Sunday, April 28, 2013

Soaking Rain in Tennessee and Texas

Surface map at 1:00 a.m. CDT April 28
Heavy thunderstorms brought inches of rain to several counties in southeast Texas and a large portion of northern Tennessee and adjacent portions of Kentucky, and both were the result of the same general weather system. The clusters of thunderstorms in Texas developed ahead of a front draped across southeast Texas. The thunderstorms in Tennessee were associated with a low pressure wave
moving northeast along that front. Precipitation from these storms topped five inches in both states, with heavier amounts more widespread in Tennessee.

The clusters of thunderstorm developed over Texas during the afternoon. Rainfall amounts exceed 6 inches on the northeast side of Fort Bend County. CoCoRaHS observers in Sugar Land reported 6.55 and 6.12 inches of rain.  Numerous rainfall reports of 4 to 5 inches was also observed in Lavaca, Harris, and Goliad counties

Southeast Texas rainfall for the morning of April 28

Here is the regional radar for that area from late afternoon on Saturday/

Regional radar at 5:57 p.m. CDT April 27, 2013

Thunderstorms rolled across Tennessee both Friday and Saturday, and two-day totals exceed 7.50 inches in Montgomery County, with 7.52 inches reported by the CoCoRaHS observer at Clarksville 10.2 WSW. The heaviest rain, generally in excess of 5 inches, fell during the day Saturday, but rain continued through Saturday night.

Flood advisories remained in effect Sunday night for a number of rivers in the Nashville area. Flood warnings are in effect for rivers in Montgomery County tonight, with area rivers expected to fall during the day on Monday.

Wednesday, April 24, 2013

A Tough Spring for Farmers

Warm weather in March last year helped farmers get an early start to planting, but expanding drought impacted crops throughout the summer. This year, unusual cold and wet weather is delaying planting and likely damaging some crops. It's already a tough year for farmers (and gardeners, too) and we're just getting started.

As of Monday, April 21 only 4 percent of the corn crop was planted, with most of it in Texas and North Carolina. That's compared to a five-year average of 16 percent - last year it was 26 percent. In the Corn Belt states of Iowa, Illinois, and Indiana, little corn has been planted (1 percent in Illinois and Indiana, nothing in Iowa), compared to about 50 percent planted last year. With the tremendous amount of rain in the past week soils are saturated and it will be at least another week to 10 days before fields dry out enough to work, providing there isn't any more heavy rain. For those areas near flooding rivers it will be even longer.


The cold weather is taking its toll as well. It has been unseasonable cold all week, and today was another record cold morning across the central U.S.  Amarillo, Texas dropped to 20°F this morning, shattering the old record of 32°F set in 1913 and again in 1958. Temperatures were in the upper teens to mid 20s across most of the Plains this morning. This is the major growing area for hard red winter wheat, and there was likely some damage to the crop especially in the southernmost states of Kansas, Oklahoma, and Texas where crop development is further along. After coping with drought last year and over the winter, wheat farmers may have taken another hit from the cold weather.

Minimum temperatures as of 7:00 a.m. CDT April 24

Of course, the drought still persists through much of that same area, and even with some improvement in the next few months there will still be lingering effects from the long term dryness.

Monday, April 22, 2013

Water, Water, Everywhere...

It's hard to believe that only five months ago the flow on the Mississippi River was so low that authorities were planning to shut down the river to barge traffic.  This morning major flooding is occurring along the Mississippi River and many other rivers in the Midwest from the torrential rain over a three-day period last week.

U.S. river observations as of April 22, 2013
From the NWS Advanced Hydrologic Prediction Service

The slow-moving weather system that moved across the country last week left more than 8.0 inches of rain in its wake. This rain fell on ground already saturated from precipitation earlier in the month, and much of the rain ran off into rivers and streams.

7-day precipitation accumulation for the period ending April 21
From the Midwestern Regional Climate Center
The highest precipitation totals reported by CoCoRaHS observers in each state for the period April 17-19 include

8.20      IA-MA-4     Pella 0.7 SE, Marion County
8.10      MI-AN-4     Fennville 0.8 W,  Allegan County
7.43      IL-DP-27     Naperville 2.1 SE,  DuPage County
7.20      IN-BN-2      New Ross 2.0 E, Boone County
6.15      MO-RN-2    Clifton Hill 1.2 SE, Randolph County

Hydrograph for the Illinois River at Peoria.
From the NWS Advanced Hydrologic Prediction Service
Flood stages approached or exceeded record levels at a number of locations. The Rock River at Moline, IL crested at 16.53 feet, breaking the record of 16.38 feet set on March 6, 2008. The Illinois River at Peoria reached a record level of 29.18 feet this morning breaking the old record of 28.8 feet set in May 1943, and is expected to crest at or above 30 ft. on April 23. The Grand River at Comstock Park in Michigan reached a record level of 17.8 feet on Sunday, April 21, breaking the old record of 17.75 feet set in March 1948.

In addition to flooding on rivers and streams there was widespread urban flooding and overland flooding of fields and rural roads in the affected states.

Here are some links to some photos of the flooding in the Midwest. You may also find other photos at individual NWS office web sites.

Grand River, Michigan flooding

Flooding on Illinois River near Marseilles, IL

Illinois River Flooding, Chillicothe, IL

The U.S. Geological Survey map of streamflow across the country is a picture of "feast or famine", Streamsflows are at very high levels in the Midwest, while they remain much below normal in much of the west and southwest, a mark of the persistent drought.

Sunday, April 21, 2013

An Elusive Spring

The far western and southeastern third of the U.S. have enjoyed a warmer than average April so far, but warm spring weather has been a hit or miss (mostly miss) proposition for the central U.S.

Temperatures from the Dakotas through central Texas have been below normal this month. Temperatures have been 10 degrees below normal across the Dakotas and Minnesota, with with departures of more than 15 degrees below normal in North Dakota. The cold is one thing, but these areas have also received 5 to 6 times normal April snowfall.

Deep snow cover over Canada has maintained the supply of cold air this spring and there is still 30 cm (12 inches) or more on the ground across the Prairie provinces.  A persistent upper level trough pattern over over the central U.S. has deflected the storm track farther south this spring and allowed the cold air to spill farther south than normal.

Snow depth over Canada and the northern U.S. as of April 20.
In the past two days more than 600 record lows and 560 record low maximum temperatures have been recorded from the Dakotas to the southern tip of Texas.

Record low temperature records set or tied on April 19, 2013.
Maps from the National Climatic Data Center
Record low temperature records set or tied on April 20, 2013.
Maps from the National Climatic Data Center

Yesterday morning lows were in the single digits in the Dakotas and Minnesota and in the 30s as far south as the Big Bend area of Texas.

Minimum temperatures for the morning of April 20, 2013

Is there light at the end of the tunnel?  There's a light, but it might be another freight train, at least in the short term. An upper level system is moving into the Pacific Northwest today and will drop into the central Rockies by Tuesday. The surface low will organize in the Central Plains and bring another round of snow to an area from Wyoming and Colorado to Minnesota. Another surge of cold air will follow this system.

Probability for 4 or more inches of snow between 7:00 a.m. CDT Monday, April 22 and 7:00 a.m. Tuesday, April 22

Forecast high temperatures on Friday, April 26.
However, a warmup is in the cards by next weekend, and there are indications that spring may finally take hold as we wrap up the month of April.    

Thursday, April 18, 2013

Wet, White, and Wild Weather

Surface map at 7:00 CDT April 18
This has been an interesting week for spring weather from the Rockies through the Midwest. In the last 24 hours there have been flooding rains, heavy snow, severe thunderstorms, and tornadoes, all related to the same weather system

Much of Colorado got more snow in the past 24 hours, with as much as 15 inches in south-central Colorado near Pueblo. Snow also accumulated 2 to 3 inches in western South Dakota and 2 to 4 inches in northern Minnesota. Snow also occurred in Nebraska and northwestern Kansas.

24 hour snowfall ending the morning of April 18

On the warm side of this system. severe weather was reported from Oklahoma to Indiana. Two tornadoes touched down in Oklahoma, baseball size hail pummeled locations in Missouri, and thunderstorm winds gusted to 90 mph in western Illinois.

The heavy rain produced by this weather system has caused flooding from the southeastern half of Iowa through northern Missouri and across the northern third of Illinois.

24 hour precipitation ending at 7:00 a.m. CDT April 18
Many rivers and streams are in flood, and record flooding is possible for some rivers in northern Illinois.  As of 10:00 a.m. CDT this morning 170 CoCoRaHS observers reported more than 4 inches of rain, and of those, 54 reported more than 5 inches of rain. Below are the highest rain amounts in the last 24 hours from CoCoRaHS observers.
CoCoRaHS reports for April 18, 2013
 It's not over, either.  More heavy rain is expected today ahead of the cold front as it sweeps through the Midwest, and severe weather is likely from Indiana eastward. Winter weather advisories are in effect from northern Kansas to Lake Superior and a winter storm warning is in effect for portions of Minnesota into northwestern Wisconsin and the Michigan U.P.

24-hour expected precipitation from 7am CDT 4/18 to 7am CDT 4/19
Watches, warnings, and advisories in effect aas of 10:00 a.m. April 18

Tuesday, April 16, 2013

The NeverEnding Winter

Snow depth the morning of April 16, 2013
Springtime warmth has made an appearance in parts of the eastern half of the nation, and April showers are rapidly turning the landscape from brown to green.  However, winter has kept an icy grip on an area from the Rockies through the Northern Plains to the upper Midwest. Late last week snow and ice fell from Nebraska to Wisconsin, and over the last few days more than a foot of snow has piled up in parts of Colorado and the Dakotas.

48 hour snowfall accumulation ending
the morning of April 16, 2013
The snow in the Dakotas resulted from a storm system that moved from Kansas and Nebraska northeast through Minnesota over the weekend. Ten to 16 inches of snow was reported from northern South Dakota through central North Dakota, with 3 to 6 inches of snow across northern Minnesota. In Bismarck, ND numerous records were shattered by this storm. On Sunday, April 14th Bismarck has 17.3 inches of snow, breaking the old record for that date of 5.0 inches set in 1986. It also set a new daily record for the month of April, breaking the old record of 15.2 inches on April 5, 1997. This was also the record snowfall for any calendar day of the year! The previous record was 15.5 inches on March 6, 1966. The storm total snowfall of 21.5 inches as of the morning of April 15 is a new record for April, topping the old record of 18.7 inches in April 1984.  A number of locations in North Dakota reported 20 or more inches of snow from this storm, with 22 inches reported by the CoCoRaHS observer in Center, ND (ND-OL-2)

The snow in Colorado yesterday was produced by another low moving across the Great Basin. This setup is ideal for snow along the Front Range. Easterly flow resulting from the low to the west and strong high pressure to the northeast forces the air to rise as it encounters the Rockies, condensing the moisture and producing precipitation.

Surface map for 2:00 a.m. EDT April 15, 2013
These storms often produce lots and lots of snow, and this system was no exception. A foot of snow and more fell across the Fort Collins, Co area, home to CoCoRaHS headquarters.
CoCoRaHS snowfall in Fort Collins, CO April 16

Snow in the Denver area ranged from around 4 inches east of the city to 12 to 24 inches in the higher terrain west of Denver, with 24.5 inches of snow reported by a CoCoRaHS observer in Golden (CO-JF-267).
CoCoRaHS snowfall for the Denver Metro area, April 16

And it isn't over yet.  The system that brought the snow to Colorado will be lifting out to the northeast, and winter storm warnings are in effect for portions of Wyoming, Nebraska, and South Dakota. Winter weather advisories are in effect for parts of Montana, Wyoming, Colorado, Utah, and Nevada.
Watches, warnings, and advisories effective 10:00 a.m. MDT April 16

If there is a silver lining to all of this it is that the moisture from these snows will certainly help provide some relief from the drought conditions that exist across the central and western U.S.
piled up in parts of Colorado and the Dakotas.

Tuesday, April 9, 2013

First Tornado Hook Echo Observed 60 Years Ago Today

Today thunderstorms and tornadoes are routinely tracked using weather radar, and in fact anyone with a computer or smart phone can pull up the latest radar images for their area.  As you might surmise, this wasn't always the case.  After World War II surplus radars were being used to study thunderstorms and precipitation. The Illinois State Water Survey, a state agency on the University of Illinois campus, was in the beginning years of a weather research program at the time, a program that continues today. It was during a project conducted by the Water Survey that the now classic "hook echo" radar signature radar was first discovered and photographed in detail. As with many scientific discoveries, it was a serendipitous event.

Meteorology building at Willard Airport and the radar used
to detect the hook echo.
In the late afternoon and early evening hours of April 9, 1953 scattered thunderstorms were moving eastward across central Illinois. At the University of Illinois Willard Airport located a few miles south of Champaign, the Illinois State Water Survey was operating a radar collecting rainfall data for a project to determine the utility of radar for the measurement of precipitation amounts. The radar was a modified 3-centimeter wavelength radar that had been used as an airborne surveillance system installed aboard U.S. Naval aircraft in World War II. A rain gauge network had been established in east-central Illinois to provide ground truth for the radar-indicated amounts.  That day, radar engineer Donald Staggs and an assistant were working at the radar. The radar was only operated as needed for this project, and the normal procedure was to turn off the radar after precipitation had passed through the rain gauge network.  However, on that afternoon Staggs noticed the peculiar radar echo with the thunderstorm and thought “I wonder if that might be a tornado.”  Ten minutes later he received a phone call from a woman who lived just north of Champaign.  She wanted to know if he was seeing "the twister that just destroyed my barn" on radar. At that point he knew that the hook echo might just indicate a tornado and kept tracking it and photographing the radar display as the storm moved into Indiana.  This distinct tornado echo, which was observed near the southwest edge of the associated thunderstorm, contained the tornado funnel.

The first hook echo identified and photographed on radar.

Although Staggs recognized the unusual nature of the radar echo and the possibility of a tornado, positive identification was not made at the time of the radar tracking.  Only when the radar film was developed the next day did the scientists realize that the distinctive hook echo was the signature of the tornado reported the afternoon before.  Field surveys confirmed the tornado, which was eventually rated an F3.

The tornado moved east and dissipated just over the Indiana state line. It had a path of about 54 miles, and destroyed eight homes and damaged 72 others. There was one fatality in Vermilion County, Illinois from the storm.

A view of the tornado on April 9, 1953 taken from near Royal, Illinois.
Tornado photograph taken by Ernie Kienietz, provided by Scott C. Truett

The original report on this historic event is available online, and contains a description of the weather conditions that day, information on the weather radar, and the results of the field survey of the tornado damage, including photographs.  It's a fascinating piece of weather history.  You can read it at the following link.

Study of an Illinois Tornado Using Radar, Synoptic Weather and Field Survey Data, Illinois State Water Survey Report of Investigation 22, Urbana, IL by F.A. Huff, H.W. Hiser, and S.G. Bigler. 1954 

In the report's conclusion, the authors of the report speculated that with more collection of tornado radar data, " may be possible to establish radar storm warning systems in tornado areas to reduce loss of lives, and to some extent property damage."  This discovery did, in fact, launch a national research program aimed at tornado detection by radar.  In 1962 the National Severe Storms Laboratory was formed out of the National Severe Storms Project, conducting research on the detection of storms with radar. Today, there are 164 weather radar sites across the U.S. that scan the skies 24/7.

Wednesday, April 3, 2013

Every Home Should Have a Weather Radio

Trained meteorologists can forecast the development of severe weather. The latest weather radar technology can detect the signatures and features that signal the formation of severe storms and tornadoes. Warnings are issued as soon as the threat is evident. 

How do you and your family receive the warnings that are issued? If there is a tornado warning your community may use sirens to alert those who are outdoors (sirens are NOT meant to warn people indoors). You may hear it if you are near a radio or television. If you are inside with the windows closed and music playing, for example, how will you know?  If it is in the middle of the night and you are sound asleep, how will you know about the warning?

The answer is a weather alert radio. Just like every home should have smoke detector, every home and business should have a weather alert radio.

In the aftermath of storms we often see people interviewed who say "It struck without warning". What that statement usually means is "I wasn't aware of a warning", because in most cases a warning was not only issued, but issued with enough time to take shelter.  Everything from the forecast to the warning can be perfect, but if people aren't receiving the information then that information can't help them.

There are over 1,000 weather radio transmitters in all 50 states. Most of the time the programming is routine forecasts and information. When the weather turns severe, however, the weather radio is your direct line to the latest storm information.  About ten years ago the NWS Weather Radio network became part of the Emergency Alert System (EAS) managed by the Federal Communications System. With this capability the public can be alerted to information about natural disasters (such as earthquakes), civil emergencies, toxic and chemical spills, and child abduction Amber alerts in addition to the weather watches, warnings, and advisories.

Weather radios come in portable models that you can take with you to outdoor events or other activities like hiking or camping. Some have crank and/or solar recharging capabilities. Desk models run on AC power with battery backup.  The prices of radios range from $25 to $135, with most desk models in the $40 to $75 range. One feature you should seriously consider is a radio with SAME (Specific Area Message Encoding) capability.  This allows users to receive messages only for their designated county or counties of interest rather than the entire broadcast area. This is especially nice at night, as your radio alert will not be activated for areas you have not selected. On the basic radios without SAME any alert issued for any area covered by a specific transmitter will be triggered on the radio.

There are only seven VHF frequencies used for NOAA Weather Radio transmissions.
NOAA Weather Radio frequencies in the U.S.

The NWS has a map page that allows you to access information about all U.S. stations and coverage areas.

NOAA Weather Radio coverage map for Oklahoma
The map interface will also let you view includes a county by county listing of weather radio stations in each state and their current status.

NOAA Weather Radio station status for Illinois counties

NOAA also has a web page with consumer information, including a list of resellers of weather radios. 

Weather radio receivers will also work in Canada. Environment Canada, the government agency responsible for producing official forecasts, operates a network of "Weatheradio" transmitters which generally operate on the same frequencies as the U.S. NOAA Weather Radio network. More information on weather radio in Canada can be found here.

It's worth repeating - every home should have a weather alert radio.

Monday, April 1, 2013

2013 Thunderstorm Season - "Impact Based" Tornado Warnings Experiment

The NWS Central Region states and offices participating
April 1st marks the start of the thunderstorm season in the central U.S. This year 38 National Weather Service offices in 14 states that comprise the NWS Central Region will be issuing tornado warnings using enhanced messaging to emphasize the particular nature and danger of a storm. These "impact based warnings" (IBW) are an experiment to better communicate the expected impact and damage from a tornado in order to provide additional information to the media and emergency managers and better motivate people to take appropriate action.

This experiment was developed after an assessment of the May 2011 tornado that devastated Joplin, Missouri killing 158 people. There were three key findings from this assessment:
  • The majority of people identified local outdoor warning systems as their first source of warning.
  • The majority of people sought confirmation from additional sources before seeking shelter.
  • Credible, extraordinary risk signals prompt people to take protective actions. 

A number of "tornado tags" will be utilized for tornado.  Two tags will indicate whether the tornado was detected by radar or observed by spotters or law enforcement. Damage threat tags will be used to convey the level of damage expected from a particular storm.  Warnings will include the particular hazard (tornado, hail), the source of the information (spotter confirmation, on-going damage), and the impact and type of damage expected.

The IBW tags allow the forecasters to distinguish between a low-impact event (for example a weak, short-lived tornado) and a high impact event (a large, long-lived tornado)  Large, damaging tornadoes are relatively infrequent, so most of us will never hear a warning for a tornado causing considerable or significant damage.

In 2012 NWS offices in Kansas and Missouri utilized the impact based warnings. Below is a warning issued last year using the enhanced wording. The changes from a "standard" warning are highlighted in red.
Tornado warning issued on April 14, 2012 for central Kansas.

At the conclusion of this storm season the IBW experiment will be independently evaluated to determine its effectiveness.

Will changes in wording actually make a difference? This is an experiment to find out. Public response to warnings is a complicated issue and something that the NWS and emergency officials have wrestled with for years. How the information is communicated (sirens, the broadcast media, the Internet) and the content of the message that is being communicated are two sides of the same coin.

You can read more about the Impact Based Warnings experimental product at this NWS Central Region page.

More background on what was learned from the 2011 Joplin tornado can be found at NWS Central Region Service Assessment Joplin, Missouri, Tornado–May 22, 2011