MODIS 0.65 µm visible channel image + Land Surface Temperature product

A comparison of AWIPS images of 1-km resolution MODIS 0.65 µm visible channel data and the corresponding MODIS Land Surface Temperature (LST) product (above) showed nearly cloud-free conditions and very hot LST values of 120 – 140 F (darker red color enhancement) across much of southern Oklahoma at 19:48 UTC or 2:48 PM local time on 03 August 2012. On this particular day, two notable temperature records were set at Oklahoma City:

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE NORMAN OK
1145 PM CDT FRI AUG 3 2012

…NEW RECORD MAXIMUM TEMPERATURE SET AT OKLAHOMA CITY…
…NEW RECORD WARM MINIMUM TEMPERATURE AT OKLAHOMA CITY…

TODAYS MAXIMUM TEMPERATURE AT WILL ROGERS WORLD AIRPORT IN OKLAHOMA CITY WAS 113 DEGREES. THIS BREAKS THE PREVIOUS RECORD MAXIMUM
TEMPERATURE OF 109 DEGREES, SET ON THIS DATE IN 2011.

THIS ALSO TIES THE WARMEST MAXIMUM TEMPERATURE ON RECORD. THE RECORD WAS LAST REACHED ON AUGUST 11TH 1936.

THE MINIMUM TEMPERATURE OF 84 DEGREES IS ALSO THE WARMEST MINIMUM ON RECORD. THE PREVIOUS RECORD WARM MINIMUM OF 83 DEGREES WAS LAST REACHED ON AUGUST 13TH 1936.

TEMPERATURE RECORDS FOR OKLAHOMA CITY DATE BACK TO 1891.

The hot LST and air temperature values combined with dry fuels due to ongoing drought conditions created a very favorable environment for wildfire activity — and several fire smoke plumes were noted on GOES-13 0.63 µm visible channel images (below; click image to play animation). With the largest of the fires located east of Norman, Oklahoma (station identifier KOUN), a number of brighter white pyrocumulus clouds could be seen popping up through the lighter gray smoke plume.

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

The dense smoke plume from the Norman fire showed up very well on the 19:52 UTC (2:52 pm local time) Aqua MODIS true color Red/Green/Blue (RGB) image (below, displayed using Google Earth).

Aqua MODIS true-color Red/Green/Blue (RGB) image

The large fire east of Norman continued to burn into the the following night, exhibiting a pronounced “hot spot” (black to yellow to red color enhancement) on the 07:57 UTC (2:57 AM local time) Suomi NPP VIIRS 3.74 µm shortwave IR image (below). The flames from this fire also had a distinct bright signature on the corresponding 0.7 µm Day/Night Band image.

Suomi NPP VIIRS 11.45 µm IR, 3.74 µm shortwave IR, and 0.7 µm Day/Night Band images

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Overshooting Tops detected over the central Atlantic

A strong tropical wave near 50 W Longitude in the central Atlantic has become a Tropical Depression. The enhanced infrared image above shows a region of active convection (as signified by the overshooting tops designated by yellow circles) near the center of the system. (Current imagery of overshooting tops can be found here). This convection is aided by abundant moisture as shown in the animation of Total Precipitable Water (TPW), below, taken from the MIMIC TPW website.

Morphed Total Precipitable Water over the north Atlantic Basin

Diagnostics from the CIMSS Tropical Weather Website (below) suggest that an inhibiting factor to rapid strengthening may be wind shear, as analyses show the storm near a region of significant westerly shear. Factors favoring slow intensification are warm sea surface temperatures and a moist surrounding atmosphere.

Infrared imagery and diagnosed wind shear over Tropical Depression #5

Analysis of dry air near Tropical Depression #5

Sea-surface temperature analysis over the central Atlantic

The National Hurricane Center forecasts slow strengthening. Should the system become a tropical storm, it will take the name Ernesto. The current projected path has the storm in the central Caribbean Sea by the weekend.

===== 02 August Update =====

The Suomi NPP VIIRS 0.7 µm Day/Night Band offered a “night-time visible image” of Tropical Depression #5 at 05:23 UTC on 02 August (below; image courtesy of William Straka, CIMSS).

Suomi NPP VIIRS 0.7 µm Day/Night Band image

During the afternoon hours, the system was upgraded to Tropical Storm Ernesto. GOES-13 0.63 µm visible channel images (below; click image to play animation) showed that while Ernesto was producing a few convective bursts near its center (IR image animation with tropical overshooting tops product), it was also exhibiting a number of well-defined surface outflow arc clouds along the northern and western periphery of the circulation. This arc cloud signature often indicates that the storm is ingesting dry air which results in the production of dry thunderstorm downdrafts — and Ernesto was both relatively close the the continent of South America, and was surrounded by a dry Saharan Air Layer.

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

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POES AVHRR 10.8 µm IR image + SPC storm reports of hail and damaging winds

A large mesoscale convective system (MCS) developed in western Tennessee, which then grew in size and intensity as it propagated southward across Alabama on 31 July 2012. An AWIPS image of 1-km resolution POES AVHRR 10.8 µm IR channel data (above) showed cloud top IR brightness temperatures as cold as -87º C (darker purple color enhancement). Overlaid on the image are the cumulative SPC storm reports of hail (green) and damaging winds (cyan).

GOES-13 10.7 µm IR channel images (below; click image to play animation) showed the increase in size of cold cloud tops as the MCS moved southward, with cloud top IR brightness temperatures as cold as -82º C (purple color enhancement).

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

A comparison of a 375-meter resolution (projected onto a 1-km AWIPS grid) VIIRS 11.45 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image (below) showed the advantage of higher spatial resolution in the identification of locations of the coldest cloud tops and their magnitude (-88º C on the VIIRS image, vs -80º C on the GOES-13 image). Also note the slight northwestward shift in the location of features on the GOES-13 image, a result of parallax due to the larger viewing angle from the GOES-East satellite located at 75º West longtude.

VIIRS 11.45 µm IR channel image + GOES-13 10.7 µm IR channel image

With illumination from moonlight, the Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) can serve as a “visible channel” at night — and a comparison with the corresponding 11.45 µm IR image (below) aided in the identification of features such as overshooting tops and thunderstorm top gravity waves. Note how some city lights can be seen through the thinner edges of the MCS cirrus canopy.

Suomi NPP VIIRS 0.7 µm Day/Night Band image + 11.45 µm IR channel image

This MCS produced a great deal of lightning, with over 2500 cloud-to-ground strikes in the 15-minute period preceeding the VIIRS DNB image (below). Also note the appearance of several brighter white “smeared” pixels, which indicated portions of the thunderstorm cloud top which were illuminated by lightning as the VIIRS instrument was scanning the area.

Suomi NPP VIIRS 0.7 µm Day/Night Band image + METAR surface reports + cloud-to-ground lightning strikes

The Blended Total Precipitable Water (TPW) product (below; click image to play animation) indicated that the MCS was moving southward toward an axis of higher TPW values (50-60 mm or 2.0-2.4 inches, red to purple color enhancement).

Blended Total Precipitable Water product

A closer view using 10-km resolution GOES-13 sounder derived product images of TPW, Lifted Index, and Convective Available Potential Energy (below) showed that there were pockets of higher moisture and instability ahead of the advancing MCS.

GOES-13 sounder Total Precipitable Water, Lifted Index, and Convective Available Potential Energy derived product images

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GOES-15 (left) and GOES-13 (right) 10.7 µm IR channel images

A tornado was observed and photographed near Mt. Evans in north-central Colorado around 2:51 PM local time or 20:51 UTC (Local Storm Report) on 28 July 2012. A comparison of McIDAS images of 4-km resolution GOES-15 (GOES-West) and GOES-13 (GOES-East) 10.7 µm IR channel data (above) showed that the thunderstorm which produced the tornado developed fairly rapidly just to the east of Copper Mountain (station identifier KCCU), but was relatively small in size and did not exhibit particularly cold cloud top IR brightness temperatures (-40º C at 20:45 UTC, and -52º C at 21:15 UTC).

AWIPS images of 1-km resolution MODIS 0.6 µm visible channel and 11.0 µm IR channel data at 20:28 UTC (below) showed that the storm was beginnng to produce a few negative cloud-to-ground lightning strikes, with a minimum IR brightness temperature around -50º C at that time.

MODIS 0.65 µm visible and 11.0 µm IR channel images (with cloud-to-ground lightning strikes)

The CIMSS Cloud Top Cooling Rate product (below) did flag the storm at 20:32 UTC as it was beginning to develop in north-central Colorado.

GOES-13 instantaneous Cloud Top Cooling Rate product

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