The airport weather sensors for Des Moines and Ames are typically called 'ASOS' sensors and lumped into the same data pile as they both have similar sensors and maintenance standards. The featured chart presents a summary of reported sky conditions at 6 AM each morning this year. While these sites are only separated by 30 some miles, there are some large differences in the number of clear mornings reported. The difference here is that the Des Moines sensor has augmentors that report cloud ceilings higher (to 25,000 feet) in the sky than the Ames sensor can (to 12,000 feet). This is just one of the data quirks that keeps life fun and various people employed to keep track of this all!

Voting:
Good = 23
Bad = 5

Tags:   clouds  

The weather these past few days has been remarkable for cool high temperatures along with mostly clear skies overhead. The featured chart attempts to look at the relationship of having cool days along with mostly clear skies or northerly winds. While the determination of these two criteria was somewhat arbitrary, the signal appears to be reasonable. Having northerly winds is common for these cool days, but least important during the summer time when the air to our north may not be that cold. Clear skies are the least common during May and June, when are surface heating rates are the largest.

Voting:
Good = 8
Bad = 5

Tags:   climate   clouds   highs  

High temperatures on Wednesday struggled in the 60s and were only a few degrees warmer than the coldest high temperatures on record for the date. This was thanks to a thick cloud cover and cold air brought in from our north. The featured chart looks at a measure of the amount of cloud cover on days were the high temperature was at record minimums and maximums. It makes intuitive sense that the coldest days are typically more cloudy during the spring, summer, and fall months as the sun is effective at warming the ground thanks to its high declination. Clouds are less important in the winter months as temperatures are dominated by organized air masses and the sun is less effective. For the warmest temperatures, having more sunny conditions are the most important in October it appears. Outside of a blip for warmest days in May, the plot has two clear annual signals!

Voting:
Good = 14
Bad = 5

Tags:   highs   climate   clouds  

The featured chart presents the hourly frequency of cloudy or mostly cloudy skies by day of the year based on observation data at the Des Moines Airport. The plot has a number of interesting features about the diurnal and annual cycles in Iowa. Firstly, a good number of our clouds are a result of day time heating by the sun. The late summer and fall months show up nicely for having fewer clouds during the night time. The forecast for the next 5-7 days continues to keep most of the clouds away with very pleasant fall weather!

Voting:
Good = 68
Bad = 14

Tags:   climate   clouds  

Our stretch of sunny days looks to continue today. The featured chart looks at the observed frequencies of having one day (black line) and three days in a row (blue line) of mostly clear or clear skies as observed at the Des Moines Airport. The chart shows September as having the highest frequencies with an interesting dip in the trend during the middle of the month. It is not clear what would be causing that, but this is another chart that would indicate perhaps fall is the best season of the year in Iowa!

Voting:
Good = 57
Bad = 15

Tags:   climate   clouds