Hurricane Winds at Landfall

Strategic Element: Advance short-term forecasts and warnings.

Principal Investigator: Mark D. Powell

Objective: Basic physical understanding, analyses, and forecasts of tropical cyclone air-sea interaction surface winds and other physical impacts. Observational studies with aircraft, radar, deployable probes, and remote sensors.

Narrative: The damage patterns in Hurricane Andrew were clearly controlled by small-scale features in the distribution of surface winds. These details made the difference between survival and destruction of many structures. For example, "mesovorticies" that formed below updrafts in the eyewall caused the worst devastation. For the last few years, meteorologists at HRD have prepared real-time analyses of surface winds based upon all available aircraft and surface observations. In the hands of hurricane specialists at TPC/NHC, the analyses provide essential guidance for coastal and marine warnings. Surface winds control the storm surge as they blow the ocean up onto the land. Storm surge usually causes even greater damage and loss of life than the winds themselves. Extrapolation of the present surface winds onshore can provide an essential preview of damage patterns for emergency managers. An often unappreciated consideration is the importance of forecasting the onset of gale-force (40 mph) wind after which time protection of property and evacuation of people in the path of the storm must cease.

HRD is addressing the crucial surface-wind problem by coordinating with university scientists and other government laboratories in the HaL (Hurricanes at Landfall) Project, designed to combine aircraft measurements and airborne radar with National Weather Service Doppler radar data and observations from a variety of mobile sensors--including high resolution Doppler radar, profilers, balloon sounders, and surface sensors to be deployed ashore ahead of the hurricane. The airborne portion of HaL has been executed five times, most notably in Hurricane Fran of 1996 when a single mobile Doppler radar was also positioned ahead of the hurricane and in Hurricane Danny of 1997 as it lingered over Mobile Bay within range of two WSR-88D Doppler radars.

Duration: 1993 through the present.

References:

Powell, M. D., S. H. Houston, and T. A. Reinhold, 1996: Hurricane Andrew's Landfall in South Florida. Part I: Standardizing measurements for documentation of surface wind fields.Wea. Forecast., 11, 304-328.

Powell, M. D., and S. H. Houston, 1996: Hurricane Andrew's Landfall in South Florida. Part II: Surface Wind Fields and Potential Real-time Applications. Wea. Forecast., 11, 329-349.

Investigations

COMPARISON STUDY OF HRD AND SLOSH MODEL SURFACE WINDS IN RECENT HURRICANES

A VERIFICATION OF NATIONAL HURRICANE CENTER FORECASTS OF SURFACE WIND SPEED RADII IN HURRICANES

TROPICAL CYCLONE WIND FIELDS AT LANDFALL FROM AIRBORNE AND LAND-BASED DOPPLER RADAR DATA