IEM Daily Feature
Thursday, 16 January 2014

Pressure Gradient Winds

Posted: 16 Jan 2014 05:55 AM


View larger image
note that the chart is only for winter season months
After a windy Tuesday, winds are on the increase today and expected to gust upwards of 50 mph. These strong winds are forced by horizontal differences in pressure as air moves from areas of higher pressure to areas of lower pressure. The featured chart presents the combination of an approximate pressure difference over the state to the observed wind speed for Des Moines. An informal forecasting rule of thumb is that for every 4 millibars difference in pressure over Iowa leads to a wind of 10 more miles per hour. For example, a 12 millibar difference should support a 30 mph wind speed. The chart would indicate that this is a fair approximation with most of the distribution near the theoretical line.

Voting:
Good = 41
Bad = 7
Abstain = 7

Tags:   forecasting   wind   pressure