U.S. researchers have developed a new technique that provides a detailed 3-D view of an approaching hurricane every six minutes, helping to determine whether the storm is gathering strength as it nears land. The technique, known as VORTRAC (Vortex Objective Radar Tracking and Circulation), has been tested in 2007 at the National Hurricane Center (NHC) and will be deployed this summer. The VORTRAC system 'relies on the existing NOAA network of Doppler radars along the Southeast coast to closely monitor hurricane winds. About 20 of these radars are scattered along the Gulf and Atlantic coastlines from Texas to Maine.' This system is the first to create a 3-D pictures of hurricanes. But read more...
You can see above a screenshot of the VORTRAC system, which 'will provide hurricane forecasters with detailed updates on hurricanes as storms approach land.' (Credit: Michael Bell, NCAR) Here is a link to a larget version (TIF format).
The development of the VORTRAC system has been led at the National Center for Atmospheric Research (NCAR) by scientist Wen-Chau Lee. He was helped by Michael Bell, his colleague at NCAR's Earth Observing Laboratory (EOL), and by Paul Harasti, of the U.S. Naval Research Laboratory (NRL). The project was funded by the US National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). It was tested in 2007 at the National Hurricane Center (NHC).
And what did the researchers find? "Rapidly intensifying storms can catch vulnerable coastal areas by surprise. Last year, Hurricane Humberto struck near Port Arthur, Texas, after unexpectedly strengthening from a tropical depression to a hurricane in less than 19 hours. In 2004, Hurricane Charley's top winds increased from 110 to 145 miles per hour (about 175 to 235 kilometers per hour) in just six hours as the storm neared Florida's southwest coast. Lee and his collaborators applied VORTRAC retroactively to the two hurricanes and found that the technique would have accurately tracked their quick bursts in intensity."
Now, let's look at an NCAR page offering information about hurricanes, typhoons and cyclones. In a paragraph called "Improving forecasts close to shore," you'll discover how VORTRAC works. "NCAR scientist Wen-Chau Lee and his collaborators developed a series of mathematical formulas that combine data from a single radar with general knowledge of Atlantic hurricane structure in order to map the approaching system's winds in three dimensions. The technique also infers the barometric pressure in the eye of the hurricane, a very reliable index of its strength. Forecasters using VORTRAC can update information about a hurricane each time a NOAA Doppler radar scans the storm, which can be as often as about every six minutes. That could enable forecasters to monitor it for the critical 10-15 hours before landfall."
Let's now return to the NCAR news release to learn how this system will improve forecasts. "To monitor the winds of a landfalling hurricane, forecasters now rely on aircraft to drop instrument packages into the storm that gather data on winds and pressure. Due to flight logistics, the aircraft can take readings no more than every hour or two, which means that a sudden drop in barometric pressure, and the accompanying increase in winds, may be difficult to anticipate. In time, VORTRAC may also help improve long-range hurricane forecasts by using data from airborne Doppler radars or spaceborne radars to produce detailed information about a hurricane that is far out to sea. Forecasters could input the data to computer models to improve three- and five-day forecasts."
For more information about this system, you can read a former NCAR news release, "New Technique Provides 3-D View of Approaching Hurricanes" (May 17, 2007) or a PowerPoint presentation called "VORTRAC -- A Utility to Deduce Central Pressure and Radius of Maximum Wind of Landfalling Tropical Cyclones Using WSR-88D Data" (15 pages, 2.04 MB).
Sources: NCAR news release, April 10, 2008; and various websites
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