These infrared, microwave, and visible images were created with data retrieved by the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite.
From the National Weather Service:
TROPICAL DEPRESSION DEAN FORECAST/ADVISORY NUMBER 40
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007
0300 UTC THU AUG 23 2007
TROPICAL DEPRESSION CENTER LOCATED NEAR 20.5N 100.0W AT 23/0300Z POSITION ACCURATE WITHIN 30 NM
PRESENT MOVEMENT TOWARD THE WEST OR 270 DEGREES AT 18 KT
ESTIMATED MINIMUM CENTRAL PRESSURE 1000 MB MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT.
Because infrared radiation does not penetrate through clouds, AIRS infrared images show either the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the storm. In cloud-free areas the AIRS instrument will receive the infrared radiation from the surface of the Earth, resulting in the warmest temperatures (orange/red).
In the AIRS microwave imagery, deep blue areas in storms show where the most precipitation occurs, or where ice crystals are present in the convective cloud tops. Outside of these storm regions, deep blue areas may also occur over the sea surface due to its low radiation emissivity. On the other hand, land appears much warmer due to its high radiation emissivity.