the warmer waters of the Gulf of Mexico “Loop Current”, where SST values were as warm as 78º F (darker orange color enhancement). As a seasonally cool northeasterly flow of air moved across the warmer Loop Current, enough instability was generated to lead to the formation of shallow cumulus clouds.

MODIS 0.65 µm visible image + MODIS Sea Surface Temperature product

MODIS 0.65 µm visible image + MODIS Sea Surface Temperature product

About 3 hours later, a similar comparison of a 1-km resolution POES AVHRR 0.63 µm visible image with the corresponding POES AVHRR Sea Surface Temperature product (below) showed a few more cumulus lines forming over the northern portion of the Loop Current, with the cumulus cloud field becoming more dense in the southern portion.

POES AVHRR 0.63 µm visible image + POES AVHRR Sea Surface Temperature product

POES AVHRR 0.63 µm visible image + POES AVHRR Sea Surface Temperature product

Yet another Northeast US winter storm

January 26th, 2011
MODIS 6.7 µm water vapor image

MODIS 6.7 µm water vapor image

The third major storm  of the 2010/2011 winter season  (storm #1 | storm #2) impacted much of the Mid-Atlantic and Northeast states on 26 January 2011 27 January 2011. An AWIPS image  of MODIS 6.7 µm water vapor channel data at 18:28 UTC  (above) revealed a large and complex dry slot, with convective elements developing ahead of the leading edge of the dry slot across Virginia. In addition, to the east of the dry slot over the western Atlantic Ocean a well-defined packet of high altitude “transverse bands” was seen (close-up view) which was forming in the right entrance region of an upper level jet streak.

On a POES AVHRR false-color Red/Green/Blue (RGB) image at that same time (below), high cloud features appeared brighter white, with low clouds taking on a slight yellow tint.

POES AVHRR Red/Green/Blue (RGB) false color image

POES AVHRR Red/Green/Blue (RGB) false color image

An animation of GOES-13 10.7 µm IR images (below; click image to play animation) showed the development of the transverse banding cloud structures — the bands were oriented perpendicular to the southwesterly high-altitude wind flow over that region. This transverse banding pattern is a cloud signature that is often associated with areas of turbulence — and in this case there were two pilot reports of moderate turbulence at altitudes of 34,000 feet and 36,000 feet.

GOES-13 10.7 µm IR images (click image to play animation)

GOES-13 10.7 µm IR images (click image to play animation)

A comparison of a GOES-13 10.7 µm IR image with the corresponding MODIS 11.0 µm IR image (below) demonstrated the advantage of higher spatial resolution, with the fine transverse band structure more apparent on the 1-km resolution MODIS image. The coldest IR brightness temperatures within the bands on the MODIS image were -58º C (red color enhancement).

MODIS 11.0 µm IR + GOES-13 10.7 µm IR images

MODIS 11.0 µm IR + GOES-13 10.7 µm IR images

A number of cloud-to-ground lightning strikes were associated with the convective elements that had formed over Virginia (below), ahead of the leading edge of the dry slot that was seen on water vapor imagery. Thundersnow was reported across a wide portion of the Mid-Atlantic and Northeast states, with snowfall rates as high as 1-4 inches per hour at some locations.

MODIS 11.0 µm IR image + lightning strikes + METAR surface reports

MODIS 11.0 µm IR image + lightning strikes + METAR surface reports

=========== 27 JANUARY UPDATE ===========

MIMIC Total Precipitable Water product (click image to play animation)

MIMIC Total Precipitable Water product (click image to play animation)

This storm was not particularly intense in terms of a low central pressure or strong winds, but it was able to tap a significant plume of deep moisture (in excess of 30-40 mm or 1.2-1.6 inches) from the Gulf of Mexico and the Caribbean, as can be seen on AWIPS images of the MIMIC Total Precipitable Water (TPW) product (above; click image to play animation) and the Blended Total Precipitable Water product (below; click image to play animation). This contributed to the high snowfall totals at many locations (Weather Underground blog| WeatherMatrix blog).

Blended Total Precipitable Water product (click image to play animation)

Blended Total Precipitable Water product (click image to play animation)

Parts of this plume of moisture represented TPW values in excess of 200% of normal (below; click image to play animation).

Percent of Normal TPW product (click image to play animation)

Percent of Normal TPW product (click image to play animation)