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Dale F. Leipper

Weather forecasts and warnings are the most important services provided by the meteorological profession. The effective development of forecasting methods rests upon comprehensive knowledge of the phenomena to be forecast. To help provide such knowledge, this review includes a chronological summary of pertinent information concerning fog on the U.S. west coast. There is increasing evidence that periods of dense fog at National Weather Service west coast stations fall within a 5- to 15-day sequence of synoptic events. Further, such sequences may be divided into four distinct phases: initial conditions, fog formation, fog development and extension, and stratus. A separate article will review West Coast fog forecasting approaches and present resulting methods.

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Dale F. Leipper

Meteorological conditions associated with the observance of a sharp smog bank near Riverside, Calif., are compared with those previously shown to be related to the development of winter fogs in California. The conditions are similar. Thus, it is proposed that three simple indices found useful in the prediction of west coast fog be used also to predict situations favorable to the shallow, sharp-banked smogs which have been observed. The indices measure the influence of the sea surface temperature field upon air warmed in downslope flow associated with easterly winds in the area.

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Dale F. Leipper

Abstract

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Dale F. Leipper

Abstract

Hurricane Hilda crossed the Gulf of Mexico in the period 30 September to 4 October 1964, developing into a very severe hurricane in the central Gulf. Sea temperature data available prior to the storm indicated what was probably a typical late summer situation with some surface temperatures running above 30C. Beginning 5 October 1964, a 7-day cruise was conducted over the area where hurricane winds had been observed. Using the GUS III of the Galveston Biological Laboratory of the Bureau of Commercial Fisheries, four crossings of the hurricane path were made. Bathythermograph observations were taken regularly to 270 m and hydrographic casts to 125 m. The data on all four crossings indicated similar patterns. The observed temperature-depth structures after the storm indicated that the warm ocean surface layers were transported outward from the hurricane center, cooling and mixing as they moved; that these waters converged outside of the central storm area with the result that downwelling to some 80 to 100 m in depth took place there; and that cold waters upwelled along the hurricane path from depths of approximately 60 m. Sea surface temperatures decreased by more than 5C over an area of some 70 to 200 ml. A cyclonic current system was observed around the area of greatest hurricane intensity. It is estimated that the total heat loss from the ocean to the atmosphere in the area of hurricane force winds was 10.8 × 1018 cal with the transfer per unit area being 4500 cal cm−2. The data collected on the GUS III cruise are the first systematic observations available immediately after a severe hurricane in deep water.

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Dale F. Leipper
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Dale F. Leipper

Abstract

Weather forecasts and warnings are the most important services provided by the meteorological profession. As one aspect of these services, a year-round fog forecasting objective is selected for California coastal sites and their surrounding areas, both alongshore and offshore. The effort was to provide a simple, straightforward forecasting method using primarily data from the coastal site, which might be supplemented and improved using the forecaster's experience, any new technology, and new results of research. The meteorological objective is to forecast light, moderate, and dense fog, the probability of each occurring, and the expected times of beginning and ending of each period of reduced visibility, both for terminals and for limited nearby areas. Forecasts of five days' duration are sought using a frequently observed sequence of synoptic events. Methods in use were reviewed. The synoptic approach, emphasizing sea–air relationships, has produced the most promising results at this time. This approach led to the method called LIBS (Leipper inversion base statistics), which is described in some detail. It is the only known method that attempts to meet the objective chosen. There are strong indications that the LIBS method is applicable to situations along the California, Oregon, and Washington coasts. Case studies are presented for Monterey, California. Further research is encouraged.

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Dale F. Leipper and Douglas Volgenau

Abstract

It has been demonstrated that a large input of energy from the ocean is necessary to establish and maintain hurricane force winds over the sea. However, there has been no suitable data which could serve as a basis for calculating this input. Now, observations are available to show that, early in the hurricane season, there are varying initial conditions in the Gulf of Mexico which could lead to significantly different total heat exchanges. The sea can provide some seven days of energy flow into a hurricane at some times and at some locations, but less than one day in others depending upon the amount of heat initially available in the Gulf waters. In the four summers represented by the data, a quantity defined as hurricane heat potential was found to vary from a low of 700 cal cm−2 column north of Yucatan to a high of 31,600 in the central east Gulf. Synoptic data on hurricane heat potential, if made regularly available to forecasters, might serve as a basis for improved forecasts of changes in Intensity and movement of hurricanes.

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Dale F. Leipper and Dwight D. Miller
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Robert C. Landis and Dale F. Leipper

Abstract

Radio-transmitted synoptic data are used to determine the change brought about in the thermal structure of the Atlantic Ocean by the passage of hurricane Betsy in 1965. Such data for sea surface temperature and bathythermograph observations are regularly available from selected areas. Although they are not highly accurate and their interpretation is difficult, they could be more widely utilized in synoptic oceanography, as in this example and in oceanographic forecasting. The data for Betsy indicate thermal changes in the sea similar to those described previously for hurricane Hilda where research data were used. They give evidence of upwelling from 200 ft near the storm track, a 4F sea surface temperature decrease, and downwelling farther away from the track.

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Interaction Between the Atmosphere and the Oceans

Report of the Joint Panel on Air-Sea Interaction

George S. Benton, Robert G. Fleagle, Dale F. Leipper, R. B. Montgomery, Norris Rakestraw, William S. Richardson, Herbert Riehl, and James Snodgrass
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