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Sunday's Screaming Southeaster


CT Rain

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Just now, powderfreak said:

I still don't understand that with those 925mb winds.  

Its hard to mix it down on the southerly component. The best LLJ also was a little east and some of those enhanced mesolows may have stole a little thunder from areas further west. I know we had mentioned it as a possibility...that if we got a little mesolow out east that to the west of it back in the interior could underperform a little.

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6 minutes ago, powderfreak said:

I still don't understand that with those 925mb winds.  

Well it's possible 925mb was also located higher up vertically. IOW, the slope of the 925mb pressure surface might be 2500' above Boston. but could be a few hundred feet higher over ORH. Why? Because SE winds upslope. It may be tough to visualize, but this can cause the pressure surface to extend up a little higher than, say, the coast. It's the reason why ORH can upslope on erly flow. You sort of push up the boundary layer a tad when you do this. But naturally winds are stronger the higher up you go, so KORH has a much better shot of those stronger winds, then downtown ORH.

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Just now, ORH_wxman said:

Its hard to mix it down on the southerly component. The best LLJ also was a little east and some of those enhanced mesolows may have stole a little thunder from areas further west. I know we had mentioned it as a possibility...that if we got a little mesolow out east that to the west of it back in the interior could underperform a little.

Yeah ORH was probably a tad too far west for that core too. 

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Just now, Cold Miser said:

Maybe someone with better weather knowledge than myself (which is everyone on this forum) can tell me the significance  (if at all) of the 130 a.m. time frame.  that seems to.be when the wind gusts were peaking and man trees went down.

That's about when the core of the Man Jet went over your hood.

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44 minutes ago, CoastalWx said:

Well it's possible 925mb was also located higher up vertically. IOW, the slope of the 925mb pressure surface might be 2500' above Boston. but could be a few hundred feet higher over ORH. Why? Because SE winds upslope. It may be tough to visualize, but this can cause the pressure surface to extend up a little higher than, say, the coast. It's the reason why ORH can upslope on erly flow. You sort of push up the boundary layer a tad when you do this. But naturally winds are stronger the higher up you go, so KORH has a much better shot of those stronger winds, then downtown ORH.

Oh I totally get it and know it well...great explanation.  That's what happens in Stowe on the east side.  We never get wind out of the southeast, because the low level jet is rising up and over us to clear Mansfield a few miles west (it's always dead calm even with a 60+kt jet at 900mb).  Then the western slopes get it as it drops over the ridge and heads down to a lower elevation on the other side.

Thats why I'm still shocked at what happened.  10/10 times I would've forecast the winds would be 1500-2000ft and above due to that upslope flow coming up the east slope.  There's no reason why it should've been crashing down into the slope instead of rising up and over it.

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21 minutes ago, powderfreak said:

Oh I totally get it and know it well...great explanation.  That's what happens in Stowe on the east side.  We never get wind out of the southeast, because the low level jet is rising up and over us to clear Mansfield a few miles west (it's always dead calm even with a 60+kt jet at 900mb).  Then the western slopes get it as it drops over the ridge and heads down to a lower elevation on the other side.

Thats why I'm still shocked at what happened.  10/10 times I would've forecast the winds would be 1500-2000ft and above due to that upslope flow coming up the east slope.  There's no reason why it should've been crashing down into the slope instead of rising up and over it.

I think perhaps the strength of the LLJ and perhaps the thermodynamics of the boundary layer allowed for the hydraulic jump to be near the east side of Mansfield. If you think of it, this was still an October event. You lack the low level cold hanging around and keeping the LLJ aloft over the picnic tables like you have in winter...when we normally have these events with crazy LLJs. We had a 5SD event occur and it occurred in October. I have to think the thermal profile played a role here. 

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5 minutes ago, CoastalWx said:

I think perhaps the strength of the LLJ and perhaps the thermodynamics of the boundary layer allowed for the hydraulic jump to be near the east side of Mansfield. If you think of it, this was still an October event. You lack the low level cold hanging around and keeping the LLJ aloft over the picnic tables like you have in winter...when we normally have these events with crazy LLJs. We had a 5SD event occur and it occurred in October. I have to think the thermal profile played a role here. 

Yeah I was also looking at when the primary Low over NY was bombing out and tracking.  Given the track and strength, we were in a favorable east side (of the low) location.  I don't know how that meso-low in ESNE factored in but the track of the primary low over the Adirondacks in hindsight looks good here.

Also interesting that strong low plowed right over the Catskills and through the high terrain of the Adirondacks on reanalysis.... so for all those times someone says it won't track over mountains, chalk this one up to that being wrong.  

Another factor here was probably the dry slot between the best forcing.  I mean we got 2" instead of 4-7" further east.  You had lift going through EMass up into NH/ME...and then strong lift on the west side of the main low in NY State.  In the middle we were more "showery" and almost cellular in nature.  I wonder if those splitting areas of lift that left a drier (weird to say 2" is a dryslot lol) area in central/northern VT allowed for better wind to mix down.  Maybe that's why SVT didn't really see much wind damage despite favorable downslope plus other areas where folks live in high terrain at 950mb.

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1 minute ago, powderfreak said:

Yeah I was also looking at when the primary Low over NY was bombing out and tracking.  Given the track and strength, we were in a favorable east side (of the low) location.  I don't know how that meso-low in ESNE factored in but the track of the primary low over the Adirondacks in hindsight looks good here.

Also interesting that strong low plowed right over the Catskills and through the high terrain of the Adirondacks on reanalysis.... so for all those times someone says it won't track over mountains, chalk this one up to that being wrong.  

Another factor here was probably the dry slot between the best forcing.  I mean we got 2" instead of 4-7" further east.  You had lift going through EMass up into NH/ME...and then strong lift on the west side of the main low in NY State.  In the middle we were more "showery" and almost cellular in nature.  I wonder if those splitting areas of lift that left a drier (weird to say 2" is a dryslot lol) area in central/northern VT allowed for better wind to mix down.  Maybe that's why SVT didn't really see much wind damage despite favorable downslope plus other areas where folks live in high terrain at 950mb.

It might help. Precip can help keep the boundary layer stable. Sometimes the smallest nuances in atmospheric profiles mean the difference of 20mph or 60+. Like, you normally really come close to getting a blown down like you did...only the lower levels were a a degree too cold too allow mixing. All it takes is a little improvement and boom...you go from 0-60 real quick. It's never linear...it either happens or it doesn't. 

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19 minutes ago, Cold Miser said:

 

Makes sense.  Was quite manly indeed.

Tropfold at the time too, going to pour over velocity data to look if there was a possible low topped spinner too, just saw some tops of trees zipped from our observation Tower.Looking way in the distance towards 201 in North Stonington. They got smoked up there

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