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Computation of Hail Size This method of computing hail size is based on the estimates of updraft and downdraft velocities in thunderstorms and the resulting probabilities of hail produced in a thunderstormFigure 6-2-18.-Surface hail prediction diagram. reaching the surface. This technique is called the Fawbush-Miller Hail Forecast method. The procedure to calculate hail size is as follows: 1. From the temperature curve at 5C, extend a dry adiabat downward until it intersects the pressure level of and read the temperature T2 at this intersection. We will call this temperature in our example, figure 6-2-19, view A.2. Calculate the difference between this temperature (T2) and 5C. Call this value A. The difference is or simplyFigure 6-2-19.-Surface-hail-size calculation: (A) Calculation example, (B) hail size graph. 3. From the intersection with the temperature curve, draw a saturation adiabat up-ward to intersect the pressure level where the air temperature is 5C, and read the temperature at this intersection. We will call this temperature T3 in our example.4. Calculate the difference between this temperature T3 and 5C. Call this value B. This difference is or simply5. Enter figure 6-2-19, view B, with values A and B to find the hail size on the Fawbush-Miller Hail Graph.6. If your WBZ is above 10,500 feet, enter figure 6-2-20 with the hail size from step 5 and your WBZ height to determine a corrected hail size.Learning Objective: Describe the computa-tion procedure for contrail formation analysis on the Skew T. |
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