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.
Mon Aug 03, 2020
Three Inch Departures
03 Aug 2020 04:54 AM
The drought situation for Iowa continues to be of great concern this growing season. The featured map displays precipitation departures over the past month with a majority of the state below average and some portions even more than three inches below average. Up until recently, west central Iowa was the epicenter for the driest conditions, but now central into eastern Iowa has joined in. The forecast continues to not look good for needed rainfalls arriving anytime soon. The clock is ticking for rains to come to help rapidly maturing crops. The only good news is that temperatures will be cooler until next weekend, which should help reduce some stress for plants.
Voting: Good - 9 Bad - 0
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03 Aug 2020 04:54 AM
The drought situation for Iowa continues to be of great concern this growing season. The featured map displays precipitation departures over the past month with a majority of the state below average and some portions even more than three inches below average. Up until recently, west central Iowa was the epicenter for the driest conditions, but now central into eastern Iowa has joined in. The forecast continues to not look good for needed rainfalls arriving anytime soon. The clock is ticking for rains to come to help rapidly maturing crops. The only good news is that temperatures will be cooler until next weekend, which should help reduce some stress for plants.
Voting: Good - 9 Bad - 0
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Tue Aug 04, 2020
July Lows Distribution
04 Aug 2020 04:07 AM
The featured chart presents the distribution of average daily low temperatures during July from Iowa's long term reporting climate sites. The distribution is presented in terms of frequency at a given temperature with the blue bars showing 2020 reports, the blue line the simple average, and the blue dashed line showing a theoretical normal distribution based on the mean and standard deviation. These values are compared with long term climatology shown by the green lines. It is very interesting to compare the two. A majority of the 2020 values are above the climatological mean, but nothing much above the high end of the climatological tail near 70 degrees. Rewording, while low temperatures were warmer than average during July, it was not extreme.
Voting: Good - 10 Bad - 2
Tags: jul20
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04 Aug 2020 04:07 AM
The featured chart presents the distribution of average daily low temperatures during July from Iowa's long term reporting climate sites. The distribution is presented in terms of frequency at a given temperature with the blue bars showing 2020 reports, the blue line the simple average, and the blue dashed line showing a theoretical normal distribution based on the mean and standard deviation. These values are compared with long term climatology shown by the green lines. It is very interesting to compare the two. A majority of the 2020 values are above the climatological mean, but nothing much above the high end of the climatological tail near 70 degrees. Rewording, while low temperatures were warmer than average during July, it was not extreme.
Voting: Good - 10 Bad - 2
Tags: jul20
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Wed Aug 05, 2020
Cool for early August
05 Aug 2020 04:43 AM
Temperatures so far this August have been rather cool and certainly brought a taste of the fall season to Iowa. The featured chart displays the daily high temperatures on 4 August for Des Moines. One has to go back to the early 1990s to find a cooler high temperature for this date. The chart highlights the large range in temperatures that have happened on this date with the max value of 110 certainly sticking out! The forecast has a warming trend with a return to weather we'd expect during the dog days of summer in early August.
Voting: Good - 8 Bad - 0
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05 Aug 2020 04:43 AM
Temperatures so far this August have been rather cool and certainly brought a taste of the fall season to Iowa. The featured chart displays the daily high temperatures on 4 August for Des Moines. One has to go back to the early 1990s to find a cooler high temperature for this date. The chart highlights the large range in temperatures that have happened on this date with the max value of 110 certainly sticking out! The forecast has a warming trend with a return to weather we'd expect during the dog days of summer in early August.
Voting: Good - 8 Bad - 0
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Thu Aug 06, 2020
Awaiting August Thunder
06 Aug 2020 04:46 AM
The featured chart presents the monthly climatology and 2020 total number for distinct days with METAR observations from the Des Moines Airport reporting thunder as a present weather condition. Our total for August 2020 remains at zero days and follows the below average total for July. Dry weather has dominated this period, so it makes sense to have fewer thunderstorms as well. A few chances of thunderstorms and associated rainfall is in the forecast, so there is at least some optimism rain will fall over Iowa during the coming days.
Voting: Good - 10 Bad - 1
Tags: thunder
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06 Aug 2020 04:46 AM
The featured chart presents the monthly climatology and 2020 total number for distinct days with METAR observations from the Des Moines Airport reporting thunder as a present weather condition. Our total for August 2020 remains at zero days and follows the below average total for July. Dry weather has dominated this period, so it makes sense to have fewer thunderstorms as well. A few chances of thunderstorms and associated rainfall is in the forecast, so there is at least some optimism rain will fall over Iowa during the coming days.
Voting: Good - 10 Bad - 1
Tags: thunder
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Fri Aug 07, 2020
D3 Returns
07 Aug 2020 04:34 AM
The weekly US Drought Monitor update was released on Thursday and further degradation was shown with the "D3 Extreme" drought category introduced over west central Iowa. This is the first D3 category over Iowa since 2018. The featured chart shows the percentage of the state covered by each of the drought categories since the last D3 in 2018. The good news is that chances of rain continue to be in the forecast, but the most significant rains are forecast to fall just outside of the state.
Voting: Good - 17 Bad - 0
Tags: usdm
07 Aug 2020 04:34 AM
The weekly US Drought Monitor update was released on Thursday and further degradation was shown with the "D3 Extreme" drought category introduced over west central Iowa. This is the first D3 category over Iowa since 2018. The featured chart shows the percentage of the state covered by each of the drought categories since the last D3 in 2018. The good news is that chances of rain continue to be in the forecast, but the most significant rains are forecast to fall just outside of the state.
Voting: Good - 17 Bad - 0
Tags: usdm
Mon Aug 10, 2020
Peak RH
10 Aug 2020 04:31 AM
The featured chart presents the daily climatology and 2020 observed values of relative humidity for Des Moines. The teal bars represent the daily range between the lowest and highest relative humidity value. The red line is a smoothed frequency of having the daily maximum relative humidity above 95%. According to this plot, mid August represents about the peak in such values. The reason being that our humid summer days and warm soil temperatures are now competing with ever lengthening night time periods which promote cooling of the air. The combination leads to saturated air (near 100% relative humidity).
Voting: Good - 18 Bad - 1
Tags: rh
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10 Aug 2020 04:31 AM
The featured chart presents the daily climatology and 2020 observed values of relative humidity for Des Moines. The teal bars represent the daily range between the lowest and highest relative humidity value. The red line is a smoothed frequency of having the daily maximum relative humidity above 95%. According to this plot, mid August represents about the peak in such values. The reason being that our humid summer days and warm soil temperatures are now competing with ever lengthening night time periods which promote cooling of the air. The combination leads to saturated air (near 100% relative humidity).
Voting: Good - 18 Bad - 1
Tags: rh
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Thu Aug 13, 2020
The Derecho of 2020
13 Aug 2020 12:58 PM
One of the most significant weather events in Iowa's history happened on Monday, 10 August 2020. A powerful complex of storms bulldozed the state and impacted the major urban centers of Des Moines, Cedar Rapids, Iowa City, and Davenport. The Aqua MODIS satellite data from Tuesday featured in today's map has been making the rounds on the Internet. The map clearly shows the extensive crop damage that happened from west of Des Moines to Davenport. We continue to await a more cloud free day to further see the extent of the crop damage from satellites. Overlain on the map is Local Storm Reports of wind gusts from the National Weather Service.
Voting: Good - 0 Bad - 0
Tags: derecho 2020derecho
13 Aug 2020 12:58 PM
One of the most significant weather events in Iowa's history happened on Monday, 10 August 2020. A powerful complex of storms bulldozed the state and impacted the major urban centers of Des Moines, Cedar Rapids, Iowa City, and Davenport. The Aqua MODIS satellite data from Tuesday featured in today's map has been making the rounds on the Internet. The map clearly shows the extensive crop damage that happened from west of Des Moines to Davenport. We continue to await a more cloud free day to further see the extent of the crop damage from satellites. Overlain on the map is Local Storm Reports of wind gusts from the National Weather Service.
Voting: Good - 0 Bad - 0
Tags: derecho 2020derecho
Fri Aug 14, 2020
75 MPH Gust
14 Aug 2020 06:00 AM
The derecho from Monday should provide fodder for the IEM Daily Feature for the foreseeable future! Today's plot presents one minute interval wind observations from the Des Moines Airport weather station. The chart shows minute by minute readings of wind speed and direction (two minute average of five second samples) and wind gust (peak 5 second sample reading). The quick rise in wind speed is readily seen with the peak value of 50 MPH sustained with gusts to 75 MPH shown. Wind gusts over 50 MPH were observed for over a twenty minute period!
Voting: Good - 21 Bad - 1
Tags: derecho 2020derecho
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14 Aug 2020 06:00 AM
The derecho from Monday should provide fodder for the IEM Daily Feature for the foreseeable future! Today's plot presents one minute interval wind observations from the Des Moines Airport weather station. The chart shows minute by minute readings of wind speed and direction (two minute average of five second samples) and wind gust (peak 5 second sample reading). The quick rise in wind speed is readily seen with the peak value of 50 MPH sustained with gusts to 75 MPH shown. Wind gusts over 50 MPH were observed for over a twenty minute period!
Voting: Good - 21 Bad - 1
Tags: derecho 2020derecho
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Sat Aug 15, 2020
Derecho Power Hit
15 Aug 2020 04:25 PM
The featured graphic is a comparison between the Suomi NPP / VIIRS satellite imagery between July 29th and August 11th. The particular band shown from the satellite is good at showing city lights during clear sky conditions at night time. The damage swath from the August 10th derecho is easily seen with the bullseye hit to Cedar Rapids well shown. Power restoration work is ongoing with full restoration expected to take weeks. See this NASA Website for a better view.
Voting: Good - 13 Bad - 0
Tags: derecho 2020derecho
15 Aug 2020 04:25 PM
The featured graphic is a comparison between the Suomi NPP / VIIRS satellite imagery between July 29th and August 11th. The particular band shown from the satellite is good at showing city lights during clear sky conditions at night time. The damage swath from the August 10th derecho is easily seen with the bullseye hit to Cedar Rapids well shown. Power restoration work is ongoing with full restoration expected to take weeks. See this NASA Website for a better view.
Voting: Good - 13 Bad - 0
Tags: derecho 2020derecho
Mon Aug 17, 2020
90 MPH SVR Warning
17 Aug 2020 05:46 AM
When the National Weather Service issues Severe Thunderstorm (SVR) Warnings, they include tags that denote the forecast max hail size and wind gust. These tags are useful to understand the threat posed by a storm and some communities trigger their outdoor sirens for SVR's with wind tags at or above 70 MPH. The featured chart presents the warning count frequency of the combination of hail and wind gust tags for SVR warnings issued by NWS Des Moines. Each warning contains both a wind gust and hail tag, so they can be compared in this manner and only the tag values at issuance are included in this chart. For the Derecho last Monday (wow, has it been a week already?!?!), NWS Des Moines issued one such warning with a 90 MPH wind gust tag. The first such usage since these tags came into operations.
Voting: Good - 16 Bad - 1
Tags: 2020derecho
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17 Aug 2020 05:46 AM
When the National Weather Service issues Severe Thunderstorm (SVR) Warnings, they include tags that denote the forecast max hail size and wind gust. These tags are useful to understand the threat posed by a storm and some communities trigger their outdoor sirens for SVR's with wind tags at or above 70 MPH. The featured chart presents the warning count frequency of the combination of hail and wind gust tags for SVR warnings issued by NWS Des Moines. Each warning contains both a wind gust and hail tag, so they can be compared in this manner and only the tag values at issuance are included in this chart. For the Derecho last Monday (wow, has it been a week already?!?!), NWS Des Moines issued one such warning with a 90 MPH wind gust tag. The first such usage since these tags came into operations.
Voting: Good - 16 Bad - 1
Tags: 2020derecho
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Tue Aug 18, 2020
2020 Derecho Wind Gust Estimate
18 Aug 2020 06:00 AM
The featured map was put together by the National Weather Service and contains a smoothed estimate of wind gusts from the 10 August derecho. This estimate is based on reported damage, observed gusts, RADAR information, and hand analysis. Two swaths of 100+ MPH wind gusts are shown. It is difficult to quantitatively compare this most recent derecho with those of the past to rank which one was the strongest, but for those that continue to feel the impacts a week later, such a ranking does not matter.
Voting: Good - 12 Bad - 0
Tags: 2020derecho
18 Aug 2020 06:00 AM
The featured map was put together by the National Weather Service and contains a smoothed estimate of wind gusts from the 10 August derecho. This estimate is based on reported damage, observed gusts, RADAR information, and hand analysis. Two swaths of 100+ MPH wind gusts are shown. It is difficult to quantitatively compare this most recent derecho with those of the past to rank which one was the strongest, but for those that continue to feel the impacts a week later, such a ranking does not matter.
Voting: Good - 12 Bad - 0
Tags: 2020derecho
Wed Aug 19, 2020
Derecho Profile
19 Aug 2020 05:37 AM
The featured chart is a preliminary plot of height profile horizontal wind speed from the ISU "Talltower" facility in Story County (north of Ames). This tower is outfitted with many sensors at various heights and records wind speeds at one second refresh intervals. The chart uses this one second data along with six sensors at various heights to construct a two dimensional analysis of horizontal wind speed during the passage of the most gusty portion of the derecho at that location. Please note that sampling winds at this time resolution more represents gusts than sustained winds. You can see lots of crazy things happen including an initial gust front that rocketed near surface winds to near 90 MPH (11:23 - 11:24 AM) to only subside for a brief moment before the most intense winds arrived. This plot indicates 90+ MPH gusts got very close to the surface with 120+ MPH gusts briefly recorded some 375 feet above ground level.
Voting: Good - 29 Bad - 0
Tags: 2020derecho talltowers
19 Aug 2020 05:37 AM
The featured chart is a preliminary plot of height profile horizontal wind speed from the ISU "Talltower" facility in Story County (north of Ames). This tower is outfitted with many sensors at various heights and records wind speeds at one second refresh intervals. The chart uses this one second data along with six sensors at various heights to construct a two dimensional analysis of horizontal wind speed during the passage of the most gusty portion of the derecho at that location. Please note that sampling winds at this time resolution more represents gusts than sustained winds. You can see lots of crazy things happen including an initial gust front that rocketed near surface winds to near 90 MPH (11:23 - 11:24 AM) to only subside for a brief moment before the most intense winds arrived. This plot indicates 90+ MPH gusts got very close to the surface with 120+ MPH gusts briefly recorded some 375 feet above ground level.
Voting: Good - 29 Bad - 0
Tags: 2020derecho talltowers
Thu Aug 20, 2020
New Iowa Wind Gust Record?
20 Aug 2020 05:36 AM
It has been ten days since the derecho of 10 August 2020 and the cleanup, damage assessment, and power restoration continues. Some new reports from the NWS have come out this week that indicate a new non-tornado wind gust record for the state was set at Atkins,IA (in Benton County) with a gust of 126 MPH reported from a personal weather station. Even higher wind gusts have been estimated based on damage. The featured table presents some of the highest gust reports / estimates from the event. The previous record is believed to be the "Corn Belt Derecho" of 1998 with a report of 123 MPH at Washington IA.
Voting: Good - 14 Bad - 1
Tags: 2020derecho
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20 Aug 2020 05:36 AM
It has been ten days since the derecho of 10 August 2020 and the cleanup, damage assessment, and power restoration continues. Some new reports from the NWS have come out this week that indicate a new non-tornado wind gust record for the state was set at Atkins,IA (in Benton County) with a gust of 126 MPH reported from a personal weather station. Even higher wind gusts have been estimated based on damage. The featured table presents some of the highest gust reports / estimates from the event. The previous record is believed to be the "Corn Belt Derecho" of 1998 with a report of 123 MPH at Washington IA.
Voting: Good - 14 Bad - 1
Tags: 2020derecho
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Fri Aug 21, 2020
Flood Warning Counts
21 Aug 2020 04:55 AM
While the derecho has, deservedly so, gotten a lot of attention these past two weeks, another "d" word is having a tremendous impact in the state. That being the ongoing drought. The updated US Drought Monitor depiction for Iowa this week continued the deteriorating condition for almost all parts of the state. One metric that indicates the lack of significant rainfall this year is to total up the number of Flood Warnings issued by NWS Des Moines as shown by the featured chart. This year's total is only slightly higher than three previous years plotted and the last major drought year of 2012 certainly sticks out. The forecast is not optimistic for meaningful rainfall with a return of very hot temperatures next week.
Voting: Good - 12 Bad - 2
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21 Aug 2020 04:55 AM
While the derecho has, deservedly so, gotten a lot of attention these past two weeks, another "d" word is having a tremendous impact in the state. That being the ongoing drought. The updated US Drought Monitor depiction for Iowa this week continued the deteriorating condition for almost all parts of the state. One metric that indicates the lack of significant rainfall this year is to total up the number of Flood Warnings issued by NWS Des Moines as shown by the featured chart. This year's total is only slightly higher than three previous years plotted and the last major drought year of 2012 certainly sticks out. The forecast is not optimistic for meaningful rainfall with a return of very hot temperatures next week.
Voting: Good - 12 Bad - 2
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Sun Aug 23, 2020
Derecho Before and After
23 Aug 2020 01:23 PM
Imagery from the KCRG-TV webcam in Cedar Rapids on the Mount Mercy campus is shown. The top picture is from August 8th and the bottom picture is from today. The difference between the two images is remarkable. The derecho from August 10th is to blame with some estimates placing over 50% of the trees in Cedar Rapids as damaged or destroyed. The downed trees devastated the power service in the area with a thousand or so customers still without power almost two weeks later.
Voting: Good - 22 Bad - 0
Tags: 2020derecho webcam
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23 Aug 2020 01:23 PM
Imagery from the KCRG-TV webcam in Cedar Rapids on the Mount Mercy campus is shown. The top picture is from August 8th and the bottom picture is from today. The difference between the two images is remarkable. The derecho from August 10th is to blame with some estimates placing over 50% of the trees in Cedar Rapids as damaged or destroyed. The downed trees devastated the power service in the area with a thousand or so customers still without power almost two weeks later.
Voting: Good - 22 Bad - 0
Tags: 2020derecho webcam
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Tue Aug 25, 2020
Warmest Five Days
25 Aug 2020 05:35 AM
It seems likely that places like Des Moines are currently experiencing their warmest five day stretch of average daily high temperature so far this year. The featured chart presents the warmest such period each year along with the frequency of an individual day of the year participating in warmest period. For the top panel, the bars are colored by the average high temperature for that period of days. The middle of July has the highest frequencies shown and that is also when the daily average high temperature peaks for the year, which would help boost the odds for a given year. Having such a stretch happen during the end of August is not unusual though with frequencies really dropping off by the second week of September.
Voting: Good - 14 Bad - 1
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25 Aug 2020 05:35 AM
It seems likely that places like Des Moines are currently experiencing their warmest five day stretch of average daily high temperature so far this year. The featured chart presents the warmest such period each year along with the frequency of an individual day of the year participating in warmest period. For the top panel, the bars are colored by the average high temperature for that period of days. The middle of July has the highest frequencies shown and that is also when the daily average high temperature peaks for the year, which would help boost the odds for a given year. Having such a stretch happen during the end of August is not unusual though with frequencies really dropping off by the second week of September.
Voting: Good - 14 Bad - 1
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Wed Aug 26, 2020
2020 Drought and Derecho
26 Aug 2020 05:01 AM
The USDA NASS weekly update released on Monday showed a deteriorating corn crop condition for Iowa with about 25% of the state's crop now rated either "poor" or "very poor". The featured chart presents the weekly values since 1986 for six states in the Midwestern US. Each year since 1986 is plotted with the big drought years of 1988 and 2012 highlighted for each state. The recent uptick in bad crop condition is thanks to the ongoing drought and damage from the August 10th Derecho. It is getting too late in the season for additional rain to help the corn crop, but it could perhaps help the soybean crop some. There is some hope for rain next week, but more hot daytime weather is in store until then.
Voting: Good - 13 Bad - 0
Tags: nass corn
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26 Aug 2020 05:01 AM
The USDA NASS weekly update released on Monday showed a deteriorating corn crop condition for Iowa with about 25% of the state's crop now rated either "poor" or "very poor". The featured chart presents the weekly values since 1986 for six states in the Midwestern US. Each year since 1986 is plotted with the big drought years of 1988 and 2012 highlighted for each state. The recent uptick in bad crop condition is thanks to the ongoing drought and damage from the August 10th Derecho. It is getting too late in the season for additional rain to help the corn crop, but it could perhaps help the soybean crop some. There is some hope for rain next week, but more hot daytime weather is in store until then.
Voting: Good - 13 Bad - 0
Tags: nass corn
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Thu Aug 27, 2020
Hurricane Laura
27 Aug 2020 02:32 AM
As if 2020 could not get any worse, Hurricane Laura came onshore around 1 AM this morning near Cameron, LA as a strong category 4 storm. This hurricane will rank as one of the most intense ever to make landfall over Louisiana. The Lake Charles, LA ASOS has reported a peak wind gust of 132 MPH, which is remarkable for an automated sensor to record. Sometimes these hurricanes can help bring rainfall to well inland places like Iowa, but this system will stay well to our south and eject quickly off to the east.
Voting: Good - 17 Bad - 0
Tags: hurricane
27 Aug 2020 02:32 AM
As if 2020 could not get any worse, Hurricane Laura came onshore around 1 AM this morning near Cameron, LA as a strong category 4 storm. This hurricane will rank as one of the most intense ever to make landfall over Louisiana. The Lake Charles, LA ASOS has reported a peak wind gust of 132 MPH, which is remarkable for an automated sensor to record. Sometimes these hurricanes can help bring rainfall to well inland places like Iowa, but this system will stay well to our south and eject quickly off to the east.
Voting: Good - 17 Bad - 0
Tags: hurricane
Fri Aug 28, 2020
August Temp Percentiles
28 Aug 2020 05:41 AM
The featured chart is from a newly added IEM "Autplot" showing temperature percentiles during August for Ames based on the hourly airport data. The top panel shows the percentile a given temperature is for a given hour of the day. The percentiles are computed over each hour, since a 80 degree temperature at 6 AM is much more extreme than a 80 degree temperature at 6 PM. The bottom panel shows this year's hourly temperature percentiles based on the period of record climatologies. The plot nicely shows how extreme our recent stretch of weather has gotten with about four to five days now with values consistently above the 80th percentile. Chances of rain and cooler weather is in the forecast as we creep closer to September.
Voting: Good - 13 Bad - 1
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28 Aug 2020 05:41 AM
The featured chart is from a newly added IEM "Autplot" showing temperature percentiles during August for Ames based on the hourly airport data. The top panel shows the percentile a given temperature is for a given hour of the day. The percentiles are computed over each hour, since a 80 degree temperature at 6 AM is much more extreme than a 80 degree temperature at 6 PM. The bottom panel shows this year's hourly temperature percentiles based on the period of record climatologies. The plot nicely shows how extreme our recent stretch of weather has gotten with about four to five days now with values consistently above the 80th percentile. Chances of rain and cooler weather is in the forecast as we creep closer to September.
Voting: Good - 13 Bad - 1
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Mon Aug 31, 2020
August Percent of Average
31 Aug 2020 05:51 AM
Precipitation has been difficult to come by this August as shown by the featured map of percent of average precipitation based on NOAA MRMS data. Only a few small portions of the state are indicated above average. Southern and particularly southeastern Iowa show very low values with some areas receiving little to no rain this month. A front with rain is working its way through the state today, but forecast totals are generally meager.
Voting: Good - 16 Bad - 0
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31 Aug 2020 05:51 AM
Precipitation has been difficult to come by this August as shown by the featured map of percent of average precipitation based on NOAA MRMS data. Only a few small portions of the state are indicated above average. Southern and particularly southeastern Iowa show very low values with some areas receiving little to no rain this month. A front with rain is working its way through the state today, but forecast totals are generally meager.
Voting: Good - 16 Bad - 0
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