IEM Daily Feature
Wednesday, 17 July 2013

Easterly winds aloft

Posted: 17 Jul 2013 05:17 AM

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The weather pattern earlier this week was a bit strange with the southern plains experiencing a storm system that traveled west! The winds well above the ground surface, that help guide storm systems, were actually from the east. The featured chart looks at the frequency of easterly winds at a height of 200 hPa (millibars), which is about 7- 8 miles above the earth surface. The chart presents 12 wind roses, one for each month for the sounding site near Omaha. The site launches a weather balloon twice per day, providing a vertical profile of temperature, humidity, pressure, and winds. The wind roses provide frequencies of wind direction and speed. Westerlies clearly dominate for all months of the year. Each month is labelled with the percentage of observations that are primarily easterly. The highest percentages (although meager) are in the summer time, which is when the jet stream (very strong westerlies) is furthest away permitting such flow to occur. So while such events are very rare, this is the time of year when they most frequently happen.

Good = 84
Bad = 16

Tags:   sounding