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.

Two areas of showers and thunderstorms located south of Tropical Storm Ignacio’s remnants are being closely watched for development. Forecasters use infrared satellite imagery to determine cloud temperatures, and get an idea about the height and strength of thunderstorms.

The Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite flies over the Eastern Pacific Ocean daily, and captured the two areas on August 27at 5:23 p.m. EDT. Although both didn’t have signature shapes of tropical cyclones yet, the National Hurricane Center reported on Friday, August 28 that the potential for development is at least 50%. So, over the weekend, there’s a potential for them to develop into tropical storms. If they do, they’d be named Jimena and Kevin.

Infrared imagery measures temperatures and not only can it see cold, high cloud tops in tropical cyclones, but also the warm ocean waters that fuel them. The colder the clouds are, the higher they are, and the more powerful the thunderstorms are that make up the cyclone.

The first area of disorganized showers and thunderstorms are located a couple of hundred miles south of Acapulco, Mexico, and are associated with a low pressure area. Because conditions are favorable for development, there’s a medium chance (30-50 percent) of the system becoming a tropical depression this weekend.

The second area of showers and thunderstorms are further west, about 950 miles south-southwest of the southern tip of Baja California. Conditions there are also favorable for development: warm waters over 80 degrees Fahrenheit and light surrounding winds. This system has the same chance to develop over the weekend.

NASA Satellite and Aircraft Data

NASA satellite imagery and aircraft data revealed Tropical Storm Danny’s center reformed a little farther north than it was yesterday. The center of his circulation is “broad and elongated” so it’s been somewhat challenging to pinpoint his center. The National Hurricane Center used NASA QuikScat data to confirm winds early this morning. From QuikScat data, they determined that “Danny does not have a typical tropical cyclone structure and has most of the strong winds located well north and east of the center.”

Another of the satellites in NASA’s fleet that provides helpful imagery is the Aqua satellite and its Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS captured an image Danny at 2:30 p.m. EDT yesterday, August 26. Satellite imagery and aircraft data since that time confirmed that Danny’s center is now near 27.4 north and 72.1 west. That’s about 370 miles east-northeast of Nassau or 575 miles south-southeast of Cape Hatteras, North Carolina.

Danny’s maximum sustained winds near 5 a.m. EDT this morning, August 27 were near 60 mph, but slow strengthening is expected. After all, Danny is near the Gulf Stream flow along the east coast. Danny is moving northwest near 10 mph, and is expected to turn north. Danny had a minimum central pressure near 1006 millibars.

The computer forecast models that the National Hurricane Center uses are “in excellent agreement on a turn toward the north on Friday as Danny moves between a ridge (an elongated area of high pressure) over the western Atlantic Ocean and a shortwave trough (an elongated area of low pressure, like a cold front) over the southeastern United States.”

NASA’s GOES Project has been busy with animating satellite imagery of Tropical Storm Danny, and has created a movie of him from August 25-27.

The short movie includes still imagery from the National Oceanic and Atmospheric Administration’s (NOAA) Geostationary Operational Environmental Satellite (GOES) called GOES-12, monitors weather conditions over the U.S. east coast. NASA’s GOES Project, located at NASA’s Goddard Space Flight Center in Greenbelt, Md. creates imagery and animations from GOES-12 data, and created the movie.

The movie begins with an image on August 25 when Danny was just a low pressure area, east of the Bahamas and not yet named. The movie continues through Danny’s formation and classification as a tropical storm during the morning of August 26, to the beginning of its journey up the U.S. East Coast today, August 27 at 2:25 p.m. EDT.

Danny’s maximum sustained winds at 11 a.m. EDT today, August 27 were near 60 mph, and slow strengthening is expected. He was located near 27.5 north and 73.1 west, or 550 miles south-southeast of Cape Hatteras, North Carolina. Danny is moving northwest near 13 mph, and is expected to turn north. Danny had a minimum central pressure near 1006 millibars.

Tropical Storm Ignacio may not be alone in the Eastern Pacific Ocean for long. There are two areas of showers and thunderstorms that forecasters are watching for development, farther east and closer to land.
NASA’s infrared satellite imagery indicates that Tropical Storm Ignacio still had some punch left in him, but that won’t be the case in the next day or two.

On August 26 at 5 a.m. EDT, Tropical Storm Ignacio had sustained winds near 50 mph, but he’s moving into an area of adverse conditions that are expected to weaken him in the next day. Ignacio was located 815 miles west of the southern tip of Baja California, near 21.2 north and 122.5 west. He was moving northwest near 14 mph, and his minimum central pressure was 1000 millibars.

The Atmospheric Infrared Sounder (AIRS), instrument that flies aboard NASA’s Aqua satellite, captured an image of Tropical Storm Ignacio yesterday that showed Ignacio still had some stronger thunderstorms around his center. That’s about to change as he’s entering cooler waters.

Infrared imagery is false-colored and higher cloud tops of stronger storms are depicted in purple. Ignacio showed a circular area of high, strong thunderstorms around his center of circulation on August 25 at 5:35 p.m. Those highest thunderstorms are as cold as or colder than 220 Kelvin or minus 63 degrees Fahrenheit (F).

Meanwhile, the other two areas in the Eastern Pacific that are holding the interest of forecasters are closer to land and both areas were captured by NOAA’s GOES-11 (Geostationary Operational Environmental) satellite earlier today, August 26.

The first area is consists of disorganized showers and thunderstorms, several hundred miles south-southwest of the southwestern coast of Mexico. The second area is a low pressure area several hundred miles south of the Guatemalan coast. Both areas have less than a 30 percent chance of developing.

The GOES-11 satellite imagery revealed that both of these clusters of showers and thunderstorms are still pretty disorganized. NASA’s GOES Project at the NASA Goddard Space Flight Center in Greenbelt, Md. created the imagery using data from the satellite.