Mesoscale Convective System along the Gulf Coast region

April 30th, 2014 |
Radar-estimated Storm Total Precipitation for the 24-hour period ending at 13:47 UTC on 30 April

Radar-estimated Storm Total Precipitation for the 24-hour period ending at 13:47 UTC on 30 April

A large Mesoscale Convective System (MCS) developed ahead of a slow-moving cold front and moved over the Gulf Coast region of the US on 29 April30 April 2014, producing record rainfall totals (WeatherUnderground) and creating widespread severe flooding across parts of southern Alabama and the western Florida Panhandle. The 24-hour WSR-88D Storm Total Precipitation as visualized using the SSEC RealEarth web map server (above) showed swaths of radar-estimated precipitation in excess of 10 inches (violet color enhancement) — but some locations reported actual storm total rainfall amounts exceeding 20 inches (NWS Mobile/Pensacola).

AWIPS images of the MIMIC Total Precipitable Water (TPW) product (below; click image to play animation; Atlantic sector animation) indicated that there were multiple northward surges of TPW values in the 45-50 mm or 1.78-2.0 inch range (darker orange color enhancement) during the 28-30 April time period.

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

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

4-km resolution GOES-13 10.7 µm IR channel images (below; click image to play animation) displayed large areas of unusually cold GOES cloud-top IR brightness temperatures (colder than -80º C, violet color enhancement) — in fact, the coldest GOES-13 10.7 µm IR cloud-top brightness temperature seen was -86º C at 12:15 UTC.

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

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

This MCS also produced very large amounts of cloud-to-ground lightning (below; click image to play animation), with the highest number of 15-minute interval lightning strikes being 5379 negative and 697 positive at 11:15 UTC.

GOES-13 10.7 µm IR channel images with cloud-to-ground lightning strikes (click to play animation)

GOES-13 10.7 µm IR channel images with cloud-to-ground lightning strikes (click to play animation)

A 1-km resolution MODIS IR image at 04:11 UTC on 30 April (below) displayed a minimum cloud-top IR brightness temperature of -87º C (darker violet color enhancement).

MODIS 11.0 µm IR channel image

MODIS 11.0 µm IR channel image

375-meter resolution (mapped onto a 1-km AWIPS grid) Suomi NPP VIIRS 11.45 µm IR channel images (below) displayed a minimum cloud-top IR brightness temperature of -90º C (dark violet color enhancement) at 06:57 UTC on 29 April.

Suomi NPP VIIRS 11.45 µm IR channel images

Suomi NPP VIIRS 11.45 µm IR channel images

1-km resolution POES AVHRR 12.0 µm IR channel images (below) exhibited a minimum cloud-top IR brightness temperature of -93º C at 10:12 UTC and 11:07 UTC on 30 April.

POES AVHRR 12.0 µm IR channel images

POES AVHRR 12.0 µm IR channel images

Brightness temperatures seen on a single-channel IR image do not always indicate the true cloud top temperature value — but in this case, the -93º C value (which was also seen on the corresponding POES AVHRR 10.8 µm IR image) agreed with minimum value on the POES AVHRR CLAVR-x Cloud Top Temperature product. The POES AVHRR Cloud Top Height product indicated values of 15-16 km in these areas of extremely cold IR temperatures (below).

POES AVHRR 10.8 µm IR channel, Cloud Top Temperature product, and Cloud Top Height product at 11:07 UTC

POES AVHRR 10.8 µm IR channel, Cloud Top Temperature product, and Cloud Top Height product at 11:07 UTC

As we have seen with previous cases of strong convection exhibiting intense overshooting tops, nighttime Suomi NPP VIIRS 0.7 um Day/Night Band imagery (below) showed that this MCS produced a large pattern of concentric mesospheric airglow waves that could be seen traveling away from the storm for a considerable distance.

Suomi NPP VIIRS 0.7 um Day/Night Band image

Suomi NPP VIIRS 0.7 um Day/Night Band image

One Response to “Mesoscale Convective System along the Gulf Coast region”

  1. olivier says:

    The last image is amazing… Tubulences (TAC) should be expected so far from the MCS

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