| OCR Text |
Show 7 periods in excess of 24 hours. Also, even though the actual precipitable water is not a parameter which can easily be directly predicted, it can be estimated by indirect means. It is known that the 500 - 1000 mb thickness is proportional to the precipitable water. The thickness pattern can be predicted by numerical techniques. Changes in the thickness can be estimated for a given locality and inferred changes in precipitable water amount can be determined. The predicted values of 700 mb or 10,000 ft. winds and precipitable water can then be used to compute the orographic precipitation rate, and this, combined with the expected duration of the orographic precipitation ( based on the curvature of the 700 mb flow), can be used to estimate the total orographic precipitation for a given period. This may be combined with expected non- orographic effects ( such as fronts, etc.) to estimate the total precipitation rates and amounts. REMARKS At the time this study was made, radiosonde data were available at 12 hourly intervals only. Thus, considerable interpolation was necessary in order to obtain data for 6 hourly intervals. This source of error should be reduced now, inasmuch as radiosonde data are available at 6 hourly intervals. This should improve the accuracy of the method. Also, radar data are now available, which should help considerably in forecasting precipitation duration, time and intensity, especially over a short time interval. This study and forecast method is only an exploratory investigation into various relationships between storm characteristics and what actually |
