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- Author or Editor: R. W. James x
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Hurricane development is identified with a steady change from anticyclonic to cyclonic absolute vorticity.
A measure of absolute vorticity, the energy ratio, is introduced, and the structure of a number of hurricanes is discussed with its aid.
Simple cyclone-models are devised, and the characteristics of hurricane structure and growth elucidated with them. It is shown that the kinetic energy of a circular vortex may increase a hundredfold or more with maturity. The initial impetus comes in the early stage of absolute anticyclonic vorticity, but the main increase of energy accrues in the mature stage of cyclonic vorticity.
The ratio of the total area of a hurricane to the inner, eye, area is approximately 100 in all stages of growth.
Abstract
Hurricane development is identified with a steady change from anticyclonic to cyclonic absolute vorticity.
A measure of absolute vorticity, the energy ratio, is introduced, and the structure of a number of hurricanes is discussed with its aid.
Simple cyclone-models are devised, and the characteristics of hurricane structure and growth elucidated with them. It is shown that the kinetic energy of a circular vortex may increase a hundredfold or more with maturity. The initial impetus comes in the early stage of absolute anticyclonic vorticity, but the main increase of energy accrues in the mature stage of cyclonic vorticity.
The ratio of the total area of a hurricane to the inner, eye, area is approximately 100 in all stages of growth.
Abstract
An enquiry is made into the way in which the mean intensities of cyclones and anticyclones vary with latitude.
For middle latitudes a linear relation is shown to hold between the mean central pressure of cyclones, and of anticyclones, and the sine of the latitude of their occurrence. This implies that the mean “potential intensity” of anticyclones is independent of the latitude. If, further, it is assumed that the pressure profile is independent of latitude, it can be shown that the total mass-excess and energy of anticyclones is approximately independent of latitude.
Abstract
An enquiry is made into the way in which the mean intensities of cyclones and anticyclones vary with latitude.
For middle latitudes a linear relation is shown to hold between the mean central pressure of cyclones, and of anticyclones, and the sine of the latitude of their occurrence. This implies that the mean “potential intensity” of anticyclones is independent of the latitude. If, further, it is assumed that the pressure profile is independent of latitude, it can be shown that the total mass-excess and energy of anticyclones is approximately independent of latitude.
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The conceptual model for height tendency presented by Hirschberg and Fritsch directly links upper-level virtual temperature tendency with low-level height tendency, overlooking the essential dynamics of mass divergence. An analysis of the complete height tendency equation shows that upper-level virtual temperature change car only indirectly induce low-level height change by driving ageostrophic circulations. To avoid misconceptions about middle- and lower-tropospheric height tendency, the dynamics of height tendency are reviewed.
Abstract
The conceptual model for height tendency presented by Hirschberg and Fritsch directly links upper-level virtual temperature tendency with low-level height tendency, overlooking the essential dynamics of mass divergence. An analysis of the complete height tendency equation shows that upper-level virtual temperature change car only indirectly induce low-level height change by driving ageostrophic circulations. To avoid misconceptions about middle- and lower-tropospheric height tendency, the dynamics of height tendency are reviewed.
The results of a questionnaire designed to gather information on how nonmeteorological scientists and engineers view meteorology and weather forecasting are summarized in this paper. The respondents were from two organizations, Texas A&M University and NASA's Marshall Space Flight Center, the first representing the academic community and the latter the engineering community. While there were some differences between the groups, in most cases answers expressed in the opinionnaire by the two groups were essentially identical. The results revealed the following: Approximately three-fourths of the respondents use meteorological data and/or weather forecasts in their profession; the meaning of probability forecasts is very unclear with only 13% indicating the correct answer; television is the main source of weather information; approximately half of the respondents had never heard of the Global Atmospheric Research Program; and the opinion was almost unanimous that satellites had contributed significantly to weather observations and/or forecasts. Also, the results indicated a number of other “problem” areas where some improvements are desired.
The results of a questionnaire designed to gather information on how nonmeteorological scientists and engineers view meteorology and weather forecasting are summarized in this paper. The respondents were from two organizations, Texas A&M University and NASA's Marshall Space Flight Center, the first representing the academic community and the latter the engineering community. While there were some differences between the groups, in most cases answers expressed in the opinionnaire by the two groups were essentially identical. The results revealed the following: Approximately three-fourths of the respondents use meteorological data and/or weather forecasts in their profession; the meaning of probability forecasts is very unclear with only 13% indicating the correct answer; television is the main source of weather information; approximately half of the respondents had never heard of the Global Atmospheric Research Program; and the opinion was almost unanimous that satellites had contributed significantly to weather observations and/or forecasts. Also, the results indicated a number of other “problem” areas where some improvements are desired.
Abstract
The topographic distortion of a cold front over the Snake River Plain (SRP) and central Idaho Mountains on 3 December 1998 is described using high-density surface observations from MesoWest, a collection of meteorological networks over the western United States. Although relatively unperturbed upstream of central Idaho, the cold front became distorted as it was deflected and accelerated up the low-elevation SRP, where a pronounced frontal bulge developed. The speed of the cold front over the SRP was comparable to the magnitude of the postfrontal winds that, due to terrain channeling, were oriented normal to the front. Meanwhile, the front advanced more slowly over the central Idaho mountains and southwest Montana, becoming increasingly diffuse over the former. Eventually, cold air surrounded the central Idaho Mountains and the two portions of the cold front merged over eastern Idaho.
The cold front intensified as it moved from the eastern to central SRP, with rapid changes in temperature and pressure observed at locations in the southern half of the SRP. Intensification of the cross-frontal temperature gradient in this region appeared to be the result of confluence between southerly prefrontal winds, which experienced downslope warming to the lee of the Jarbidge–Caribou Highlands, and terrain-channeled postfrontal winds. Although the rapid changes in temperature and pressure suggested that the front developed the local structure of a gravity current, the frontal motion over the SRP was not consistent with gravity current theory and instead appeared to be the result of advection of the front by the terrain-induced flow field.
The case study illustrates the value of high-density and multielevation MesoWest observations for advancing knowledge of frontal evolution over the western United States and improving operational surface analyses. Such observations aid in the identification of large-scale airmass and circulation changes that can be masked by boundary layer processes, valley inversions, and local and mesoscale terrain-induced wind systems.
Abstract
The topographic distortion of a cold front over the Snake River Plain (SRP) and central Idaho Mountains on 3 December 1998 is described using high-density surface observations from MesoWest, a collection of meteorological networks over the western United States. Although relatively unperturbed upstream of central Idaho, the cold front became distorted as it was deflected and accelerated up the low-elevation SRP, where a pronounced frontal bulge developed. The speed of the cold front over the SRP was comparable to the magnitude of the postfrontal winds that, due to terrain channeling, were oriented normal to the front. Meanwhile, the front advanced more slowly over the central Idaho mountains and southwest Montana, becoming increasingly diffuse over the former. Eventually, cold air surrounded the central Idaho Mountains and the two portions of the cold front merged over eastern Idaho.
The cold front intensified as it moved from the eastern to central SRP, with rapid changes in temperature and pressure observed at locations in the southern half of the SRP. Intensification of the cross-frontal temperature gradient in this region appeared to be the result of confluence between southerly prefrontal winds, which experienced downslope warming to the lee of the Jarbidge–Caribou Highlands, and terrain-channeled postfrontal winds. Although the rapid changes in temperature and pressure suggested that the front developed the local structure of a gravity current, the frontal motion over the SRP was not consistent with gravity current theory and instead appeared to be the result of advection of the front by the terrain-induced flow field.
The case study illustrates the value of high-density and multielevation MesoWest observations for advancing knowledge of frontal evolution over the western United States and improving operational surface analyses. Such observations aid in the identification of large-scale airmass and circulation changes that can be masked by boundary layer processes, valley inversions, and local and mesoscale terrain-induced wind systems.
Abstract
The position and surface wind direction field of Hurricane Eloise was observed by measuring sea backscatter from the Gulf of Mexico through the use of an HF skywave radar situated in central California. A radar map of the surface wind direction field was compiled from the direction of the ocean gravity waves 8 m long, and compared to the surface wind directions measured at National Oceanic and Atmospheric Administration Data Buoy Office open ocean moored buoys EB10 and EB04. Agreement to within 10% was found. A radar position fix was determined from the radar-derived surface wind map and showed agreement to within 35 km of the position estimated from the official National Hurricane Center track.
Abstract
The position and surface wind direction field of Hurricane Eloise was observed by measuring sea backscatter from the Gulf of Mexico through the use of an HF skywave radar situated in central California. A radar map of the surface wind direction field was compiled from the direction of the ocean gravity waves 8 m long, and compared to the surface wind directions measured at National Oceanic and Atmospheric Administration Data Buoy Office open ocean moored buoys EB10 and EB04. Agreement to within 10% was found. A radar position fix was determined from the radar-derived surface wind map and showed agreement to within 35 km of the position estimated from the official National Hurricane Center track.
