Typically, during the peak of hurricane season, from late August to mid-September, tropical cyclones of interest to U.S. coastal regions form around the Cape Verde Islands off Africa. NASA satellites are critical for helping forecasters determine if all of the ingredients are coming together to create a hurricane. If a hurricane forms, it is critical to know how strong it may be, which coastal communities or sea lanes will be at risk.
NASA provides researchers and forecasters with space-based observations, data assimilation, and computer climate modeling. NASA sponsored measurements and modeling of global sea surface temperature, precipitation, winds and sea surface height have also improved understanding of El Nino and La Nina events, which respectively tend to suppress and enhance Atlantic and Gulf hurricane development.
Thirty years ago, meteorologists were unable to see the factors in hurricane formation and could only spot a hurricane with still pictures from the TIROS-N satellite. Over the past 10 years, visible and infrared satellite sensors were the workhorses for monitoring hurricanes. Today, multiple NASA satellites exploit everything from radar pulses to microwaves to enhance forecasts, providing data to researchers several times a day.
The first ingredient in the hurricane recipe is sea surface temperature of at least 82 F. Unlike traditional infrared satellite instruments, the Aqua satellite's Advanced Microwave Scanning Radiometer (AMSR-E) and the Tropical Rainfall Measuring Mission's (TRMM) Microwave Imager can detect sea surface temperatures through clouds. This valuable information can help determine if a tropical cyclone is likely to strengthen or weaken. The Jason-1 satellite altimeter provides data on sea surface height, a key measurement of ocean energy available to encourage and sustain hurricanes.
Another necessary ingredient is rotating winds over the ocean's surface, precursors to tropical cyclone development. The NASA provided SeaWinds instruments aboard Japan's Midori 2 and NASA's QuikSCAT satellites can detect these winds before other instruments, providing even earlier notice of developing storms to forecasters and scientists.
Air temperature and humidity are also important factors. The Atmospheric Infrared Sounder (AIRS) experiment suite aboard the Aqua satellite obtains measurements of global temperature and humidity throughout the atmosphere. This may lead to improve weather forecasts, improved determination of cyclone intensity, location and tracks, and the severe weather associated with storms, such as damaging winds.
Rainfall intensity is the final ingredient, and the Precipitation Radar provided by Japan for the TRMM satellite provides CAT scan-like views of rainfall in the massive thunderstorms of hurricanes. TRMM instruments probe young tropical systems for rainfall intensity and the likelihood of storm development. TRMM also sees "hot towers" or vertical columns of rapidly rising air that indicate very strong thunderstorms. These towers are like powerful pistons that convert energy from water vapor into a powerful wind and rain-producing engine. Once a storm develops, TRMM provides an inside view of how organized and tightly spiraled rain bands are, key indicators of storm intensity.
TRMM provides tropical cyclone intensity information from the safe distance of space allowing the National Oceanic and Atmospheric Administration's (NOAA) National Hurricane Center and the Department of Defense Joint Typhoon Warning Center to turn to TRMM, QuikSCAT and other NASA satellites for early assessment of storms in the open ocean. The hurricane monitoring capabilities enabled by these satellites are funded by NASA's Earth Science Enterprise, which is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather, and natural hazards using the unique vantage point of space.
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