Convective outflow boundary and softball-size hail in southern Wisconsin

May 11th, 2011 |
GOES-13 0.63 µm visible channel images + surface reports (click image to play animation)

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

AWIPS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation) showed a convective outflow boundary (originating from strong thunderstorms earlier in the day over northeastern Wisconsin) propagating southward across the eastern portion of the state on 11 May 2011. The leading edge of the outflow boundary moved farther to the south over the nearshore waters of Lake Michigan, where surface friction was less than that over land. Later in the day, clusters of severe thunderstorms were seen to develop over southcentral and southeastern Wisconsin, along an advancing warm frontal boundary.

A 1-km resolution POES AVHRR 10.8 µm “IR window” image (below) at 19:08 UTC (2:08 pm local time) revealed a number of overshooting tops, which exhibited IR brightness temperature values as cold as -70 to -78º C (black to white color enhancement). Overlaid are the numerous SPC reports of hail that had occurred up through 22:06 UTC — hail was as large as 1.75 inches in diameter in Dane County (where observation station Madison KMSN is located), and as large as 4.25 inches (softball-size) just to the east in Jefferson county (where observation station Watertown KRYV is located). A subtle signature of outward-propagating concentric gravity waves could also seen on the IR image of this hail-producing storm, which was especially evident over the northern portion of the cold cloud shield.

CIMSS participation in GOES-R Proving Ground activities includes making a variety of POES AVHRR images and products available for National Weather Service forecasters to add to their AWIPS workstations. A “POES and AVHRR Satellite Products in AWIPS” VISIT training lesson is also available to help users understand the products and their applications to weather analysis and forecasting.

POES AVHRR 10.8 µm IR image + SPC hail reports

POES AVHRR 10.8 µm IR image + SPC hail reports

A closer look at the aforementioned leading edge of the outflow boundary over the nearshore waters of Lake Michigan is offered using 250-meter resolution MODS true color and false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below). Multiple wave fronts can be seen associated with this density current as it moved southward near the Wisconsin/Illinois border region.

MODIS true color and false color Red/Green/Blue (RGB) images

MODIS true color and false color Red/Green/Blue (RGB) images

Fire in the Okefenokee Swamp region of of Georgia

May 6th, 2011 |
GOES-13 0.63 µm visible channel images (click image to play animation)

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) showed the smoke plume emanating from a large fire that was burning in the Okefenokee Swamp in far southern Georgia on 06 May 2011. This fire originally began on 28 April as a result of a cloud-to-ground lightning strike.

AWIPS images of GOES-13 3.9 µm shortwave IR data (below; click image to play animation) displayed the rapid growth in size of the associated fire “hot spot” (black to red to yellow color enhancement). The hot spot first became apparent around 17:31 UTC (1:31 pm local time), and quickly grew as drier air moved across the region in the wake of a passing cold frontal boundary.

GOES-13 3.9 µm shortwave IR images (click image to play animation)

GOES-13 3.9 µm shortwave IR images (click image to play animation)

A comparison of AWIPS images of 1-km resolution POES AVHRR 3.7 µm and 4-km resolution GOES-13 3.9 µm shortwave IR data (below) demonstrated the advantage of better spatial resolution for locating the fire boundaries. CIMSS participation in GOES-R Proving Ground activities includes making a variety of POES AVHRR images and products available for National Weather Service offices to add to their local AWIPS workstations. A “POES and AVHRR Satellite Products in AWIPS” VISIT training lesson is also available to help users understand the products and their applications to weather analysis and forecasting.

POES AVHRR 3.7 µm + GOES-13 3.9 µm shortwave IR image comparison

POES AVHRR 3.7 µm + GOES-13 3.9 µm shortwave IR image comparison

===== 07 MAY UPDATE =====

On the following day, a comparison of 250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) revealed the dense smoke plume (which appeared as varying shades of  gray on the true color image), as well as the large size of the burn scar (which appeared as darker shades of darker red to brown on the false color image) resulting from this fire that had been burning for several days. Also evident was the fact that several active, very hot fires were burning at this time along the edges of the burn scar — these hot fires appeared as the brighter pink areas on the false color image. Many of these fire “hot spots” could even be detected through the dense smoke.

MODIS true color and false color images

MODIS true color and false color images

Southeast US tornado outbreak of 27 April 2011

April 27th, 2011 |
GOES-13 0.63 µm visible images (click image to play animation)

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

The tornado outbreak that affected much of the Southeast US on 27 April 2011 was one of historic proportions, in terms of the number of strong to violent tornadoes produced and the number of resulting fatalities. McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation; also available as a QuickTime movie) showed the multiple clusters of severe thunderstorms that developed across the region during the day. The GOES-13 satellite had been placed into Rapid Scan Operations (RSO), supplying imagery as frequently as every 5-10 minutes. Zoomed-in versions of GOES-13 RSO 0.63 µm visible images covering the period of the long-track (80 mile) EF-4 Tuscaloosa (KTCL) / Birmingham (KBHM) tornado are available here, which show that the storms exhibited a number of distinct overshooting tops during the time period between 20:40 UTC and 23:25 UTC.

AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data with overlays of severe weather reports (below; click image to play animation) showed the first round of large storms with cold cloud top IR brightness temperatures (red to black to white color enhancement) that moved through the area during the pre-dawn hours (which produced mainly damaging wind reports), followed by the development later in the afternoon and early evening hours of the stronger storms that produced numerous reports of large hail and strong tornadoes ahead of an advancing cold front (SPC storm reports). Zoomed-in versions of GOES-13 RSO 10.7 µm IR images covering the period of the long-track (80 mile) EF-4 Tuscaloosa (KTCL) / Birmingham (KBHM) tornado are available here — cloud top IR brightness temperature values during the 20:40 UTC to 23:25 UTC time period were as cold as -75º C at 22:25 UTC.

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

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

With the higher 1-km spatial resolution of the POES AVHRR IR imagery (below), more detail could be seen in the cloud top IR brightness temperature structure, and much colder cloud top temperatures could be detected in the vicinity of the strongest overshooting tops (as cold as -83º C, violet color enhancement). Other similar 1-km resolution POES AVHRR IR and MODIS IR image examples (with overlays of storm reports) are available at 16:28 UTC, 18:10 UTC, 18:12 UTC, 18:35 UTC, 19:48 UTC, 19:52 UTC, 20:13 UTC, 00:01 UTC, and 03:34 UTC.

POES AVHRR 12.0 µm IR image + SPC storm reports

POES AVHRR 12.0 µm IR image + SPC storm reports

Although there was widespread cloudiness across much of the Southeast US, hourly GOES-13 Sounder Convective Available Potential Energy (CAPE) derived product images (below) were still able to provide some indication as to the instability of the air mass that was feeding northward into the region that morning.

GOES-13 Sounder CAPE derived product imagery

GOES-13 Sounder CAPE derived product imagery

Another important ingredient was the approach of a strong trough aloft, along with an associated strong mid-level jet streak as seen in a comparison of 1-km resolution MODIS 6.7 µm water vapor imagery and CRAS model 500 millibar (hPa) wind speeds (below).

MODIS 6.7 µm water vapor channel image + CRAS model 500 MB wind speeds

MODIS 6.7 µm water vapor channel image + CRAS model 500 MB wind speeds

CIMSS participation in GOES-R Proving Ground activities includes making a variety of POES AVHRR, MODIS, and additional GOES Sounder images and products available for National Weather Service offices to add to their local AWIPS workstations. The VISIT training lessons “POES and AVHRR Satellite Products in AWIPS”, “MODIS Products in AWIPS“, and “Water Vapor Imagery and Potential Vorticity Analysis” are available to help users understand these products and their applications to weather analysis and forecasting.

To prepare for the upcoming GOES-R era, new products are being developed and tested at CIMSS using the current generation of satellite data — in fact, some of these new products are now being distributed to and evaluated by a few NWS Offices. Specially-tailored products such as Convective Initiation, Overshooting Tops, and Enhanced-V will allow for the automatic detection of the various developmental stages of convection.

 

Slide the “Set Fade Level” button located under examples of these images (above) to fade between the CIMSS Convective Initiation (CI) and CIMSS Overshooting Tops (OT) products (derived from satellite observations), along with Cloud-to-Ground (CG) lightning strikes observed from ground-based sensors. Note that there is good agreement between the locations of the satellite-derived CI and OT products and the SPC storm reports for the day (below).

 

 

Undular bore over the Gulf of Mexico

April 27th, 2011 |
GOES-13 0.63 µm visible channel images (click image to play animation)

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) showed an excellent example of an undular bore propagating southeastward off the coast of Texas and out over the Gulf of Mexico on 27 April 2011. This bore exhibited multiple wave fronts, with as many as 10-15 being visible at various times. Also note the presence of thick haze both ahead of and behind the bore: this was due to smoke from fires burning in southern Mexico and Central America (which was moving northward across the Gulf of Mexico ahead of the bore) and also from fires burning in Texas and northern Mexico (which was moving southeastward behind a cold frontal boundary that was trailing the bore).

A comparison of AWIPS images of POES AVHRR and MODIS visible channel data with overlays of hourly MADIS atmospheric motion vectors (or cloud-tracked winds) showed that the undular bore was moving southeastward at a speed of 20-30 knots.

POES AVHRR and MODIS visible images + MADIS atmospheric motion vectors

POES AVHRR and MODIS visible images + MADIS atmospheric motion vectors