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Dale A. Lowry

Abstract

Climatological relationships among precipitable water, thickness and precipitation are presented in such a manner that a line of saturation thickness may be defined. One year of data were used to develop such a line and the subsequent year's data were used to check the validity of the line. The equation for this line is hs = 5550 + 300 In W + 0.1 E, where the saturation thickness (hs) is given in meters when the precipitable water (W) is in inches and the elevation (E) is expressed in meters. The equation is valid over a wide region cast of the Rocky Mountains during all seasons of the year. A weakness in the relationship occurs under extreme cold and dry conditions. Possible applications include the use of observed (or predicted) fields to produce diagnostic (or forecast) values of atmospheric moisture, including precipitation.

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Dale A. Lowry

As the various industries in Greece grow and the needs of the nation continue to change, the requirement for expanded meteorological services is unavoidable. This expansion includes improvements in facilities, technological advances, and training. These items are discussed in detail, and emphasis is placed on the most recent years when many significant advances occurred. There is much hope for continued advances through better understanding of numerical weather prediction, through the gradual implementation of the World Weather Watch, and through the efforts of the newly formed Applied Research Group in Greece.

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Dale A. Lowry and Harry R. Glahn

Abstract

A dynamical-statistical model for use in probability of precipitation forecasting out to 60 h is described. This model has been fully operational twice daily in the National Weather Service (NWS) since January 1972. The acronym for the model is PEATMOS PoP, for Primitive Equation And Trajectory Model Output Statistics, Probability of Precipitation. All inputs to the PoP model are provided at the National Meteorological Center by the normal outputs of the Primitive Equation and Trajectory models. We have continued to modify and adjust the model in the various ways described in order to improve its performance. An evaluation of performance shows that the accuracy of the forecasts produced by this model has continued to increase from year to year. PoP forecasts going to the public from NWS local offices have also improved with time. This improvement is likely the result of better guidance (PEATMOS PoP), although there was a slight adjustment period that lasted only a few months when the objective guidance was introduced.

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HAROLD M. JORDAN and DALE A. LOWRY

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No Abstract Available.

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ROBERT O. COLE and DALE A. LOWRY

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No Abstract Available.

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Harry R. Glahn and Dale A. Lowry

Abstract

A simple numerical model for use in short-period forecasting (up to 24 hr) in the eastern United States is described. This model has been used operationally twice daily in the National Weather Service since June 1968. The forecast cycle is determined by the needs of the forecast service rather than by the upper air observation times. All hourly surface reports available on teletype for the eastern and central United States and Canada are used as input. The mesh length is approximately 50 mi, one-fourth that used for the large-scale, hemispheric models at the National Meteorological Center (NMC).

Verifications of sea-level pressure and precipitation forecasts from SAM are presented. It is concluded that the use of this relatively inexpensive model, along with the other centralized guidance produced by NMC, can be a definite help in preparing local, short-period forecasts.

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Dale A. Lowry and Harry R. Glahn

Abstract

Linear regression equations are presented which relate the natural logarithm of total precipitable water in the atmospheric column below 500 mb to surface dew point, sky cover and weather at 1200 GMT over the eastern and central United States and southern Canada. About 86% of the yearly variance is explained by these three variables. Lowest cloud height, sea-level pressure, surface temperature, surface wind, station elevation, latitude and longitude do not add appreciably to this reduction of variance. Stratification by month, region, or both, while increasing the reduction of variance slightly, does not appear to be necessary for this particular geographic area.

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Harry R. Glahn and Dale A. Lowry

Abstract

Model Output Statistics (MOS) is an objective weather forecasting technique which consists of determining a statistical relationship between a predictand and variables forecast by a numerical model at some projection time(s). It is, in effect, the determination of the “weather related” statistics of a numerical model. This technique, together with screening regression, has been applied to the prediction of surface wind, probability of precipitation, maximum temperature, cloud amount, and conditional probability of frozen precipitation. Predictors used include surface observations at initial time and predictions from the Subsynoptic Advection Model (SAM) and the Primitive Equation model used operationally by the National Weather Service. Verification scores have been computed, and, where possible, compared to scores for forecasts from other objective techniques and for the official forecasts. MOS forecasts of surface wind, probability of precipitation, and conditional probability of frozen precipitation are being disseminated by the National Weather Service over teletype and facsimile. It is concluded that MOS is a useful technique in objective weather forecasting.

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DALE A. LOWRY and EDWIN F. DANIELSEN

Abstract

The most striking shortcomings of previous 1000-mb. forecast models have been over-intensification of pressure systems, especially anticyclones, and inferior predictions in and near mountains. In this article a graphical-numerical two-level prediction model that incorporates a variable mean stability is developed and tested. When the mean stability is small, the 1000-mb. prediction is determined primarily by the 500-mb. steering and height changes. As the stability increases the 500-mb. control decreases and the effective mountain wind exerts more control over the 1000-mb. changes, Since the stability is generally larger in anticyclones than cyclones the anticyclones are steered by a smaller percentage of the 500-mb. wind and are more influenced by the mountain topography.

Twenty-four-hour forecasts were handproduced daily for the month of September 1965. Predictions were also prepared using a constant stability model, and the forecasts of the two models were compared statistically by rigorous verification techniques. It was found that a definite improvement in the overall product can be expected by application of the variable stability model as opposed to the constant stability technique, especially in the mountainous areas and around anticyclones.

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John J. Cahir, John M. Norman, and Dale A. Lowry

Abstract

Real-time computer graphics systems are being introduced into weather stations throughout the United States. A sample of student forecasters used such a system to solve specific specialized forecasting problems. Results suggest that for some types of problems, involving timing, their forecasts were better than those made by forecasters who did not have access to the system.

Examples are given of the diagnostic use of some of the available analyses.

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