Advisories on Tropical Storm Bill were initiated when the system organized and intensified off the coast of Texas at 03 UTC on 16 June 2015 (GOES-13 IR image animation). Bill moved inland during the afternoon hours on 16 June, as can be seen in a comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 1916 UTC (above).

Late in the day on 17 June, the general appearance of downgraded Tropical Depression Bill on GOES-13 6.5 µm water vapor channel imagery (below) began to suggest that the system might be undergoing an extratropical transition (intrusion of dry air in the southern quadrant, along with a blosominig comma head signature on the northern quadrant) — but Bill maintained sufficient tropical characteristics to continue being named a tropical depression.

The circulation of TD Bill maintained its identity on satellite imagery as the storm remained over land for the next 3+ days, curving northeastward and moving across the Ohio River Valley region. Slow-moving TD Bill dropped over 12 inches of rain at some locations in Texas and Oklahoma, with amounts exceeding 8 inches in Missouri and 6 inches in Indiana (WPC storm total rainfall totals), before being designated a post-tropical feature at 21 UTC on 20 June (WPC advisories).

The history of Bill can be followed in a multi-day animation of GOES-13 10.7 µm IR channel imagery (above); in addition, the lower-tropospheric circulation of Bill can be followed using the CIMSS 850 hPa relative vorticity product (below).

As the post-tropical remnants of Bill emerged over the Atlantic Ocean early in the day on 21 June, it still appeared to be associated with an arc of deep convection as seen on a comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 1742 UTC (below). A similar comparison of Terra MODIS visible and IR images at 1514 UTC can be seen here.

View only this post Read Less

An explosion occurred along a natural gas pipeline near Lindenau, Texas just after 01 UTC on 15 June 2015 (8:00 pm local time on 14 June). The thermal signature or “hot spot” of the resulting fire was detected on both GOES-15 (GOES-West) and GOES-13 (GOES-East)  3.9 µm shortwave IR imagery (above; click image play animation). The images have overlays of surface reporting stations (yellow), Interstate highways (cyan), and primary highways (gray). The relatively small but very hot fire exhibited IR brightness temperatures as high as 341.1 K on GOES-13 and 340.0 K on GOES-15, which is close to the saturation temperature for the 3.9 µm detectors on those satellites. Since GOES-13 was in Rapid Scan Operations (RSO) mode at the time, the fire hot spot was first detected by that satellite (at 0107 UTC) — and the IR brightness temperature remained at 341.0 K for another 40 minutes after initial detection (0115 to 0155 UTC).

A subtle signature of the fire’s smoke plume (lighter gray enhancement) could be seen moving northwestward and then northward away from the fire hot spot. On the 0125 UTC GOES-13 shortwave IR image (below), and overlay of the CRAS model winds showed them turning from southeastward at the surface (in agreement with regional METAR surface reports) to southerly at an altitude of 3 km, suggesting that the smoke plume may have reached that height.

View only this post Read Less

GOES-14, in SRSO-R mode, captured the quick development of severe thunderstorms over northern Illinois late in the afternoon on 10 June 2015. Many of these storms produced large hail — especially in Will County and in Grundy County, where the second largest hailstone on record for the state of Illinois was measured (NWS Chicago summary). This event is also discussed on the GOES-R Hazardous Weather Testbed (HWT) Blog: before initiation, during convective initiation, lightning jumps and ProbSevere (first post, second post), and Overshooting top detection. The animation above compares GOES-14 SRSO-R imagery (top) with GOES-13 in Routine Scanning mode (until 2045 UTC) and in Rapid Scan Operations (RSO) mode after 2115 UTC on 10 June 2015 (a smaller version of this large animated gif is also available as an mp4).

The GOES-14 SRSO-R imagery depicts the convection evolving in a fluid atmosphere. Even the relatively fast GOES-13 RSO time-step cannot capture the full evolution and decay of overshooting tops.  On the 1-minute GOES-14 images, note the development of prominent cloud-top plumes which spread out southeastward away from the more robust overshooting top regions, and also cloud-top gravity waves which form along the southeastern flank of some of the larger thunderstorm anvils. Another advantage of SRSO-R compared to the routine scanning strategy using visible imagery is discussed here.

A wider-scale view of the evolution of the atmosphere on 10 June over the Upper Midwest is available here as a YouTube video, here as an mp4, and here as an animated gif image (warning: 300+ Megabyte file). A closer-scale view of the developing convection with GOES-14 visible images is available as an mp4 movie file, or on YouTube; an animation of GOES-14 10.7 µm IR images is available as an mp4 file.

The line of severe thunderstorms developed just ahead of a cold frontal boundary (animation) that was sagging southward and stalling across northern Illinois during the day on 10 June. About an hour before the 4.75-inch diameter hail was reported in Minooka IL (located about 12 miles southwest of Joliet, KJOT), a 1-km resolution POES AVHRR 12.0 µm IR image at 2316 UTC (above) showed that particular cluster of thunderstorms just southwest of the Chicago area around the time of initial hail report (1.25 inch diameter at 2318 UTC); less than a half hour later there was a report of 2.00 inch hail at 2345 UTC. Farther to the southwest, the larger thunderstorm complex was also producing hail and damaging winds, near and to the southwest of the region of coldest cloud-top IR brightness temperatures (-77º C) exhibited by the overshooting tops.

Hourly derived product images (DPI) of GOES-13 sounder Lifted Index (above) and Total Precipitable Water (below) revealed that a broad axis of instability and moisture existed across northern Illinois ahead of the approaching cold frontal boundary. Lifted Index values reached the -8º to -10º C range (red colors); Total Precipitable Water values were generally in the 40 to 50 mm or 1.6 to 2.0 inch range (red colors), with some locations as high as 53 mm or 2.1 inches (violet colors). The presence of this instability and moisture helped to create an environment favorable for the rapid growth of strong to severe convection.

View only this post Read Less

The Storm Prediction Center in Norman OK had the Plains of northeast Colorado and adjacent States in a Slight Risk (or higher) threat of severe weather on 4 June 2015. The visible image, above, shows a tornado-producing severe thunderstorm over Elbert County that produced a long-lived tornado, according to the SPC Storm Reports. The reported start and end points of the tornado (and observed times) are indicated as well. Elbert (farther northeast) and El Paso (farther southwest) counties are outlined.

The evolution of the tornadic cell was captured while GOES-14 was operating in SRSO-R mode. An animated gif of the evolution from 1915 UTC 4 June through 0130 UTC on 5 June is (warning: 190M animation!) here. A YouTube video of the mp4 is below. Note that the tornado formed along the obvious moisture boundary made visible by the arc of cumulus clouds south and east of the severe storm. (This post from the Hazardous Weather Testbed blog shows the moisture gradient as a gradient in CAPE) One-minute imagery allows an extraordinarily detailed look at features in the very dynamic cloud-top; overshooting tops develop and decay very quickly as the storm develops and matures. An animation of 10.7µm imagery from 2100 UTC through 0600 UTC on 5 June is available on YouTube here. Click here (180M gif) for a storm-centered animated gif of the tornadic storm (Also available as an mp4 and on YouTube).

View only this post Read Less