Very cold air has settled into the state thanks to a robust area of high pressure. The altimeter reading (a measure of pressure) yesterday morning was a few hundredths of an inch below the highest value reported so far this year. The featured chart presents the yearly events of when the highest and lowest altimeter readings were observed. The first chart compares the air temperature against the day of the year for the observation. The highest pressure events are associated with colder temperatures than low pressure events as confirmed by the second chart. Low pressure events tend to be with dynamic storm systems (upward motion) that are windier than high pressure events (downward motion). The last chart shows the time of day that each event type occurs. High pressure events mostly occur during the morning hours when the atmosphere is still cooling, while low pressure events happen about any time of day.

Voting:
Good = 22
Bad = 6

Tags:   climate   pressure  

An epic winter storm has most of Iowa shut down this Wednesday morning with snowfall amounts approaching a foot and a half in areas. The big story now is the blowing snow thanks to strong winds blowing over 30 mph sustained. These winds are due to a tremendous pressure gradient over the state. The featured image shows the pressure drop yesterday for the Des Moines ASOS at 34 millibar in a 24 hour period. This rapid change, perhaps unprecedented, in pressure will help keep winds strong today and roads in Iowa impassable.

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Good = 86
Bad = 8

Tags:   blizzard   bomb   pressure  

When you get old like me, your bones and joints become the best predictor of the weather. The development of powerful storm system yesterday and today has dropped our surface pressure by around 0.7 inches of mercury (~ 24 millibars) in just over 24 hours. This is close to the "bombogenesis" criteria (24 mb in 24 hrs), which is just a cool sounding term to describe another cool sounding term, rapid cyclogenesis.

Voting:
Good = 12
Bad = 6

Tags:   bomb   pressure