POES AVHRR 0.86 µm visible channel + 12.0 µm IR channel images at 20:23 UTC

A daily record of 1.18 inches of rainfall was recorded at McCarran International Airport in Las Vegas, Nevada on 11 September 2012 — this was also the highest daily rainfall total on record for any day in the month of September. Some locations in the Las Vegas metro area received as much as 2.09 inches (Public Information Statement), with 3.35 inches falling in the higher elevations (7450 feet) to the west of the city at Mt. Charleston. AWIPS images of 1-km resolution POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel images at 20:32 UTC (above) and 21:26 UTC (below) showed evidence of overshooting tops and cloud top IR brightness temperatues as cold as -65º C (darker red color enhanement).

POES AVHRR 0.86 µm visible channel + 12.0 µm IR channel images at 21:26 UTC

10-km resolution GOES Sounder Total Precipitable Water (TPW) derived product images (below) showed the TPW values were as high as 45 mm (1.78 inches) across parts of Clark County in southern Nevada during the hours leading up to the development of the thunderstorms.

GOES Sounder Total Precipitavble Water derived product imagery

The Blended Total Precipitable Water (TPW) Percent of Normal product (below) indicated that TPW values across the region were in excess of 200% of normal (yellow color enhancement).

Blended Total Precipitable Water Percent of Normal product

With afternoon heating, GOES Sounder Convective Available Potential Energy (CAPE) values (below) exceeded 2600 J kg-1 (darker yellow color enhancement) in the pre-convective environment.

GOES Sounder Convective Available Potential Energy (CAPE) product

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AVHRR Sea Surface Temperature Estimates

Tropical Storm / Hurricane Leslie moved very slowly over the western tropical Atlantic Ocean between 6 September and 7 September (see, for example, this graphics animation from the National Hurricane Center, and the storm track from the CIMSS Tropical Cyclones site below). Strong winds associated with the cyclonic circulation around a hurricane or tropical storm will cause upwelling, forcing cooler waters to the surface. An AWIPS image of the POES AVHRR Sea Surface Temperature (SST) product above shows the result: SST values as cool as 67.9º F (green color enhancement) occur southeast of Bermuda (TXKF) around 26 N, 63 W, the region through which Leslie had moved very slowly over the course of several days. Such cool water upwelling limits the intensification potential of tropical cyclones that move slowly.

Track of Tropical Storm Leslie

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GOES-15 0.62 µm Visible Imagery at time of Tornado

Tornadoes touched down on Long Island within the confines of New York City on September 8th, 2012. This image shows the terminal radar velocities from Newark associated with the two touch downs. This google map link shows both Canarsie and Breezy Point on a map of eastern Long Island.

The GOES-15 image above, from 1500 UTC, (Here is the same image without a map drawn on it) is for the approximate time of the tornadic touch down in Canarsie — GOES-15 was scanning across Long Island at 1504 UTC. The oblique view allows the satellite to see under the anvil of a glaciated storm over central Long Island, and to view a storm of modest appearances over eastern Long Island that produced the tornado. This tornadic cell is part of a convergence line that stretches southward down the coast of New Jersey. Stretching of local convergence by a strong updraft can cause brief tornadic events.

GOES-13 0.63 µm visible and 10.7 µm IR images (click image to play animation)

GOES-13 (GOES-East) also viewed this cell. Unfortunately, the touch-down occurred when GOES-13 was performing a routinely scheduled full-disk image, so imagery at 1445 UTC and 1515 UTC is available, and at 1545 UTC (housekeeping on GOES-13 is performed for 10 minutes starting at 1534 UTC). The routine schedule for GOES-13 is here. Nevertheless, the animation of the Visible and IR imagery shows the development of the tornadic cell along the convergence line. The 30-minute timestep between images, however, makes computation of convective predictors such as Cloud-top Cooling ineffective. The tornadoes were on the ground in between the 1445 UTC and 1515 UTC GOES-East images. Note that Canarsie is indicated by the red square in the infrared imagery.

GOES-14 0.63 µm visible and 10.7 µm IR images (click image to play animation)

GOES-14 was in SRSOR on September 8th, and its every-minute imagery captured the evolution of the tornadic cell very well. The animation above plays steps more slowly for the times when the tornado is on the ground. The animation reinforces the notion that the tornadic cell in the visible imagery is prosaic. The 1-minute imagery allows careful scrutiny of the cloud-top temperature as the cells evolve. The loop below, from 1445 UTC to 1509 UTC, spans the time of tornadic activity, and the initial cloud-top cooling and subsequent anvil spreading is readily apparent. This graph shows the coldest IR Brightness temperature over the developing/evolving tornadic cell as a function of time. It’s uncertain from the imagery alone whether the cloud-top cooling is occurring because the top of the cloud is reaching higher into the atmosphere, or because thickening clouds at lower levels are limiting the amount of radiation upwelling through the cloud. There is certainly a cooling trend, however, at the time of the tornadoes.

Magnified GOES-14 10.7µm IR images (click image to play animation)

(Added: Click here for a QuickTime movie of the visible imagery on September 8th from 1415 UTC to 1859 UTC. Click here to see an animated gif loop that compares the temporal coverage of GOES-13 — present GOES — to that of GOES-14 — simulating GOES-R)

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GOES-13 0.63 µm visible channel images

Hurricane Michael became the first Category 3 hurricane of the 2012 Atlantic Basin season on 06 September. GOES-13 0.63 µm visible channel images (above) and GOES-13 10.7 µm IR channel images (below) from the CIMSS Tropical Cyclones site showed that Michael displayed a well-defined eye.

GOES-13 10.7 µm IR channel images

A comparison of 375-meter resolution Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images (below) offered a more detailed view of the eye structure at 15:42 UTC.

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

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