T-Storms Part 2 : "North and West of the city!"

[Nittany88]

Was just going back and looking at old warnings and it's apparently pretty common practice (especially in the central region) to call a storm with a TDS a "confirmed tornado" and then put the source (radar confirmed) in a subsequent line. 

 

I know they're doing the impact based stuff there... but there's no ambiguity with the fact they're using the phrase "confirmed tornado" when there's a TDS. Why the discrepancy between regions?

 

The Impact based warnings are technically still "experimental".

 

"In 2012 the NWS Central Region identified five offices to begin the impact based convective warning experimental product to better communicate threats to partners and constituents. The “Impacts-Based Warnings” demonstration was well received and the demonstration was expanded to all 38 Central Region offices in the spring of 2013. The positive feedback is supporting an expansion in the spring of 2014 to include 5 Southern Region offices, 1 in Eastern Region and 2 in Western Region."

 

http://www.weather.gov/impacts/#.U9cTvrEzNnU

 

Why? They reference a "confirmed tornado" when a spotter sees a tornado - why wouldn't you say "confirmed tornado" when radar shows one. The literature shows that a TDS "guarantees" a tornado on the ground... and the NWS own training documents say a TDS is more reliable than a spotter report of a tornado. 

 

If you say "Radar confirmed a tornado over Revere moving northeast at 25 mph" or something like that I think that gets the message across. 

 

The 2 hours of waiting for them to say it "was a tornado" is ridiculous IMO. There was no question it was a tornado by 9:35 a.m. Why wait until 11:40 to say it when radar guaranteed a tornado did in fact touchdown?

 

I think that's just the "Northeast Mentality" of fake tornadoes and wanting to see the damage first before confirming anything so it doesn't lead to false reports. Of course you're right, this was a special case.

[Tornadomachine]

65 Buildings were damaged per the mayor of Revere. 12 uninhabitable. Sure it was fairly weak and wasn't on the ground long, but you drop anything like that in a city in Metro Boston area you are going to have damage.

We don't have the same wind load codes as storm prone regions, so less wind is needed for significant damage. Plus, max winds at 120 mph is any think but weak, that's fairly strong as far as storms go. You are right on point about urban vulnerabilities, though.

[Tornadomachine]

I've seen "radar confirmed tornado" from other offices. WDTB training also says a TDS is more accurate conformation than a spotter report!

Bigger question would be why is the WDTB suffering from major funding cuts? Their advanced training has been canceled for several seasons now, and are just now upgrading to AWIPS 2. It is probable that training, or a potential lack thereof (wasn't there so I can't say for sure), was a major factor in the brouhaha.

On that note, I highly recommend everyone check out their website, much of their lessons are online, and the wealth of information available is stunning. Great place to learn all about radar interpretation for all event types.

[CoastalWx]

Our building codes are pretty good. 120mph winds that have vertical component to them will do that damage in most places. As you saw, a lot if it is roof damage. Seems typical to me.

OCMs in the area don't seem into dual pol. I've rarely heard them even mentioning or talking about it so I'm not surprised they are waiting for NWS to say something. Frankly, a lot of the morning people probably put out a quick rip n' read forecast and then go on Bloomingdales.com to buy a new dress. If it weren't for sim radar and NWS snow graphics, I don't know where they would be.

[Christina311]

It was an interesting day. I've never experienced a tornado so close to home before. It touched down about a mile from my house. And I missed it!

 

Red circle is where I am. The A pointy thing is where it touched down.

 

 

I took my time getting ready this morning to track the weather, and I was waiting for the storms to pass before taking a shower (I was paranoid about lightening coming through the pipes and being found electrocuted/naked). Around 9:15 or so it still hadn't let up so I decided to take my chances. I was already going to be late for work. I checked the radar one more time and saw a suspicious looking cell over the Needham area and it was getting really dark towards the southwest.

 

I had the fastest shower ever, during which the electricity went out and I couldn't see anymore. It was dark in my house like it was the middle of the night at a few minutes before 9:30. Then the rain and hail became really loud and seemed to be whipping the sides of my house like someone was throwing it with buckets. When I looked outside it was impossible to see anything. It was like trying to see a storm during the night. I was trying to use the lightening flashes to see the clouds.

 

I've never seen it get that dark during the day. You've all probably seen the Joplin videos, it was like that. THAT dark. Not exaggerating. That was the biggest clue to me that something significant was going on. I couldn't check the radar or get online or anything. No power and my phone wasn't getting any signal. The weather radio was still announcing severe thunderstorm and flash flood warnings.

 

In a couple of minutes it passed and the sun came out to the west. That's about the time I heard a tornado warning for Essex county (I don't think they said Suffolk county?). Still no electricity.  It wasn't until I was driving to work that I heard what happened in Revere on the radio. So close and I didn't see a thing!

 

I have no pictures except for one I took around 9:45 after it had passed.I did get some nice ones in Woburn tonight. I uploaded them to a photobucket album if anyone wants to take a look. The best ones are on the 2nd page. Cute little scud clouds and some mammatus. http://s1366.photobucket.com/user/mindspin71/library/7-28-14

 

 

 

 

[HoarfrostHubb]

Very cool experience

[HoarfrostHubb]

Any repost out of Maine? Eric posted a good damage pic

[MaineJayhawk]

This was in Limington yesterday.  About two dozen trees uprooted, houses were involved.  GYX is sending in investigators.

 

[dryslot]

Lol. Where can I get one of them tornado inducing radars?

 

I thought those are the ones you install.............lol

[dryslot]

There are reports it was a funnel, But not confirmed in Limington

[kevin1927]

Epic day yesterday. Glad there were no serious injuries/fatalities. My house was literally a couple hundred yards from the tornado path. I live right along the Revere/Chelsea border and Revere Beach Parkway where it started. The damage I saw on Revere Beach Parkway was stunning. Never thought I would ever see anything like that here.

 

 

I posted this picture yesterday. That metal piece in the picture I believe is actually a piece of the roof from the Cronin ice skating rink right across the highway.

[eekuasepinniW]

That tree on the right aint even mad.

[kevin1927]

That tree on the right aint even mad.

I know right. The house next to it has it's roof torn off, and the tree is completely fine. haha.

[MarkO]

Is there an email address we can send photos to Taunton?

[CoastalWx]

I'm still amazed  mets are just throwing fake pics of this tornado on air.

[bobbutts]

Our building codes are pretty good. 120mph winds that have vertical component to them will do that damage in most places. As you saw, a lot if it is roof damage. Seems typical to me.

OCMs in the area don't seem into dual pol. I've rarely heard them even mentioning or talking about it so I'm not surprised they are waiting for NWS to say something. Frankly, a lot of the morning people probably put out a quick rip n' read forecast and then go on Bloomingdales.com to buy a new dress. If it weren't for sim radar and NWS snow graphics, I don't know where they would be.

120mph must be close the limit for stick built houses even with good codes?  With tornadoes I think you can withstand a bit higher vs. hurricane due to the short duration of the event.  From going through Charlie in FL there was near complete damage to stick homes that had top winds in the same range, and I assume also strong building codes.

[CoastalWx]

120mph must be close the limit for stick built houses even with good codes?  With tornadoes I think you can withstand a bit higher vs. hurricane due to the short duration of the event.  From going through Charlie in FL there was near complete damage to stick homes that had top winds in the same range, and I assume also strong building codes.

 

You might be right. However, even an EF0 could overturn a car. Tornadoes have a motion in the vertical too, so when you combine the motion of the winds...it can turn a weak tornado into something that normal horizontal winds could not do. 

[OceanStWx]

Was just going back and looking at old warnings and it's apparently pretty common practice (especially in the central region) to call a storm with a TDS a "confirmed tornado" and then put the source (radar confirmed) in a subsequent line. 

 

I know they're doing the impact based stuff there... but there's no ambiguity with the fact they're using the phrase "confirmed tornado" when there's a TDS. Why the discrepancy between regions?

 

Ha. This is probably a pretty minor example.

 

As we discussed yesterday, the key to using the dual-pol data is that we need to be clear it is radar confirmed and also that a tornado HAS occurred, not necessarily IS occurring.

[CT Rain]

How did TBOS look yesterday with Revere? I didn't pull up the TDWR and can't get it from NCDC yet. 

[CT Rain]

Ha. This is probably a pretty minor example.

 

As we discussed yesterday, the key to using the dual-pol data is that we need to be clear it is radar confirmed and also that a tornado HAS occurred, not necessarily IS occurring.

 

Yeah - unless some WFOs have a policy against using the term "confirmed tornado" for a TDS. I'm not sure if any do - you would know better than me. 

[weathafella]

How did BOS get 0.11 while storrow drive was flooded and closed?...lol

[CoastalWx]

How did BOS get 0.11 while storrow drive was flooded and closed?...lol

 

Very sharp cutoff...lol. 

[OceanStWx]

Yeah - unless some WFOs have a policy against using the term "confirmed tornado" for a TDS. I'm not sure if any do - you would know better than me. 

 

Certainly not local policy here. I would support using the TDS terminology in a warning.

 

Anything that provides added confirmation I think is valuable to getting the right public reaction. I mean we would update a warning based on a spotter report, how is a TDS any different really? There is no other known phenomenon that produces that signature besides a tornado.

[radarman]

Certainly not local policy here. I would support using the TDS terminology in a warning.

 

Anything that provides added confirmation I think is valuable to getting the right public reaction. I mean we would update a warning based on a spotter report, how is a TDS any different really? There is no other known phenomenon that produces that signature besides a tornado.

 

A very large hail core can produce CC values on par with a weak debris sig, but of course you wouldn't expect that to be collocated with a strong velocity couplet and also you would expect a wider swath of small hail signature, yielding a smoother gradient than a true TDS.  The only possible exception I could see would be in the rare case of an embedded weak tornado in a fast moving MCS, where the base velocity signature was muted by mean storm motion and hail cores spread throughout making physical analysis more difficult (ie. not obviously situated in a supercell FFD or something).  Regardless, I agree the trained radar op should be able to say 99/100 times that a TDS=tornado.

 

At shorter wavelengths it can be a bit harder due to differential attenuation and often lower power.  In this case a BWER could potentially appear similar to TDS, though it wouldn't guarantee a touch down...

[OceanStWx]

A very large hail core can produce CC values on par with a weak debris sig, but of course you wouldn't expect that to be collocated with a strong velocity couplet and also you would expect a wider swath of small hail signature, yielding a smoother gradient than a true TDS.  The only possible exception I could see would be in the rare case of an embedded weak tornado in a fast moving MCS, where the base velocity signature was muted by mean storm motion and hail cores spread throughout making physical analysis more difficult (ie. not obviously situated in a supercell FFD or something).  Regardless, I agree the trained radar op should be able to say 99/100 times that a TDS=tornado.

 

At shorter wavelengths it can be a bit harder due to differential attenuation and often lower power.  In this case a BWER could potentially appear similar to TDS, though it wouldn't guarantee a touch down...

 

Right. And of course there is the fast storm motions issue at times as well. Because of how the dual-pol scans are done, the TDS could actually show up upstream of the velocity couplet (for those not in the know our radar scans reflectivity and dual-pol first, velocity second on consecutive "sweeps" then moves up to the next tilt).

[CT Rain]

A very large hail core can produce CC values on par with a weak debris sig, but of course you wouldn't expect that to be collocated with a strong velocity couplet and also you would expect a wider swath of small hail signature, yielding a smoother gradient than a true TDS.  The only possible exception I could see would be in the rare case of an embedded weak tornado in a fast moving MCS, where the base velocity signature was muted by mean storm motion and hail cores spread throughout making physical analysis more difficult (ie. not obviously situated in a supercell FFD or something).  Regardless, I agree the trained radar op should be able to say 99/100 times that a TDS=tornado.

 

At shorter wavelengths it can be a bit harder due to differential attenuation and often lower power.  In this case a BWER could potentially appear similar to TDS, though it wouldn't guarantee a touch down...

 

Out of the hundreds and hundreds of TDSs observed I think there's been 1 false alarm (in Georgia, I believe?). That certainly is a better track record than spotter reports of tornadoes!

[OceanStWx]

Out of the hundreds and hundreds of TDSs observed I think there's been 1 false alarm (in Georgia, I believe?). That certainly is a better track record than spotter reports of tornadoes!

 

And I believe that was a case of being too eager to use the TDS and it was actually inflow reducing the CC.

[CT Rain]

And I believe that was a case of being too eager to use the TDS and it was actually inflow reducing the CC.

 

The fast moving QLCS TDS case can be caught by anticipating the TDS to be a bit ahead of the velocity sig. If you're expecting 50+ knot storm motions it seems like you could easily account for that for confirming the presence of a TDS.

[radarman]

Kumjian, Rhyzhkov, Melnikov, and Shuur, 2010, have a paper published in Monthly Weather Review found here:

https://sites.google.com/site/matthewkumjian/pdf/2010_MWR_rapid.pdf?attredirects=0

 

There's quite a bit of dual pol analysis of a non-tornadic supercell.  Figure 16 in particular is a good example of the rare case where a TDS could be misidentified by a non-expert.  There is a CC drop only somewhat displaced from the region you might expect a tornado, which they attribute to non-uniform beam filling combined with differential attenuation even at S band.   

 

That said, I agree with Ryan that a TDS is as good as anything else to 'confirm' a tornado.

[kevin1927]

Was surprised driving around seeing all the downed trees/limbs up and down broadway Revere and some of the streets near Revere High School. The tornado basically just took a path straight up broadway. The worst damage I saw though was Revere Beach Parkway near Chelsea. The city did a great job cleaning up that area since yesterday when it looked like a war zone.