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Richard J. Pasch and Max Mayfield

Abstract

An account of the 1994 hurricane season in the eastern North Pacific Ocean is given. The numbers of hurricanes and tropical storms were near normal, but the activity tended to occur farther to the west in the basin than usual. Hurricane Rosa was the only system of the season to make landfall.

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Eric S. Blake and Richard J. Pasch

Abstract

The hurricane season of 2008 in the eastern North Pacific basin is summarized, and the individual tropical cyclones are described. Official track and intensity forecasts of these cyclones are also evaluated. The 2008 eastern North Pacific season was relatively quiet, with overall activity at about 75% of the long-term median. A total of 16 tropical storms formed, of which 7 became hurricanes and 2 became major hurricanes. One hurricane, one tropical storm, and two tropical depressions made landfall in Mexico, causing eight direct deaths in that country along with significant property damage. In addition, Tropical Storm Alma was the first tropical cyclone on record to make landfall along the Pacific coast of Nicaragua. On average, the official track forecasts in the eastern Pacific for 2008 were quite skillful and set records for accuracy from 1 to 3 days. However, no appreciable improvement in mean intensity forecast skill was noted.

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Lixion A. Avila and Richard J. Pasch

Abstract

A total of 70 tropical waves (also known as African or easterly waves) were counted in the Atlantic basin during the 1993 hurricane season. These waves led to the formation of 9 of the 10 total number of tropical cyclones in the Atlantic hurricane basin. It appears that tropical waves led to the formation of practically all of the eastern Pacific tropical cyclones in 1993.

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Richard J. Pasch and Lixion A. Avila

Abstract

A total of 69 tropical waves (also known as African and easterly waves) were counted in the Atlantic basin during the 1992 hurricane season. As was the case in 1991, the waves were, in general, relatively weak. These waves led to the formation of only four tropical depressions in the Atlantic hurricane basin, of which one intensified into a tropical storm and another intensified into Hurricane Andrew. Andrew was the only 1992 Atlantic hurricane to originate from a tropical wave. There were five additional tropical depressions that were primarily initiated by systems of nontropical origin. These produced three hurricanes and one tropical storm. It appears that tropical waves led to the formation of practically all of the eastern Pacific tropical cyclones in 1992.

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Richard J. Pasch and Edward N. Rappaport

Abstract

The 1993 hurricane season is summarized. and individual tropical storms and hurricanes are described. Overall, the season was relatively inactive, but tropical storms and hurricanes were responsible for a large number of deaths in South America, Central America, and Mexico. Only one hurricane, Emily, made landfall in the United States.

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Lixion A. Avila and Richard J. Pasch

Abstract

The 1991 hurricane season in the Atlantic basin featured 73 tropical waves (also known as African waves), most of which were relatively weak. These waves generated fewer than normal Atlantic tropical cyclones: seven tropical depressions, of which only three intensified into tropical storms. Remarkably, none of these systems became hurricanes. The remainder of the Atlantic tropical cyclones formed from other sources. African waves triggered nearly all of the eastern Pacific tropical cyclones in 1991.

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Richard J. Pasch and Lixion A. Avila

Abstract

The 1991 hurricane season is summarized, including accounts of individual storms. Eight tropical storms were tracked, of which four became hurricanes. Only one tropical cyclone, Hurricane Bob, hit the United States.

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Richard J. Pasch and Lixion A. Avila

Abstract

A summary of the 1996 Atlantic hurricane season is given, and the individual tropical storms and hurricanes are described. This was the second active year in a row with a large number of intense hurricanes. Hurricane Fran, which hit the coast of North Carolina, was the strongest system to make landfall, and also the most destructive.

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Richard J. Pasch, Lixion A. Avila, and Jiann-Gwo Jiing

Abstract

Totals of 70 and 63 tropical waves (also known as African or easterly waves) were counted in the Atlantic basin during the 1994 and 1995 hurricane seasons. These waves led to the formation of 9 of the 12 total number of tropical cyclones in 1994 and 19 of the 21 total number of tropical cyclones in 1995. Tropical waves contributed to the formation of 75% of the eastern Pacific tropical cyclones in 1994 and 73% in 1995. Upper- and lower-level prevailing wind patterns observed during the below-normal season of 1994 and the very active one of 1995 are discussed. Tropical wave characteristics between the two years are compared.

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Georg A. Grell, Ying-Hwa Kuo, and Richard J. Pasch

Abstract

In this paper, we consider three disparate classes of cumulus parameterization schemes, applied to cases of severe midlatitude convective storms observed during SESAME-1979. Objective analysis of the observed data was carded out and verifying heat and moisture budgets were computed. For the three types of schemes–Arakawa-Schubert, KreitzbM-Perkey, and Kuo–the underlying closure assumptions and cloud models are tested within the generalized framework of dynamic control, static control, and feedback. Using the semiprognostic approach, single time step predictions of the heating and drying rates due to convection are obtained for the three schemes and are compared with those diagnosed from the observed budgets. The results presented should have important implications for models with a resolution of more than 1 80 km.

The vertical distributions of warming and drying are fairly well reproduced by the Arakawa-Schubert scheme, however, excessive amounts are predicted in most of the lower troposphere and insufficient drying is predicted just near the surface. This was ameliorated by incorporating moist convective-scale downdrafts into the parameterization. Although the downdraft mass flux is highly sensitive to some arbitrary parameters, the inclusion of downdrafts is shown to be crucial to predict the feedback correctly in the midlatitude environment. A test of the quasi-equilibrium assumption for these severe storm cases showed that it was valid (as had previously been demonstrated for the tropics). For the Kreitzberg-Perkey scheme, the most severe limitations were found to be a lack of dependence on large-scale destabilizing effects in the dynamic control and the assumption that clouds instantly decay and mix with their environment in the feedback. For the Kuo-type schemes, tests of its dynamic control demonstrated the need to include mesoscale moisture convergence in order to correctly predict the vertically integrated heating and drying rates, unless the resolved scale is fairly small and the moistening parameter is set to zero. Tests with the feedback-wherein the vertical distribution of heating and drying is dictated by the differences between cloud and environmental thermodynamic properties-revealed serious shortcomings. In particular, this scheme is unable to predict heating maxima for atmospheric layers exhibiting high static stability. Such stable layers are frequently noted in the midlatitude environment of severe convective storms.

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