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James L. Franklin, Lixion A. Avila, Jack L. Beven, Miles B. Lawrence, Richard J. Pasch, and Stacy R. Stewart

Abstract

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.

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Anu Simon, Andrew B. Penny, Mark DeMaria, James L. Franklin, Richard J. Pasch, Edward N. Rappaport, and David A. Zelinsky

Abstract

This study discusses the development of the Hurricane Forecast Improvement Program (HFIP) Corrected Consensus Approach (HCCA) for tropical cyclone track and intensity forecasts. The HCCA technique relies on the forecasts of separate input models for both track and intensity and assigns unequal weighting coefficients based on a set of training forecasts. The HCCA track and intensity forecasts for 2015 were competitive with some of the best-performing operational guidance at the National Hurricane Center (NHC); HCCA was the most skillful model for Atlantic track forecasts through 48 h. Average track input model coefficients for the 2015 forecasts in both the Atlantic and eastern North Pacific basins were largest for the European Centre for Medium-Range Weather Forecasts (ECMWF) deterministic model and the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) ensemble mean, but the relative magnitudes of the intensity coefficients were more varied. Input model sensitivity experiments conducted using retrospective HCCA forecasts from 2011 to 2015 indicate that the ECMWF deterministic model had the largest positive impact on the skill of the HCCA track forecasts in both basins. The most important input models for HCCA intensity forecasts are the Hurricane Weather Research and Forecasting (HWRF) Model and the Coupled Ocean–Atmosphere Mesoscale Prediction System-Tropical Cyclone (COAMPS-TC) model initialized from the GFS. Several updates were incorporated into the HCCA formulation prior to the 2016 season. Verification results indicate HCCA continued to be a skillful model, especially for short-range (12–48 h) track forecasts in both basins.

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James L. Franklin, Lixion A. Avila, John L. Beven II, Miles B. Lawrence, Richard J. Pasch, and Stacy R. Stewart

Abstract

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.

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Lixion A. Avila, Richard J. Pasch, John L. Beven II, James L. Franklin, Miles B. Lawrence, and Stacy R. Stewart

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.

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Richard J. Pasch, Miles B. Lawrence, Lixion A. Avila, John L. Beven, James L. Franklin, and Stacy R. Stewart

Abstract

The 2002 Atlantic hurricane season is summarized. Although the season's total of 12 named storms was above normal, many of these were weak and short-lived. Eight of the named cyclones made landfall in the United States, including Lili, the first hurricane to hit the United States in nearly 3 yr.

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Miles B. Lawrence, Lixion A. Avila, Jack L. Beven, James L. Franklin, John L. Guiney, and Richard J. Pasch

Abstract

The 1999 Atlantic basin hurricane season produced 4 tropical storms and 8 hurricanes for a total of 12 named tropical cyclones. Seven of these affected land. Hurricane Floyd—the deadliest U.S. hurricane since Agnes in 1972—caused a disastrous flood event over the U.S. mid-Atlantic and northeastern coastal states, resulting in 56 U.S. deaths and 1 death in the Bahamas. Heavy rain from a tropical depression contributed to some 400 inland flood deaths in Mexico.

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John L. Beven II, Lixion A. Avila, James L. Franklin, Miles B. Lawrence, Richard J. Pasch, and Stacy R. Stewart

Abstract

The tropical cyclone activity for 2003 in the eastern North Pacific hurricane basin is summarized. Activity during 2003 was slightly below normal. Sixteen tropical storms developed, seven of which became hurricanes. However, there were no major hurricanes in the basin for the first time since 1977. The first hurricane did not form until 24 August, the latest observed first hurricane at least since reliable satellite observations began in 1966. Five tropical cyclones made landfall on the Pacific coast of Mexico, resulting in 14 deaths.

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John L. Beven II, Lixion A. Avila, Eric S. Blake, Daniel P. Brown, James L. Franklin, Richard D. Knabb, Richard J. Pasch, Jamie R. Rhome, and Stacy R. Stewart

Abstract

The 2005 Atlantic hurricane season was the most active of record. Twenty-eight storms occurred, including 27 tropical storms and one subtropical storm. Fifteen of the storms became hurricanes, and seven of these became major hurricanes. Additionally, there were two tropical depressions and one subtropical depression. Numerous records for single-season activity were set, including most storms, most hurricanes, and highest accumulated cyclone energy index. Five hurricanes and two tropical storms made landfall in the United States, including four major hurricanes. Eight other cyclones made landfall elsewhere in the basin, and five systems that did not make landfall nonetheless impacted land areas. The 2005 storms directly caused nearly 1700 deaths. This includes approximately 1500 in the United States from Hurricane Katrina—the deadliest U.S. hurricane since 1928. The storms also caused well over $100 billion in damages in the United States alone, making 2005 the costliest hurricane season of record.

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T. N. Krishnamurti, S. Pattnaik, L. Stefanova, T. S. V. Vijaya Kumar, B. P. Mackey, A. J. O’Shay, and Richard J. Pasch

Abstract

The intensity issue of hurricanes is addressed in this paper using the angular momentum budget of a hurricane in storm-relative cylindrical coordinates and a scale-interaction approach. In the angular momentum budget in storm-relative coordinates, a large outer angular momentum of the hurricane is depleted continually along inflowing trajectories. This depletion occurs via surface and planetary boundary layer friction, model diffusion, and “cloud torques”; the latter is a principal contributor to the diminution of outer angular momentum. The eventual angular momentum of the parcel near the storm center determines the storm’s final intensity. The scale-interaction approach is the familiar energetics in the wavenumber domain where the eddy and zonal kinetic energy on the hurricane scale offer some insights on its intensity. Here, however, these are cast in storm-centered local cylindrical coordinates as a point of reference. The wavenumbers include azimuthally averaged wavenumber 0, principal hurricane-scale asymmetries (wavenumbers 1 and 2, determined from datasets) and other scales. The main questions asked here relate to the role of the individual cloud scales in supplying energy to the scales of the hurricane, thus contributing to its intensity. A principal finding is that cloud scales carry most of their variance, via organized convection, directly on the scales of the hurricane. The generation of available potential energy and the transformation of eddy kinetic energy from the cloud scale are in fact directly passed on to the hurricane scale by the vertical overturning processes on the hurricane scale. Less of the kinetic energy is generated on the scales of individual clouds that are of the order of a few kilometers. The other major components of the energetics are the kinetic-to-kinetic energy exchange and available potential-to-available potential energy exchange among different scales. These occur via triad interaction and were noted to be essentially downscale transfer, that is, a cascading process. It is the balance among these processes that seems to dictate the final intensity.

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Lixion A. Avila, Richard J. Pasch, Jack L. Beven, James L. Franklin, Miles B. Lawrence, Stacy R. Stewart, and Jiann-Gwo Jiing

Abstract

The 2001 eastern North Pacific hurricane season is reviewed. It was a near-average season in terms of the number of systems, with 15 named tropical cyclones of which 8 became hurricanes. One tropical cyclone made landfall in Mexico and two reached category 3 or higher on the Saffir–Simpson hurricane scale. A description of each named cyclone is provided, and track and intensity forecasts for the season are evaluated.

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