GOES-13 6.5 µm water vapor channel image + Pilot report of extreme turbulence

United Airlines flight 1727 from Tampa, Florida to Houston, Texas (aircraft flight path | plot of aircraft altitude/speed, from FlightAware.com) encountered extreme turbulence near the coast of Louisiana just before 12:00 UTC on 04 April 2012, which resulted in injures to 12 passengers. An AWIPS image of 4-km resolution GOES-13 6.5 µm water vapor channel data at 11:40 UTC with the text of the pilot report is shown above — note that there was also a pilot report of moderate turbulence at 37,000 feet just to the north.

A southward-propagating squall line was intensifying during the morning hours as it crossed the Gulf Coast — the leading edge of the squall line was evident from the numerous cloud-to-ground lightning strikes  (below; click image to play animation).

GOES-13 6.5 µm water vapor images + Lightning strikes (click image to play animation)

4-km resolution GOES-13 10.7 µm IR channel images (below; click image to play animation) showed a few cold overshooting cloud tops, with an IR brightness temperature as cold as -70 C at 11:01 UTC and -67 C at 11:40 UTC.

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

1-km resolution POES AVHRR 12.0 µm IR channel images before and after the turbulence encounter (below) revealed cloud top IR brightness temperatures as cold as -77 C over Louisiana at 09:03 UTC.

POES AVHRR 12.0 µm IR images

One interesting question to ask is: was this southward-propagating squall line initiated by outflow boundaries from the large mesoscale convective system that produced the widespread large hail and tornado event across northeastern Texas during the afternoon and evening hours on 03 April? A long sequence of GOES-13 10.7 µm IR channel images (below; click image to play animation) does suggest a possible connection.

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

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

AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel images (above; click image to play animation) showed the development of a line of severe thunderstorms along an advancing cold frontal boundary as it approached the Dallas/Fort Worth, Texas region during the afternoon hours on 03 April 2012. These storms produced a number of tornadoes, hail as large as 2.75 inches in diameter, and damaging winds (SPC storm reports | NWS Fort Worth outbreak summary).

A closer view using a 1-km resolution MODIS 11.0 µm IR channel image at 17:29 UTC (below) showed much better details regarding the cloud top IR brightness temperature structure of the storms. In particular, note the pronounced cold/warm (-63º C / -52º C, respectively) thermal couplet exhibited by the storm located just east of Cleburne (station identifier KCPT), where the first tornado was reported by spotters at 17:35 UTC.

MODIS 11.0 µm IR channel image + Surface reports + Surface frontal analysis + Cloud-to-ground lightning strikes

A comparison of the 1-km resolution MODIS 11.0 µm IR channel image with the corresponding 4-km resolution GOES-13 10.7 µm IR channel image (below) demonstrated (1) the advantage of higher spatial resolution for more accurately identifying and quantifying storm top signatures, and (2) the parallax shift of the storm top features, due to the large viewing angle from the GOES-13 (GOES-East) satellite.

GOES-13 10.7 µm IR channel image + MODIS 11.0 µm IR channel image

A similar MODIS vs GOES-13 IR image comparison about 90 minutes later (below) again showed how the numerous cold overshooting tops were much more apparent on the 1-km resolution MODIS image.

MODIS 11.0 µm IR channel image + GOES-13 10.7 µm IR channel image

Even greater detail could be seen on a 375-meter resolution Suomi NPP VIIRS 11.450 µm IR channel image at 19:33 UTC (below), which showed a number of cold overshooting tops with IR brightness temperature values in the -70 to -79 C range (dark black to white color enhancement). Hail of 2.0 inches in diameter was being reported just to the west and just to the east of Dallas/Fort Worth International Airport (DFW) at 19:30 UTC.

Suomi NPP VIIRS 11.450 µm IR channel image

Suomi NPP VIIRS 0.64 µm visible channel + 11.450 µm IR channel images (McIDAS)

A comparison of the 375-meter resolution Suomi NPP VIIRS 0.64 µm visible channel and 11.450 µm IR channel images can be seen using McIDAS (above) and AWIPS (below).

Suomi NPP VIIRS 0.64 µm visible channel + 11.450 µm IR channel images (AWIPS)

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GOES-15 6.5 µm water vapor channel images (click image to play animation)

McIDAS images of 4-km resolution GOES-15 6.5 µm water vapor channel data (above; click image to play animation) displayed the development of a classic “dry swirl” water vapor signature indicating the transition to an occluded cyclone during the 01 April – 02 April 2012 time period. The Ocean Prediction Center was forecasting large areas of hurricane force winds associated with this storm (00 UTC | 06 UTC | 12 UTC).

A sequence of AWIPS images of 1-km resolution MODIS 11.0 µm and POES AVHRR 12.0 µm IR channel data (below) showed a variery of small-scale banding structures during various stages of development of the storm.

MODIS 11.0 µm + POES AVHRR 12.0 µm IR channel images

The approach of a strong Potential Vorticity (PV) anomaly helped the storm to intensify rapidly, with with CRAS model fields indicating the tropopause (taken to be the pressure level of the PV1.5 surface) lowering to around the 900 millibar level by 06 UTC on 02 April (below).

Although the storm was near the edge of the GOES-15 sounder scan, an image of the GOES-15 sounder Total Column Ozone product (below) showed that the PV anomaly was situated along a strong ozone gradient (which is often the case).

GOES-15 6.5 µm water vapor image + GOES-15 sounder Total Column Ozone product (with overlays of CRAS model PV1.5 pressure)

The MIMIC Total Precipitable Water (TPW) product (below) showed the storm tapped an area of moisture that was situated north of the Hawaiian Islands, eventually stretching this moisture into a thin filament along the storm’s cold frontal boundary.

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

Later in the day, an overpass of a EUMETSAT MetOp satellite provided ASCAT ocean surface winds over the large occluded storm as it was moving slowly off the coast of British Columbia, Canada. A comparison of 1-km resolution MODIS 0.65 µm visible channel and MODIS 11.0 µm IR channel images with an overlay of ASCAT wind vectors is shown below.

MODIS 0.65 µm visible channel and 11.0 µm IR channel images + MetOp ASCAT scatterometer surface winds

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

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) revealed the cyclonic circulation of a Mesoscale Convective  Vortex (MCV) that was moving northeastward across Mississippi on 30 March 2012. This MCV appeared to play a role in helping to initiate new convective cells ahead of it as the atmosphere destabilized during the late morning and early afternoon hours.

AWIPS images of GOES-13 10.7 µm IR channel images (below; click image to play animation) helped to identify the apparent origin of the MCV — a large mesoscale convective system that developed along the Texas coast after about 15 UTC on the previous day (29 March).

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

A closer look at the parent mesoscale convective system using a 1-km resolution MODIS 11.0 µm IR image with overlays of cloud-to-ground lightning strikes (below) showed that the storm was producing a large number of lightning strikes. The coldest MODIS cloud top IR brightness temperatures were -70 C (darker black color enhancement).

MODIS 11.0 µm IR channel image + Cloud-to-ground lightning strikes

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