GOES-13 0.63 µm visible channel images

A tornado produced EF1 damage and was responsible for one fatality (NWS Green Bay summary) as it moved though the town of Wausaukee in far northeastern Wisconsin during the late afternoon hours on 19 August 2011. This event brought the number of tornado deaths to 550 so far in 2011, making this the 4th deadliest year on record so far in terms of tornado-related fatalities.

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above) showed the development of the thunderstorm along the Wisconsin/Michigan border region around 18:00 UTC (1:00 pm local time), which then moved southeastward ahead of an advancing cold frontal boundary. The “W” overlaid on the images indicates the location of Wausaukee. Some features to note on the GOES visible imagery include: (1) the formation of a series of northwest-to-southeast oriented boundary layer horizontal convective roll clouds in the vicinity of Iron Mountain (station identifier KIMT), which marked the location of a residual convective outflow boundary from a squall line which moved eastward across the Upper Peninsula of Michigan during the early morning hours on 19 August, (2) subtle storm top shadowing indicating the presence of vigorous overshooting tops, and (3) the development of a well-defined back-sheared storm top anvil along the western edge of the storm toward the end of the animation. A photo of the back-sheared anvil was taken from the Green Bay, Wisconsin area around 00:40 UTC, looking northeast toward the storm (below, courtesy of Peg Zenko).

Photo of back-sheared anvil (courtesy of Peg Zenko)

AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data (below) showed that cloud top IR brightness temperatures associated with this storm cooled to about -60ºC (darker red color enhancement), but no distinct “enhanced-v” or other severe storm top signatures were apparent.

GOES-13 10.7 µm IR channel images

However, about an hour and 45 minutes before the tornado moved through Wausaukee, a comparison of a 1-km resolution POES AVHRR 10.8 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image around 20 UTC (below) illustrated the distinct advantage of higher spatial resolution for detecting the presence of colder overshooting cloud tops (-69ºC on POES AVHRR, compared to -57ºC on GOES) as well as important cold/warm thermal couplets (the POES AVHRR image displayed a well-defined cold/warm thermal couplet of -69ºC/-49ºC).

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

The GOES-13 sounder Convective Available Potential Energy (CAPE) derived product image at 19:00 UTC (below) revealed that there were pockets of CAPE in the 2300-2900 J/kg range (brighter yellow color enhancement) just ahead of the developing storm, which at that time was centered just west-northwest of Land O Lakes, Wisconsin (station identifier KLNL).

GOES-13 sounder Convective Available Potential Energy (CAPE)

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GOES-14 visible channel image of TD #8

A strong tropical depression has been moving west-northwestward through the Caribbean, and is north of Honduras on August 19th. The visible image loop above, using data from GOES-14 (over the Equator at 105º West Longitude), shows the disturbance at 1330 UTC on August 18th and on August 19th. Some modest increase in organization is discernable, as well as the motion to the west-northwest.

Stereoscopic view of TD #8

Data from GOES-14 and GOES-13 can be used to produce a stereoscopic view of the tropical depression, above. Three dimensions become visible using this technique. This allows the strong thunderstorms near the depression center to pop up out of the screen, and it also facilitates viewing the thin cirrus at the edges of the disturbance.

Data available at the CIMSS Tropical Weather Website shows the tropical depression over very warm water and in an environment of low shear. Despite proximity to land, it is expected to strengthen to Tropical Storm status on the 19th; if it does, it will be named Harvey.

(Update: Harvey achieved tropical storm status at 1800 UTC on 19 August)

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GOES-13 / GOES-14 visible channel image

The Atlantic Tropical Season’s seventh named storm, Gert, was southeast of the island of Bermuda on Monday August 15th on a projected path that keeps it well to the east of Bermuda. The morning full-resolution visible imagery (above) from GOES-13 (left) and GOES-14 (right) show a well-defined Central Dense Overcast through which are penetrating a few overshooting tops. These tops are far more easily visualized with the more oblique viewing angle afforded by GOES-14 (overhead at 105º West Longitude vs. 75º West Longitude for GOES-13). AVHRR Infrared Imagery from NOAA-16 shows brightness temperatures below -75º C with the coldest of the overshoots.

GOES-13 Enhanced Infrared and Observed Shear

Gert is at present in a region of small shear, as shown in the analysis above taken from the CIMSS tropical weather website. However, the projected path is towards higher shear. Strengthening to hurricane status may be difficult because of the increase in shear and because of progressively colder water along the projected path of Gert into the northern Atlantic. There has not yet been a hurricane season in the Atlantic during which none of the first 7 named storms — ‘A’ through ‘G’ — achieved hurricane status. (In 2002, Gustav was the first Hurricane after 6 Tropical Storms).

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The following appeared in the Area Forecast Discussion issued by the National Weather Service forecast office at State College, PA on the morning of 12 August 2011:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
523 AM EDT FRI AUG 12 2011

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
HIGH PRESSURE AND ASSOCIATED DRY AIR MASS PRODUCING A NEARLY CLOUDLESS MORNING OVER CENTRAL PA. 07Z MODIS 11-3.7UM IMAGERY SHOWS FOG HAS DEVELOPED IN THE VALLEYS OF WESTERN PA…WHERE COOL AIR IN CONTACT WITH RELATIVELY WARMER RIVER/STREAM WATER. ANY FOG SHOULD BURN OFF BY 8-9AM.

AWIPS images of the 1-km resolution MODIS fog/stratus product along with the corresponding 4-km resolution GOES fog/stratus product image (below) demonstrated the improvement in river valley fog detection that is possible with higher spatial resolution. Note the river valley fog on the MODIS image that was mentioned across western Pennsylvania, as well as other areas of river valley fog across parts of southern New York and northern West Virginia.

1-km resolution MODIS and 4-km resolution GOES fog/stratus product images

About 3 hours later, a similar comparison of 1-km resolution POES AVHRR and 4-km resolution GOES fog/stratus product images (below) show that river valley fog had increased across parts of western and northern Pennsylvania. The large amount of noise on the GOES fog/stratus product made it difficult to accurately locate where river valley fog features had formed.

1-km resolution POES AVHRR and 4-km resolution GOES fog/stratus product images

CIMSS participation in GOES-R Proving Ground activities includes making a variety of POES AVHRR and MODIS images and products available for National Weather Service offices to add to their local AWIPS workstations. Currently there are 49 NWS offices receiving MODIS imagery and products from CIMSS.

The VISIT training lessons “POES and AVHRR Satellite Products in AWIPS” and “MODIS Products in AWIPS” are available to help users understand these products and their applications to weather analysis and forecasting.

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