GOES-13 0.65 µm visible channel images

McIDAS images of the GOES-13 0.65 µm visible channel data (above) showed the development of a well-defined plume of blowing dust/sand that appeared to originate from the White Sands, New Mexico area on 29 April 2010 — this plume of airborne aerosols very quickly reached the Texas/New Mexico border by about 21 UTC. Very strong winds (gusting to 50-70 mph) across the region were responsible for the widespread areas of blowing dust, which restricted surface visibilities to below 3 miles at a number of sites across New Mexico.

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First official GOES-15 10.7 µm longwave IR image (click image to enlarge)

The first official GOES-15 full disk InfraRed (IR) images became available at 17:30 UTC on 26 April 2010. The GOES-15 Imager 10.7 µm longwave IR image is shown above – similar images are available for the 0.65 µm visible channel, the 3.9 µm shortwave IR, the 6.5 µm water vapor channel, and the 13.3 µm CO2 channel.

GOES-15 was launched on 04 March 2010, with the first visible images from the Imager instrument available on 06 April and from the first visible images from the Sounder instrument on 08 April. GOES-15 will have a Post Launch Test beginning in August 2010.

GOES-15 multi-panel display of the Imager visible and IR channels

A multi-panel display showing all 5 of the  GOES-15 Imager channels is shown above. For comparison purposes, a similar multi-panel display  of all five of the GOES-13 Imager channels is shown below.

GOES-13 multi-panel display of the Imager visible and IR channels

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GOES-13 and GOES-15 10.7 µm longwave IR images

Some close-up comparisons of GOES-13 and GOES-15 IR images show similar results from the two satellites. The image above uses GOES-13 and GOES-15 10.7 µm longwave IR channel data to display a cluster of strong convection over the far eastern Gulf of Mexico, between Florida and Cuba — the coldest 10.7 µm IR brightness temperatures seen were 196.2 K (-77.0º C) on GOES-13, vs 194.9 K (-78.3º C) on GOES-15.

The image below is a comparison of the 13.3 µm CO2 channels. Note that the Field of View (FOV) of the 13.3 µm CO2 channel has improved from 8 km on GOES-13 to 4 km on GOES-15 — as a result, the edges of cloud features now appear much smoother on the GOES-15 13.3 µm image.

GOES-13 and GOES-15 13.3 µm CO2 channel images

Looking farther to the west, the image below shows the Gulf of Mexico Loop Current, using the 3.9 µm shortwave IR channel data from GOES-13 and GOES-15. AWIPS images of the Sea Surface Temperature (SST) products from MODIS and AVHRR indicated that the SST values were as warm as 80º F within the Loop Current, surrounded by waters with SST values in the 70-75º F range.

GOES-13 and GOES-15 3.9 µm shortwave IR images

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GOES-13 and GOES-15 6.5 µm water vapor images

A comparison of the GOES-13 and GOES-15 6.5 µm water vapor channels (above) showed a pocket of very dry air (yellow to orange color enhancement) to the north of the aforementioned strong convection located between Florida and Cuba. This dry air was a signature of a well-defined  “jet stream break”, as verified by GFS model 250 hPa wind speed isotachs (below).

GOES-13 water vapor image + GFS 250 hPa wind speed isotachs

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GOES-13 6.5 µm water vapor imagery + surface fronts

On a rare “High Risk” SPC Convective Outlook day, a significant tornado outbreak occurred across the Deep South region of the US on 24 April 2010 which produced long-track tornadoes that were responsible for at least 10 fatalities across parts of Mississippi (SPC storm reports | NWS Jackson MS event summary). AWIPS images of the GOES-13 6.5 µm water vapor channel data with overlays of surface fronts (above) showed a cold frontal boundary advancing eastward across the region, with a strong punch of dry air aloft associated with an upper level jet stream. The NAM model fields suggested that the maximum winds within the jet core were in the 140-145 knot range, but there were a number of MADIS 1-hour interval atmospheric motion vectors with speeds of 155-157 knots along the sharp dry-to-moist water vapor gradient.

Widespread cloudiness obstructed a good view of the amount of Total Precipitable Water (TPW) that was available using the GOES Sounder or MODIS, but the Blended Total Precipitable Water product (below) showed that TPW values of 40 – 50 mm (red to violet color enhancement) were in place within the warm sector ahead of the cold front.

Blended Total Precipitable Water product

An animation of GOES-13 10.7 µm IR images (below) revealed that the cluster of severe convection appeared to intensify as it crossed the Mississippi River from Louisiana into Mississippi after about 16 UTC. While there was not the typical “enhanced-v” storm top signature that is often seen with severe convection, the GOES-13 IR cloud top brightness temperatures did cool to -60º C and below (darker red color enhancement) after 13:40 UTC, reaching a minimum value of -63º C at 18:32 UTC.

Closer views of the IR imagery showed that these storms were characterized by a great deal of cloud to ground lightning strikes (24-hour total lightning strikes) as they produced a number of tornado and damaging wind reports. Farther to the north, there was a report of softball-size hail (4.5 inches in diameter) in western Tennessee at 21:00 UTC.

GOES-13 10.7 µm IR images + METAR surface reports

A comparison of a 1-km resolution MODIS 11.0 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image as the core of the storm was crossing the Mississippi River around 16:30 UTC (below) demonstrates (1) the improvement in accuracy of storm top brightness temperature detection with higher spatial resolution (-69º C with MODIS, versus -58º C with GOES), and (2) the “parallax shift” associated with the relatively large geostationary satellite view angle (note that the storm features are shifted a bit to the northwest on the GOES-13 image). The SPC storm reports of tornadoes and damaging winds within the 16:14 – 17:55 UTC time range are also plotted on the two IR images. A similar AVHRR 10.8 µm IR image at 18:40 UTC with an overlay of SPC severe reports can be seen here.

MODIS 11.0 µm IR and GOES-13 10.7 µm IR images (with overlays of severe reports)

===== 25 April Update =====

Comparison of MODIS true color images from 15 April and 25 April 2010

Viewing a comparison of “before” (15 April) and “after” (25 April) 250-meter resolution MODIS true color images (above) and false color images (below), from the SSEC MODIS Today site, the subtle signature of a portion of the tornado damage path can be seen. Viewing the MODIS true color image using Google Earth, the southwest-to-northeast oriented tornado damage path can be seen extending from the eastern half of Yazoo county into the southern portion of Holmes county in Mississippi. The tornado that struck the Yazoo City area has been given a preliminary damage assessment rating of EF4, with a maximum damage path width of 1.75 miles.

Comparison of MODIS false color images from 15 April and 25 April 2010

===== 28 April Update =====

A comparison of 250-meter resolution Aqua MODIS visible Band 1 and Band 2 images from 28 April 2010  (below) reveals portions of the tornado damage path across parts of Issaquena and Yazoo counties in Mississippi. In areas with a higher density of trees, the tornado damage path appears as a lighter shade of gray on the Band 1 image, and as a darker shade of gray on the Band 2 image.

Portions of the tornado damage path on MODIS visible band 1 and visible band 2 images

Related sites:

• Weather Underground radar images

• AccuWeather WeatherMatrix blog post

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Spring convection and associated severe weather returned to the southern Plains on April 22nd. Did predictors of convection do a good job in locating the severe cells?

CIMSS has recently started to produce synthetic satellite imagery from the Weather Research and Forecasting (WRF) model run at the National Severe Storms Laboratory (NSSL). Output from daily runs at 00 UTC is produced for 9 infrared bands that correspond to those of the Advanced Baseline Imager (ABI) that will fly on GOES-R. The hourly loop of the 11.2-micrometer channel, above, for the period between 1800 UTC 22 April and 00 UTC 23 April, shows convection initially forming along the dryline in the Texas Panhandle between 1900 and 2000 UTC before progessing northeastward into Oklahoma and Kansas. Synthetic imagery of the middle of 3 ABI water vapor channels (6.95 microns), show a similar story. Model predictions give clues on where to look for convective development. How did real-time predictors of convective development perform?

The UW Convective Initiation algorithm combines observations of 10.8-micron cooling (from GOES-13) with cloud phase changes. When cooling occurs as cloud phase is changing (suggesting growing cumulus towers that are glaciating), GOES-13 pixels are flagged as showing convective initiation. Depending on the cloud phase — all water, mixed water and ice, or all ice, the initiation is flagged in the screengrabs from N-AWIPS above as pre-CI cloud growth (blue), CI likely (green), or CI occurring (yellow). Once glaciation has occurred, CI detection turns off. A previous blog entry on this method is here.

UWCI does flag individual cells that subsequently develop, ignoring adjacent towering cumulus. Thus, it can draw forecaster attention to the updrafts that, for whatever reason, are the most vigorous. For example, the image at 1701 UTC show convective initiation indicated in one spot along the dryline in west Texas. By 1745 UTC, convection has developed. Shortly after 1800 UTC, UWCI identifies individual cells along a line from the extreme western portion of the Oklahoma panhandle northward into east central Colorado. These cells subsequently spawn severe weather. UWCI also flags nascent convective development for cells that eventually develop into an arc of convection over central Kansas at 2301 UTC. Note also that UWCI flags specific convective towers within a large cumulus field over the southern Panhandle. (Consider the three images at 2131 UTC and 2145 UTC and at 2231 UTC; convection initiation flagged at the earlier two images develops most vigorously as shown in the final image). This can focus forecaster attention to the clouds that are growing most rapidly.

The two images above show where convective initiation was diagnosed to be ongoing at some time on 22 April, as well as a preliminary Storm Report from the Storm Prediction Center. Note the good general overlap of UWCI points over the High Plains and storm reports. That more Storm reports exist than UWCI points reflects the UWCI philosophy of keeping the false alarm rate low, perhaps at the expense of detection.

There are several UWCI hits over the northeast on 22 April as well. There, cold air at upper levels promoted self-destructing sunshine and shower and thunderstorm development. Clear skies early in the day (1431 UTC) gave way to cumuliform development. The strongest updrafts likely yield the strongest cloud-top-cooling signal (as shown in this loop) and evolve into the most vigorous shower or thundershower. Even though severe weather was not reported with these cells, lightning was produced, starting around 1900 UTC as shown here. Cloud-top cooling can give a forecaster a head’s up that a particular cell might become vigorous enough to electrify.

(Note: this post has been corrected to remove images from before 1645 UTC on 22 April that may have included mis-navigated regions of convective initiation).

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