Thunderstorm Forecasting Research Articles

A Lower-Tropospheric Thermodynamic Climatology for March through September: Some Implications for Thunderstorm Forecasting

Abstract A thermodynamic climatology was constructed to investigate source regions of low-level moist airmasses and lower mid-tropospheric dry airmasses that contribute to the production of convective instability, and thunder-storms, over the United States. Mean monthly 1200 UTC values of potential temperature, mixing ratio, and geopotential height were computed at the surface and 750 mb for March through September (1966–1980) for 69 upper-air stations in the continental United States and Mexico. Analyses indicated that the Gulf of Mexico is the most significant source of low-level moisture east of the Continental Divide for all months, but the Atlantic Ocean also becomes a significant source in summer. The Gulf of California was found to be the most important source of low-level moisture west of the Continental Divide in summer. A distinct synoptic scale dryline was found over west Texas from March to June and analyses suggested that the strongest drylines occur in April and May. Northwest Mexico and the...

An Assessment of VAS-Derived Retrievals and Parameters Used in Thunderstorm Forecasting

VAS satellite retrievals and derived parameters used in forecasting severe local storms were evaluated against corresponding radiosonde values. VAS products were also compared with the first-guess input to the retrieval algorithm. The evaluation methodology was to pair each radiosonde observation with the closest VAS retrieval within 50 km during a four-month period in 1986. VAS temperatures agreed closely with radiosonde values; dewpoints showed less agreement. Sounding differences were poorly correlated with the number of pixels from which the retrievals were prepared. VAS discrepancies usually were not well correlated with first-guess errors. Horizontal gradients of VAS products were stronger than those from radiosondes. VAS precipitable water agreed better with ground truth than did dewpoints at individual levels, but VAS thicknesses were not much improved. Results for severe storms forecasting parameters indicated that discrepancies increased with the amount of manipulation required during computation. The lifted index showed the best agreement; positive bouyant energy showed poor comparisons.

An Evaluation of Stability Indices for Thunderstorm Prediction in Greater Cyprus

Abstract The effectiveness of a number of forecasting indices for non-frontal thunderstorm activity has been investigated for the Greater Cyprus area. The indices include the humidity index (HI), the Pickup index (PI), the K-stability index, the Yonetani index in its original II and modified IIc, form, and the Showalter stability index (SSI) for the Mediterranean area. Combinations of some of these indices with information of the flow curvature are also considered. Two data sets, representative of coastal and inland locations are used to evaluate the accuracy of these indices. Verification statistics indicate that Yonetani's indices II and IIc, are more successful than the HI, PI, and K indices in the forecast of air mass thunderstorms. The addition of the flow curvature at 500 hPa improves the effectiveness of most indices and its inclusion should be seriously considered for the Eastern Mediterranean area.

Instability indices for the Cyprus area

In this paper, forecasts of thunderstorms for the Cyprus area, are examined, by using various instability indices. In addition, some combinations of the indices are proposed since they proved more successful in thunderstorms forecasting. A statistical method pointed out that the Pickup index (PI) and the suggested combination of the humidity index (HI) with cyclonic curved flow at 500 hPa are more successful than the other ones examined in this study.

Severe Thunderstorm Forecasting: A Historical Perspective

Abstract Techniques that have evolved during the hundred years that scientific severe thunderstorm forecasts have been prepared are reviewed. The early empirical rules developed by Finley, Showalter and Fulks, Fawbush, Miller and Starrett, and others have been corroborated by more recent theoretical work. While significant efforts have been devoted to defining the severe thunderstorm environment, it is now obvious that these storms can occur under a variety of synoptic conditions. Severe thunderstorm forecasting consists in not only identifying the time and place that an environment compatible with such storms will exist but also in identifying suitable triggering mechanisms in that environment.

Objective Predictions of Thunderstorm Location and Severity for Aviation

This paper presents a computerized technique for medium-range (12-48 h) prediction of both the location and severity of thunderstorms, utilizing atmospheric predictions from the National Meteorological Center's limitedarea fine mesh model. A regional-scale analysis scheme is first used to examine the spatial and temporal distribution of forecasted variables associated with the structure and dynamics of mesoscale systems over an area of approximately 10 km . The final prediction of thunderstorm location and severity is based upon an objective combination of these regionally analyzed variables. Medium-range thunderstorm predictions are presented for the late afternoon period of April 10, 1979, the day of the Wichita Falls, Texas tornado. The National Severe Storms Forecast Center's operational predictions are presented with the case study to demonstrate the possible application of this objective technique in improving 12-48-h thunderstorm forecasts for aviation.

Comments on “Automated 12–36 Hour Probability Forecasts of Thunderstorms and Severe Local Storms”

Comments on “Automated 12–36 Hour Probability Forecasts of Thunderstorms and Severe Local Storms”

Automated 12–36 Hour Probability Forecasts of Thunderstorms and Severe Local Storms

Abstract Probability equations were developed for 12–36 h forecasts of thunderstorms, severe local storms, and major or family tornado outbreaks. The equations were derived by applying screening regression techniques to relate manually digitized radar (MDR) data and severe storm reports to large-scale meteorological predictors obtained from numerical forecast models. The probability forecasts are prepared once daily on the NOAA computer system and are transmitted over facsimile and teletypewriter circuits. One of the more important innovations in the forecast equations was the development of an interactive predictor which takes into account the seasonal variations in thunderstorm occurrence, yet is responsive to the daily synoptic situation. This predictor is formed by combining the K stability index with daily mean thunderstorm relative frequencies estimated from MDR data. Local variations in thunderstorm occurrence over the MDR grid were also included in the generalized equation by incorporating probabi...

The AFOS Program and Future Forecast Applications

Abstract The Automation of Field Operations and Services (AFOS) program of the National Weather Service will provide a new dimension to local weather analysis and forecasting. By providing minicomputers, video displays and high-speed communications to over 200 weather stations around the country, AFOS will greatly increase the forecaster's ability to assess, process, display and disseminate meteorological information. New prediction techniques will become feasible such as automatically monitoring and updating aviation terminal forecasts, providing computer-worded objective public forecasts, and using digitized radar data to update and improve precipitation, hydrologic and thunderstorm forecasts. The progress of research projects to develop these new analysis and forecast method for local application in the AFOS system is described, and the latest status of the AFOS program is discussed.

The Thunderstorm Forecasting System at the Kennedy Space Center

One of the major problems concerning meteorologists at the Kennedy Space Center, Fla, involves the forecasting of thunderstorm activity and associated adverse weather phenomena. The purpose of the study is to outline some of the more successful diagnostic tools which have been developed to aid the forecaster. These involve a variety of statistical procedures including conditional probabilities, exposure-period probabilities, and systems of multiple-regression equations based on nonlinear predictors.

AN OBJECTIVE METHOD OF THUNDERSTORM FORECASTING FOR WASHINGTON NATIONAL AIRPORT, WASHINGTON, D.C.1

ABSTRACTThe literature was reviewed in order to determine the variables likely to be important in forecasting thunderstorms. A stepwise discriminant analysis was performed on these variables to determine those significantly related to thunderstorm occurrence. Eight variables were selected. These were then used to produce a forecasting equation by means of the linear discriminant analysis technique. This equation was then tested against the Showalter and Total Totals indexes for forecasting skill, and was found to have higher skill.

A stability index for thunderstorm forecasting over Delhi

Showalter (1953) developed an objective method for forecasting of thunderstorms by the use of "Stability Index" derived from local radiosonde data. Tripathi (1956) and Joseph (1957) tried to investigate the application of this method in the forecasting of thunderstorms over Poona and Madras respectively and found the method to be reasonably useful. Their findings were based on one radiosonde as-cent a day, viz., that of 1500 GMT, and the same was correlated with the occurrence or otherwise of thunderstorm during the next 24 hours. The changes in the upper air temperature and humidity conditions within the next 24-hour period and prior to the occurrence or otherwise of thunderstorm had obviously to be ignored in those studies. Since then two radiosonde ascents daily at 00 and 12 GMT have been introduced at a number of stations in India, and in this note an attempt has been made to find out by utilising data of two radiosonde ascents a day, as to what extent Showalter's "Stability Index" method could be applied with success in the forecasting of thunderstorm over Delhi during the premonsoon months (April, May and June).

The Divergence Equation as Related to Severe Thunderstorm Forecasting

The divergence form of the equations of motion is developed and the terms of the equation are related to several local thunderstorm forecast parameters. It is found that the divergence equation provides the physical basis for evaluating the validity of several forecast rules under differing synoptic situations. In order that the magnitudes of the several terms can be compared, a numerical solution for a particular severe local thunderstorm producing synoptic situation is shown.

A Semi-objective Technique for Forecasting Thunderstorms in Eastern Virginia

A thunderstorm forecast technique is evaluated on a day by day basis during the months May through September, 1960. The over-all verification probability is 0.92. In a comparison test with persistence forecasts, the semi-objective method has a 24 per cent greater verification probability and shows more than thrice the skill factor.

A Stability Index for Thunderstorm Forecasting

A Stability Index for Thunderstorm Forecasting

ON THUNDERSTORM FORECASTING IN THE CENTRAL UNITED STATES

Abstract This study is directed toward a better understanding of the occurrence and forecasting of thunderstorms as an element of general weather patterns or sequences of patterns. The principal area studied is the Central United States. Following a review of the literature, the climatology of thunderstorms is examined. Then, from an analysis of many thunderstorm situations, the typical features and important synoptic patterns of areas of thunderstorm activity and their movement and life cycle are described. Finally some of the parameters suggested by the study are incorporated into a systematic technique to aid in the preparation of forecasts of thunderstorms during a 24-hour period at Chicago. The procedure is based upon 850-mb. chart types, previous occurrence of thunderstorms, and moisture and stability. A test on independent data gives good results.

AN OBJECTIVE AID FOR FORECASTING SEPTEMBER THUNDERSTORMS AT DENVER, COLO.

The climatology of September thunderstorms at Denver, Colo., is discussed. Data as near as possible to the time of occurrence of thunderstorms are studied to determine variables related to the occurrence of thunderstorms. The same variables from earlier data are investigated to determine their forecasting value. Three variables taken from the 2000 MST raobs and 700-mb. charts are ultimately used to obtain an objective aid for forecasting thunderstorms between midnight and midnight following the 2000 MST upper air chart. It is pointed out that for practical purposes this constitutes a forecast of afternoon and evening thunderstorms, or a forecast for 12–20 hours in advance. The conclusion is drawn that the objective aid developed should prove of value in forecasting September thunderstorms at Denver.

The use of pyrheliometer records in objective weather forecasting

The amount of solar and sky radiation received on a horizontal surface is used for objective forecasting of summer thunderstorms and shower type precipitation. Methods for establishing a radiation value which is critical for precipitation and ways of evaluating the records used in forecasting are explained. The results of forecasts made on this basis over a period of seven years, for the months of June, July, and August, show appreciable skill above chance.

大氣の垂直不安定度の變動機構と雷雨豫報への示唆

大氣の垂直不安定度の變動機構と雷雨豫報への示唆