Tornadoes rip Massachusetts, killing 4

The governor declared a state of emergency in Massachusetts last night after two rare and powerful tornadoes ripped through the state's third largest city, Springfield (population 150,000.) Separate tornadoes hit the city near 4:30 pm and 6:20pm EDT, killing four people, injuring 40, and causing extensive damage. The four deaths ties 2011 with 1973 as Massachusetts' deadliest tornado year since 1953, when 90 people died in an F-4 tornado that hit Worcester. NOAA's Storm Prediction Center logged seven preliminary reports of tornadoes in Massachusetts yesterday. The region was in their "Slight Risk" area for severe weather. The tornadoes were spawned by a large low pressure system centered over Canada that trailed a cold front southwards over New England. Record heat pushed northwards ahead of the cold front, with Newark, Washington D.C., Burlington, and Montpelier all recording record highs for the date. The contrast between the cold, dry air flowing south from Canada and the record warm, moist air ahead of the cold front created an extremely unstable atmosphere, helping fire off unusually intense thunderstorms over New England. And as we've seen so often this year, the jet stream over the thunderstorm region was unusually strong and had plenty of wind shear--a sharp change in wind speed and direction with height. This wind shear created shearing forces on the air over New England that helped get it spinning, creating rotating supercell thunderstorms capable of producing strong tornadoes.


Figure 1. Yesterday's tornadoes caused damage characteristic of at least an EF-2 tornado with 110 - 137 mph winds in Springfield, Massachusetts. Image credit: Springfield Falcons hockey team, via the cbslocal.com Boston website.


Video 1. Incredible tower cam view from wfsb.com of the June 1, 2011 Springfield, Massachusetts tornado crossing the Connecticut River. Another amateur video posted here on Youtube shows the tornado crossing I-91 in Springfield during rush hour (many swear words on this one!)

Springfield damage characteristic of an EF-2 tornado
Damage photos I've seen of the Springfield tornadoes show destruction characteristic of at least an EF-2 tornado with 111 - 135 mph winds. The damage photo above (Figure 1) shows the collapse of the top story walls of a brick building. According to the Storm Prediction Center's Description of Damage for this type of structure, the winds needed to do this type of damage typically range between 103 and 143 mph, or EF-2 speeds. I wouldn't be surprised if some of the damage gets rated EF-3, since there is a report of a 3-story building that collapsed (EF-3 winds are 136 - 165 mph.)


Figure 2. Satellite image taken at 6:01pm EDT June 1, 2011, showing the line of tornadic thunderstorms over Massachusetts, and Invest 93L near Tampa, Florida. Image credit: NASA/GSFC.

Massachusetts tornado history
One of yesterday's Springfield tornadoes pulled debris from Springfield and deposited it 45 miles to the east-northeast in Millbury, according to an NWS storm report. Powerful, long-track tornadoes like this are rare in New England. Most tornadoes in the region are small, weak, EF-0 and EF-1 twisters that touch down briefly and do minor damage. Only once every eight years, on average, does a strong or violent EF-3 or EF-4 tornado hit Massachusetts. According to the tornadohistoryproject.com, since 1951, there have been only eight strong to violent EF-3 or stronger tornadoes in Massachusetts:

May 29, 1995: An F4 tornado killed 3 and injured 24 in Great Barrington. The tornado tracked for 11 miles, and damage was estimated at more than $5 million.
Jun 22, 1981: An F3 tornado injured 3 people in Worcester County.
Sep 29, 1974: An F3 tornado injured one person as it hit Middlesex and Essex Counties.
Aug 28, 1973: An F4 tornado killed 4 and injured 36 in West Stockbridge as it tracked 9 miles from New York into Berkshire County.
Sep 13, 1971: An F3 tornado killed one person in Worcester County.
Oct 3, 1970: An F3 tornado killed one person in Worcester County. This tornado was on the ground for 35 miles.
Jun 9, 1953: The great 1953 Worcester tornado killed 90 and injured 1228 when it hit Worcester. The tornado had a path 40 miles long and up to 900 yards wide.
Jun 9, 1953: A separate F3 tornado hit Franklin in southern Massachusetts on the same day as the great Worcester tornado, injuring 17 people. The Franklin tornado had a path length of 28 miles.

Florida's surprise tropical disturbance 93L weakens
Invest 93L sped over Florida yesterday afternoon, bringing welcome rains of 1 - 3 inches over the center part of the state. Winds gusted as high as 29 mph at Daytona Beach as the storm came ashore. The storm has a rather unusual origin for a tropical disturbance--it began as a cluster of thunderstorms called a Mesoscale Convective System (MCS) that pushed across southern New England on May 30. On May 31, the MCS emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build on Tuesday. By Wednesday morning, 93L had grown organized enough to earn the designation 93L from NHC. However, passage over Florida disrupted 93L, and the storm is moving with such a fast forward speed--about 25 mph--that it has struggled to regroup. Wind shear is a low 5 - 10 knots, and SSTs in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, so it is possible that 93L could make a comeback. NHC is currently giving 93L a 0% chance of developing into a tropical depression by Saturday. I think these odds should be higher, at least 10%, given the recent increase in heavy thunderstorm activity near the center of 93L, as seen on satellite imagery. Steering currents will keep 93L moving quickly to the west-southwest today and Friday, and 93L should make landfall in Mexico just south of Brownsville, Texas, on Saturday afternoon.


Figure 3. Radar-estimated precipitation from 93L's passage over Florida yesterday.

Central Caribbean disturbance
Disorganized heavy thunderstorm activity continues in the region between Central America and Jamaica. Wind shear has fallen to the moderate range, 10 - 20 knots, and is predicted to continue to fall over the next two days. This should allow the disturbance to increase in organization, though it will take many days for it to approach tropical depression status, since it is so large and poorly organized. The computer models are generally showing only very slow development of the disturbance over the coming week. NHC is giving the disturbance a 20% of developing into a tropical depression by Saturday. A surge of moisture accompanying a tropical wave may aid development when the wave arrives in the Western Caribbean on Sunday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, Cuba, the Cayman Islands, Haiti, Honduras, and Nicaragua should anticipate the possibility that heavy rains of 2 - 4 inches may affect them today through Sunday. Heavy rains have already hit Jamaica, where a flash flood watch is posted.


Figure 4. Morning satellite image of the Central Caribbean disturbance.

Catch my intro to the 2011 hurricane season on Internet radio
I'll be discussing the coming hurricane season on our Internet radio show, the Daily Downpour, today (Thursday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner and Tim Roche will be hosting the show. We'll talk about the latest model runs, hurricane research, modeling accuracy, and hurricane climatology, and answer any questions listeners email in or call in. The email address to ask questions is broadcast@wunderground.com. We'll also discuss the Massachusetts tornadoes.

Jeff Masters