The featured chart presents an analysis of averaged surface wind speed and direction over the domain of a Storm Prediction Center issued tornado watch that was centered over Iowa. The wind values are for a period near issuance. The symbols represent the number of tornadoes reported within the watch box. The plot nicely shows that winds from the southeast to southwest are the most common with a sharp cutoff at the southwest direction. Tornadoes form in environments of wind sheer where wind speeds and/or direction change with increasing height in the atmosphere. So having surface winds out of the southeast and upper level winds out of the west provide the sheared environment in Iowa.

Voting:
Good = 17
Bad = 9

Tags:   spc   tornado  

The tornado outbreak of yesterday may go down in the record books as the largest in US history. The featured chart displays, at five minute intervals, the total number of active tornado warnings and areal coverage of these warnings expressed in square kilometers. Since 3 PM on Tuesday, there has been at least one active tornado warning making for a streak of 39 straight hours (at the time of this writing). At its peak yesterday evening, the areal coverage of would have been large enough to cover roughly one third of Iowa. I'll update this chart once the streak ends and post the final duration number.

Update The streak ended at 8:45 AM CDT

Voting:
Good = 23
Bad = 7

Tags:   tornado   outbreak  

A handful of powerful supercell storms lifted northeast along the warm front Saturday evening putting down a number of tornadoes. The featured map is a summary of the local storm reports with most of those tornado reports coming from one supercell that developed north of Omaha and survived all the way to northcentral Iowa. This situation was particularly dangerous as many of the tornadoes occured after sunset. The town of Mapleton was particularly hard hit with reports this morning of over half of the town heavily damaged.

Voting:
Good = 15
Bad = 3

Tags:   tornado  

Iowa's first real taste of severe weather season arrived on Tuesday with a powerful low pressure system pushing through the state late in the afternoon. Numerous frontal boundaries were present over southern Iowa late Tuesday afternoon and helped to spin up some brief tornadoes. The featured image from Tyler Love of Creston shows the photogenic tornado on the northwest side of town. Major temperature changes are in store with a return to winter like conditions for the remainder of the week.

Voting:
Good = 41
Bad = 3

Tags:   tornado  

Around 7 PM on Saturday Night, a thunderstorm just to the northwest of Fort Dodge produced a funnel cloud and brief tornado. No damage was reported... This tornado was easily visible from miles around in about every direction and many people took some great photographs.

Voting:
Good = 37
Bad = 17

Tags:   tornado  

The official NWS rating for the Parkersburg tornado is EF5. This places the tornado in the top-most category. This rating is based on a survey of the damage compared against a series of damage indicators. This tornado is the strongest Iowa has seen in 32 years. Let us hope it will be at least another 32 years before seeing another this strong.

Voting:
Good = 32
Bad = 8

Tags:   tornado  

Tuesday was an amazing weather phenomena day. The morning started with Kelvin-Helmholtz instability waves that produced remarkable cloud formations and velocity signatures on NEXRAD. The featured image contains a trace of temperature and dew point from the roof of the Agronomy Building at ISU and the visible satellite image from 3 PM. A large area of rain formed well ahead of the cold front limiting the daytime heating, but it dramatically moistened the lower atmosphere and with the help of strong and warm southerly winds underneath the cloud shield, temperatures and dew points rose in tandem (which is rather rare)! The severe weather threat increased as skies cleared in Southern Iowa ahead of the front during the late afternoon. This bumped surface air temperatures only a few degrees, but provided instability for thunderstorms to develop. The strongly sheered environment along the sharp cold front (notice very sharp drop in the trace) provided the ingredients necessary for a few brief tornados to form, including a tornado that flipped a few cars in Des Moines! What a day!

Voting:
Good = 33
Bad = 2

Tags:   khwave   tornado   interesting  

It has already been a year since a night time tornado ripped through downtown Iowa City causing millions of dollars of damage, but thankfully, no deaths. Unfortunately, there was a death from a different Eastern Iowa tornado that evening. Here are some links to various resources on the event: KCRG-TV, Flickr, the IEM's archive of images, and an excellent page on the Iowa City Public Library website. Don't forget about Wikipedia either.

Voting:
Good = 37
Bad = 12

Tags:   tornado  

Yesterday afternoon brought some very interesting storms to Northcentral Iowa. The featured image is of a landspout near Dayton (Webster County) and the NEXRAD reflectivity during that time. These funnels form during the initial storm updraft stretches atmospheric spin in the vertical. These funnels are brief and not all of them reach the ground. Here is a collection of other funnels from Thursday.

Voting:
Good = 27
Bad = 8

Tags:   tornado  

Up until about 7 PM, Thursday would have went down in Iowa weather lore for being a record warm day. All of that heat helped to fire an explosive thunderstorm complex that brought numerous reports of large hail and unfortunately a number of destructive tornados to Eastern Iowa. More severe weather is possible today and especially again on Saturday as severe weather season 2006 continues on at a record pace.

Voting:
Good = 58
Bad = 31

Tags:   tornado  

Severe storms developed late Saturday afternoon in SW Iowa and raced to the northeast producing 9 tornados along the way. Schoolnet8's network of webcameras caught two (Madrid and Ames) of these tornados. Be sure to check out these helicopter storm survey photos courtesy of the good folks at Iowa Helicopter. The National Weather Service has an excellent summary page of the event.

Voting:
Good = 24
Bad = 4

Tags:   tornado   webcam  

Thursday was a wild day for weather on the ISU Campus. A weak tornado touched down on campus and produced a narrow path of extensive tree damage. The Agronomy Building, which houses the IEM, took a direct hit. The featured image is a shot from the webcamera sitting ontop of the Agronomy Building just before it hit. Unfortunately, the big-foot image quality may tend to discredit its veracity, but the dark cloud in the middle matches up very well with the damage path and time of the tornado. Meteorology undergrad Scott Lincoln put together an excellent page detailing the damage.

Voting:
Good = 43
Bad = 20

Tags:   webcam   tornado  

It is time again to play your favorite online game, Tornado or Not Tornado. The image was shot by someone near Farhamville last night. If you are having trouble making up your mind, here are some more photos for your evaluation.

Voting:
Good = 32
Bad = 8

Tags:   tornado  

KCCI SchoolNet's webcam in Webster City captured one of the many tornados on Friday. This tornado is actually ~15 miles to the SW of the camera! You can view a movie generated by this camera: 3 MB .avi or 400 KB .avi. Internet service for the Webster City site is provided by WMTEL.net.

Tags:   webcam   tornado