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Gentle, nurturing showers discussion


Damage In Tolland

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I would guess the best chance is SW too. Maybe NY and PA..points SW? But it could clip western areas.

yeah seems that way right now. certainly hints at stuff coming over the top on all the op runs...but not much reason to suggest it will be NE of where they place it right now...we'd usually adjust SW anyhow. 

 

suppose there's plenty of time for the overall ridge to shift further east...but looks pretty stable out there

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** POSSIBLE SIGNIFICANT WEATHER EVENT for NE USA *** 

There are some strong signs that there COULD be.. COULD BE.. a derecho event on August 28 running from MI / eastern Great lakes and into Northeast US -- PA NY NJ and New England... 

at this this time the pattern does NOT ... NOT ... NOT support a derecho event for MD DEL WVA VA 

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** POSSIBLE SIGNIFICANT WEATHER EVENT for NE USA *** 

There are some strong signs that there COULD be.. COULD BE.. a derecho event on August 28 running from MI / eastern Great lakes and into Northeast US -- PA NY NJ and New England... 

at this this time the pattern does NOT ... NOT ... NOT support a derecho event for MD DEL WVA VA 

LOL at this. strong signs that there COULD be COULD BE. talk about giving yourself an out. 

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Lance Bosart gave the keynote at VU's conference this Spring.  It was about the predictability of derechoes, using June 31, 2012 as the primary example.  Short version: there is no predictability.  Even in a "ring of fire" pattern, the chances of a dreceho (not an MCS, but a full-fledged derecho) increase from something like 2% to 5% (not that these are the actual numbers, but the idea he put forth was that even when chances double, they're still very low).  There isn't really a "classic derecho day" like there is a "classic tornado day" since the set-ups that do tend to produce derechoes are just null cases more frequently than the set-ups that tend to produce tornadoes are.  This is why you usually see SPC blanketing areas in a 5% or a low-end SLGT in such a pattern and only increasing probs when there's a very clear signal (like on June 12, 2013 - the Chicago High Risk day).

 

tl;dr version: Hyping about derechoes seven days out is ridiculous.

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Does the Euro support the GFS derecho scenario?

The Euro looks similar with timing, but isn't as impressive. The GFS develops a low over the eastern Great Lakes and drops that SE. The Euro keeps most of the energy to the north, but could probably still support some sort of MCS on Wednesday.

 

Edit: 12z GFS keeps any sort of MCS SW of New England, FWIW.

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Lance Bosart gave the keynote at VU's conference this Spring.  It was about the predictability of derechoes, using June 31, 2012 as the primary example.  Short version: there is no predictability.  Even in a "ring of fire" pattern, the chances of a dreceho (not an MCS, but a full-fledged derecho) increase from something like 2% to 5% (not that these are the actual numbers, but the idea he put forth was that even when chances double, they're still very low).  There isn't really a "classic derecho day" like there is a "classic tornado day" since the set-ups that do tend to produce derechoes are just null cases more frequently than the set-ups that tend to produce tornadoes are.  This is why you usually see SPC blanketing areas in a 5% or a low-end SLGT in such a pattern and only increasing probs when there's a very clear signal (like on June 12, 2013 - the Chicago High Risk day).

 

tl;dr version: Hyping about derechoes seven days out is ridiculous.

 

 

Ah wait a second there.   If this (bold) statement is just a dramatic paraphrase of his overall conclusion, that's one thing, but to say there is no predictability is not really true.  

 

Recognizing the patterns that produce Derechos is half the battle and giant leap in positive predictability, over having no clue at all what environmental parameters need to at least be in place for them to thrive.   I can see/imagine a lecture where one says the details of the derecho impact are far less determinable, and I would agree.  But I specifically recall 7 to 10 days prior to the June 2012 event posting that the pattern was conducive to them; other Mets did as well, and viola.  It was not unpredictable in that case.  

 

I think what DT is keying on is such pattern recognition, and I agree. I posted this 2 days ago myself, and Scott (another Met on the board has also given mention).  Whenever you have +2SD heat anomaly situated W/SW of a NW flow aloft, and your location is close to the ridge rim/kissing the westerlies, you are at risk for experiencing them, and that is inherently better than no predictability, at all.  

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Ah wait a second there.   If this (bold) statement is just a dramatic paraphrase of his overall conclusion, that's one thing, but to say there is no predictability is not really true.  

 

Recognizing the patterns that produce Derechos is half the battle and giant leap in positive predictability, over having no clue at all what environmental parameters need to at least be in place for them to thrive.   I can see/imagine a lecture where one says the details of the derecho impact are far less determinable, and I would agree.  But I specifically recall 7 to 10 days prior to the June 2012 event posting that the pattern was conducive to them; other Mets did as well, and viola.  It was not unpredictable in that case.  

 

I think what DT is keying on is such pattern recognition, and I agree. I posted this 2 days ago myself, and Scott (another Met on the board has also given mention).  Whenever you have +2SD heat anomaly situated W/SW of a NW flow aloft, and your location is close to the ridge rim/kissing the westerlies, you are at risk for experiencing them, and that is inherently better than no predictability, at all.  

 

What you said is pretty much what he said, only perhaps not quite as optimistically.  I apologize if I characterized it wrongly. 

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Ah wait a second there.   If this (bold) statement is just a dramatic paraphrase of his overall conclusion, that's one thing, but to say there is no predictability is not really true.  

 

Recognizing the patterns that produce Derechos is half the battle and giant leap in positive predictability, over having no clue at all what environmental parameters need to at least be in place for them to thrive.   I can see/imagine a lecture where one says the details of the derecho impact are far less determinable, and I would agree.  But I specifically recall 7 to 10 days prior to the June 2012 event posting that the pattern was conducive to them; other Mets did as well, and viola.  It was not unpredictable in that case.  

 

I think what DT is keying on is such pattern recognition, and I agree. I posted this 2 days ago myself, and Scott (another Met on the board has also given mention).  Whenever you have +2SD heat anomaly situated W/SW of a NW flow aloft, and your location is close to the ridge rim/kissing the westerlies, you are at risk for experiencing them, and that is inherently better than no predictability, at all.  

 

I think it's just simply there is no predictability when it comes to determining whether that set up produces a derecho or an MCS (severe or otherwise).

 

We shouldn't overstate June 2012 either. Pattern recognition was good, as were the forecasts, but maybe there was a little confirmation bias because a derecho did happen. What about all those forecast for a conducive pattern that produce nothing? People forget those but remember the big correct one in 2012.

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While some severe weather threats may certainly exist at some point if we are able to get into the better heat/humidity and steeper lapse rates but I don't think the GFS looks impressive at all for the end of next week.  While we are in the NW flow aloft thanks to being just east of the ridge axis, the stronger pressure gradient exist across the northern Plains into southern Canada so the stronger atmospheric flow is located there.  Eventually though those stronger winds may continue rotating across the crest of the ridge and spill into the region.  

 

Also, if we are going to get into the hotter/more humid airmass it may not occur until after next weekend when it appears a warm front may slide east/north through the region but that's way out there.  

 

The end of next week we are also under a northerly flow at the surface and low levels so it may actually be rather seasonal, even perhaps slightly below average and low dewpoints.

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