GOES sounder « CIMSS Satellite Blog

Severe thunderstorms across Missouri, Illinois, and Indiana

April 28th, 2012

GOES-13 sounder Total Precipitable Water derived product imagery

AWIPS images of 10-km resolution GOES-13 sounder Total Precipitable Water (TPW) derived product imagery (above) and the corresponding GOES-13 sounder Convective Available Potential Energy (CAPE) derived product imagery (below) showed that moisture (TPW values as high as 45 mm or 1.78 inches near Saint Louis, Missouri at 16 UTC) and instability (CAPE values as high as 4300 J /kg acorss southern Illinois at 20 UTC) was in place along and to the south of a quasi-stationary warm frontal boundary that was located from eastern Missouri across southern Illinois and southern Indiana during the late morning and early afternoon hours on 28 April 2012.

GOES-13 sounder CAPE derived product imagery

4-km resolution GOES-13 10.7 µm IR channel images (below; click image to play animation) indicated that thunderstorms developed in Missouri and southern Illinois, and then tracked east-southeastward along the warm frontal boundary. These storms produced a long swath of large hail and severe wind gusts, as can be seen by the SPC storm reports overlaid on the IR imagery. Later in the afternoon, some of the organized convection began to exhibit well-defined “enhanced-V” storm top signatures, which often denotes thunderstorms that are likely producing (or will soon produce) either large hail, damaging wind gusts, or tornadoes.

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

Greater details can be seen in a 1-km resolution POES AVHRR 10.8 µm IR image with overlays of METAR surface reports and cumulative SPC storm reports of large hail and damaging wind gusts (below). A long swath of hail and damaging winds can be seen, including one incident where a wind gust of 50 mph blew over an outdoor beer garden tent around 20:50 UTC (resulting in a number of injuries and one fatality).

POES AVHRR 10.8 µm IR image + cumulative SPC storm reports of hail and wind gusts

A compariosn of the 1-km resolution POES AVHRR 0.63 µm visible channel image with the corresponding 10.8 µm IR channel image (below) again showed great detail in the overshooting top and cloud top thermal couplet structure.

POES AVHRR 0.63 µm visible channel image + 10.8 µm IR channel image

A comparison of the 1-km resolution POES AVHRR 10.8 µm IR channel image with the corresponding 4-km resolution GOES-13 10.7 µm IR image (below) demonstrates the value of higher spatial resolution for detecting important cloud top temperature patterns. In this case, the coldest cloud top IR brightness temperature on the POES AVHRR image was -78º C, compared to -69º C on the GOES-13 IR image. Also note the slight northward parallax shift in the GOES-13 IR image.

GOES-13 10.7 µm IR channel image + POES AVHRR 10.8 µm IR channel image

Posted in AVHRR, GOES sounder, GOES-13, POES, Severe convection | No Comments »

Historic Late April Nor’easter Storm

April 23rd, 2012

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

A historic late-April “nor’easter” storm affected much of the northeastern US during the 22 April – 23 April 2012 period. This storm produced heavy snowfall (as much as 23.3 inches at Laurel Summit, Pennsylvania), heavy rainfall (as much as 5.74 inches at New Boston, New Hampshire), and wind gusts as high as 94 mph at Mount Washington, New Hampshire. AWIPS images of 4-km resolution GOES-13 6.5 µm water vapor channel images (above; click image to play animation) showed the development of various features of the storm on 23 April, including a large and well-defined comma head, dry slot, and deformation zone.

By tracking the movement of various water vapor image features between consecutive images, atmospheric motion vectors can be calculated which give an indication of the wind direction and wind speed within the middle to upper troposphere. GOES-13 6.5 µm water vapor images with overlays of MADIS 1-hour interval water vapor winds are shown below (click image to play animation).

GOES-13 6.5 µm water vapor images + MADIS 1-hour water vapor winds (click image to play animation)

Satellite-derived water vapor winds can also be used to calculate an upper-tropospheric (150-300 mb) divergence product (below), which in this case showed persistent divergence aloft over much of the northeastern US on 23 April. This upper-level divergence created an environment that favored upward vertical motion within the atmospheric column, helping to enhance and prolong the ongoing precipitation over those areas.

GOES-13 water vapor images + Upper-level divergence derived from water vapor winds

A series of 1-km resolution MODIS 11.0 µm IR and POES AVHRR 12.0 µm IR images (below; click image to play animation) indicated that enhanced areas of colder clouds (some exhibiting a banding structure) developed over the region of persistent upper level divergence.

MODIS 11.0 µm IR + POES AVHRR 12.0 µm IR images

The 10-km resolution GOES-13 sounder Total Column Ozone (TCO) product (below; click image to play animation) revealed an anomalously large area of elevated TCO covering much of the eastern US, indicative of a lowered tropopause associated with the large upper-level trough of low pressure.

GOES-13 sounder Total Column Ozone + RUC 500 hPa geopotential heights

===== 24 April Update =====

MODIS 6.5 µm visible channel image + MODIS false-color RGB image

A comparison of the 1-km resolution MODIS 0.65 µm visible channel image at 16:09 UTC (12:09 pm local time) with a corresponding false-color Red/Green/Blue (RGB) image created using the MODIS 2.1 µm “snow/ice detection” channel (above) helped to identify high-elevation areas with significant snow cover remaining after the passage of the storm — snow appears brighter white on the visible image, and darker red on the false-color image. Note that cirrus clouds appear as a lighter shade of red in the RGB image.

A 250-meter resolution MODIS true color image from the SSEC MODIS Today site (below; viewed using Google Earth) showed even better detail of the snow-covered high terrain.

MODIS true-color RGB image (viewed using Google Earth)

Posted in AVHRR, GOES sounder, GOES-13, Google Earth, MODIS, POES, Red/Green/Blue (RGB) images, Satellite winds, Winter weather | No Comments »

Intense Eastern Pacific / Gulf of Alaska storm

April 2nd, 2012

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.