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- Author or Editor: Billy M. Lewis x
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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.
Abstract
The National Hurricane Center and the National Hurricane Research Laboratory joined forces in an effort to improve techniques for forecasting hurricane motion in the spring of 1959 when the latter moved its headquarters from West Palm Beach to Miami into offices adjacent to those occupied by the principal hurricane forecast office in the United States. Results now available from verification of forecasts made during the period 1954 through 1966 show that there has been a significant improvement in the accuracy of hurricane forecasts during the period of increased cooperation between the research and operational forecasting groups. This improvement is indicated by a reduction in the mean error of hurricane forecasts of approximately 10 and 12 percent, respectively, for the two principal hurricane forecast areas near the eastern coasts of the United States.
Abstract
The National Hurricane Center and the National Hurricane Research Laboratory joined forces in an effort to improve techniques for forecasting hurricane motion in the spring of 1959 when the latter moved its headquarters from West Palm Beach to Miami into offices adjacent to those occupied by the principal hurricane forecast office in the United States. Results now available from verification of forecasts made during the period 1954 through 1966 show that there has been a significant improvement in the accuracy of hurricane forecasts during the period of increased cooperation between the research and operational forecasting groups. This improvement is indicated by a reduction in the mean error of hurricane forecasts of approximately 10 and 12 percent, respectively, for the two principal hurricane forecast areas near the eastern coasts of the United States.
Abstract
Multiple regression equations for predicting 5-day mean temperatures in the United States were originally computed from 5-day mean values of both 700-mb. height and surface temperature, but they gave better results operationally when applied to properly weighted 46-hour forecasts of height and temperature. Since re-derivation from daily instead of mean data yielded poorer results, it appears that use of prognostic daily values as input in equations computed from mean data produces the best mean forecast under current operating conditions.
In an effort to obtain daily temperature forecasts for several days in advance, 5-day mean objective temperature predictions were tested a s forecasts of daily mean temperature on each of the individual days comprising the forecast period. Although perfect mean forecasts would have been most accurate for the middle day of the period, the objective prognoses attained maximum accuracy a day or two earlier. Comparison is made with chance, persistence, climatology, and daily predictions prepared at local forecast offices. The objective forecasts were superior to these controls on each day of the 5-day period, with maximum difference on day 3. Additional tests of the skill of the objective predictions as 2- and 3-day forecasts are described, and it is concluded that the objective method can be of assistance in the routine preparation of 72-hour forecasts.
Abstract
Multiple regression equations for predicting 5-day mean temperatures in the United States were originally computed from 5-day mean values of both 700-mb. height and surface temperature, but they gave better results operationally when applied to properly weighted 46-hour forecasts of height and temperature. Since re-derivation from daily instead of mean data yielded poorer results, it appears that use of prognostic daily values as input in equations computed from mean data produces the best mean forecast under current operating conditions.
In an effort to obtain daily temperature forecasts for several days in advance, 5-day mean objective temperature predictions were tested a s forecasts of daily mean temperature on each of the individual days comprising the forecast period. Although perfect mean forecasts would have been most accurate for the middle day of the period, the objective prognoses attained maximum accuracy a day or two earlier. Comparison is made with chance, persistence, climatology, and daily predictions prepared at local forecast offices. The objective forecasts were superior to these controls on each day of the 5-day period, with maximum difference on day 3. Additional tests of the skill of the objective predictions as 2- and 3-day forecasts are described, and it is concluded that the objective method can be of assistance in the routine preparation of 72-hour forecasts.
Abstract
A statistical screening procedure is used to derive linear multiple-regression equations which express 5-day mean surface temperature as a function of 5-day mean 700-mb heights centered 2 days earlier. Application of these equations to heights obtained from barotropic prognoses would have produced temperature predictions of positive skill during the test winter of 1957–58.
The forecasts can be considerably improved by including as a predictor the local value of 5-day mean surface temperature for a period 4 days earlier than the forecast period. When this term was combined with the barotropically-estimated heights, objective temperature predictions comparable in accuracy to conventional forecasts were made by multiple-regression equations. Further work is in progress to obtain additional improvement by screening the entire field of surface temperature.
Abstract
A statistical screening procedure is used to derive linear multiple-regression equations which express 5-day mean surface temperature as a function of 5-day mean 700-mb heights centered 2 days earlier. Application of these equations to heights obtained from barotropic prognoses would have produced temperature predictions of positive skill during the test winter of 1957–58.
The forecasts can be considerably improved by including as a predictor the local value of 5-day mean surface temperature for a period 4 days earlier than the forecast period. When this term was combined with the barotropically-estimated heights, objective temperature predictions comparable in accuracy to conventional forecasts were made by multiple-regression equations. Further work is in progress to obtain additional improvement by screening the entire field of surface temperature.
Abstract
A portable gas chromatograph designed for real-time studies in diffusion has been successfully tested in an airborne application. A 10-mi low-level plume of colorless, odorless non-toxic sulfur hexafluoride (SF6) was laid down over northwest Andros Island, Commonwealth of Bahama Islands, by the Research Flight Facility's (NOAA) C-130. An accompanying DC-6 carrying the analyzer made 81 in-flight samples over a period of less than 3 hr. The chromatograph has a sensitivity limit of 0.03 parts per billion and completes the analysis for SF6 less than 2 min after the sample is injected into the column. Of the more than 80 in-flight chromatograms, 11 indicated positive identification of the inert tracer gas. Confirmation of the on-site analyses was provided by bottle samples taken in flight and analysed later in the laboratory.
Abstract
A portable gas chromatograph designed for real-time studies in diffusion has been successfully tested in an airborne application. A 10-mi low-level plume of colorless, odorless non-toxic sulfur hexafluoride (SF6) was laid down over northwest Andros Island, Commonwealth of Bahama Islands, by the Research Flight Facility's (NOAA) C-130. An accompanying DC-6 carrying the analyzer made 81 in-flight samples over a period of less than 3 hr. The chromatograph has a sensitivity limit of 0.03 parts per billion and completes the analysis for SF6 less than 2 min after the sample is injected into the column. Of the more than 80 in-flight chromatograms, 11 indicated positive identification of the inert tracer gas. Confirmation of the on-site analyses was provided by bottle samples taken in flight and analysed later in the laboratory.
