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Aug 8th-10th Severe Wx


free_man

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The one thing too about the SPC which JoeD has mentioned, especially on twitter is that the SPC deals with more higher end severe weather events and outbreaks while setups like what we have here are typically handled more by local forecast offices so you typically won't see the SPC really crazy for these types of setups.

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The one thing too about the SPC which JoeD has mentioned, especially on twitter is that the SPC deals with more higher end severe weather events and outbreaks while setups like what we have here are typically handled more by local forecast offices so you typically won't see the SPC really crazy for these types of setups.

well it's also areal coverage too. 

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Oh definitely... QLCSs are a nightmare for warning operations. This one was sort of interesting in that you had one relatively long lasting embedded supercell (with a TDS and TS for about 30 minutes from what I saw) that was unwarned... with at times a delta v of nearly 90 knots. 

 

I've seen a lot of cases where much weaker embedded vorticies are warned like the forecaster is handing out candy at halloween so it's a real tough balance... I'm not sure what the answer is because you're right the strongly worded SVR should be sufficient. 

 

 

And that's the rub really, you can't avoid issuing the TOR because what if it ends up being a sustained TVS? Can you really feel comfortable waiting for the next volume scan when a tornado could be on the ground? I wouldn't.

 

 

Not that it's a controversial statement but I agree that QLCS' are extremely difficult to warn on.  Our best example in Oklahoma was April 2nd 2010...  What appeared to be an ordinary looking early morning squall line very quickly changed characteristics and produced highly damaging winds. (>75 kts)  Check out the differences in appearance in a 3 minute stretch:

 

 

 

And to make matters worse, look at the differences in reflectivity with height:

 

 

The top image is only 1700 feet OTG and the bottom 1200'.  What's clearly a BWER at 1200' is barely distinguishable at only 1700'.  And this was extremely close to the radar which was fortunate, but in general these will be sampled much higher.   I will say the velocity sig is more evenly distributed at least in the lowest kilometer.  But because the storm motion greatly affects the couplet in base velocity, to issue a TOR it really helps to have an indication of rotation in the reflectivity and to look at SRV of course. 

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The NAM is on crack - it's blowing up that LLJ out of nowhere. 

Certainly much more amped up than the GFS, despite the two models looking similar overall with the upper air pattern. Will still be interesting to see how the 12z GFS handles it.

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Certainly much more amped up than the GFS, despite the two models looking similar overall with the upper air pattern. Will still be interesting to see how the 12z GFS handles it.

 

Yeah obviously the NAM has some serious convective feedback going on. 

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Yeah obviously the NAM has some serious convective feedback going on. 

Looks like it, with the model continuously blowing up a 3hr precip max of over 1" for several runs now, while several of even the SREF members show much lighter amounts. Obviously the Euro and GFS are also showing much lower precipitation amounts.

 

EDIT: The 12z GFS looks a little more impressive, but still nothing as crazy as the NAM.

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From BOX:
FEEL ANY THUNDERSTORMS WILL CONTAIN A HEAVY RAIN AND GUSTY TO DAMAGING WIND  
THREAT. COULD SEE ROTATION WITH STORMS AND THE POTENTIAL FOR A BRIEF  
SPIN-UP MAY NEED TO BE MONITORED. FEEL ACTIVITY WILL GET INTO  
WESTERN AND CENTRAL PORTIONS OF NEW ENGLAND LATER THIS AFTERNOON  
AND INTO THE EVENING HOURS.  

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From BOX:

FEEL ANY THUNDERSTORMS WILL CONTAIN A HEAVY RAIN AND GUSTY TO DAMAGING WIND  

THREAT. COULD SEE ROTATION WITH STORMS AND THE POTENTIAL FOR A BRIEF  

SPIN-UP MAY NEED TO BE MONITORED. FEEL ACTIVITY WILL GET INTO  

WESTERN AND CENTRAL PORTIONS OF NEW ENGLAND LATER THIS AFTERNOON  

AND INTO THE EVENING HOURS.  

 

Is there a disconnect between SPC and BOX ?    This kind of wordage might lend to a "Slight" at least.

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Is there a disconnect between SPC and BOX ?    This kind of wordage might lend to a "Slight" at least.

 

I think any coverage will be pretty limited though. There is an area with enlongated hodographs this afternoon and early evening across N CT and W MA. Certainly worth watching if any mesocyclones can spin on up.

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I think any coverage will be pretty limited though. There is an area with enlongated hodographs this afternoon and early evening across N CT and W MA. Certainly worth watching if any mesocyclones can spin on up.

 

And I wonder if that stripe is just normally there for SW gradients.  Seems the wind needs to bend around oriographic features out that way, anyway -- but you'd know more about that local-studies out that way

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6 inch amounts for all?

 

Oh I didn't even look at QPF - but the setup would give Wiz a heart attack. 

 

Looks like the NAM is generating a convectively induced LLJ that just rips across SNE. That would be a pretty significant tornado threat if it verified but I'm not counting on it lol. 

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Oh I didn't even look at QPF - but the setup would give Wiz a heart attack. 

 

Looks like the NAM is generating a convectively induced LLJ that just rips across SNE. That would be a pretty significant tornado threat if it verified but I'm not counting on it lol. 

 

The SPC WRF generates a lot of morning QPF. Not sure how believable it is, but I wonder of its LLJ induced. If that were to happen..would be interesting for sure...but it seems too bullish.

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Oh I didn't even look at QPF - but the setup would give Wiz a heart attack. 

 

Looks like the NAM is generating a convectively induced LLJ that just rips across SNE. That would be a pretty significant tornado threat if it verified but I'm not counting on it lol. 

 

Gotta love the NAM, lol.

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Oh I didn't even look at QPF - but the setup would give Wiz a heart attack. 

 

Looks like the NAM is generating a convectively induced LLJ that just rips across SNE. That would be a pretty significant tornado threat if it verified but I'm not counting on it lol. 

 

I agree.  I wrote about this earlier that I thought the whole evolution might be a bit fed-back.  Usually MCS/convection doesn't force the synoptic hand - so to speak - at it "seems" that's what the NAM is trying to do.  

 

But wow -- what a sick short duration flood thread that would be for SE NY through western MA and SW NH, to go along with the other.

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