GOES-12 IR images

Bill became the first Atlantic hurricane of the 2009   season  on 17 August 2009. GOES-12 IR images from the CIMSS Tropical Cyclones site (above) displayed a canopy of very cold cloud tops around the center of the hurricane. The CIMSS satellite-derived wind shear product indicated that the storm environment was characterized by low shear, allowing intensification to progress.

A comparison of a 10:15 UTC GOES-12 IR image with a DMSP SSM/IS 85 GHz microwave image from a couple of hours earlier (below) showed a well-organized banding structure beneath the central dense overcast of cold cloud tops.

GOES-12 IR image + SSM/IS microwave image

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GOES-12 IR images

GOES-12 IR images from the CIMSS Tropical Cyclones site (above) showed that Tropical Storm Claudette intensified fairly quickly during the morning hours on 16 August 2009, with the areal coverage of cold cloud tops increasing rapidly during the 09-15 UTC time period. A DMSP SSM/IS 85 GHz microwave image at 13:02 UTC (below) revealed the formation of convectiove banding within the eastern semicircle of the storm.

DMSP SSM/I microwave image

While there was a report of 40 knot winds from a Carnival Cruise Line vessel to the northeast of the center of Claudette (below), this wind report was probably not representative of the winds at the surface (due to the large size of the ship and the height of the wind measuring equipment).

GOES-12 visible image with ship reports

AWIPS images of the MODIS 11.0 µm IR channel (below) revealed cloud top brightness temperatures as cold as -76º C (lighter red color enhancement) south of the center of Claudette during the late morning and early afternoon hours.

MODIS 11.0 µm IR images

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GOES-12 IR images

GOES-12 IR images from the CIMSS Tropical Cyclones site (above) showed that Tropical Storm Bill began to exhibit a well-defined curved banding structure during the early  daytime hours  on 16 August 200. In addition, the IR imagery displayed the formation of  a large convective burst near the center of the circulation.

GOES-12 IR image + deep layer mean winds

The CIMSS deep layer mean winds product overlaid on a GOES-12 IR image (above) as well as an animation of GOES-12 water vapor images (below) indicated that there was a large subtropical ridge of high pressure in place to the north of Bill, which would act to keep the storm moving on a west-northwesterly path for several days.

GOES-12 water vapor images + model forecast tracks

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GOES-12 visible images

GOES-12 visible images from the CIMSS Tropical Cyclones site on 15 August 2009 (above) showed that the low-level circulation of Tropical Storm Ana (the first named Atlantic Basin tropical storm of the 2009 season) had become exposed from the main area of deep convection located farther to the east. This suggested that  Ana was moving into a region of increasing westerly wind shear, though the CIMSS deep layer wind shear product (below) only showed about 5-10 knots of  shear over the tropical cyclone at that time.

GOES-12 IR images + deep layer wind shear product

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