Past IEM Features tagged: aug
The high temperature for Sioux City on Saturday reached a mere 66 degrees. There is a fair chance that this could be the day with the coldest high for the month. How rare is it for the coldest high to occur this early in August? The featured chart attempts to answer that question with the frequency of a given day of August having the coldest temperature. This situation is not all that infrequent with plenty either years having the coldest high temp this early in the month. The pleasant temperatures look to continue this week.
The heat is on for late August with high temperatures nearing 100 degrees in Iowa. This hot weather is thanks to a strong ridge of higher pressure centered just to our south. Ridge is a meteorological term that describes an area of higher pressure that tends to create sinking motions in the atmosphere and steer storm systems around it. The featured map presents a composite of 18 August events where the high temperature reached 100 degrees for Des Moines. The field plotted is geopotential height at 500 millibars. This is a measure of the depth of the atmosphere up to 500 mb. The composite field shows approximately our current weather situation with a strong ridge centered just to our south. The approximate geographic center of the ridge is plotted on the map as an x for each case. Our weather will remain hot and dry as long as the strong ridge remains in place.
Tags: ridge aug
For Ames, July ended up on the cool side of average for temperature. The featured chart presents the combination of August vs July average temperature for each year since 1893. A number of extreme years are labelled. While some recent feature plots have shown this year trending like 1947, the near term forecast does not indicate this August will be as warm as that. We could certainly use rain more than anything right now.
Tags: jul aug
Muggy weather returned over Labor Day weekend with humidity levels running more like what we would have expected in August. For Des Moines, the dew point on Monday was slightly higher than even the highest dew point for all of August. The featured chart shows the yearly combination of highest September versus August dew point. Points above the one to one line would represent years like this year with a higher dew point in September. This combination is somewhat rare and last happened in 1998.
Tags: aug sep
The mostly dry conditions and lack of robust vegetation have lead to very dry conditions for this time of year. Dew points have accordingly been running very low this month. The featured chart presents the maximum and minimum dew point for the first 19 days of August for each of the past years since 1933 for Des Moines. Both values this year are some of the lowest on record and the lowest they have been in quite some time. The red bars are years at or lower than 2012. In order for the first freeze to occur, the dew point has to drop to freezing temperature as well. Could the low dew points be a harbinger of things to come, namely an early freeze?
Tags: 2012 dewpoint aug
The past few days have been a welcome relief from much warmer weather in July and the first few days of August. The featured chart compares the July average temperature departure from average against the following August departure. The low correlation and visual appearance would indicate that one does not necessarily beget the other. The departure so far this August is about the same as July. The forecast has temperatures near average for the next week or so.
Tags: jul aug