Super Typhoon Francisco

October 19th, 2013 |
MTSAT-2 10.8 µm IR channel images (click to play animation)

MTSAT-2 10.8 µm IR channel images (click to play animation)

Super Typhoon Francisco became the third Category 5 tropical cyclone of 2013 on 19 October 2013, as it intesified over the West Pacific Ocean northwest of Guam. 4-km resolution MTSAT-2 10.8 µm IR channel images (above; click image to play animation) showed the evolution and track of the eye of Francisco during the 17-19 October period (the island of Guam is in the lower right corner of the images). Note the trochoidal motion or “wobble” that is exhibited by the eye of the tropical cyclone as it tracked northwestward – this is caused by changes within the inner core structure of the storm, such as convective asymmetries.

1-km resolution MTSAT-2 0.73 µm visible channel images (below; click image to play animation) revealed better details of the eye and eyewall structure during the daylight portion of 18-19 October. The lowering October sun angle tended to more brightly illumimate the sloped surface of the northern quadrant of the eye.

MTSAT-2 0.73 µm visible channel images (click to play animation)

MTSAT-2 0.73 µm visible channel images (click to play animation)

A McIDAS-V comparison of 375-meter resolution Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm thermal IR channel images at 15:48 UTC on 18 October (below; images courtesy of William Straka, CIMSS) showed a good example of the so-called “stadium effect”: the eye diameter appeared larger on the VIIRS IR image than on the corresponding “visible image at night” from the VIIRS Day/Night Band, because the clouds along the edges of the eye were steeply sloping outward with height.

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Mesoscale bands of snow cover in Kansas

October 19th, 2013 |
Suomi NPP VIIRS 0.7 µm Day/Night Band, IR BTD "Fog/Stratus Product", and 11.45 µm IR images

Suomi NPP VIIRS 0.7 µm Day/Night Band, IR BTD “Fog/Stratus Product”, and 11.45 µm IR images

Parts of Kansas received up to 5-6 inches of snowfall on 18 October 2013 (NWS Local Storm Reports). The following night, after the clouds associated with the storm system had moved eastward, the southwest-to-northeast oriented bands of snow cover could be clearly seen on an AWIPS image of Suomi NPP VIIRS 0.7 µm Day/Night Band data at 08:33 UTC or 3:33 AM local time (above). Due to ample illumination from a Full Moon, the bands of fresh snow appeared quite bright, as did the back edge of the stratus cloud deck that covered far eastern Kansas and western Missouri (which showed up well on the IR brightness temperature difference “fog/stratus product” image). A thin patch of mid-level clouds was also moving over north-central Kansas — the 11.45 µm IR brightness temperatures of that cloud feature were generally warmer than -20º C (cyan color enhancement).

After sunrise on the next day (19 October), GOES-13 0.63 µm visible channel images (below; click image to play animation) showed that the bands of snow cover melted rather quickly, due to the relatively high October sun angle.

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

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