Hurricane Structure and Intensity
Strategic Element: Short-Term Warnings
Principal Investigator: Frank D. Marks
Objective: Basic physical understanding and forecasts of tropical cyclone intensity and structure. Observational studies with aircraft, radar and other remote sensors. Forecasting and process models.
Narrative: On the night of 3-4 October 1995, hurricane Opal accelerated toward the U.S. Gulf of Mexico coast. As the storm's motion increased, so did its intensity--from category 3 to category 4 (based on wind) in 18 h. Similarly, Hurricane Andrew intensified nearly to category 5 in 36 hours. "Rapid deepening" is almost invariably part of the process that makes major hurricanes--often so quickly that events outrun forecasts. Passage over unusually warm water, the Gulf Stream for example, and interaction with atmospheric features such as midlatitude troughs or upper lows are clearly factors. Although we know something about the physical processes that control intensity change in general terms, we do not understand them well enough to make predictions that outperform the simplest statistical extrapolations.
Meteorologists need to invest in deeper physical understanding of intensity change before predictions can improve. Fortunately, many of the intellectual and physical tools for this investigation have already been developed to improve track forecasts. Research aircraft missions to study the ocean, the surrounding atmosphere from the surface to the base of the stratosphere, and the structure of the storms themselves are essential. The dynamics of the interaction between a vortex and surrounding winds is a subtle and challenging problem in fluid mechanics. It may be that the energy source for hurricanes in the warm ocean sets an upper limit that few hurricanes reach because other factors, such as vertical variations of the surrounding wind, interfere with development. Or it may be that the ocean energy availability, in combination with the air's thermal structure outside of the storm, is a limiting factor in most storms. We need to resolve this, and other fundamental scientific dilemmas, before future intensity forecasts can become as reliable as track forecasts are today.
Duration: 1954 through the present
Reference:
Preprints: Symposium on Tropical Cyclone Intensity Change, 11-16 January 1998, Phoenix, AZ, American Meteorological Society, Boston, 175 pp.
Investigations
MODELING THE HURRICANE DYNAMICS WITH EXPLICIT MOIST CONVECTION
A VERIFICATION OF NATIONAL HURRICANE CENTER FORECASTS OF SURFACE WIND SPEED RADII IN HURRICANES
CLOUD-TO-GROUND LIGHTNING AND TROPICAL CYCLONES
TROPICAL CYCLONES ELECTRIFICATION STUDIES
RAPID SCAN AIRBORNE DOPPLER OBSERVATIONS OF HURRICANE STRUCTURE AND EVOLUTION
THREE-DIMENSIONAL VARIATIONAL ANALYSIS OF AIRBORNE DOPPLER OBSERVATIONS
KINEMATIC VELOCITY STRUCTURE OF HURRICANE GILBERT (1988)
WIND FIELD AND REFLECTIVITY STRUCTURE AND EVOLUTION OF HURRICANE OLIVIA ON 24 SEPTEMBER 1994
WIND FIELD AND REFLECTIVITY STRUCTURE AND EVOLUTION OF HURRICANE OLIVIA ON 25 SEPTEMBER 1994
OBJECTIVE ANALYSIS OF THE HURRICANE AND ITS ENVIRONMENT
SATELLITE IMAGERY INVESTIGATIONS OF TROPICAL CYCLONE ACTIVITY
AN EMPIRICAL INLAND WIND DECAY MODEL FOR THE NEW ENGLAND REGION