Thoughts on Today’s Tornado

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An EF-2 tornado touched down at 9:32 this morning in the town of Revere, Massachusetts just north of Logan Airport. This was the first tornado to strike Suffolk County, Mass since the modern tornado record began in 1950! There are a few things about this storm that are worth noting.

The storm exhibited weak rotation for quite some time prior to tornadogenesis. Rotation never reached an “alarming” level but was certainly at a “we should watch this storm” level. 3 minutes prior to tornadogenesis at 9:29 a.m. radar shows a fairly broad/weak low level mesocyclone.

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930 UTC KBOX 0.5 BR/BV/ZDR/CC clockwise from top left.

By 934 UTC doppler radar has confirmed that a tornado touched down. Not only is there 85 knots of gate-to-gate delta-V there is a classic and clear tornado debris signature. All the criteria are met here with high Z, CC <0.8, strong low level rotation, and ZDR near of below 0.

934 UTC KBOX 0.5 BR/BV/ZDR/CC clockwise from top left.

934 UTC KBOX 0.5 BR/BV/ZDR/CC clockwise from top left.

By the 939 UTC volume scan the low level mesocyclone has virtually disappeared – though lofted debris remains in the sky (>2000 ft AGL) from the prior tornado touchdown.

939 UTC KBOX 0.5 BR/BV/ZDR/CC clockwise from top left.

939 UTC KBOX 0.5 BR/BV/ZDR/CC clockwise from top left.

Unfortunately, the tornado warning wasn’t issued until 9:44 a.m. – a full 10 minutes after radar detected lofted tornado debris!

TORNADO WARNING  
NATIONAL WEATHER SERVICE TAUNTON MA  
944 AM EDT MON JUL 28 2014  
  
THE NATIONAL WEATHER SERVICE IN TAUNTON HAS ISSUED A  
  
* TORNADO WARNING FOR...  
  SOUTH CENTRAL ESSEX COUNTY IN NORTHEAST MASSACHUSETTS...  
  
* UNTIL 1030 AM EDT  
      
* AT 944 AM EDT...DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM  
  CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED  
  OVER SWAMPSCOTT...OR OVER SALEM...AND WAS MOVING NORTHEAST AT 55  
  MPH.  
  
* SOME LOCATIONS IMPACTED INCLUDE...  
  LYNN...REVERE...PEABODY...SALEM...BEVERLY...SAUGUS...DANVERS...  
  WAKEFIELD...MARBLEHEAD...NORTH READING...SWAMPSCOTT...LYNNFIELD...  
  MIDDLETON...MANCHESTER AND NAHANT.  
  
PRECAUTIONARY/PREPAREDNESS ACTIONS...  
  
TAKE COVER NOW! DO NOT WAIT TO SEE THE TORNADO. GO TO A BASEMENT OR  
INTERIOR ROOM ON THE LOWEST FLOOR OF A STURDY BUILDING...AWAY FROM  
WINDOWS. IF IN A VEHICLE...A MOBILE HOME OR OUTDOORS...GET TO THE  
CLOSEST SHELTER. PROTECT YOURSELF FROM FLYING DEBRIS. 

So what went wrong?

It would have been virtually impossible to provide any lead time with a tornado warning in this situation. The tornadic circulation developed and fell apart within about 10 minutes. What is bizarre is that the tornado warning didn’t come out until 10 minutes after the tornadic signature was on radar.

Additionally, the National Weather Service’s Warning Decision Training Branch guidance for tornado warnings says that a tornado debris signature – like the one seen today in Revere – confirms a tornado was or is on the ground.

What the TDS will give you is confirmation of a damaging tornado, and that when properly trained to know what you are looking at, this signature is as good if not better than a spotter report of a tornado. – WDTB training document

Even when the Tornado Warning was issued, in my opinion, there should have been language in the text indicating radar confirmed a tornado was – at some point – on the ground. If not in the warning text than on NWS Chat or other means of dissemination.

Additionally, after the fact when it was clear a tornado did touch down based on the debris signature, local media waited more than 2 hours for the National Weather Service to say a tornado touched down. 2 hours of storm coverage was spent pondering whether it was a tornado are whether it was a microburst. Why? If radar confirms there is a tornado on the ground why are we waiting? Just say it’s a tornado and provide details about the tornado (path length, width, intensity) after the fact.

Some people wondered if the Storm Prediction Center dropped the ball by not issuing a tornado watch prior to the Revere tornado. In my opinion they did not! This was a very localized case that was not widespread enough to warrant a watch. The Storm Prediction Center and the National Weather Service both did a nice job mentioning the potential for isolated tornadoes. The forecast 24 hours to just prior to the event was spot on. We were mentioning the potential for tornadoes here in Connecticut as well given the setup and the way things looked to us.

This isn’t the first time a Tornado Debris Signature has shown up on radar here in the northeast and wasn’t mentioned by the NWS in warnings or statements. There were 2 cases in Albany last year and a third in Pennsylvania in 2012 where TDSs were present on radar and they weren’t mentioned in statements. The killer EF-2 tornado in Madison County, NY earlier also had a tornado debris signature – yet was not even covered by a tornado warning!

The National Weather Service has invested a lot of money in fantastic technology that can help us get more timely and accurate warnings to the public. SAILS and dual polarization technology is huge! We have the technology and the science at our disposal – let’s use it!

Active Severe Weather Day Monday

An elevated risk for severe thunderstorms tomorrow is becoming a bit more clear this afternoon. Today, we had a convective shower (little/no lightning) produce a brief/weak tornado in Wolcott. Radar showed 30 knots of gate-to-gate shear at 4,000 ft AGL which is quite marginal but apparently sufficient for a tornado.

wolcott

 

Monday’s setup is much more intriguing. Around daybreak strong low level shear develops along with fairly sizable instability.

18_GFS_018_41.65,-72.65_skewt_ML

While the GFS is more muted with the amount of instability present the NAM is much more impressive. Depending on how quickly dry air advects in during the midday a second round of severe weather is possible later in the day.

All severe hazards are possible tomorrow in the strongest storms – flash flooding, large hail, damaging winds, and tornadoes. If surface based convection can develop around daybreak we will have to watch closely for tornadoes.

Tomorrow promises to be an active day – stay weather aware!

Severe Weather Likely Today

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Storms today will mean business! We’re expecting a fairly sizable severe weather event in the northeast this afternoon and while we can never say with certainty that the severe will strike our backyard – odds are pretty good we’ll get some nasty weather in Connecticut. Any storm that develops today has the potential to produce winds strong enough to take down trees and power lines and could produce a tornado or two. We’re expecting a “high impact” day of weather across the state.

500_140715_12A deep and anomalous closed low over the Great Lakes has allowed copious amounts of moisture to come north under a strengthening mid level flow on the eastern seaboard. Dew points in the low to mid 70s are common across the region. This is a climatologically favored pattern for severe weather in Connecticut – even down to the beaches.

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The morning weather balloon launch on Long Island shows a fairly unstable environment that’s loaded with moisture. There is a bit of a cap this morning for surface based convection that models show eroding by early afternoon. High resolution models develop some nasty storms in western Connecticut that move in later today. In addition, models show a spike in storm relative helicity (a way to measure the shear or turning of winds in the lower atmosphere) as the storms approach.

hrrr_ref_neng_11 (1)

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With strengthening wind fields just above the surface any storms will have to be watched closely today. Below is the 12 hour NAM forecast valid at 18z today. Note the >30 knot low level jet at 850mb that has developed from NYC to central Massachusetts. Any time the 850mb flow increases above 30 knots in a setup like this it’s worth watching closely – especially on a day like today with lifted condensation levels as low at 500 meters.

namNE_850_spd_012

 

Damaging winds at the ground, lots of lightning, flooding rains, and tornadoes are all possible today. Keep an eye to the sky – or to Twitter!

Severe Weather Likely Monday & Tuesday

There are a few kinds of severe weather setups here in Connecticut. There’s the classic high-end severe weather outbreak that is generally characterized by northwesterly flow aloft, high/extreme instability, and strong wind shear (e.g. July 1989, May 1995, May 2010). There’s the more common borderline instability/shear setup that can favor borderline “pulse” storms or weakly organized line segments. And then there’s the Monday/Tuesday setup.

namUS_500_avort_036

The warm season cut-off low can be a prolific severe weather and flooding maker. While high-end or significant severe is unlikely it’s not out of the question. I blogged a bit about this kind of setup last June and a good example of a high-end severe weather day from an anomalous cut-off in July is the 2008 New Hampshire F2.

So what’s the deal with Monday and Tuesday’s severe weather threat? The NAM and GFS both show a strengthening low level jet on Monday and several shortwaves embedded in the southwesterly flow aloft moving through. The 9z SREF shows MLCAPE around 1000 j/kg Monday afternoon.

9z SREF / Courtesy: SPC

9z SREF / Courtesy: SPC

With modest instability and strengthening low level shear low topped supercells are quite possible tomorrow. Damaging winds and tornadoes will be possible. Lifted condensation levels will be quite low as 0-1km shear ramps up – that means we’ll have to watch the radar closely!

If that weren’t enough it looks like we could do it all over again on Tuesday with another low CAPE/high shear environment. The details will come down to mesoscale details that are tough to figure out this far in advance. In addition, flash flooding is a possibility with excessive rain possible. Here’s the WPC/NCEP precipitation forecast for the next 72 hours.

d13_fill

As I like to say – beware the Upper Level Low. These cut-offs can produce pretty nasty weather in the warm season, particularly in July and August when water temperatures in the Sound and south of Long Island are near their climatological peak.

Here’s something interesting based on this morning’s NAM solution for Monday. The CIPS analog guidance looks for other days with similar synoptic setups and looks at what kind of weather was reported that day (damaging winds, tornadoes, or even snow amounts in winter). Below I’ve posted the probability from CIPS of probability >5 severe reports and also >1 tornado.

SVRall_N5_110km_nam212F036

SVRtorn_N1_110km_nam212F036

25 Years Ago – The 1989 Tornado Outbreak

There are only a few “classic” northeastern U.S. tornado outbreaks that jump out in your mind. The 1985 Pennsylvania outbreak is one, the 1998 Pennsylvania/New York outbreak is another, and so is the 1989 northeast outbreak. The epicenter of that outbreak was right here in Connecticut with an F4 tornado touchdown in Hamden and New Haven.

The atmosphere couldn’t have been more primed for a big tornado event. Here’s the morning weather balloon launch and sounding from Albany.

1989071012.72518.skewt.parc

A classic elevated mixed layer with a dry adiabatic layer from 625mb through 750mb is present. What is most striking, however, is the exceptional wind shear in the atmosphere. Winds at  500mb are out of the northwest at 80 knots while in the boundary layer winds are out of the south-southeast at 10 knots! That’s about as strong as it gets.

The presence of the “EML” allowed for significant instability to develop during the heating of the day. Prior to the tornado in Connecticut temperatures reached the low and middle 80s with dew points in excess of 70F. A quick and dirty modification of that sounding for 30/22 shows just how explosively unstable the atmosphere was.

Courtesy: Schoharie County Emergency Management

Courtesy: Schoharie County Emergency Management

The first tornado touched down in upstate New York west of Albany and was on the ground for an incredible 42 miles. That same supercell went on to produce a series of tornadoes in Connecticut. The first tornado touched down near Route 4 in Cornwall and continued south into Bantam. The second tornado touched down in Watertown and Waterbury. The most violent of the tornadoes touched down in Hamden and continued south into New Haven.

The weather charts during the event were just incredible for a northeastern U.S. tornado outbreak with a strong disturbance moving out of southern Quebec into northern New England.

071018

 

Through the day 500mb heights actually rise over southern New England with the best QG forcing displaced far to the north. Still, after the initial convective initiation in the morning those storms were able to propagate southeast into our area. The elevated mixed layer not only allowed strong instability to develop – it likely also helped keep convection relatively discrete. The atmosphere in many locations was “capped” – just enough CIN to prevent widespread convective initiation – but not capped enough to prevent all convection. The best QG forcing to the north also helped convection remain relatively scattered.

The damage in Connecticut was substantial with hundreds and hundreds of homes and businesses destroyed. Many people in the New Haven suburbs – including North Haven and North Branford were caught in the hail core of the storm with golf ball size hail or larger. Southeast of where the tornado lifted in Newhallville substantial wind damage occurred with many of the pine trees near Lake Saltonstall on the Branford/East Haven line snapped in half.

Here is some of our coverage from the 11 p.m. news on July 10, 1989 and the 6 p.m. news on July 11, 1989.

There were other tornadoes that day – some in northern Massachuetts, others just west of Danbury in Putnam County, and another swarm in northern New Jersey. If we were able to look at radar data (which sadly, we cannot) we’d probably see a line of supercells across the region.

On a personal note, the 1989 tornado event is my first weather memory as a kid. At the time I was living in Branford but on vacation with my family on Cape Cod. When I heard about the tornado back home I was devastated! I couldn’t believe that I missed “the big one” back home. I guess I’ve been a weather weenie for 25 full years now!