Kudos to the United States Air Force Reserve (USAFR) Hurricane Hunters that flew into Tropical Storm Chantal earlier this week.
Both NOAA and the USAFR supply the National Hurricane Center with recon data. The USAFR does most of the operational flights while NOAA focuses primarily on research missions (the research data is also of great value to the NHC). During Chantal, the USAFR flew the operational missions.
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There is no doubt that satellites are considered the primary observing systems for tropical cyclone forecasters. Geostationary satellite images primarily give forecasters a continuous view of the tops of clouds. Polar-orbiting and other low-Earth orbiting satellites have a variety of sensors that can provide extremely valuable data that can penetrate the clouds, although these orbiting satellites are only available over a given area when they happen to pass over that specific area.
Satellite data is indispensable to the forecasters, but in the weak stages of a tropical cyclone, the so-called “cloud system center” and the maximum intensity provided to the NHC from the various satellite analysts can vary considerably.
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Aircraft reconnaissance provides in-situ data to the forecasters that is not available from satellite. The Hurricane Hunters can fly directly into the tropical cyclone’s circulation to report flight level winds and, in strong tropical cyclones, surface winds. Instruments called dropsondes can be released when flying through the eyewall of a hurricane to determine wind, temperature, humidity, and pressure from flight level all the way down to the surface. A dropsonde can also be released in the eye or center of a tropical cyclone to determine the lowest pressure at the surface.
On Wednesday, the USAFR Hurricane Hunter crew repeatedly flew into Chantal at low levels (frequently below 1,500 feet). Although Chantal looked impressive on satellite, the plane was unable to send a “vortex message,” meaning that there was no identifiable circulation center meeting the reconnaissance criteria.
Once the Hurricane Hunters confirmed that there was no identifiable center Wednesday, the NHC wrote the last advisory on Chantal, unless regeneration occurs. There is currently a medium chance it could redevelop into a tropical cyclone.
I commend the dedicated crews and support staff of the 53rd Weather Reconnaissance Squadron for providing invaluable data to the NHC this week. At least for now, a lot of people in Florida and the Bahamas are grateful to be out of the “cone.”
I spent many years forecasting tropical cyclones at the NHC. Perhaps someday an observing platform even better than aircraft reconnaissance will come along. Until then, I hope the current NHC hurricane specialists never have to make a forecast and issue watches and warnings on a significant tropical cyclone threatening land areas without aircraft reconnaissance.