Thursday, May 22, 2014

One Hail of a Day

View from my car at 2:33 p.m. MDT May 21
just west of Denver International Airport
Yesterday was a first in my long career and interest in the weather. It occurred as I was returning home from a meeting in Colorado, a meeting coincidentally about CoCoRaHS and related programs. The sky was dark as I drove south on I-25 toward Denver, but it appeared more ominous as I headed east from I-25 toward Denver International Airport. I encountered some rain about 10 miles out and witnessed a few spectacular cloud-to-ground lighting strokes. About 2:30 p.m. I was within five miles of the airport when small hail began falling. The hail became more intense and I was seeing 1/4 to occasionally 1/2 inch hail. Traffic slowed to a halt as the hail continued and began to pile up on the ground.  By time it ended about 20 minutes later there was 3 to 4 inches of hail covering the ground and the road. In other areas, the hail was estimated to be 8 inches deep or more. I've never experienced hail like this before.

Hail on Pena Blvd approaching Denver International Airport at 3:23 p.m. MDT
Photo by Nancy Selover

The hail covered a fairly large area, including the at and around the airport terminal. Many flights were cancelled and many more delayed because of this storm. A number of the cancelled flights were due to damage to aircraft by the hail. Automobile traffic in and out of the airport was at a crawl because of the accumulation of hail. In some places, roads were flooded when hail clogged the storm drains.

At the same time, a rain-wrapped tornado was on the ground about 8 miles south of the airport moving east along I-70. I wasn't aware of this until I made it into the airport terminal.  The radar image below is probably sometime around 2:00 p.m. MDT. The area outlined in pink is the tornado warning. The storm was moving northeast and there were multiple reports of rotation.

Radar image about 2:00 p.m. MDT May 21.
Credit: NWS Denver/Boulder

This image was the radar at 3:24 p.m. MDT.  The storm has cleared the airport and remains intense. The tornado icons along I-70 are locations where spotters reported a tornado.  This storm complex continued on for several more hours. Interestingly this was the second consecutive day where a severe storm moved right over the Denver airport.

Radar image at 3:24 MDT May 21.

My phone had been alerting me about severe thunderstorm warnings back home as I made my way
through the terminal.Once checked in and through security I fired up my laptop to check out the weather in Denver and back home. I soon learned that hail from 3 to 4 inches in diameter was falling from the skies just 20 or so miles southwest of my home in Champaign County, IL in the city of Tuscola. That was the really big stuff. Hail from 1 to 2 inches in diameter fell in many other areas. At Champaign's Willard Airport 1.75 inch hail and high winds (gust to 63 mph) produced significant damage to vehicles, and also damaged the World War II B-17 Liberator "Aluminum Overcast" which is visiting the area.

Photo of 2.5 inch hail by CoCoRaHS observer
at IL-DG-11 in Douglas County, IL

3 to 4 inch hail in Tuscola, IL on May 21.
Photo by Brooke Messer, via JC Fultz, WAND-TV

Denver and my home in Illinois were the focus of my attention yesterday, but they weren't the only locations with severe weather and large hail. Hail measuring from 2.00 to 2.75 inches was reported in southern Illinois, Indiana, and Ohio.

Large hail was also reported today, this time in Pennsylvania and New York.  The largest hail was in Amsterdam, NY where hail three and four inches in diameter was reported this afternoon.

Tuesday, May 13, 2014

Another Slow Moving Weather System

The first two weeks of May have seen almost the entire spectrum of weather from snow to record heat to severe thunderstorms and tornadoes. The upper level weather pattern has been amplified since late April, and this week another large trough is making its way across the country.  This started out as a double-headed low, with one low center over the Canadian Rockies and a second that came ashore in the Pacific Northwest on Friday.

500 millibar map for 7:00 a.m. CDT May 11, 2014

The Pacific center dropped southeast into the Four Corners region on Sunday. Sunday morning's surface weather map had one long frontal system extending east from southern California through the central U.S. to off the New Jersey coast.

Surface map for 7:00 a.m. Sunday, May 11, 2014

Snow falling in Walden, CO (Jackson County) on Sunday,
where about 10 inches accumulated. Photo by Peg Brocker.
Heavy snow fell on the cold side of this system on both sides of the Continental Divide, but the heaviest snow fell from southern Wyoming south through central Colorado.  Two to three feet of snow was reported in Wyoming, with 43 inches west of Encampment, WY. 20 to 30 inches fell in northern Colorado, with 6 to 8 inches in Fort Collins and 3 to 5 inches in Denver. 12 inches of snow fell in parts of the Nebraska Panhandle.

72-hour snowfall ending the morning of Tuesday, May 13.
Meanwhile, south of the front temperatures soared to summer like readings in the 80s and 90s from Texas north to Kansas and east to southern Michigan and Ohio on Sunday. The warm weather was also accompanied by dewpoints in the 60s.

Temperature (L) and dew point (R) at 4:00 p.m. CDT Sunday, May 11.
The warm, unstable air and the frontal boundary produced conditions ripe for severe weather, and the worst storms occurred along the front in an arc from southwestern Kansas to southeastern Nebraska, southern Iowa and northern Illinois.  Severe weather continued along the system Monday and today, but severe weather reports were far fewer in number.

24-hour precipitation ending at 7:00 CDT 5/13/2014
Thunderstorms also dropped heavy rain in many areas. Some of the more impressive totals were found in eastern Texas, where there were numerous reports of 24-hour amounts of 4 to 6 inches of rain and one report of 8.30 inches in Colorado County. Unfortunately the rain produced by this system missed the bone-dry areas of central and western Texas and Oklahoma.

The slow-moving upper trough and the associated surface front will spend the next three days moving through the eastern half of the country. Showers and thunderstorms weill continue to develop in the warm humid air ahaead of the front, while showers will occur in the cool air behind the front beneath the upper level low.

Quantitative precipitation forecast for the 3-day period ending Friday at 7:00 p.m. CDT

Wednesday, May 7, 2014

Winter Slowly Retreats, Summer Quickly Advances

The last vestiges of winter are still clearly evident in the Great Lakes, which remain nearly 16 percent ice covered as of May 6. You may recall that on March 6, Great Lakes ice cover  peaked at over 92 percent, the second highest concentration since 1973. Most of the current ice is over the eastern end of Lake Superior and some of the bays on Lakes Michigan and Huron, and on the western end of Lake Erie.

Ice cover on the Great Lakes as of May 6, 2014.

There is also still snow on the ground in the Arrowhead of Minnesota and along the northern edge of the Upper Peninsula of Michigan, particularly in the forested areas.

The average date of last ice (10 percent) is usually from mid March into April for most of the lakes, so last ice is significantly later this year.

At the start of May, Lakes Superior, Michigan, and Huron had two to three times as much ice as they did on the same date in 1979, the season with the greatest ice coverage. It's possible there still could be ice on Lake Superior in June given the current amount of 34 percent.

The view looking west over Copper Harbor, MI on the Keeweenaw Peninsula.
Credit: Northwoods Cam Network
The slow melting of the ice and slow warming of the water will likely mean that spring lake breezes are going to be mighty chilly for some time to come for those area normally affected.

Maximum temperatures for May 6, 2014
It's just the opposite situation in the Central and Southern Plains where temperatures have soared into the 90s and even triple digits over the past week.  The high on Sunday, May 4th reached 102°F in Wichita, KS burying the old record of 94 for May 4. It was also the earliest triple-digit day on record there. Abilene, Texas, reached 104°F on Monday, May 5th, the second-earliest 104-degree day on record. The earliest recorded 104°F reading in Abilene occurred only two years ago on April 25, 2012.

The unseasonably high heat and tinder-dry conditions from the Extreme drought  have resulted in extreme fire danger for parts of Texas, New Mexico, Colorado, Oklahoma, and Kansas. A wildfire broke out this past weekend near Guthrie, Oklahoma, and another broke out yesterday in Woodward, Oklahoma.The fires have already prompted thousands of evacuations and resulted in one death.

Fire Weather outlook issued by the Storm Prediction Center.