Tropical Storm Debby
GOES-13 10.7 µm IR images + OSCAT surface scatterometer winds
Tropical Storm Debby formed in the eastern Gulf of Mexico on 23 June 2012 — Debby was the earliest “D”-named (4th storm of the season) Atlantic Basin tropical cyclone on record. GOES-13 10.7 µm IR channel images with an overlay of Oceansat-2 OSCAT surface scatterometer winds from the CIMSS Tropical Cyclones site (above) showed that Debby was embedded within a very broad cyclonic circulation that was present over the Gulf of Mexico — and Debby also formed over an area of high ocean heat content.
The low-level circulation center of Debby was generally exposed, but a large area of deep convection persisted within the eastern semi-circle of the storm. A number of Tropical Overshooting Tops were also seen associated with this deep convection (below).
GOES-13 10.7 µm IR images + Tropical Overshooting Tops
A comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR chnanel data (below) showed a detailed view of the low-level circulation center and the cold IR cloud tops of the deep convection.
Suomi NPP VIIRS 0.64 µm visible channel + 11.45 µm IR channel images
Abundant moisture was present over the entire Gulf of Mexico, as revealed by the MIMIC Total Prcipitable Water (TPW) product (below; click image to play animation). TPW values in excess of 60 mm (2.4 inches) were common.
MIMIC Total Precipitable Water product (click image to play animation)
During the following overnight hours, a comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel data (below) showed cloud top IR brightness temperatures as cold as -90º C (dark violet color enhancement), while the Day/Night Band image revealed a few bright white pixels indicating cloud illumination due to concentrated lightning activity. The bright lightning illumination pixels appeared to be “smeared” along the scanning direction of the VIIRS instrument. Also evident in the northwestern Gulf of Mexico were numerous small lights associated with extensive offshore drilling operations.
Suomi NPP VIIRS 0.7 µm Day/Night Band image + 11.45 µm IR image
During the afternoon hours of 24 June, another comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel data (below) showed that some areas of deep convection had begun to develop into the northern semi-circle of the storm.
Suomi NPP VIIRS 0.64 µm visible channel + 11.45 µm IR channel images
===== 25 June Update =====
MODIS 11.0 µm IR, VIIRS 11.45 µm IR, and AVHRR 10.8 µm IR images
Even though the center of Tropical Storm Debby remained offshore, a large convective burst developed over the Florida Panhandle region on 25 June 2012. In the sequence of three 1-km resolution IR images (from the MODIS, VIIRS, and AVHRR instruments) shown above, the coldest cloud top IR brightness temperature was -91 C on the 16:21 UTC MODIS image.
The corresponding animation of 4-km resolution GOES-13 10.7 µm IR images is shown below .
GOES-13 10.7 µm IR images (click image to play animation)