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- Author or Editor: David P. Jorgensen x
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Abstract
The eyewall structure of Hurricane Alien is examined from analyses of multiple aircraft data on two days, 5 and 8 August 1980. These data sets are unique in that, for the first time, three instrumented aircraft executed coordinated radial penetrations of the eyewall at multiple levels. The data collected on 5 August illustrate the persistence of various features on horizontal scales > 10 km over several hours. Composite cross sections constructed from the 8 August data show similar structure, although the eye diameter had decreased to less than half that of 5 August.
The convergence of air in the eyewall was highly two-dimensional. This convergence supported organized ascent that was along the inner edge of the high reflectivity region and displaced inward several kilometers from the radius of maximum wind (RMW). A mean eyewall updraft of 5–6 m s−1 is computed from integration of the two-dimensional continuity equation. Embedded within the two-dimensional eyewall were cores of high reflectivity that were 2–5 km in diameter, three-dimensional, and generally not traceable from pass to pass (∼20 min intervals). These convective-scale entities had highest updraft velocities of 7–9 m s−1. Upward mass flux in the eyewall was 4–5 times greater than that diagnosed by Zipser and others for a GATE slow-moving convective line. This greater mass flux was accomplished not through larger vertical velocities within convective cares, but by a greater area covered by active updrafts within the low-level convergence zone.
Abstract
The eyewall structure of Hurricane Alien is examined from analyses of multiple aircraft data on two days, 5 and 8 August 1980. These data sets are unique in that, for the first time, three instrumented aircraft executed coordinated radial penetrations of the eyewall at multiple levels. The data collected on 5 August illustrate the persistence of various features on horizontal scales > 10 km over several hours. Composite cross sections constructed from the 8 August data show similar structure, although the eye diameter had decreased to less than half that of 5 August.
The convergence of air in the eyewall was highly two-dimensional. This convergence supported organized ascent that was along the inner edge of the high reflectivity region and displaced inward several kilometers from the radius of maximum wind (RMW). A mean eyewall updraft of 5–6 m s−1 is computed from integration of the two-dimensional continuity equation. Embedded within the two-dimensional eyewall were cores of high reflectivity that were 2–5 km in diameter, three-dimensional, and generally not traceable from pass to pass (∼20 min intervals). These convective-scale entities had highest updraft velocities of 7–9 m s−1. Upward mass flux in the eyewall was 4–5 times greater than that diagnosed by Zipser and others for a GATE slow-moving convective line. This greater mass flux was accomplished not through larger vertical velocities within convective cares, but by a greater area covered by active updrafts within the low-level convergence zone.
Abstract
Meteorological events in the upper and lower troposphere in Hurricane Gertrude and vicinity are examined for causal effects related to the sudden dissipation of Hurricane Gertrude. Mesoscale and synoptic-scale meteorological observations reveal that the hurricane rapidly decreased in intensity as it overtook a westward propagating upper tropospheric trough. Quantized radar observations are presented, which show the marked decrease in storm-generated precipitation which occurred as Gertrude approached the vicinity of this trough. This study indicates that the dissipation of Gertrude resulted from large vertical wind shear and upper level synoptic-scale convergence with accompanying subsidence in the upper troposphere in the vicinity of the storm.
The marked decrease in convective activity and storm organization occurred in spite of favorable sea surface temperatures, favorable lower troposphere stability, and convergence of air toward the storm center in the boundary layer. This study reveals the amount of control that upper atmospheric motion has on storm development.
Abstract
Meteorological events in the upper and lower troposphere in Hurricane Gertrude and vicinity are examined for causal effects related to the sudden dissipation of Hurricane Gertrude. Mesoscale and synoptic-scale meteorological observations reveal that the hurricane rapidly decreased in intensity as it overtook a westward propagating upper tropospheric trough. Quantized radar observations are presented, which show the marked decrease in storm-generated precipitation which occurred as Gertrude approached the vicinity of this trough. This study indicates that the dissipation of Gertrude resulted from large vertical wind shear and upper level synoptic-scale convergence with accompanying subsidence in the upper troposphere in the vicinity of the storm.
The marked decrease in convective activity and storm organization occurred in spite of favorable sea surface temperatures, favorable lower troposphere stability, and convergence of air toward the storm center in the boundary layer. This study reveals the amount of control that upper atmospheric motion has on storm development.
