Track Forecast Guidance Improvements for Early Warnings of Tropical Cyclones
The disastrous impacts of tropical cyclones in terms of loss of lives and damage to the economies of all nations affected by these storms are well known. This paper will present an overview of progress achieved in the last decade in providing tropical cyc
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Track Forecast Guidance Improvements for Early Warnings of Tropical Cyclones RussELL
L.
ELSBERRY
Department of Meteorology, Naval Postgraduate School, Room 254, 589 Dyer Road, Monterey, California, USA, E-mail: [email protected]
Abstract 1 1.1 1.2 1.3 1.4
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Introduction 167 Impacts of Tropical Cyclones 167 Meteorological Aspects of the Tropical Cyclone Landfall Forecast Problem 169 Meteorological Forecast and Warning Infrastructure 170 Plan of Paper 171
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Advances in Tropical Cyclone Track Prediction 171 2.1 Western North Pacific 171 2.1.1 RSMC-Tokyo Typhoon Center 171 2.1.2 Joint Typhoon Warning Center 173 Atlantic 174 2.2 2.3 Eastern North Pacific 175 2.4 Southern Hemisphere 176 2.5 North Indian Ocean 177 3 3.1 3.2 3.3 3.4
4 4.1 4.2 4.3 4.4
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How has the Track Guidance Improvement Been Achieved? 178 Understanding Track Motion 178 Observations 179 Analysis and Data Assimilation 179 Numerical Models 179 Future Strategy for Track Guidance Improvement 180 Understanding and Research 180 Observations 180 Analysis and Data Assimilation 181 Numerical Models 181 From Better Track Guidance to Earlier Warnings 182 References
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Abstract The disastrous impacts of tropical cyclones in terms of loss of lives and damage to the economies of all nations affected by these storms are well known. This paper will present an overview of progress achieved in the last decade in providing tropical cyclone track forecast guidance at a number of regional and national centers. In many cases, the accuracy of the 72-hour track forecasts is equivalent to that of the 48-
hour forecasts only 10 years ago. Contributions from various factors that have led to these track forecast improvements will be described. Future needs to continue this improvement will be proposed. A number of issues that must be addressed to convert improved track forecast guidance to more accurate and earlier warnings will be suggested.
1 Introduction 1.1 Impacts of Tropical Cyclones 1
Tropical cyclones are one of the most damaging of the natural disasters. Even as recently as 1991, more than 125000 people were killed in a tropical cyclone that struck Bangladesh. Most of these people were killed on low-lying islands or coastal areas by the storm surge. Typical increases of sea level associated with surges are several meters, but extreme surges of up to 10m may occur. The spatial distribution and amplitude of the storm surge depend in a complicated way on the ocean bottom topography as well as the size, intensity, direction and speed of movement of the tropical cyclone. The definition of storm surge does not include shorter term phenomena such as surface waves, breakers, or spray, but the peak water level will be in association with the astronomical tides. 1
The generic title tropical cyclone will be used here to include all stages, which include: tropical disturbance - a region of organized convection with diameter of 200-600 km having a non-frontal migratory character; tropical depression - weak tropical cyclone with a definite closed surface cir
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