Past IEM Features tagged: may

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May Dew Points at Temperature

23 May 2016 05:34 AM
The weather this past weekend was rather amazing with warm temperatures and low humidities for much of the state. Only portions of extreme western Iowa got in on the muggy air on Sunday afternoon. The rest of the state was in the upper 70s and lower 80s with dew points well below those levels. The featured chart displays the average dew point at a given temperature in May for Des Moines. The average of 60 degree dew points is shown for temperatures in the lower 80s. So the weather we just experienced was certainly a treat! Things will change this week with numerous rounds of storms expected and muggier conditions.

Voting:
Good: 10
Bad: 2

Tags:   may  

Coldest May Day

12 May 2015 04:29 AM
Monday was a chilly and windy departure from the near summer like weather we have recently been experiencing in May. The high and low temperature were both the coldest so far this month for many sites in the state. The featured chart looks at the frequency of a given May day being the coldest for the month. Having the 11th be the coldest day is not out of the ordinary and the chart would indicate that perhaps our coldest weather of the month is now behind us!

Voting:
Good: 11
Bad: 11
Abstain: 7

Tags:   may  


AM Rain

28 May 2013 05:38 AM
A majority of Iowa's summer time rainfall comes during the overnight hours. During the drought of 2012, this contribution was largely missing. So far, 2013 has been a different story with multiple heavy rainfall events happening during the overnight hours. The featured chart presents the hourly precipitation totals for Des Moines and the long term climatology for May. The 3-8 AM totals have far exceeded climatology. The totals shown were up until 12 AM this morning and another half inch was fallen today.

Voting:
Good: 91
Bad: 7

Tags:   may  


48 degrees

02 May 2013 03:40 AM
May Day felt more like Mother Nature yelling "mayday" as very cold air along with snow entered the state. The cold front still bisected the state by mid afternoon on Wednesday leaving the far eastern portions in the warm air. Temperatures soared well into the 80s while northwest Iowa was near freezing. The featured top chart displays the hourly temperature difference between Burlington and Sioux City since 1 March. The largest difference was 48 degrees with Burlington reporting 82 degrees while Sioux City was at 34. Based on IEM archives, this was the largest temperature difference between the sites on record for May. The largest difference for any month is 61 degrees on 14 Dec 2008.

Voting:
Good: 59
Bad: 9

Tags:   2013   front   may  


Northwestern Iowa wettest this May

31 May 2012 05:36 AM
The last day of May is at hand and while more rain is failing today, the current difference between May rainfall totals for a location in far NW Iowa is compared against far SE Iowa in today's featured chart. Based on preliminary data, Rock Rapids has seen just over four inches more precipitation than Keokuk so far this May. This would be the largest difference since the early 1970s. Typically, the largest rainfall totals are over SE Iowa in May with the smallest over NW Iowa. So this May has seen a reversal of that, but it is not uncommon.

Voting:
Good: 30
Bad: 7

Tags:   may  


Coolest day in May

30 May 2012 05:44 AM
May is going to end on a cool note with high temperatures in the 60s for most Iowans and low temperatures into the 40s! This may be the coolest high and low temperatures for the month. The featured chart presents the frequency of a day in May having the coolest high or low temperature. The earlier part of the month is certainly more frequent than the latter part and it has happened previously that the end of the month was the coolest.

Voting:
Good: 34
Bad: 6

Tags:   may  


Importance of May

29 May 2012 05:37 AM
With May now winding to a close, it appears this month will come in well below average for most of the state. May is an important month to the yearly contribution of precipitation as shown by the featured chart. The chart shows the frequency of having a month with the same direction of departure as the year long total. For example, having this May be below average precipitation along with having the year of 2012 be below average precipitation. Interestingly, May has the largest frequencies in both directions. Precipitation in May can help "set the table" for the rest of the summer, as a wet May leads to wetter soils and more precipitation chances for the summer. A dry May can have the opposite effect. Most concerning is that this chart would indicate a 75% chance of having below average precipitation for 2012.

Voting:
Good: 33
Bad: 7

Tags:   may   climate   precip  


May Precipitable Water

24 May 2012 05:55 AM
One of the reasons for our recent lack of rainfall has been the dearth of precipitable water. Precipitable water is a measure of depth of water in a column of air if all phases found were converted to liquid. The featured chart presents the combination of preciptable water analyzed by a weather forecast model and the total rainfall for that day. The upper chart presents the frequency of having rainfall on a given May day partitioned by preciptable water value. Increasing water content in the atmosphere increases our chances of rain. The lower chart presents the combination of daily precip observations against the precipitable water value. The one to one line shows that often the preciptable water value provides an upper bound to the amount of rainfall we may receive. Advection processes help to replenish atmospheric water content so we can get rainfall totals greater than the amount of water in the column of air ("in this house we obey the conservation of mass law").

Voting:
Good: 30
Bad: 6

Tags:   preciptablewater   may  


Severe Weather in May

17 May 2012 05:56 AM
May is an active month for severe weather in Iowa. The featured chart presents the number of county based warnings issued in Iowa by day of May for each year since 1986. The beginning of May this year certainly started off active with severe weather each day, but has recently been very quiet. Humidity values have been on the dry side recently, which among other factors have prevented storms from developing over the past week. Thunderstorms are an important part of our climate as they bring a majority of the yearly rainfall to the state, so we have to take the good (needed rainfall) with the bad (severe weather).

Voting:
Good: 34
Bad: 5

Tags:   may  


Quite hot for May

26 May 2010 05:09 AM
This past Sunday and Monday saw high temperatures over 90 for most of the state and lows around 70. For May, these two days were some of the warmest on record and the warmest for days prior to 25 May as shown by the featured illustration. The two days were also exceptional for having low temperatures above 70, which was only the sixth time that has happened in May dating back to 1893. All of these values are statewide areal averages computed by the IEM.

Voting:
Good: 19
Bad: 6

Tags:   may10   may  


7 days below 60!

14 May 2010 06:07 AM
The abnormally cool stretch of weather ended up lasting a full week for Ames with high temperatures not reaching 60 degrees. According to IEM data, this sets a record for consecutive days below 60 in May. The featured chart displays the monthly records for Ames and the most recent year the record was set or tied. During the winter months, a large number of years had the entire month below 60. It is interesting to see that July never has had a high temperature below 60 for Ames since 1893. Temperatures will approach 70 today!

Voting:
Good: 48
Bad: 8

Tags:   may10   highs   may  


The week after a high of 80

07 May 2010 05:34 AM
It was just on Tuesday that high temperatures soared into the 80s here in Ames. The featured chart looks at the observed frequencies of high temperatures above 80 and below 60 after a day with a high above 80. The climatological occurrence of having a sub 60 and above 80 day in May is shown as well (flat lines). With forecasted highs on Friday and Saturday in the 50s (day 3 and day 4), the chart would indicate this is rather rare. Our average highs are in the upper 60s, so we will be well below normal with some locations struggling to even reach 50 on Saturday.

Voting:
Good: 67
Bad: 14

Tags:   may