The featured chart looks back at the recent blizzard experience for the state and compares IEM estimates of State Patrol road travel advisories and closures with statewide estimates of mean wind speed and NEXRAD reflectivity coverage. The chart shows that the peak in snowfall coverage came before the maximum wind intensities. You can also see a very clear relationship between the improvement of road condition with the decrease in wind speed on Wednesday evening (Dec 9th).

Voting:
Good = 53
Bad = 14

Tags:   blizzard   road   nexrad  

A bit of late summer sunshine and some cool air overhead are often enough to fire off a few scattered showers and thunderstorms. The featured plot is a timeseries from Thursday of mean surface air temperature for Iowa along with the portion of the state covered by showers. The plot shows how the coverage of storms peaked late afternoon and rapidly diminished as the temperature cooled off as well (reducing instability). The same situation looks to repeat on Friday with near record minimum high temperatures expected!

Voting:
Good = 26
Bad = 16

Tags:   nexrad  

A few weeks ago, the result of a significant hail storm in Northeast Iowa was featured by showing the impact on vegetation. Another major hail storm left a similar scar over Central Iowa on Sunday and its effect can be seen as well. The featured image transitions from the Terra MODIS imagery to NEXRAD maximum reflectivity composite. Like with the previous feature, you can see the correlation between the highest reflectivites and the damage on the ground.

Voting:
Good = 20
Bad = 5

Tags:   satellite   nexrad   hail  

Last Friday, an extremely strong thunderstorm complex dropped a bunch of large hail over NE Iowa and SW Wisconsin. The NWS has an excellent summary of this event here and here. The featured image is a combination of Terra MODIS satellite for yesterday and maximum NEXRAD reflectivity for the event. The area shown initially in gray is unfortunately massive crop damage as the green leaves were shredded by the large hail and the area no longer appears to be lush green from space. You can see the streaks in the damage as the storms moved off to the southeast.

Voting:
Good = 39
Bad = 3

Tags:   hail   nexrad   satellite  

The featured image is a time composite of maximum NEXRAD reflectivity for Thursday showing what is commonly referred to as a "ring of fire". This is a result of a strong high pressure / ridge that suppresses thunderstorm development and shunts other storms to an arc surrounding it. This pattern pumps moist air from the gulf up into Iowa.

Voting:
Good = 48
Bad = 12

Tags:   nexrad  

The featured graph is a timeseries of the areal coverage of NEXRAD base reflectivity returns based on IEM generated composites. The values represent the percentage of the state covered by precipitation over time. Yesterday afternoon saw afternoon showers pop up due to daytime heating. This plot nicely shows how the peak coverage of storms occured around the time of peak heating from the sun (when the sun is the "highest" in the sky. Coverage amounts then decrease until sunset. More showers are expected today.

Voting:
Good = 41
Bad = 25

Tags:   nexrad  

The featured image presents the past 15 years of 6 AM NEXRAD composite on the first of May. Outside of a few light showers shown currently this morning, most of the years looked dry at this time. This image is a preview of a dataset the IEM is close to finalizing, close to one kilometer resolution NEXRAD composites at a 5 minute interval back to 1995! This dataset will at least provide lots of material for future features! :)

Voting:
Good = 34
Bad = 14

Tags:   nexrad  

A large storm system to our south on Monday brought rain and snow showers to Iowa. A considerable amount of dry air had to be saturated in order for the rain and snow to reach the ground. The featured graph is of 5 minute NEXRAD base reflectivity and temperature timeseries for Ames. The initial difference between the temperature and dew point begins to narrow once the shower passes overhead. The dew point increases as the air saturates and the temperature decreases as evaporation occurs.

Voting:
Good = 21
Bad = 6

Tags:   nexrad  

The featured map is a time summary of NEXRAD reflectivity for a period of 6 PM Tuesday evening till 7 AM this Wednesday morning. The plot is the total amount of time during that period that a 30+ dbZ radar reflectivity was observed in the base composite generated by the IEM. The speckles in the plot indicate areas of persistent ground clutter (where the radar sees objects on the ground instead of rain/snow). The darker reds coincide nicely with an area that picked up 3-7 inches of snowfall over night.

Voting:
Good = 24
Bad = 4

Tags:   nexrad  

The featured map is of max composite RADAR reflectivity for a 24 hour period ending 7 PM on Monday night. It is interesting to see how much of the country is currently experiencing stormy weather. Those of you that follow the Storm Prediction Center outlooks, you may have noticed the abnormally large slight risk areas recently.

Voting:
Good = 24
Bad = 10

Tags:   nexrad  

The storm system that brought freezing rain, sleet, and snow to Iowa has finally shifted off to the east this morning. A large area of the midwest from Oklahoma to Michigan saw significant ice accumulations. The featured map overlays freezing rain and ice reports on top of a max reflectivity composite from Monday. It is interesting to know how well these reports line up with the northside (the colder surface side) of the stronger NEXRAD reflectivities. Areas in green probably saw larger amounts of sleet or snow. You can find archives of these products on the iem, including the max reflectivity composite and GIS shapefiles of storm reports.

Voting:
Good = 14
Bad = 4

Tags:   ice   nexrad  

Cold air aloft and strong June sunshine helped to generate daytime showers and thunderstorms this weekend. Since the storms were driven by surface heating and in the presense of some vertical wind sheer, some of them produced brief funnel clouds as updrafts are stretched. Our weather maker is finally moving away today, but there are a number of distrubances forecasted to keep our weather unsettled this week.

Voting:
Good = 18
Bad = 12

Tags:   nexrad  

During clear nights like last night, the ground and air near the surface will cool off creating a temperature inversion. When the inversion is strong, it will play havoc with EM waves from the NWS 88d RADAR. The beam will be refracted back toward the ground and start bouncing off objects like semi trucks. The featured image shows the result of this process with higher reflectivity values aligning with the interstate and highways. If the traffic motion is radial from the radar, you will also be able to see the traffic speeds in the doppler velocity data!

Voting:
Good = 53
Bad = 3

Tags:   inversion   nexrad  

After complaints of March being boring, Mother Nature is working overtime this week to make things interesting. Sunday afternoon was very windy with record high temperatures and then a round of thunderstorms rolled through bringing lightning, small hail, and gusty winds. The highlighted animation shows the smoke plune from a large grass fire in Pottawattamie County. The strong winds and deep mixed surface layer quickly moved this smoke upwards to a reported 15,000 feet. The weather this week looks to be a bumpy ride, so hold on tight!

Voting:
Good = 15
Bad = 6

Tags:   smoke   nexrad  

This is always a bad time of year for driving near dawn and dusk. The sun rises directly east and sets directly west, which lines up nicely with many of our east-west roads. Des Moines RADAR indicated the sun rose directly east by the eastward pointing solar spike. About a year ago, I made this movie of the movement of the solar spike during sunset for the timeperiod of a year.

Tags:   nexrad