Search Results
You are looking at 1 - 9 of 9 items for
- Author or Editor: Robert C. Sheets x
- Refine by Access: All Content x
Abstract
The National Hurricane Center (NHC) is one of three national centers operated by the National Weather Service (NWS). It has national and international responsibilities for the North Atlantic and eastern North Pacific tropical and subtropical belts (including the Gulf of Mexico and the Caribbean Sea) for tropical analyses, marine and aviation forecasts, and the tropical cyclone forecast and warning programs for the region. Its roots date back to the 1870s, and it is now in the forefront of the NWS modernization program. Numerous changes and improvements have taken place in observational and forecast guidance tools and in the warning and response process over the years. In spite of all these improvement, the loss of property and the potential for loss of life due to tropical cyclones continues to increase rapidly. Forecasts are improving, but not nearly as fast as populations are increasing in hurricane prone areas such as the United States East and Gulf Coast barrier islands. The result is that longer and longer lead times are required for communities to prepare for hurricanes.
The sea land over lake surge from hurricanes (SLOSH) model is used to illustrate areas of innudation for the Galveston/Houston, Texas; New Orleans, Louisiana, southwest Florida; and the Atlantic City, New Jersey areas under selected hurricane scenarios. These results indicate the requirement for lengthy evacuation times. The forecast and warning process is then illustrated, starting with tropical analyses, numerical guidance, the meteorological/hydrological coordination of the forecast, and finally the warning coordination and response process. Examples are used to illustrate the sensitivity of the warning and response process to preplanning based upon SLOSH model results, the coordination between NWS and local and state officials, and the critical role played by the media for motivating people to take the desired action in an orderly fashion. These examples illustrate how this process worked to near perfection during Hurricane Hugo, but was disrupted in the Galveston/Houston area by conflicting information reaching local officials and the public during Hurricane Gilbert.
Finally, a brief look into the future is attempted, with emphasis upon new observing systems, next generation numerical models and expected improvements in tropical cyclone track and intensity forecasts and the warning process at landfall and inland. The next generation weather radar (NEXRAD) systems in the modernized and restructured NWS are expected to play a major role in improving short-term warnings of flash floods, high winds, and possible tornadoes as hurricanes move inland and start to decay.
Abstract
The National Hurricane Center (NHC) is one of three national centers operated by the National Weather Service (NWS). It has national and international responsibilities for the North Atlantic and eastern North Pacific tropical and subtropical belts (including the Gulf of Mexico and the Caribbean Sea) for tropical analyses, marine and aviation forecasts, and the tropical cyclone forecast and warning programs for the region. Its roots date back to the 1870s, and it is now in the forefront of the NWS modernization program. Numerous changes and improvements have taken place in observational and forecast guidance tools and in the warning and response process over the years. In spite of all these improvement, the loss of property and the potential for loss of life due to tropical cyclones continues to increase rapidly. Forecasts are improving, but not nearly as fast as populations are increasing in hurricane prone areas such as the United States East and Gulf Coast barrier islands. The result is that longer and longer lead times are required for communities to prepare for hurricanes.
The sea land over lake surge from hurricanes (SLOSH) model is used to illustrate areas of innudation for the Galveston/Houston, Texas; New Orleans, Louisiana, southwest Florida; and the Atlantic City, New Jersey areas under selected hurricane scenarios. These results indicate the requirement for lengthy evacuation times. The forecast and warning process is then illustrated, starting with tropical analyses, numerical guidance, the meteorological/hydrological coordination of the forecast, and finally the warning coordination and response process. Examples are used to illustrate the sensitivity of the warning and response process to preplanning based upon SLOSH model results, the coordination between NWS and local and state officials, and the critical role played by the media for motivating people to take the desired action in an orderly fashion. These examples illustrate how this process worked to near perfection during Hurricane Hugo, but was disrupted in the Galveston/Houston area by conflicting information reaching local officials and the public during Hurricane Gilbert.
Finally, a brief look into the future is attempted, with emphasis upon new observing systems, next generation numerical models and expected improvements in tropical cyclone track and intensity forecasts and the warning process at landfall and inland. The next generation weather radar (NEXRAD) systems in the modernized and restructured NWS are expected to play a major role in improving short-term warnings of flash floods, high winds, and possible tornadoes as hurricanes move inland and start to decay.
The 13th Technical Conference on Hurricanes and Tropical Meteorology was held in Miami Beach, Fla., during 1–5 December 1980. The special emphasis of this conference was placed upon hurricanes in recognition of the 25th anniversary of the formation of the National Hurricane Research Project. Participants came from around the world and 167 people registered for the conference. The first six sessions of the conference were devoted to invited survey or overview papers focused upon advancements in hurricane research and prediction during the past 25 years.
The 13th Technical Conference on Hurricanes and Tropical Meteorology was held in Miami Beach, Fla., during 1–5 December 1980. The special emphasis of this conference was placed upon hurricanes in recognition of the 25th anniversary of the formation of the National Hurricane Research Project. Participants came from around the world and 167 people registered for the conference. The first six sessions of the conference were devoted to invited survey or overview papers focused upon advancements in hurricane research and prediction during the past 25 years.
Abstract
The variational optimization technique is used to develop analysis equations for the high-energy portion of the hurricane. The specified functional contains an observational constraint, two low-pass filter terms, and a dynamic constraint, the gradient wind condition. The two nonlinear analysis equations resulting from the functional are solved simultaneously. That is, information contained in the pressure and wind fields as measured from an aircraft is used to determine the resulting gradient wind. These winds are illustrated for selected scales of motion in a total form as well as component form, i.e., contributions from pressure gradient, centrifugal and Coriolis terms. These results are then compared with those obtained by use of the analysis equation without the gradient wind constraint. Also, a comparison is made between the gradient wind computed from the analyzed pressure field and the analyzed wind speed profiles where the analysis equation respectively does and does not contain the gradient wind constraint. All analyzed fields referred to are those obtained by application of the set of derived analysis equations with the degree of filtering being dependent upon the relative weights applied to the various terms within the equation.
Abstract
The variational optimization technique is used to develop analysis equations for the high-energy portion of the hurricane. The specified functional contains an observational constraint, two low-pass filter terms, and a dynamic constraint, the gradient wind condition. The two nonlinear analysis equations resulting from the functional are solved simultaneously. That is, information contained in the pressure and wind fields as measured from an aircraft is used to determine the resulting gradient wind. These winds are illustrated for selected scales of motion in a total form as well as component form, i.e., contributions from pressure gradient, centrifugal and Coriolis terms. These results are then compared with those obtained by use of the analysis equation without the gradient wind constraint. Also, a comparison is made between the gradient wind computed from the analyzed pressure field and the analyzed wind speed profiles where the analysis equation respectively does and does not contain the gradient wind constraint. All analyzed fields referred to are those obtained by application of the set of derived analysis equations with the degree of filtering being dependent upon the relative weights applied to the various terms within the equation.
Abstract
A variational optimaization technique is used to develop an analysis scheme for application to the high energy portion of a hurricane. Derived analysis equations are used to filter the date in an attempt to obtain the signal for selected seales of motion. The selection of the particular filters used is based on empirical evidence. The analysis scheme is applied to data collected from airborne platforms in Hurricane Debbie of 1969 during two modification attempts. Results of these analyses are then used to define a more explicit seeding hypothesis, which can be used in the explanation and statistical evaluation of future seeding experiments. While it is felt that strong physical inferences can be drawn from the analysis results, more such data analyses are required before definitive statistical support can be claimed.
Abstract
A variational optimaization technique is used to develop an analysis scheme for application to the high energy portion of a hurricane. Derived analysis equations are used to filter the date in an attempt to obtain the signal for selected seales of motion. The selection of the particular filters used is based on empirical evidence. The analysis scheme is applied to data collected from airborne platforms in Hurricane Debbie of 1969 during two modification attempts. Results of these analyses are then used to define a more explicit seeding hypothesis, which can be used in the explanation and statistical evaluation of future seeding experiments. While it is felt that strong physical inferences can be drawn from the analysis results, more such data analyses are required before definitive statistical support can be claimed.
Abstract
Some "mean hurricane soundings" have been computed from 92 radiosonde observations collected within 100 n mi of the centers of hurricanes. High correlations between various parameters and the sea-level pressures of the observations are shown. The data have been stratified By sea-level pressure, giving more than one mean hurricane sounding. Diurnal variations were investigated and temperature differences that are statistically significant were found to exist in the middle and upper troposphere. In addition, potential buoyancies and available instability energies were computed for some of the mean soundings. Potential and equivalent potential temperatures were found to increase, while the net available instability energy decreased, and the tropopanse became higher and colder as the sea-level pressures of the observations decreased. The mean soundings are shown to be conditionally unstable in the lower levels and very stable inthe upper troposphere.
Abstract
Some "mean hurricane soundings" have been computed from 92 radiosonde observations collected within 100 n mi of the centers of hurricanes. High correlations between various parameters and the sea-level pressures of the observations are shown. The data have been stratified By sea-level pressure, giving more than one mean hurricane sounding. Diurnal variations were investigated and temperature differences that are statistically significant were found to exist in the middle and upper troposphere. In addition, potential buoyancies and available instability energies were computed for some of the mean soundings. Potential and equivalent potential temperatures were found to increase, while the net available instability energy decreased, and the tropopanse became higher and colder as the sea-level pressures of the observations decreased. The mean soundings are shown to be conditionally unstable in the lower levels and very stable inthe upper troposphere.
Abstract
Two automatic ice particle counters, one operating in the visible and the other in the infrared spectrum, were tested. The operation of both units is based upon the cross-polarization technique for discriminating between ice and water particles. The results indicate that, although even small water droplets produce a signal, it is possible to distinguish between large water drops and small ice crystals because of the relatively large sensitivity for solid or crystalline materials. The signal strength depends upon the structure of the particle as well as its size. That is, smooth-sided crystals result in larger signals than similar sized, rough-sided particles. The capability of these instruments to provide real-time readouts of ice crystal counts is quite important for operational use in cloud modification experiments.
Abstract
Two automatic ice particle counters, one operating in the visible and the other in the infrared spectrum, were tested. The operation of both units is based upon the cross-polarization technique for discriminating between ice and water particles. The results indicate that, although even small water droplets produce a signal, it is possible to distinguish between large water drops and small ice crystals because of the relatively large sensitivity for solid or crystalline materials. The signal strength depends upon the structure of the particle as well as its size. That is, smooth-sided crystals result in larger signals than similar sized, rough-sided particles. The capability of these instruments to provide real-time readouts of ice crystal counts is quite important for operational use in cloud modification experiments.
Abstract
Hurricane Gladys, 17 October 1968, is studied with data collected by Aollo 7 manned spacecraft, ESSA's especially instrumented aircraft, weather search radar, the ATS-III and ESSA 7 satellites, and conventional weather networks. This is the feast time data from all of these observing tools have been used to study the structure and dynamics of a hurricane. Techniques used in computing and integrating the various types of data are described and illustrated.
A dominant feature of this immature hurricane was a large cloud which provided a major link between the low- and high-level circulations of the storm. Evidence is presented to suggest this type of cloud and its attendant circulation are features representative of tropical cyclones passing from the tropical storm to the hurricane stage.
Abstract
Hurricane Gladys, 17 October 1968, is studied with data collected by Aollo 7 manned spacecraft, ESSA's especially instrumented aircraft, weather search radar, the ATS-III and ESSA 7 satellites, and conventional weather networks. This is the feast time data from all of these observing tools have been used to study the structure and dynamics of a hurricane. Techniques used in computing and integrating the various types of data are described and illustrated.
A dominant feature of this immature hurricane was a large cloud which provided a major link between the low- and high-level circulations of the storm. Evidence is presented to suggest this type of cloud and its attendant circulation are features representative of tropical cyclones passing from the tropical storm to the hurricane stage.
