Iowa has gone from drought conditions to flooding with the wettest spring on record. Mason City has already received more precipitation this year (21.42 inches) than all of last year (20.42 inches)! The featured chart presents the date of the year when the total precip exceeded the total from the previous year. This condition does not happen every year, so those years have no value plotted. This year beats any other year by 30+ days!

The featured map presents an analysis of National Weather Service Local Storm Reports (LSRs) of one inch plus diameter hail since 2003. The analysis is a kernel density estimate using a Gaussian kernel and attempts to show the spatial distribution of hail reports. Hail is reported and collected by humans, so it is natural to see urban centers in the state show local maxima for reports. The general pattern is for fewer reports as one travels from southwest to northeastern Iowa. The geography of the Midwest drives the meteorology which favors more instability over the plains. This instability feeds thunderstorm development in the late afternoon hours that tends to produce hail. These thunderstorms then truck it east, congeal and loose their ability to produce hail.

This featured chart presents the number of days this year, last year, and on average that the daily high temperature was within the given temperature range. This year has seen one more day in the 50s than last year, but that is because there were so many more days last year warmer than that level. The 80 to 90 degree level really tells the story as this year has seen 21 fewer days in the 80s than last year and is about half of long term average. The forecast looks to continue the cool weather and perhaps we'll be back in the 80s next week.

Temperatures struggled to reach 70 degrees again yesterday in Iowa. June has gotten off to a cold start with the highest temperature reported by Des Moines so far of only 72 degrees. The featured chart presents the range of daily high temperatures for Des Moines for the first five days of June. Only 1903 and 1927 got off to a colder start of only 71 degrees. Interestingly, this year is tied with 1993! Of course, that was the great flood year in the Midwest. The forecast does hold hope that we may hit 80 degrees next week.

Besides the commonly displayed reflectivity and velocity presentations of RADAR, the NWS NEXRAD system is also running algorithms on this data attempting to identify and track storms. This information is disseminated as a product called Storm Attributes Table and comes with every volume scan. The IEM archives this product and the featured chart presents a summary of this information from the Des Moines NEXRAD. The histogram presentation shows the most common combinations of storm speed + motion and motion + day of the year. The vast majority of storms have a motion from the southwest moving to the northeast at a speed around 20-40 mph. The bottom chart shows the annual cycle of storm motion in Iowa. Storms transition from coming mostly from the WSW to WNW by late July and then back to mostly WSW. The physical reason is due to the synoptic scale flow patterns that change with the seasons.

The cool start to June has not helped to recover the growing degree day deficit that has built up so far this growing season. The featured chart presents the 1 May to 9 Jun GDD departure and then the change in this value to finish the growing season on 1 Oct. There have been a few years with a slower start to GDD accumulation and still finish the season above average. The forecast for this week at least has our temperatures in the 80s instead of struggling to reach 70 that we have experienced so far this June.

Getting the crops planted this year has been a major struggle after a snow event to start May, cool temperature, and frequent rain events since. The featured map is an analysis of the maximum time period in between hours with at least 0.05 inch of precipitation. Restating, the longest we have gone since 1 May in between rain events. The region with the most difficult time planting this season clearly shows up from northcentral Iowa up through central Wisconsin. Areas around La Crosse are shown in the 5-6 days range. Most of the corn is finally planted, but soybeans are still way behind. The near term forecast has chances of heavy rainfall for these same areas.

Portions of southcentral Nebraska experienced an intense heat burst event during the early morning hours on Tuesday. The featured chart presents one minute interval observations from the Grand Island, Nebraska ASOS. Heat bursts are caused by decaying thunderstorms driving very warm and dry air to the ground. The classic signature is a rapid rise in temperature along with a rapid drop in dew point. The chart appears to show four heat burst events with the two after 5 AM being extremely intense as the temperature goes from the 70s to 100 degrees in a few minutes. These events tend to also bring gusty winds with some gusts over 50 mph reported in the area.

A number of tornadoes were observed in Iowa yesterday and the featured image is the result of one in Belmond, Iowa. That tower with weather instruments on it should be on the top of the school in town, but the tornado thought it looked better laying sideways on the ground. Fortunately, there were no injuries in town reported with this tornado and unfortunately, the sensors did not record any interesting data as the tornado passed by. More severe weather arrives tomorrow and for the weekend.

Farmers struggled to get the corn planted this growing season due to cold temperatures and wet conditions. Since most plant corn before planting soybean, it is obvious that the planting progress for soybean is well behind average for most states. The featured map displays the USDA reported soybean planting progress as of 9 June compared with the average value for the second week of June. Iowa and Wisconsin are the furthest behind average. These values do not tell the entire story as it is hard to account for all of the acres that were drowned out and will need to be replanted. Also there will be some fields abandoned for the year. Unfortunately, more rain will fall today and this weekend.

The featured chart displays estimated areal coverage of at least 0.05 inches of daily precipitation for Iowa since 1 April. The past 31 days have only seen four completely dry days in the state as Sunday was. The forecast for this week calls for mostly dry conditions. It is summertime though, so you can never completely rule out late afternoon to evening showers.

Skies were mostly clear on Monday allowing mid June sunshine to nicely warm us into the 80s and even 90s. Humidity levels were very comfortable with afternoon dew points in the 50s. Des Moines reported a 90 degree temperature along with a dew point in the lower 50s. The featured chart presents the frequency of a given afternoon temperature having a sub 55 degree dew point in the top chart and the daily frequency of such dew points overall. The 90 degree temperatures comes with about 10% probably, so our weather yesterday was certainly not the norm. The humidity is scheduled to return later in the week with heat indices near 100 degrees.

The Heat Index has not been a prominent topic so far this summer as temperatures have been cool and the warm days have mostly seen limited humidity levels. The featured chart attempts to provide a climatology for heat index for Des Moines. The contours on the plot are the temperature difference the heat index is from the air temperature. For example, at 90 degrees and 50% relative humidity the heat index adds two degrees to the temperature. The color pixel values are the relative frequency of the given relative humidity at the given temperature, meaning that each column has a sum of 100%. The point of the plot is to show the most common combinations of temperature and relative humidity along with the heat index that produces. Thankfully, as the temperature increases the relative humidity tends to decrease which limits the heat index (the water content of the air does not change only the water holding capacity). The chart also indicates that the heat index is rarely adding over 14 degrees to the temperature and typically something less than 6 degrees. The forecast has some of the warmest heat index values of the year so far set to arrive this weekend.

While we have yet to reach the half way point of 2013, the precipitation totals have already eclipsed the 2012 totals for some locations in the state as shown by the featured image. The largest differences are shown in an area south of Waterloo. This year experienced a wet winter season followed by the wettest spring season on record. The result has nearly eliminated the drought in Iowa (only some dryness in northwestern Iowa).

It is somewhat ironic that the first day of summer also is the first day with shortening daylight time. The featured map shows the idealized change in daylight time from Friday to Saturday. Iowa will loose just over four seconds! Of course, this change accelerates as the summer moves along. The start of the summer season will also feature some of the hottest and muggiest weather we have seen so far.

The featured map presents 72 hour precipitation estimates from the NOAA NMQ project centered over NE Iowa and SW Wisconsin. This area has seen numerous rounds of intense thunderstorms and some places are estimated to have received over a foot of rain in the past 72 hours. This has created dangerous flooding in the area. Unfortunately, more thunderstorms are in the forecast just about every day this week.

A heat burst event occurred in Iowa on Sunday morning with the classic signature of having the temperature rapidly rise and dew point fall at the same time along with an increase in speed. The featured chart shows the heat burst event at the KCCI-TV schoolnet site in Farnhamville (near Fort Dodge). Please note that the 92 mph wind gust reported at the site is probably due to the sensors high location on top of a building. The wind sensor is not at a standard 30 foot and unobstructed height. These events are caused by rapidly decaying storms that drive a layer of warm air to the surface that warms even more thanks to the ideal gas law (increase in pressure leading to increase in temperature).

The featured chart displays two daily frequencies of tornado and severe thunderstorm warnings in the United States. The green bars are the percentage of years since 2002 that at least one tornado or severe thunderstorm warning occurred on. The blue bars are the simple average number of total warnings issued per day. So while the number of warnings peaks in mid June, just about every day during the summer season sees severe weather somewhere in the US. In fact, this chart shows there has not been a day in July without severe weather since 2002. More severe weather is possible today in Iowa along with continued heavy rainfall events.

The main goal of the IEM is to archive data and then provide that data for download on the website. The featured chart displays the daily archive size of the imagery and data files stored. Some labels are shown when new datasets were added to the archive routine that significantly increased the daily archive size. The current daily archive is around 15 gigabytes in size, which is many times greater than that of just a few years ago. Thankfully, data storage continues to decrease in cost and the ability to archive many terabytes per year is tenable.

The National Weather Service RADAR network (NEXRAD) is constantly sampling the atmosphere and sensing objects that reflect its transmitted energy. The NEXRADs also measure the doppler shift of the reflected energy to provide an estimate of the reflected particles speed toward or away from the RADAR. Algorithms run on this information and organized storm motions are diagnosed. The featured map shows the location of tornado vortex signatures (TVS) diagnosed from the five RADAR sites covering the state. The TVS reported from the NEXRAD is a indication of a storm capable of producing or is already producing a tornado. Due to physical mechanics of doppler RADAR, these signatures can only be diagnosed at a range close to the RADAR. On the map, you'll notice many areas in Iowa without any reports. The reason is not that they don't have any tornados, but they are too far away from the closest RADAR for the algorithm to work.

Our recent bout with muggy weather looks to be taking a respite in the coming days. The featured chart presents the longest periods of having a dew point at or above the given temperature based on hourly observations from Des Moines. For example, back in 2011 the dew point was above 65 degrees for nearly 40 days straight. The upcoming drop in dew point will help limit heavy rainfall events as we really need to dry out in the state.

An intense thunderstorm complex brought high winds to bear on Wichita, Kansas Thursday evening. A heat burst event followed shortly thereafter. The featured chart presents one minute interval temperatures and pressure from the Wichita Airport sensor. The classic heat burst signature is clearly shown as the rapid increase in temperature is paired with a rapid decrease in dew point. This is a result of very warm and dry air rushing to the surface. Click on the 'heatburst' tag shown with this feature to view other events the IEM has documented in recent years.