Another New York Tornado Debris Signature

An EF-1 tornado in North Chemung, NY touched down last week on September 2. According to a Public Information Statement from the National Weather Service in Binghamton, NY the tornado was on the ground for 6 miles and felled numerous trees and also produced some roof and siding damage to a few homes. Additionally, a pickup truck was picked up and moved 6 feet by the strong winds. This is how the storm looked on radar shortly after touchdown.

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The QLCS (quasi-linear convective system) contained a somewhat unimpressive couplet (rotation) through the tornado’s life. While occasionally exceeding 50 knots of gate-to-gate Delta-V it was generally not particularly intense.

What is impressive is that for 10 minutes – this tornado produced a clear tornado debris signature on radar. You can see in the above image near North Chemung depressed correlation coefficient and near-zero ZDR – all coincident with an area of rotation and sufficiently high Z (reflectivity).

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The tornado debris signature on radar appeared from 2309 UTC and disappeared by 2323 UTC. It was on the lowest elevation slice and the debris reached a height of 6,000 ft AGL at one point. What is so concerning about this is that the signature was completely missed by the National Weather Service. No tornado warning was issued for Chemung County, NY.

The Severe Thunderstorm Warning in effect for Chemung County contained no mention of possible tornadoes, no enhanced wording about more extreme wind damage, and in fact was a fairly boilerplate warning for a large geographic area including parts of 6 counties.

This isn’t the first time the NWS has “missed” a tornado debris signature which is, in fact, confirmation of a tornado touchdown. The Revere tornado this July is one example and Lancaster County PA in 2012. Both of these examples are tornadoes that occurred with no warning. Other tornadoes in the northeastern U.S. that were covered by tornado warnings have occurred with no mention of tornado confirmation by the TDS in statements (May 2013 near Albany). Earlier this year – the NWS in Albany did mention a TDS which is the first mention, to my knowledge, in this area.

Given how many tornado signatures on radar in the northeast are fairly “borderline” – dual pol and tornado debris signatures can provide the information needed to pull the trigger. Even weak tornadoes a fair distance from the radar site have produced debris signatures around here!

While a TDS can’t provide lead time for the initial touchdown it can certainly give lead time to people living farther down a tornado’s path. If it’s a training issue or something like that within the NWS – we need to fix it! I also implore television meteorologists to become more comfortable interpreting dual pol products. It is certainly possible now to give viewers a “confirmation” of a tornado without someone actually having to see it. Extra urgency in coverage with specific mention of debris being lofted by a tornado can help get people to safety. Being able to explain “what” a TDS is is now just as important as explaining what rotation means on radar to viewers – particularly in New England where tornadoes are relatively infrequent.

We have another weapon in our meteorological arsenal – let’s use it and use it well! We should educate the public about what radar indicated/radar confirmed means. We should be very clear and unambiguous about what a TDS means and we should get the word out as soon as possible. If it can’t make it into a NWS statement in a timely – put it out on NWS Chat! If some meteorologists at the NWS aren’t using dual pol products during severe weather operations – they need to start and start now!

The lack of a warning west of Binghamton last week with evidence of a confirmed tornado available via radar is completely unacceptable. We can do better and I’m sure we will.

A Snowy Winter? Quite Possibly!

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With weeks and weeks of weather boredom we were talking in the weather center yesterday about the Blizzard of 2013. Our thundersnow reminiscing during August is a clear sign that we need some weather excitement in our lives!

Naturally, one has to wonder what the upcoming winter season will bring to Connecticut. If you love winter cold and snow you may be in luck! Of course, all 6-month forecast caveats (and there are many) apply here. 

The main driver of the global circulation is frequently the El Nino-Southern Oscillation. Locally, there is a correlation between ENSO state and the amount of snow we get in a winter. Generally, a strong La Nina or very strong El Nino is bad for snow-lovers. A weak/moderate El Nino is generally most favorable for a snowier than average winter. 

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Presently, above normal sea surface temperatures are present in the equatorial Pacific and the Climate Prediction Center gives El Nino a 2 out of 3 chance for developing by early winter. Additionally, they say a strong El Nino is unlikely. That’s good news!

At least for the time being, a warm pool of water in the Gulf of Alaska is also present. If this can have some staying power a -EPO is favored which can really help deliver the cold (EPO is a better predictor of temperature in southern New England than the famous NAO). This can certainly change quickly but at least for now it’s a welcome sign. 

Of course, a lot can change. Long range forecasting is exceptionally challenging and can be wildly inaccurate. That said, there is some skill (i.e. better than chance/climatology) in picking out global signals that have a correlation to local weather variables (seasonal snowfall, precipitation, temperature, etc.).  We’re only a few months away from waxing our skis and heading north – let’s cross our fingers for a big winter! 

 

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.

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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.

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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.

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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!