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cold pool hailers 7/1/2015?


weatherwiz

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A rather strong s/w will be moving through southern Canada in association with a deep trough which will slide through New England.  The s/w and digging trough will allow for rather anomalously cold 500mb temperatures to overspread the region with the GFS projecting 500mb temperatures in the -12C to -14C range.  The cold mid-level temperatures should yield to some fairly steep mid-level lapse rates perhaps on order of 6.5-7 C/KM.  With such a strong s/w and trough, winds aloft should be quite strong as well, perhaps pushing 30-35 knots around 700mb and upwards of 50 knots at 500mb.  

 

Down at the surface, depending on degree of heating, surface temperatures may climb into the lower 80's with surface dewpoints in the mid tp perhaps even upper 60's which is actually pretty decent in these type of setups.  

 

Depending on timing of the s/w and attendant cold front which will be associated with the trough, the potential would exist for numerous showers and t'storms to develop during peak heating hours.  Given the degree of cold air aloft and potential for modest instability, any t'storm would have the potential to produce hail.  

 

We'll see how this transpires over the upcoming days but cold pool aloft setups are among my favorites and they can have a tendency to overproduce.  

 

 

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The NAM now just getting into range but it's definitely not as anomalous with the cold associated with the trough as it digs in at 500mb.  The NAM barely gets 500mb temps at -10C.  the GFS, on the other hand, continues to show 500mb temps as cold as -12C to -14C but as of the 6z run the core of the colder temps don't arrive until early evening Thursday.  Fortunately with these cold pool setups loss of daytime heating isn't much of a killer b/c cooling temps in the mid-levels can allow for instability to remain or slightly increase even after sunset.  

 

One thing I find intriguing though are modeled dewpoints...mid to upper 60's.  Not too often do we see dews that high in these setups...typically we see them more right around 60F and if we're lucky into the lower 60's

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The NAM now just getting into range but it's definitely not as anomalous with the cold associated with the trough as it digs in at 500mb.  The NAM barely gets 500mb temps at -10C.  the GFS, on the other hand, continues to show 500mb temps as cold as -12C to -14C but as of the 6z run the core of the colder temps don't arrive until early evening Thursday.  Fortunately with these cold pool setups loss of daytime heating isn't much of a killer b/c cooling temps in the mid-levels can allow for instability to remain or slightly increase even after sunset.  

 

One thing I find intriguing though are modeled dewpoints...mid to upper 60's.  Not too often do we see dews that high in these setups...typically we see them more right around 60F and if we're lucky into the lower 60's

 

Not a bad assessment of the set up. SREF SPC calibrated severe probabilities showing some potential, especially farther south closer to the better instability. Oftentimes you can think of this product as akin to an outlook graphic, where 15% corresponds to slight risk and so on.

post-44-0-57819800-1435508574_thumb.gif

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Not a bad assessment of the set up. SREF SPC calibrated severe probabilities showing some potential, especially farther south closer to the better instability. Oftentimes you can think of this product as akin to an outlook graphic, where 15% corresponds to slight risk and so on.

attachicon.gifSREF_24HR_SVR_PROBS__f084.gif

 

Sometimes it seems the SPC outlooks pretty much exactly mirror this graphic lol.  

 

With these setups I feel the best chance for stronger storms is in fact not in the area of max instability.  Max instability in these instances is usually displaced further from the "cold core" aloft so you're likely getting higher dews and sfc temps the further south you go.  However, further north you get your instability from the steep lapse rates in place.  

 

That's why this setup is quite intriguing to me...seeing dews well into the mid to upper 60's even inside the core of coldest temps aloft.  

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Sometimes it seems the SPC outlooks pretty much exactly mirror this graphic lol.  

 

With these setups I feel the best chance for stronger storms is in fact not in the area of max instability.  Max instability in these instances is usually displaced further from the "cold core" aloft so you're likely getting higher dews and sfc temps the further south you go.  However, further north you get your instability from the steep lapse rates in place.  

 

That's why this setup is quite intriguing to me...seeing dews well into the mid to upper 60's even inside the core of coldest temps aloft.  

 

Well modeled low level moisture is pretty poor, so there are pretty big instability error bars.

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Well modeled low level moisture is pretty poor, so there are pretty big instability error bars.

 

yeah that's true.  

 

I just noticed something...was looking at the 18z GFS it has some pretty decent height falls through much of the afternoon but between 21z and 0z heights actually begin to rise.  Is this b/c of the way the trough begins to lift somewhat as it moves through SE Canada which would allow for heights to pump back up a bit?

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yeah that's true.  

 

I just noticed something...was looking at the 18z GFS it has some pretty decent height falls through much of the afternoon but between 21z and 0z heights actually begin to rise.  Is this b/c of the way the trough begins to lift somewhat as it moves through SE Canada which would allow for heights to pump back up a bit?

 

It looks like there is some shortwave ridging ahead of it. Looks like the best vorticity advection is into Canada, leaves SNE in the WAA and heights rebound a little.

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It looks like there is some shortwave ridging ahead of it. Looks like the best vorticity advection is into Canada, leaves SNE in the WAA and heights rebound a little.

 

something to definitely watch over the next few days.  Luckily though conditions do appear favorable for some activity earlier on.  Still have to see about timing though...timing in these cases can really slow down

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I mean we have plenty of shear, so it's a question (on Wednesday now) if we can get in some decent lapse rates. NAM doesn't even consider this an event, but the Euro and GFS at least have marginal lapse rates to work with.

 

Yeah the GFS manages ~6.5 C/km - not bad. Shear is pretty good as that LLJ begins to crank as well. 

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I was gonna ask if you felt better after the last severe threat produced, but um...yeah...

That was one event. Besides that we haven't really had anything...CNE and NNE has had the brunt of the activity and that's not saying much.

We can't even sniff a threat...it's like these added risk categories jinxed us

Going to the bar for a few $1.50 beers then going home and sleeping and working tomorrow

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