FABIAN, ISABEL OFFER WEALTH OF DATA TO NOAA HURRICANE RESEARCHERS

The almost back-to-back major hurricanes Fabian and Isabel offered NOAA hurricane researchers a wealth of information about the extreme ocean surface winds and sea swell so the agency can better predict changes in storm intensity before landfall. NOAA is an agency of the U.S. Department of Commerce.

“The hurricanes offer us an opportunity to make measurements we’ve never made before,” said Peter Black of NOAA’s Hurricane Research Division at the Atlantic Oceanographic and Meteorological Laboratory in Miami, Fla.

During Fabian, while it was a category 4, and Isabel, while a rare category 5 hurricane, researchers drew new intricate flight plans specifically for the latest hurricane intensity research programs.

The effort required immense collaboration between multiple partners, including NOAA’s Aircraft Operations Center, Hurricane Research Division (HRD), the National Environmental Satellite, Data and Information Systems (NESDIS), and the U.S. Air Force Reserve Command’s 53rd Weather Reconnaissance Squadron, as well as multiple university partners.

“This has been a fantastic team effort,” Black said.

This season, HRD's hurricane research field program focuses heavily on intensity change and the Coupled Boundary Layer Air-Sea Transfer (CBLAST) experiment, funded in part by a grant from the Office of Naval Research (ONR). CBLAST is a collaborative research effort that brings NOAA hurricane researchers together with 17 scientists from other NOAA offices, universities and
government research agencies from Boston to San Diego.

Current understanding of the air-sea transfer process that drives hurricane intensification is based on field measurements in winds up to tropical storm force (36 miles per hour). Large extrapolations must be made to obtain estimates in intense hurricanes. Hurricanes Fabian and Isabel offered an opportunity to measure this energy transfer in the stronger winds present in more intense hurricanes that NOAA’s National Weather Service would like to be able to forecast with greater accuracy.

“Different things happen in high winds than in low winds,” Black said.

Recent observations in Hurricanes Fabian and Isabel included NOAA’s two WP-3D aircraft as well as the USAF C-130 all flying into the hurricane eye at similar altitudes, a feat that required significant communication to keep all three planes at an appropriate distance. The research plan uses a multifaceted approach, employing airborne instruments used in a new and unique way, as well as oceanographic buoys and floats.

One such instrument is the Best Air Turbulence (BAT) probe developed by Tim Crawford, a NOAA scientist who suffered a fatal stroke in 2002 while flying a research field study. Crawford’s design was enhanced by his colleague, Jeff French, and is being used during the CBLAST flights.

HRD scientists coordinated these experiments, using forecasts from the National Hurricane Center to determine where the Air Force Reserve Command’s 53rd Weather Reconnaissance Squadron should place the ocean instruments in front of Fabian. There they successfully measured surface winds, ocean currents and air and sea temperatures as Fabian passed overhead. Meanwhile, NOAA aircraft flew at various altitudes between 400 and 7,500 ft. where precision alignment and timing was required to gather specific wind speed data. These missions also required hurricane hunters to occasionally fly at much lower altitudes than typical, sometimes only 250 feet above the tumultuous ocean surface in hurricane force winds.

This is a collaborative effort with the NESDIS Ocean Winds program to derive a more accurate algorithm for mapping hurricane ocean surface winds from satellite scatterometers. This is being done with the UMASS C- and K-band airborne scatterometers that also supply CBLAST with a wealth of new data.

The primary goal of CBLAST is to improve understanding of air-sea interactions in high winds, specifically in the complex hurricane environments where sea swell, sea spray and circulations in the lower 1 kilometer of the atmosphere play a role. The ultimate goal and prime motivation for this work is to characterize these new observations and improve the accuracy of hurricane intensity prediction.

While forecasts of hurricane track have improved during the past decade, the ability to forecast hurricane intensity has changed little. The goal of intensity research is to understand and describe the physical processes that lead to the extreme winds and heavy precipitation in a hurricane, and to use this knowledge to develop an integrated hurricane simulation and forecasting system that produces skillful forecasts of intensity change and precipitation in hurricanes striking the United States.

The Commerce Department's National Oceanic and Atmospheric Administration (NOAA) Office of Oceanic and Atmospheric Research is dedicated to enhancing economic security and national safety through research to better understand weather and climate-related events and to manage wisely our nation's coastal and marine resources.

On the Web:

NOAA Atlantic Oceanographic and Meteorological Laboratory Hurricane Research Division: http://www.aoml.noaa.gov/hrd

Coupled Boundary Layer Air-Sea Transfer(CBLASY): http://cblast.ecs.umass.edu/cblast/index.php

NOAA Aircraft Operations Center: http://www.aoc.noaa.gov/

NOAA National Environmental Satellite, Data, and Information Services: http://www.nesdis.noaa.gov/