Past Features

This page lists out the IEM Daily Features for a month at a time. Features have been posted on most days since February 2002. List all feature titles.

Features for Jul 2017

Mon Jul 03, 2017
June Sigma Departures
03 Jul 2017 05:26 AM
With the calendar now saying July, it is a good time to look back on June in Iowa. The featured chart compares June growing degree day and precipitation departures for a statewide Iowa average value. These departures are expressed in terms of standard deviations (sigma) from the mean. This allows for a comparison between variables that have different units of measure, but have similar statistical distributions. The value for 2017 came in just above average for GDDs and below average for precipitation. Years that are on the fringes of the plot are labelled as well.
Voting: Good - 6 Bad - 0

Tags:   jun  
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Tue Jul 04, 2017
July Temps and Dew Points
04 Jul 2017 05:45 AM
The muggy conditions that most Iowans equate with July was present on Monday for most of the state. Dew point temperatures reached the lower 70s for about the southern 2/3rd s of the state. The featured chart looks at the combination of average dew point at a given temperature along with the resulting dew point. The relative humidity plot shows a rather smooth relationship as once temperatures start reaching the mid 70s, our relative humidities start to drop. We should be thankful for this relationship was it allows some level of suitability to our weather as temperatures warm mostly independently of dew point. The general flat portion of the relative humidity curve below the mid 70s are indicative of the common near saturated condition that supports warm over night temperatures.
Voting: Good - 5 Bad - 0

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Wed Jul 05, 2017
Northwest Moving Storms
05 Jul 2017 05:38 AM
Our current stretch of weather with daily scattered thunderstorms continued on Tuesday. These storms were a bit unique with a storm motion to the northwest. The featured chart displays a histogram of RADAR derived storm motion from the Des Moines NEXRAD. RADAR algorithms attempt to track storm cells and derive a storm motion (direction and speed). The top panel displays frequencies for period of record data archived by the IEM. The bottom panel displays this information just for storms on the 4th. So yesterday's storm motion was somewhat rare, but not as rare as a pure east to west motion.
Voting: Good - 15 Bad - 0
Thu Jul 06, 2017
Sioux City YTD Precipitation
06 Jul 2017 05:33 AM
The US Drought Monitor continues to analyze much of northwestern and southeastern Iowa in "D0" (abnormally dry) condition. The featured chart looks at year to date precipitation for Sioux City. It is kind of interesting to see how this year compares with 1976, which was the driest year on record for the site. Even more interesting is to note that just a month ago, the wettest, driest, and this year were all at about the same value! The best precipitation chances today look to be for the eastern half of the state.
Voting: Good - 15 Bad - 0

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Fri Jul 07, 2017
90 Degree Day Departures
07 Jul 2017 12:01 AM
The high temperature on Thursday reached the 90s for most of the state. We have seen our fair share of days with a high of 90+ this year. The featured map is an analysis of the number of days at or above 90 this year for the year to date period against a simple average of the same period of days for the years 1981 to 2016. Positive departures, like in Iowa, mean that we have had more 90+ degree days this year than on average. This data is based on the Oregon State PRISM gridded dataset. It is interesting to see the large negative departures over the deep south where they have seen plenty of rain this summer season.
Voting: Good - 12 Bad - 0
Mon Jul 10, 2017
Past 24 Days
10 Jul 2017 05:33 AM
The dry conditions have have developed this summer remain the main story this growing season. The entire state has not been dry though. The featured map displays NOAA MRMS estimates since 16 June. The analysis indicates the driest areas over this period being south of Ames and north of Sioux City. One need not travel very far north and east to find substantial totals over this same period. The heaviest rainfalls over Sunday night and into Monday morning were over northeastern Iowa.
Voting: Good - 18 Bad - 0

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Tue Jul 11, 2017
3 inches over 30 days
11 Jul 2017 05:30 AM
The featured chart displays IEM estimated areal coverage of Iowa that received at least 3 inches of precipitation over a 30 day trailing window of days. The present value of about 50% is an improvement over late June. Of course, this time of year having three inches over 30 days is a below average total with average monthly precip between April and September all being over three inches. The continues to be more chances of rain in the forecast, but it remains to be seen if the areas with the deficits can be filled in.
Voting: Good - 12 Bad - 0

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Wed Jul 12, 2017
Where did 11 July rains fall?
12 Jul 2017 05:33 AM
The featured chart is an attempt to access where the rain fell in Iowa on Tuesday. The blue bars represent the areal coverage of precipitation departures for the previous 31 days prior to Tuesday. The orange bars represent the areal coverage of 0.20+ inch rainfalls over the state that coincided with the given categorical departure value. So the combination allows an assessment of where yesterday's rain fell. Overall, about 25% of the state received 0.20+ inches of rain on Tuesday, but some areas with current deficits did receive some rain along with other areas that did not need it (already at large positive departures). A majority of the rain did fall over areas that needed it! This plot is a first attempt at illustrating this metric, so your feedback on usefulness is certainly welcome!
Voting: Good - 6 Bad - 2

Tags:   mrms  
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Thu Jul 13, 2017
Clayton County Flooding
13 Jul 2017 05:42 AM
It is currently an interesting dichotomy in Iowa currently with some parts of the state experiencing drought and others flooding. One such area experiencing flooding is Clayton County up in far northeastern Iowa. The featured map shows 12 hour estimated precipitation from MRMS between Tuesday evening and Wednesday morning. The RADAR-only based estimates peg amounts over eight inches and one need not travel far to the south and west to find values of zero! This is the time of year for such extreme and highly localized precipitation events to occur as storms tend not to move very fast and can train over the same locations given a feed of moist air into the thunderstorm complex.
Voting: Good - 18 Bad - 0
Fri Jul 14, 2017
Increasing D1 Drought
14 Jul 2017 05:35 AM
While yesterday's IEM Daily Feature discussed flooding rains in one part of the state, today's feature discusses the worsening drought situation for other parts of the state. The featured chart displays the weekly coverage of analyzed US Drought Monitor condition in the state since June 2016. The D1 (Moderate Drought) category was expanded over the state this week. The current near term forecast is not very optimistic for needed rains over the dry areas of the state.
Voting: Good - 12 Bad - 0

Tags:   drought  
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Mon Jul 17, 2017
Lots of Goose Eggs
17 Jul 2017 05:32 AM
Since the end of May, rainfall has been difficult to come by for Ames. The featured chart displays daily precipitation reports from the Ames Airport since May 28th. Plenty of goose eggs (zeros) appear on the chart with only one significant rain shown of 1.65 inches back on the 14th of June. There are some chances of rain in the forecast this week, but it remains to be seen how much places like Ames will see. Certainly the driest areas of southern Iowa do not look to fare well this week with the best rain chances confined to northern Iowa.
Voting: Good - 8 Bad - 0

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Tue Jul 18, 2017
Isolated Shower
18 Jul 2017 05:23 AM
A lone thunderstorm was somehow able to fire over southern Iowa late Monday afternoon and dumped much needed rainfall over a very limited area. The featured map displays NOAA MRMS precipitation estimates based on RADAR and shows a very small area just to the northwest of Chariton and southeast of Indianola picking up an inch or more. This is a critical time of year to receive precipitation for a corn crop that is currently tasseling. These types of rainfalls can go a long ways to explaining differences in final crop yield between neighboring farmers and fields. Hopefully expected rainfall on Tuesday can be a bit more widespread, but some dry areas of the state will almost certainly miss out again.
Voting: Good - 17 Bad - 1
Wed Jul 19, 2017
30, 60, and 90 Day Arridity
19 Jul 2017 05:32 AM
Some of the driest conditions in the state currently can be found over southeastern Iowa. The featured chart looks at the arridity index calculated over 30, 60, and 90 trailing day periods for this year for an areal averaged value representing southeastern Iowa climate district. This index combines temperature and precipitation departures to access water stress. Since early June, the chart shows the increasing stress for this area. There are more chances of rain in the forecast, but the best chances are over northern Iowa.
Voting: Good - 13 Bad - 0

Tags:   arridity  
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Thu Jul 20, 2017
Missing Driest Areas
20 Jul 2017 07:47 AM
Our rainfall patterns this summer have been quite interesting. Overall, the state has seen plenty of days with rain falling somewhere in the state, but these rains have been avoiding the driest areas. For example, the featured map displays the combination of rainfall estimates for 19 July and the current US Drought Monitor analysis valid on 18 July. It is remarkable to see how the heaviest totals in southwestern and northeastern Iowa avoided the dry areas of the state. More rain is in the forecast, but it would appear that the wet areas of northeastern Iowa will have the best chances again.
Voting: Good - 18 Bad - 0
Fri Jul 21, 2017
80 Degree Dew Point Days
21 Jul 2017 05:34 AM
Dew point temperatures got a bit excessive on Thursday with a number of observation sites in the state reporting 80+ degree readings. The featured map presents an analysis of long term hourly observation sites for the average number of days per year that the dew point reaches at least 80 degrees. The areas immediately near the Gulf of Mexico, Gulf of California, and Atlantic Ocean waters see the highest readings as water temperatures near 80 will help support such humid dew points. In Iowa, we get the transport of humid air from the south and the enhanced crop transpiration this time of year to help us reach 80 degrees.
Voting: Good - 13 Bad - 1

Tags:   dewpoint  
Mon Jul 24, 2017
Highest Heat Index
24 Jul 2017 05:32 AM
The brutally warm and humid conditions of last week were thankfully mostly gone from the state for the past weekend. The combination of high temperatures and dew points created for extreme heat index values. The featured map displays computed maximum heat index values for the airport weather stations in the state over the past week. These are based on available hourly observations, so actual maximum values could have been a degree or two higher. The highest value shown is 118 degrees for Fort Madison on 20 July. The forecast for this week has warm conditions, but nothing like what we experienced last week.
Voting: Good - 19 Bad - 0

Tags:   jul17   2017  
Tue Jul 25, 2017
Limited Help for Drought
25 Jul 2017 05:32 AM
The publication of the US Drought Monitor update for this week is currently in progress. It considers the precipitation that has fallen up to Tuesday morning of each week and is released on Thursday. The featured map displays the combination of the current drought monitor issued last week and the seven days of precipitation that roughly fell since its issuance. The hatched areas on the map are the drought monitor categories. In general, there was little help for the rain that did fall last week for the driest areas of the state. Some localized dry places did pick up an inch or two, but that amount of water only meets current intensive crop demands. The most significant and flooding rains fell almost completely away from the dry areas.
Voting: Good - 21 Bad - 0

Tags:   usdm  
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Wed Jul 26, 2017
2017 Corn Crop Condition
26 Jul 2017 05:36 AM
The featured chart displays weekly USDA NASS crop condition reports by state. Each tan line represents the weekly progression of the statewide coverage of corn crop reported to be in either bad or very bad condition. Three years are highlighted for this presentation, which are the years of 2012, 2016 and 2017. For this year, Iowa is shown to be in about as good of shape as any of the others highlighted here. The worst conditions are shown in Indiana, who has seen flooding rains this season.
Voting: Good - 9 Bad - 0

Tags:   nass   corn  
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Thu Jul 27, 2017
2017 Precipitation Bins
27 Jul 2017 05:51 AM
The Sioux City Airport weather station reported just over 6 tenths of an inch of rain on Wednesday, which was very much needed. The location is still running a significant deficit for the year and the featured chart attempts to illustrate if the location has missed out on the big rainfalls or little rainfalls so far this year. The long term daily precipitation record is partitioned into five bins, with each bin contributing an equal amount of rain volume for the year. The chart shows the average number of days for the year to date period with that amount of precipitation being reported. The percentages express the difference in precipitation totals for this year from this average for the bin. So the plot shows that for the highest three bins, this year has come up short both on the number of days and total amounts. For example, we should have seen about ten days with a total of at least 0.53 inches. This year, only five have happened so far.
Voting: Good - 6 Bad - 0

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Fri Jul 28, 2017
July Precip Distribution
28 Jul 2017 05:27 AM
The large disparity with July precipitation in Iowa does not look to change with the few days left in the month. The featured chart displays the distribution of July precipitation totals for the long term climate sites tracked by the IEM. The distribution this year is shown to be shifted a bit to the left of the long term climatology, assuming a normal distribution. The actual histogram for this year shows many more sites with below average precip than would be indicated by normal.
Voting: Good - 7 Bad - 0

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Mon Jul 31, 2017
July 2017 Precip Ranks
31 Jul 2017 05:38 AM
With a mostly dry day expected to end the month of July, it is likely safe to plot up climate district based precipitation ranks for this year. There is a good amount of variability over the region with top five wettest contrasted with top 20 driest over not that far of a distance. These climate district averages are unofficial totals estimated by the IEM.
Voting: Good - 9 Bad - 0

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Features for Jul 2017