Tuesday, November 26, 2013

Eastern Storm Messes with Holiday Travel

Surface map at 10:00 p.m. EST November 26
A low pressure system winding up in the southeast tonight has already caused problems for holiday
travel with heavy rain, freezing rain, and expected snow.

This surface low low is associated with the cutoff upper low that has been slowly crossing the southern U.S. this week. The cutoff low is in the process of phasing with the trough moving through the Great Lakes and it will be one large trough over the eastern U.S. on Wednesday.

500 millibar map analysis for 7:00 p.m. EST November 26

Rainfall totals in the Gulf Coast states exceeded 4 inches in Louisiana and Mississippi. Further to the northeast in the colder air up to a quarter inch of freezing glazed portions of North Carolina, northern Georgia, and Virginia.  Two to three inches of additional rain fell today in the mid-Atlantic states.

24 hour precipitation ending at 7:00 a.m. EST November 26
The surface low will move northeast along the coast on Wednesday, and is expected to be centered off the central New Jersey coast by early Wednesday afternoon.

Forecast surface map for 1:00 p.m. EST Wednesday, November 27.
A large band of snow and some freezing rain is expected west of the low track extending from the southern Appalachians to northern New England

Probability for the 24-hour period ending at 7:00 p.m. Wednesday, November 27

By Thanksgiving morning the low will be in eastern Quebec with light snow and flurries lingering over northern New England and lake effect snow showers from Michigan east through New York.

Monday, November 25, 2013

Big Chill Spreads Across Lower 48 States

It has been cold the past few days, but it was last week when the stage was set for an early appearance of winter weather across the country.  A broad upper level trough was located over the western U.S., and a surge of Arctic air was moving into the northern Rockies. On Thursday the trough became stronger, and by Friday a strong upper level low became disconnected from the westerlies (a "cutoff" low) while the northern portion of the trough continued east, driving cold air as far south as Texas and as far east as the Appalachians.

500 millibar analysis for last Wednesday though Friday
Surface weather map for Friday, November 22.
The surface low associated with the cutoff along with strong high pressure dropping south from Canada was responsible for high winds and heavy snow in the western U.S. from the coast to the Rockies and from Arizona to Idaho. Wind gusts reached 80 mph and resulted in power outages throughout the region.

A reinforcing surge of Arctic air pushed through the central U.S. on Saturday, and by Sunday morning the leading edge of the cold air mass had pushed well into the Gulf of Mexico and halfway through Florida.

Surface weather map for Sunday, November 24.
Meanwhile, the upper low continued to spin over the southwestern U.S. producing snow across the Four Corners region and in Texas. Freezing rain developed from New Mexico eastward across Oklahoma turning roads into skating rinks.

Snowfall for the 48 hours ending at 7:00 a.m. local time Monday, November 25.
In the eastern U.S. cold air flowing across the relatively warm waters of the Great Lakes produced snow from Ohio through New York.

As of this morning snow cover was extensive across Canada and the central Rockies.

How cold has it been? In the central two-thirds of the country temperatures the last week have been well below normal. Over the weekend minimum temperatures dropped into the single digits and teens as far south as the Ohio River and below freezing from central Texas eastward through central Mississippi and Alabama.

Minimum temperatures for 7:00 a.m. EST Sunday, November 24.

Thursday, November 21, 2013

Summary of Sunday's Tornado Outbreak

We will never know how many lives were saved or injuries avoided because of the timely and accurate warnings issued during Sunday's severe weather outbreak. It's easier to speculate on what could have been had there not been enough advance for people to take cover, and that picture isn't pretty.

The science of meteorology and the art and science of forecasting have come a long way in the last two decades. Technology has advanced, the forecasts are much better, there has been a greater effort at public education, and there are now multiple avenues to disseminate this information, including social media. Nevertheless, it takes the skill of the forecasters, the cooperation of the media, and the efforts of volunteer storm spotters for the system to work.  It certainly worked well on Sunday, November 17.  More importantly, those in the storm's path heeded warnings and took shelter.

The Storm Prediction Center had indicated the possibility of severe weather on Sunday as early as Thursday. As the forecast became clearer the outlook issued Saturday indicated a Moderate Risk for severe storms on Sunday.

The outlook issued early Sunday morning upgraded that to a High Risk for portions of Illinois and Indiana. SPC expanded that High Risk area in the next update issued at 8:00 a.m. CST through Indiana and into Ohio. High Risk outlooks for severe weather are pretty rare in November.

The SPC forecasters are very skilled at what they do, but often Mother Nature throws curveballs and forecasts aren't always perfect. On Sunday, however, they hit a home run out of the park (to maintain the baseball analogy). Here is map of all the storm reports received superimposed on the outlook map issued Sunday morning. Note that all but a few tornadoes occurred in the High Risk area, and all reports fell within the area outlined by the Slight Risk (yellow) - most were within the Moderate Risk area..

To go along with the above map, here is a summary map of all the watches and warnings issued between Saturday morning and Monday morning.

What made this day particularly challenging was the forward speed of the supercells and thunderstorms. Many were moving at 60 to 65 mph, so a delay in issuing a warning even for five minutes meant that a storm was five miles closer to a particular location.  Fortunately advances in radar technology allow forecasters to detect tornado potential before a tornado actually forms providing more lead time for a warning. Residents in Washington, IL were warned 15 minutes before the monster hit, no doubt a reason that more people weren't killed or injured.

Here is a summary of the strongest tornadoes that occurred on Sunday. There were a total of 24 tornadoes in Illinois and 24 in Indiana (preliminary numbers). Tornadoes also occurred in Kentucky, Missouri, Michigan, Ohio, and Tennessee. Seven tornadoes have been rated EF-3 and two have been rated EF-4 on the Enhanced Fujita Scale.  Of those nine EF3/EF4 tornadoes two tornadoes, including the EF-4 that hit Washington, Illinois, traveled over 40 miles and two others traveled more than 29 miles.

Tornado Est. Path Max
Location Intensity Max Wind  Length Width
Washington, IL (Tazewell/Woodford County) EF4 190 46.2 1/2 mile
New Minden, IL (Washington County) EF4 166 10.6 200 yds
Gifford, IL (Champaign/Vermilion) EF3 140 29.7 1/4 mile
Villa Grove (Douglas and Champaign) EF3 140 15.0 1/4 mile
Lafayette, IN EF3 NA 29.2 NA
Woodville, KY EF3 145 42.0 500 yds
Hopkins County, KY EF3 140 8.0 200 yds
Union/Henderson County. IL EF3 145 14.5 200 yds
Scott County, MO EF3 140 19.0 600 yds

Most of the damage surveys are complete, but the data presented here is still preliminary and subject to change as more storm reports come in. NWS offices are still updating information on their web pages. The NWS Chicago office and NWS Lincoln, IL office both have extensive information, maps, videos, and photographs on their web sites, as well as links to the other NWS offices with storm information on this outbreak.

Sunday, November 17, 2013

A Tragic November Day in the Midwest

Convective outlook issued at 8:00 a.m. CST, November 17, 2013
Residents of the Midwest aren't usually thinking about tornadoes in mid-November, especially less than a week since the first measurable snow of the season. However, they woke up this morning to an outlook for a High risk of severe weather from Illinois east through Indiana and into western Ohio and southern Michigan.

At 8:00 a.m. CST radars were clear of any storms in Illinois and showers and thunderstorms were exiting southeastern Indiana.  By 9:00 a.m. storms were beginning to fire in Illinois ahead of a strong cold front, and not long after the first severe weather warnings were being issued.

Surface map at 12:00 CST Sunday, November 17

Southwest winds were already gusting to 40-50 mph in the warm sector, and wind profiles through the atmosphere were favorable for large and long-track tornadoes. Sometime around 10:00 a.m. the first tornado warnings were being issued for areas west of Peoria, Illinois. Over the next six hours there were more than 65 tornado reports in Illinois, Indiana, and western Kentucky.  Forward motion of the individual storms was as high as 65 mph.

Storm reports for November 17
NWS Storm Prediction Center

Some of the worst tornado damage occurred in central Illinois as a supercell moved northeast spawning multiple tornadoes. One of the hardest-hit communities was Washington, IL, about 10 miles east of Peoria. Damage also occurred in many other communities through central and Illinois and the western half of Indiana, including Gifford, IL only 17 miles north of my home in Champaign County. One of our CoCoRaHS observers was able to photograph this tornado as it passed to the north of her location.

Gifford, IL tornado taken from approximately 3.5 miles south of Gifford at 12:51 p.m. CST.
Photo by Jessie Starkey

Kokomo, IN, north of Indianapolis, suffered major damage and a state of emergency was established until 6:00 a.m. Monday morning. Several other Indiana communities also suffered major damage. As of this post, there have been six confirmed fatalities from the storms, all in Illinois and dozens of people injured in all the states affected.

Damage assessment teams from the National Weather Service will be out over the next two days to confirm and rate the tornadoes. It seems likely that there will be at least one EF4 tornado.

How rare is a tornado outbreak for the Midwest in November?  Like spring, fall is a transition season from the warm season to winter, and there is a secondary peak in severe weather in the fall. However, tornado outbreaks like today are rare. The last time there was a high risk for severe weather in November was in 2002 and in 2005. These high risk areas were further south than the one issued today.

Here's an interesting fact from the NWS Chicago office.

"Since 1986 there have been 194 tornado warnings issued in Illinois during the month of November. Of those 194 warnings issued, 101 of them (52%) were issued today. Credit to meteorology professor Victor Gensini (Northern Illinois University and College of Dupage) for researching this stat."

The National Weather Service Chicago has a great summary of the November 17 severe weather outbreak in the Midwest. There are also links to storm information from other NWS offices who dealt with the storms

Thursday, November 14, 2013

A Rare Dry November Day Across the U.S.

This morning's CoCoRaHS precipitation map was very gray this morning. The lack of color on the map meant that there were few reports of measurable precipitation across the country. As of 8:00 p.m. CST today a total of 7,277 reports had been submitted to CoCoRaHS, but only 450, or 6 percent had measurable precipitation in the U.S. and Canada!  Compare that to November 1, when 56% of the 10,950 reports submitted had measurable precipitation.

The highest precipitation amount reported today was 1.26 inches at Hawaii station HI-HI-13, Volcano 4.3 SSE. The highest amount reported in the lower 48 was 0.95 inches at FL-MD-30, South Miami 0.5 N.

The main reason behind the dry weather was the massive high pressure system that covered the eastern two-thirds of the country yesterday and was the center of a cold, very dry air mass. The only precipitation to speak of in the continental U.S. was some light rain in the Pacific Northwest, some precipitation associated with the frontal system moving into the Rockies and High Plains, scattered snow showers in New York and Pennsylvania, and showers and thunderstorms in southern Florida.

Surface weather map for 4:00 p.m. EST November 13, 2013

November is typically a stormy month across the U.S. as it marks the end of the transition from fall to winter weather patterns. A dry day such as this in November over such a large portion of the country is a rare event. Below is the 30-year average precipitation for the U.S. for November 14. There is, on average, a relatively good chance for precipitation for most of the southeastern half of the country and the Pacific Northwest.  You won't see many precipitation maps like today's during the month of November.

Friday, November 8, 2013

The "White Hurricane" of 1913

One hundred years ago this week a massive storm battered the Great Lakes over a period of four days, November 7-11. The storm lingered over the region for four days, generating hurricane force winds (74 mph or greater) over the lakes, heavy snow and blizzard conditions, and 35 foot waves on the Great Lakes. A dozen ships were lost on the lakes, 33 others were damaged, and 250 lives were lost. This storm still remains as the worst U.S. maritime disaster.

The "White Hurricane" was the result of two separate weather systems that merged into one huge system that covered the entire eastern half of the country. In some respects the evolution of this system has some similarities to the evolution of Superstorm Sandy last year. On November 7-8 a strong low was moving across the northern U.S. trailing a strong Arctic cold front. This system primarily impacted Lakes Superior and Michigan, producing storm force winds, heavy snow, and high waves. Several large ships were damaged or run aground as this system moved across the lakes. In the meantime, weak low was moving northeast out of the Gulf states and over the southeastern United States on November 8.

Surface weather map for the morning of November 8, 1913 with notations showing the location of the cold front, the Arctic air, and the low in the southeast U.S.,

Over the next 24 hours the low over the Great Lakes phased, or merged, with the low in the southeast, resulting in explosive and rapid intensification, what we call a meteorological "bomb". On the morning of November 9, 1913 the intense storm was centered over Washington DC.

Surface weather map for the morning of November 9, 1913.

Instead of moving out to sea, the storm turned to the north northwest. The circulation of the storm was tapping the cold Arctic air on it's west side and feeding off abundant moisture from the Atlantic. By the morning of November 10 the center of the storm was located over Lake Ontario.

Winds associated with the storm were estimated to be at hurricane force (74 mph or greater) for a period from 10 to 20 hours over the Great Lakes. Survivors reported wind gusts to 90 mph on Lake Huron on November 9. Winds on Lake Erie were 50 to 70 mph with gust to 85 mph. The ferocious winds for a prolonged period of time over he lakes produced waves up to 35 feet occurring as often as every three minutes. Ships of the day were not capable of withstanding these extreme conditions, especially with whiteout conditions and buildup of ice on the ships . A total of 12 ships were lost and 33 others were damaged during the four-day period. Several ships lost during the storm were never located.

Location of ships lost during the White Hurricane of November 7-10, 1913.
Credit: National Weather Service Detroit, MI

Snowfall blanketed much of the Great Lakes region from this storm. Heavy snow fell across eastern Ohio, West Virginia, and western Pennsylvania with moderate snowfall extending west into Michigan. The Great Lakes were still relatively warm in early November, and the frigid Arctic air streaming over the warm waters resulted in heavy lake enhanced snow. Record snowfall occurred in Cleveland, OH  with 17.4 inches falling in a 24 hour period and a three day total of 22.2 inches.

It was November 11 before the storm finally began to pull away from the region. This storm had, as you might imagine, widespread impact. In some areas freezing rain glazed telephone, telegraph, and power lines prior to the snow and combined with the high winds caused extensive damage. The total damages from this storm were more than $117 million in today's dollars.

You can read more about this epic storm at the following web sites:

Centennial Anniversary Storm of 1913 - NOAA

The "White Hurricane" Storm of November 1913 - A Numerical Model Retrospective - NWS Detroit

November 9-11, 1913: Great Lakes Hurricane - Ohio Historical Society

Frozen Fury: The 1913 White Hurricane - Lake Superior Magazine

There has also been a book written about this storm.  "White Hurricane - A Great lakes November Gale and America's Deadliest Maritime Disaster" by David G. Brown