GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (above; click to play animation; also available as an MP4 movie) revealed the presence of mesovortices within the eye of Category 4 Hurricane Iselle on 04 August 2014. Mesovortices are sometimes seen in the eye and eyewall of tropical cyclones that are going through a period of intensification.

Before sunrise, a 10:30 UTC comparison of GOES-15 10.7 µm IR and TRMM TMI 85 GHz microwave images from the CIMSS Tropical Cyclones site (below) showed that Iselle was beginning to exhibit the appearance of an annular hurricane; note that the ring of high-intensity rainfall within the eyewall was much larger on the microwave image than the “cloud-free” eye that was seen on the IR image.

GOES-15 10.7 µm IR and TMI 85 GHz microwave images

========================= Update, 5 August 2014 ==========================

Hourly imagery from 1300 UTC on 4 August to 1300 UTC 5 August shows Iselle maintaining a generally westward track. Cloud-top temperatures have warmed over the 24 hours shown, however, and the eyewall is becoming less distinct. Iselle’s path has been over SSTs that are progressively cooler. Further weakening is expected today.

GOES-15 10.7 µm infrared channel images (click to play animation)

Suomi NPP overflew Iselle late in the afternoon of the 4th, and a true color image of the storm is shown below (Image Source: NOAA Hawaii X/L Antenna). A mesovortex can be identified in the eye in this high-resolution image.

Suomi NPP True Color Imagery of Iselle, 2300 UTC 4 August 2014 (click to enlarge)

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

Large wildfires continued to burn during much of the month of July in the Northwest Territories of Canada, and McIDAS-X images of GOES-13 0.63 µm visible channel data on 28 July 2014 (above; click image to play animation) showed large amounts of smoke aloft streaming southwestward across the western and southwestern portion of Hudson Bay. This pattern of middle-tropospheric smoke transport was caused by the juxtaposition of a highly-amplified ridge of high pressure over central Canada and a deep area of low pressure over Quebec (500 hPa map). During the later part of the day, the clearing of patchy low clouds and the thinning of the smoke aloft revealed the presence of large ice floes over southwestern Hudson Bay. According to the Canadian Ice Service, this was thick first year ice from the previous winter season, with ice concentration values as high as 9-10/10s.

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image combination prepared using McIDAS-V (below; courtesy of Joleen Feltz, CIMSS) showed the variety of smoke, ice, and cloud formations over Hudson Bay at 18:45 UTC.

Suomi NPP VIIRS true-color RGB image

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

A supercell thunderstorm intensified as it moved eastward across the Chesapeake Bay (just ahead of an approaching surface cold front) on the morning of 24 July 2014 — as it reached the Virginia shore of the Delmarva Peninsula, it produced an EF-1 tornado and damaging straight line winds that were responsible for 2 fatalities and 36 injuries at the Cherrystone Family Camping Resort (located at the * symbol on the images). The storm also produced golf ball to baseball size hail (NWS damage survey | SPC storm reports). McIDAS images of GOES-13 10.7 µm IR channel data (above; click image to play animation; also available as an MP4 movie file) showed that the cloud-top IR brightness temperatures associated with the storm cooled quickly, from -45º C at 11:15 UTC to -64º C at 12:30 UTC. The temperature value was close to that of the tropopause (at a height of 15.4 km) on the 12 UTC rawinsonde data from Wallops Island, Virginia.

The corresponding GOES-13 0.63 µm visible channel images (below; click image to play animation; also available as an MP4 movie file) revealed the presence of an overshooting top at 12:30 UTC  (the time that the IR cloud-top brightness temperature values reached their minimum), which was also flagged by the automated Overshooting Tops detection algorithm.

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

AWIPS-II images of the NOAA/CIMSS ProbSevere product (below) followed the radar feature associated with the supercell thunderstorm. Around 11:30 UTC, the ProbSevere value was low, around 5-10%, a result of weak satellite-detected growth (and moderate glaciation) early in the storm’s life, along with low values of MRMS Maximum Expected Size of Hail (MESH). Environmental parameters from the Rapid Refresh model that were supportive of convection: MUCAPE exceeded 2200 J Kg and Shear values were greater than 30 m/s. As the cell tracked to the east and began to move over Chesapeake Bay, both MUCAPE and Shear gradually increased, to values near 2400 J/kg and 35 m/s, respectively. MRMS MESH was oscillating as the cell approached Chesapeake Bay, from 0.44 inches at 11:42 UTC (ProbSevere value of 10%) to 0.37 inches at 11:46 UTC (ProbSevere of 7%) to 0.65 inches at 11:48 UTC (ProbSevere of 29%) to 0.56 inches at 12:00 UTC (ProbSevere of 18%). As the storm moved over the Bay, MESH sizes jumped, to 0.86″ at 12:04 UTC (ProbSevere of 58%, the first crossing of the 50% threshold), to 1.02″ at 12:06 UTC (ProbSevere of 71%), to 1.86″ at 12:12 UTC (ProbSevere of 92% , the first crossing of the 90% threshold), and to 3.09″ (!) at 12:16 UTC (ProbSevere of 91%). At 12:20 UTC, when the Tornado Warning was issued, MRMS MESH was 3.51″ and ProbSevere remained at 91%. Thus, the warning was issued 16 minutes after ProbSevere exceeded 50%, and 8 minutes after ProbSevere was greater than 90%. The NWS storm survey indicated that the campsite fatalities occurred around 12:33 UTC, or 13 minutes after the issuance of the tornado warning.

NOAA/CIMSS ProbSevere product

The rapid intensification of the system as it moved over the Chesapeake begs the question: was instability diagnosed? In the animation below, GOES-13 sounder Derived Product Images (DPI) of Lifted Index (top panel) and CAPE (bottom panel) showed a rich source of instability just south of the cloud-obscuring convection (and ahead of the southward-moving cold front). Lifted Index values derived at 1147 UTC were around -6 at the mouth of the Chesapeake Bay (bright yellow enhancement); CAPE values were around 2500 J/kg (yellow and red enhancements).

GOES-13 Sounder DPI estimates of Lifted Index (top) and CAPE (bottom) [click to play animation]

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Meteosat-10 10.8 µm infrared channel images (click to enlarge)

An Air Algerie Flight AH5017 crashed less than an hour after taking off from Ouagadougou, Burkina Faso (the southern asterisk in the animation above). Contact was lost at 0155 UTC (Press Report) and wreckage was found southeast of the Gossi, Mali (the northern asterisk in the animation above). Cloud-top IR Brightness Temperatures in the Mesoscale Convective System through which the plane flew were as cold as -78º C.

Suomi NPP was flying over Mali and Burkina Faso at 0152 UTC on 24 July and provided high-resolution infrared and Day/Night Band imagery along the flight path. The toggle below, of the VIIRS 11.45 µm infrared and 0.70 µm Day/Night Band (Imagery courtesy of William Straka, UW CIMSS) shows the convective storm. The bright lights of Ouagadougou are evident, as well as lightning streaks within the storm. (Click for zoomed-in versions of 11.45 µm and Day Night Band images)

Suomi NPP VIIRS 11.45 µm infrared and 0.7 µm Day/Night Band images (click to enlarge)

============================= Added 28 July 2014 =========================

Suomi NPP VIIRS 0.7 µm Day/Night Band image (click to enlarge)

The image above includes the light flare from the actual plane crash, circled in red. Suomi NPP was passing over the crash site between 1:55:00 and 1:55:30 UTC on 24 July 2014 (Link, navigation computed from Two Line Element files). The animation below shows Day/Night Band imagery (also courtesy of William Straka, UW CIMSS) from before the crash (21 July), the time of the crash on the 24th, and after the crash (25 July).

Suomi NPP VIIRS 0.7 µm Day/Night Band imagery on three days in July (click to Animate)

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