Last week, Hurricane Bill moved north parallelling the U.S. East Coast, and that’s currently what forecasters at the National Hurricane Center are expecting for Tropical Storm Danny. Danny’s forecast track also takes him near eastern North Carolina, by eastern Massachusetts and into Nova Scotia, Canada, just as Bill did. NASA’s Aqua satellite and NOAA’s GOES-12 satellite are providing forecasters with valuable data about Danny.

As Tropical Storm Danny is poised to continue its northern track, paralleling the U.S. East Coast tropical storm watches are posted for the North Carolina coast from Cape Lookout northward to Duck, including the Pamlico and Albemarle Sounds. Interests elsewhere from the Carolinas northward to New England and the Canadian Maritimes should monitor the progress of Danny. More watches and warnings may be posted later today, August 28.

At 8 a.m. EDT, Danny was still hanging onto tropical storm status, with sustained winds near 40 mph. He’s located about 355 miles south of Cape Hatteras, North Carolina, near 30.1 north and 75.2 west. Danny is moving north-northwest near 9 mph, and he’s expected to shift north and speed up later today. The estimated minimum central pressure is 1008 millibars.

The Atmospheric Infrared Sounder (AIRS) flies on NASA’s Aqua satellite and captures infrared images of tropical cyclones take the temperatures of thunderstorm’s cloud top temperatures to determine their strength.

How does infrared imagery know how high clouds are in the sky? The coldest ones are higher in the sky (because in the troposphere, the lowest layer of atmosphere where weather happens, temperatures fall the higher up you go until you get to the stratosphere).

The highest clouds are as cold as or colder than 220 Kelvin or minus 63 degrees Fahrenheit (F) and second highest level of clouds are about 240 Kelvin, or minus 27F. The colder the clouds are, the higher they are, and the more powerful the thunderstorms are that make up the cyclone. AIRS imagery revealed that Danny had some high, strong thunderstorms in the center of his circulation on August 28 at 2:17 a.m. EDT, indicating he was still holding onto tropical storm status with powerful convection.

Another satellite that NASA uses is the Geostationary Operational Environmental Satellite, or GOES. GOES-12 covers the Atlantic Ocean, and is managed by NOAA. On August 28 at 9:32 a.m. EDT, GOES-12 captured Tropical Storm Danny as the large area of clouds of the southeast U.S. coast.

Danny is a big storm with tropical storm force winds extending 410 miles in diameter. He’s expected to pass offshore of the outer banks of North Carolina early Saturday. Residents in eastern North Carolina and up and down the U.S. East Coast should be aware that Danny, like Bill last week, is producing large and dangerous surf and life-threatening rip currents.