Rare November Tornado Outbreak Kills 6; Subtropical Storm Melissa Forms

A rare and deadly late-season tornado and severe weather outbreak blitzed the Midwest U.S. on Sunday, killing at least six people and leaving widespread significant damage. A tornado preliminarily rated as a violent EF-4 touched down in New Minden, Illinois, east of St. Louis, carving a path of destruction three miles long, killing two people, and blowing semi trucks off of I-64. The twister was one of only twenty EF-4s to occur in the U.S. in November dating back to 1950, and was the third most northerly November EF-4 ever observed, according to data from the Tornado History Project. The most widespread damage from Sunday's outbreak occurred in the town of Washington (population 16,000), about 140 miles southwest of Chicago, where another powerful EF-4 tornado destroyed or heavily damaged 250 - 500 homes and an apartment complex. A northern Illinois man says he discovered mail belonging to Washington residents on his property in Channahon, about 80 miles northeast Washington, according to the (Peoria) Journal-Star. Three other tornado deaths occurred in Massac County in the far southern part of Illinois, making Sunday the deadliest November tornado outbreak in Illinois history. NOAA's Storm Prediction Center logged 68 preliminary tornado reports, along with 412 reports of high wind gusts and 32 reports of hail. Sixteen of the wind gusts were in excess of 74 mph (hurricane strength.)


Figure 1. A view of part of Washington, Illinois from Mackenzie Street on Sunday, Nov. 17, 2013 after a tornado tore through the area. (AP Photo/Alex Kareotes)


Figure 2. Radar reflectivity image of the supercell thunderstorm that spawned the Washington, Illinois tornado of November 17, 2013.

A strange 2013 tornado season
Sunday's tornado outbreak is yet another anomaly in what has been a very unusual 2013 tornado season. The top three tornado outbreaks have occurred in November, January, and October--well outside the usual spring/summer peak of tornado season:

Top Five Tornado Days of 2013
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01/29/13: 62 tornadoes
11/17/13: 68 (filtered) tornadoes, but likely to decrease once damage surveys completed
10/31/13: 42 tornadoes
05/20/13: 32 tornadoes
05/31/13: 30 tornadoes

It's been an unusually slow severe weather season, with the 2013 preliminary tally of 818 tornadoes before Sunday the lowest year-to-date count since the extreme drought year of 1988. However, when severe weather outbreaks have come, they have been unusually destructive. According to Aon Benfield, there have been five severe weather outbreaks topping $1 billion in damages this year. This is the third highest number of such disasters on record, going back to 1980. The record is shared by 2011 and 2012, with seven billion-dollar-plus severe weather outbreaks, according to NOAA's National Climatic Data Center. According to Aon Benfield, "prior to Sunday’s outbreak, both economic and insured losses attributed to severe weather were slightly below the 10-year average in 2013. Thus far, economic losses from convective storm events were roughly USD15.7 billion and approximately USD9.2 billion of those losses were covered by insurance. The 2003-2012 averages are USD17 billion and USD11 billion, respectively. It remains too early to project losses from Sunday’s event." The most expensive and deadliest severe weather outbreak of 2013 hit on May 20, when Moore, Oklahoma was devastated by an EF-5 tornado that killed 23 people and did $2 billion in damage. Yesterday's damage was severe and widespread, and there is a good chance the outbreak will become the first-ever billion-dollar severe weather outbreak to hit in November.


Figure 3. Prior to Sunday's severe weather outbreak, there were seven billion-dollar weather disasters in the U.S. in 2013. Five of these disasters were severe weather outbreaks--the third highest such total in history.

November tornado outbreaks: how rare?
Since 1950, there have been 2211 November tornadoes, killing 251 and injuring 5060.

Deadliest: 24 killed, 11/06/2005, F-3 tornado near Evansville, Indiana
Longest path: 160 miles, 11/23/1992, F-3 tornado in North Carolina
Most November tornadoes: 154 in 2004 (both 2005 and 1992 had 153)

Here is a list of the largest November tornado outbreaks since 1950:

95 tornadoes: November 21–23, 1992, Texas to Mississippi and into the Ohio Valley. The most intense and largest November outbreak on record in U.S. history. Produced violent tornadoes from Texas to Mississippi and into the Ohio Valley, including six F4s and two extremely long-track tornadoes, 160 miles and 128 miles.
75 tornadoes: November 9–11, 2002, Southeast U.S. and Ohio Valley. Very large and deadly outbreak produced multiple killer tornadoes across the Ohio Valley and Southeastern United States. A violent F4 hit Van Wert, Ohio, killing four people. Deadly F3 also hit Mossy Grove, Tennessee, killing seven.
67 tornadoes: November 23–24, 2001, Southeast U.S. Thirteen people killed.
50 tornadoes: November 15, 2005, Central and Southeast U.S. One person killed.
50 tornadoes: November 15 - 16, 1987, Oklahoma, Texas, and Mississippi
46 tornadoes: November 27–28, 2005, Central and Southeast U.S. One person killed.
44 tornadoes: November 15, 1988, Central and Eastern U.S.
40 tornadoes: November 15 - 16, 1989, Produced a deadly F4 that struck Huntsville, Alabama, at rush hour. Strong tornadoes touched down as far north as Quebec.

Sunday's outbreak will probably rank as the fourth most prolific November tornado outbreak since 1950. But what was really remarkable about the outbreak was how far north it extended, with severe thunderstorms and tornado warnings issued in Wisconsin and Michigan. NWS Gaylord has confirmed an EF-0 at I-75 near Waters yesterday, which closed the highway. This is the farthest north there's been a tornado in Michigan in November or this late in the year in the period of modern tornado records (1950-present), and only the seventh November tornado recorded in Michigan. In Southeast Lower Michigan where I live, I've never seen such a powerful and long-lasting high wind event during the 40 years I've lived here. As I sawed up the downed tree blocking my street last night, accompanied by wild winds, flashing lightning, and the eerie orange glow of a nearby electrical transformer blowing, I reflected once again how the severe weather season has become increasingly noticeable in cold season months here. These events are rare enough and our database is so poor that we can't make any definitive statements on how climate change may be affecting them, but one would expect to see cold-season severe weather events become increasingly common farther to the north in a warming climate. According to the Chicago NWS, prior to Sunday’s tornado outbreak, there had been just twelve November tornadoes since 1950 in the 23-county region of Northeast Illinois and Northwest Indiana that they service (six of these twisters touched down on November 12, 1965.) Preliminary tornado reports indicate that as many as six tornadoes may touched down Sunday in the region (four in Will County, one in Grundy County, and one in Newton County.) November tornadoes tend to be strong and destructive, and any shift to a climate with more of these beasts will be unwelcome. The Chicago NWS wrote: "Eight of the twelve previous November tornadoes were EF-2 or stronger, showing that when tornadoes do occur in November, there is a decent likelihood they will be significant (EF-2 or stronger). The primary reason for this is strong dynamics and wind field that tend to be present in the cool season (late autumn and winter), which add to a greater amount of wind shear.  This is a key component to tornadoes, and the greater the wind shear the more likelihood for significant tornadoes."


Figure 4. MODIS image of Subtropical Storm Melissa, taken at 13:30 UTC (8:30 am EST) November 18, 2013. Image credit: NASA.

Subtropical Storm Melissa forms
A large low pressure system centered about 740 miles east-southeast of Bermuda acquired enough organization to become Subtropical Storm Melissa, the 13th Atlantic named storm of 2013. The storm is generating sustained winds in excess of tropical storm force, as seen on the latest ASCAT satellite wind map. Ocean temperatures are near 27°C, which is about 1°C above average, and plenty warm enough to support tropical storm formation. While wind shear is currently a high 30 - 40 knots, it is expected to drop to the moderate range on Tuesday before increasing again on Wednesday. Satellite loops show that Melissa has a large band of heavy thunderstorms displaced more than 100 miles from the center of circulation, which is characteristic of a subtropical storm. Heavy thunderstorm activity near the center is beginning to build, so it is possible that NHC would classify this system as Tropical Storm Melissa on Tuesday. Melissa will not be a threat to any land areas.

Jeff Masters