Abstract The 2003 Atlantic hurricane season is described. The season was very active, with 16 tropical storms, 7 of which became hurricanes. There were 49 deaths directly attributed to this year’s tropical cyclones.
The 2000 Atlantic hurricane season is summarized and the year's tropical and subtropical cyclones are described. While overall activity was very high compared to climatology, with 15 cyclones attaining tropical (or subtropical) storm intensity, much of this activity occurred outside of the deep Tropics, over open waters north of 25°N. The season's tropical cyclones were responsible for 54 fatalities, with most of these occurring in Central America in association with Hurricanes Gordon and Keith.
Abstract The 2004 eastern North Pacific hurricane season is reviewed. It was a below-average season in terms of number of systems and landfalls. There were 12 named tropical cyclones, of which 8 became hurricanes. None of the tropical storms or hurricanes made landfall, and there were no reports of deaths or damage. A description of each cyclone is provided, and track and intensity forecasts for the season are evaluated.
Abstract The 2005 eastern North Pacific hurricane season is summarized, the individual tropical cyclones are described, and official track and intensity forecasts are verified and evaluated. The season’s overall activity was, by most measures, below average. While a near-average 15 tropical storms formed, many of them were relatively weak and short-lived. Seven of these storms became hurricanes, but only one reached major hurricane status (an intensity of 100 kt or greater on the Saffir–Simpson hurricane scale) in the eastern North Pacific basin. One of the hurricanes, Adrian, approached Central America in May but weakened to a tropical depression prior to landfall. Adrian was the only eastern North Pacific tropical cyclone to make landfall during 2005, and it was directly responsible for one fatality.
Abstract The 2004 Atlantic hurricane season is summarized, and the year’s tropical and subtropical cyclones are described. Fifteen named storms, including six “major” hurricanes, developed in 2004. Overall activity was nearly two and a half times the long-term mean. The season was one of the most devastating on record, resulting in over 3100 deaths basinwide and record property damage in the United States.
With the multitude of cloud clusters over tropical oceans, it has been perplexing that so few develop into tropical cyclones. The authors postulate that a major obstacle has been the complexity of scale interactions, particularly those on the mesoscale, which have only recently been observable. While there are well-known climatological requirements, these are by no means sufficient. A major reason for this rarity is the essentially stochastic nature of the mesoscale interactions that precede and contribute to cyclone development. Observations exist for only a few forming cases. In these, the moist convection in the preformation environment is organized into mesoscale convective systems, each of which have associated mesoscale potential vortices in the midlevels. Interactions between these systems may lead to merger, growth to the surface, and development of both the nascent eye and inner rainbands of a tropical cyclone. The process is essentially stochastic, but the degree of stochasticity can be reduced by the continued interaction of the mesoscale systems or by environmental influences. For example a monsoon trough provides a region of reduced deformation radius, which substantially improves the efficiency of mesoscale vortex interactions and the amplitude of the merged vortices. Further, a strong monsoon trough provides a vertical wind shear that enables long-lived midlevel mesoscale vortices that are able to maintain, or even redevelop, the associated convective system. The authors develop this hypothesis by use of a detailed case study of the formation of Tropical Cyclone Oliver observed during . In this case, two dominant mesoscale vortices interacted with a monsoon trough to separately produce a nascent eye and a major rainband. The eye developed on the edge of the major convective system, and the associated atmospheric warming was provided almost entirely by moist processes in the upper atmosphere, and by a combination of latent heating and adiabatic subsidence in the lower and middle atmosphere. The importance of mesoscale interactions is illustrated further by brief reference to the development of two typhoons in the western North Pacific.
The 2002 eastern North Pacific hurricane season is summarized and the year's tropical cyclones are described. The season featured 12 named tropical storms, of which 6 became hurricanes. Five of the six hurricanes reached an intensity of 100 kt or higher. There were two landfalling cyclones, Tropical Storm Julio and Hurricane Kenna. Kenna, which made landfall near San Blas, Mexico, with winds of near 120 kt, was responsible for four deaths.
The 2004 Atlantic hurricane season is summarized, and the year’s tropical and subtropical cyclones are described. Fifteen named storms, including six “major” hurricanes, developed in 2004. Overall activity was nearly two and a half times the long-term mean. The season was one of the most devastating on record, resulting in over 3100 deaths basinwide and record property damage in the United States.
OCTOBER 2003 AMERICAN METEOROLOGICAL SOCIETY | S harp et al. (2002, hereafter SBO) reported on the use of surface winds derived from the SeaWinds scatterometer on the QuikSCAT satellite for the “early detection” of tropical cyclones (TCs). They applied a vorticity-based detection tool to QuikSCAT wind data from the 1999–2000 hurricane seasons over the tropical Atlantic basin. They indicated that their technique could provide advance notice of the formation of TCs prior to their official designation. However, SBO’s study provides a misleading impression of the current ability of the Tropical Prediction Center/National Hurricane Center (TPC/NHC) to identify and track pre-TC disturbances. Indeed, current operational detection techniques, that do not rely on QuikSCAT, usually provide considerably longer lead times than shown in SBO. The current observing system, used routinely by the TPC to identify and track tropical weather systems, includes conventional surface and upper-air observations, reconnaissance aircraft reports, and satellite data, including QuikSCAT. Among these, geostationary satellites are the most critical observing tool over the tropical oceans, because of their nearly continuous spatial and temporal coverage over the Tropics and the relative paucity of data from other sources. Using a technique developed by Dvorak (1984), visible and infrared images from these satellites are routinely analyzed by meteorologists at the TPC’s Tropical Analysis and Forecast Branch (TAFB) and at other operational centers. This technique classifies the stage of TC development, if any, of a tropical weather system based on the evolution of the satellite-observed cloud pattern. The two essential requirements for the assignment of a Dvorak “T-number,” that is, a “classification,” are the following: a center of cyclonic circulation indicated by the cloud pattern (usually confirmed by animation of the images); and persistent deep convection in a curved band (or bands). It is quite typical, in the pre-TC stages of a system, for a circulation, or lowerto midtropospheric cyclonic turning, to be evident in the imagery while the associated deep convection is sporadic or not organized in curved bands. In such cases, the system is considered “too weak to classify” (TWTC), and a center position is given although no T number is assigned. Thus a weather system can be tracked by the TPC regardless of whether it is a TC or even classifiable by the Dvorak technique. Tables 1 and 2 show a comparison of the lead (early detection) times, prior to TC formation, of the TAFB’s first operational Dvorak classification or TWTC designation versus SBO’s QuikSCAT detection technique during the 1999–2000 Atlantic hurricane seasons, Comments on “Early Detection of Tropical Cyclones Using SeaWindsDerived Vorticity”
