| September 10, 2003 NASA Satellites Extract Ingredients in Hurricane Recipe to Improve Forecasts The Atlantic Ocean becomes a meteorological mixing bowl from June 1 to November 30, replete with all needed ingredients for a hurricane recipe. NASA turns to its cadre of satellites to serve up a feast of information to the forecasters who seek to monitor and understand these awesome storms. 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 Niño and La Niña 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. ###
Contacts:
Elvia H. Thompson
Headquarters, Washington
(Phone: 202/358-1696)
Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-4044)
Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-0474)
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Take Warm Water, Stir
What makes a hurricane? First, warm water - at least 82 degrees, in fact. Several weeks after the Sun shines brightest on the tropics in late June in the northern hemisphere, the waters reach their warmest. Here, orange and red indicate the necessary 82-degree and warmer water, sea surface temperatures (SSTs) taken by the Advanced Microwave Scanning Radiometer-EOS (AMSR/E) aboard the Aqua satellite from May 2002. Next, add a disturbance, generally easterly waves off of Africa, formed from winds resulting from the clash between the hot Sahara Desert and the cooler Gulf of Guinea. These waves provide the initial energy and spin required for a hurricane to develop, as imaged by the Geostationary Operational Environmental Satellite (GOES, operated by NOAA) on Sept. 1-15, 2001. Credit: NASA 
Mix Thoroughly, Bake
With the right mix of winds and SSTs, an ordinary cluster of tropical thunderstorms can explode into a tropical storm. Winds converge, forming the familiar circular pattern of clouds. Warm, rising air in the storms draws water vapor up from the ocean. The vapor condenses in clouds and releases heat, warming the eye, evaporating more surface water and feeding the hurricane's heat engine, continuing the cycle.
Data from Hurricane Erin, Sept. 10 - 15, 2001.
a) wind speed/direction, from Seawinds instrument on QuikScat satellite [NASA]
b) cloud structure, from Visible and Infrared Scanner (VIRS) on the Tropical Rainfall Measuring Mission (TRMM) satellite [NASA/NASDA]
c) rainfall rates (green, in excess of 0.5 inches per hour), Microwave Imager (TMI) and Precipitation Radar (PR) on TRMM [NASA/NASDA]
d) eye warmth (red), Convection And Moisture EXperiment (CAMEX) [NASA]
e) GOES [NASA/NOAA]
Credit: NASA 
Hurricane Heat Engine
Hurricanes essentially act as engines, drawing energy up from warm tropical ocean waters to power the intense winds, powerful thunderstorms, and immense ocean surges. Water vapor from the warm ocean surface evaporates, forming towering convective clouds that surround the eyewall and rainband regions of the storm. As the water vapor cools and condenses from a gas back to a liquid state it releases latent heat. The released heat warms the surrounding air, making it lighter and promoting more clouds. Because the hurricane-speed winds surrounding the clear eye are often absent from the center of a hurricane, the heaviest rain clouds are pushed out to form a ring around the center, leaving a relatively fair-weather eye. Credit : NASA 
Model Hurricane
By synthesizing data from multiple instruments and satellites, scientists get a full picture of the many ingredients of a hurricane. Satellites that monitor Earth day-to-day give pictures of both normal and unusual terrestrial, oceanic, and atmospheric activity. Scientists then build physical and computer models of the interactions and activity, which they can study to find patterns and ultimately make predictions. Scientists can use these models to make better predictions of severe weather patterns. Credit: NASA |
