Hot weather forecasting hacks for the hobbyist 

Posted: 5:38 pm Friday, June 10th, 2016

By Kirk Mellish

Some down and dirty rules of thumb for when to forecast hot weather:

A.) When the 500 mb height level reaches or exceed 588.

B.) When the 1000-500 mb thickness level reaches or exceeds 576.

C.) When the 850 mb temperature reaches or exceeds 20C.

A 588 500 mb contour can indicate max temperatures near 90. An 850 mb temp of 15C often means 90 while 20 can mean 95 and 25 can mean 100.

If you combine 500 mb heights of 591-595 with thickness values of 582 or more and 850 mb temperatures of 20-25 or higher this suggests upper level ridging with subsidence lots of sun and compression heating to go with radiational and advective heating. In such cases 95-100 would be common with 110-115 readings in spots.

For example, here are three such forecast maps for this Sunday June 12th:

Screen Shot 2016-06-10 at 4.56.36 PM


Screen Shot 2016-06-10 at 5.32.07 PM

AND here are the computer’s forecast high temperatures for that day:

Screen Shot 2016-06-10 at 5.16.39 PM

Thus, even an amateur would be able to forecast the heat even without access to computer temperature prediction output just by applying the forecast rules of thumb.