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Forecasting Tmin via Craddock & Pritchard method

 
T at 12 UTC (°C)
Td at 12 UTC (°C)

Mean* cloud amount (oktas) 0-2
2-4
4-6
6-8
Mean* geostrophic wind speed (kn) 0-12
13-25
26-38
39-51
* = mean of forecast values for 1800, 0000 and 0600 UTC

Calculated Tmin °C
Calculated Tmin grass °C


 
Used formula:
 

Tn = (0.316 * T) + (0.548 * Td) - 1.24 + a

Tg = Tn - a2

(a = adjustment which depends upon the forecast cloud amount and geostrophic wind speed)

(a2= adjustment which depends upon the forecast cloud amount and geostrophic wind speed)

Tn = Tmin
Tg = Tmin grass

 

Note: this method was obtained from statistical investigation of 16 stations in eastern England not close to sea.

 

 

Source: Forecasters' reference book - ISBN 0 86180 306 X

 

 

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