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weatherwiz

Wednesday, August 7, 2019 Severe Potential

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The 3k NAM looks to be a bit out of lunch imho with the line. The other mesos seem to have a more realistic looking grasp. Late evening line, then a second overnight line.

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Unless there's pig mechanical forcing ... close this thread down and never return to it -

  • Haha 2

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2 minutes ago, Typhoon Tip said:

Unless there's pig mechanical forcing ... close this thread down and never return to it -

Today ...

Warm front lifts north across the area this morning. The front
should come thru mainly dry but can`t rule out an isolated shower or
thunderstorm. Low clouds and patchy dense fog will accompany the
boundary this morning. These low clouds and fog will lift and burn
off later this morning giving way to at least partial sunshine this
afternoon. Breaks of sunshine and 850 mb temps of +15C to +16C will
support highs in the mid to upper 80s, 75-80 south coast given SSW
winds off the ocean. These warm temps are about 5 degs warmer than
normal and combined with dew pts in the upper 60s to lower 70s,
summer heat and humidity will be in effect this afternoon. These
temps and dew pts will also support CAPEs on the order of 1500-2500
j/kg. Thus moderate to high CAPE environment in warm sector this
afternoon.

Meanwhile a vigorous short wave will be tracking across NY state
this afternoon. This feature will provide fairly strong mid level
forcing for ascent, increase wind field aloft along with low level
convergence from attending surface trough, all focused across
western/northwest portions of CT/MA. While scattered thunderstorms
are expected farther southeast and east across CT/RI and eastern MA,
convection will be more widespread along with stronger storms over
western and northwest portions of MA/CT. Given the moderate to high
CAPE profiles coupled with increasing mid level wind field, damaging
winds are a concern with the strongest storms this afternoon. In
addition, models have been signaling a 25-30 kt low level SSW jet
moving across southern New England 18z-00z. This may enhance 0-1 km
helocity sufficiently for low risk of an isolated tornado in the CT
river valley of MA where winds typically back more than models
indicate due to the terrain of the CT river valley. Also dew pts
rising into the low 70s will yield lower LCLs which is also another
favorable parameter. However tornado threat higher farther northwest
into NY state where meso-low is expected to track.

Other concern today will be torrential downpours and risk for
localized flooding given strong storms coupled with PWATs
approaching 2 inches and surface dew pts in the lower 70s.

It`s possible southeast MA remains mainly dry today given forcing
for ascent is focused much farther to the northwest.

Tonight ...

Global and Hi Res models coming into better agreement on potential
two rounds of convection, one this afternoon and a 2nd round this
evening and overnight from a trailing short wave to move across the
area. The first round of convection this afternoon should impact
northwest CT into much of western-central MA, possibly into
northeast MA. The second round this evening and overnight appears to
focus across RI and eastern MA especially southeast MA.

Despite loss of daytime heating dew pts in the low 70s coupled with
some height falls/cooling temps aloft models offering 1000-1500j/kg
of CAPE across RI and eastern MA. This combined with trailing mid
level speed max of up to 35 kt at H7 may result in a second round of
strong storms tonight across RI and eastern MA. Strong winds and
localized torrential downpours/flooding would be the concerns. Also
given shear profiles rotating storms are possible.

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9 minutes ago, sbos_wx said:

Today ...

Warm front lifts north across the area this morning. The front
should come thru mainly dry but can`t rule out an isolated shower or
thunderstorm. Low clouds and patchy dense fog will accompany the
boundary this morning. These low clouds and fog will lift and burn
off later this morning giving way to at least partial sunshine this
afternoon. Breaks of sunshine and 850 mb temps of +15C to +16C will
support highs in the mid to upper 80s, 75-80 south coast given SSW
winds off the ocean. These warm temps are about 5 degs warmer than
normal and combined with dew pts in the upper 60s to lower 70s,
summer heat and humidity will be in effect this afternoon. These
temps and dew pts will also support CAPEs on the order of 1500-2500
j/kg. Thus moderate to high CAPE environment in warm sector this
afternoon.

Meanwhile a vigorous short wave will be tracking across NY state
this afternoon. This feature will provide fairly strong mid level
forcing for ascent, increase wind field aloft along with low level
convergence from attending surface trough, all focused across
western/northwest portions of CT/MA. While scattered thunderstorms
are expected farther southeast and east across CT/RI and eastern MA,
convection will be more widespread along with stronger storms over
western and northwest portions of MA/CT. Given the moderate to high
CAPE profiles coupled with increasing mid level wind field, damaging
winds are a concern with the strongest storms this afternoon. In
addition, models have been signaling a 25-30 kt low level SSW jet
moving across southern New England 18z-00z. This may enhance 0-1 km
helocity sufficiently for low risk of an isolated tornado in the CT
river valley of MA where winds typically back more than models
indicate due to the terrain of the CT river valley. Also dew pts
rising into the low 70s will yield lower LCLs which is also another
favorable parameter. However tornado threat higher farther northwest
into NY state where meso-low is expected to track.

Other concern today will be torrential downpours and risk for
localized flooding given strong storms coupled with PWATs
approaching 2 inches and surface dew pts in the lower 70s.

It`s possible southeast MA remains mainly dry today given forcing
for ascent is focused much farther to the northwest.

Tonight ...

Global and Hi Res models coming into better agreement on potential
two rounds of convection, one this afternoon and a 2nd round this
evening and overnight from a trailing short wave to move across the
area. The first round of convection this afternoon should impact
northwest CT into much of western-central MA, possibly into
northeast MA. The second round this evening and overnight appears to
focus across RI and eastern MA especially southeast MA.

Despite loss of daytime heating dew pts in the low 70s coupled with
some height falls/cooling temps aloft models offering 1000-1500j/kg
of CAPE across RI and eastern MA. This combined with trailing mid
level speed max of up to 35 kt at H7 may result in a second round of
strong storms tonight across RI and eastern MA. Strong winds and
localized torrential downpours/flooding would be the concerns. Also
given shear profiles rotating storms are possible.

Well...whomever that forecaster is .. does mention " ...Vigorous short wave ..." among other mechanical arguments so we'll see.. 

Haven't spent much time on it... I just know from 35 years of New England life and travails that when you are bum-jammed with low clouds because the warm sector can't commit to pure barotropical and tries to just WAA saturate the llvs the whole way... it also ends up far better on paper than in practice. 

If we start mixing out and the sun shines... heh

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17 minutes ago, Typhoon Tip said:

Unless there's pig mechanical forcing ... close this thread down and never return to it -

:weenie:

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8 minutes ago, Typhoon Tip said:

Well...whomever that forecaster is .. does mention " ...Vigorous short wave ..." among other mechanical arguments so we'll see.. 

Haven't spent much time on it... I just know from 35 years of New England life and travails that when you are bum-jammed with low clouds because the warm sector can't commit to pure barotropical and tries to just WAA saturate the llvs the whole way... it also ends up far better on paper than in practice. 

If we start mixing out and the sun shines... heh

Already had a lot of sun here, and any of this high level debris should be long gone in a few hours. Already seeing some CU on vis sat.

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Looking at the models...

It looks to me as if this is all a pretty late show outside of the W and NW portions. All of the daytime stuff forms and lifts to NNE or W NY.

It's evening time and overnight for everyone else.

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4 hours ago, Damage In Tolland said:

One round is west. One round is East. Little in the middle, but she got much back. Pretty straightforward 

next

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Pay attention to the storms along the warm front moving northward now across central CT, RI and Interior SE MA and southwest Boston METRO region.  Could produce a few tornado warnings as some supercells develop within a highly unstable environment.

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Tonight's severe weather risk looks to explode from RI to Cape Cod, MA as the mesolow over MD right now is vigorous and should maintain the vigor as it moves along the South Coast of CT, Ri and SE MA.

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4 minutes ago, USCAPEWEATHERAF said:

Pay attention to the storms along the warm front moving northward now across central CT, RI and Interior SE MA and southwest Boston METRO region.  Could produce a few tornado warnings as some supercells develop within a highly unstable environment.

There is not even a remote chance these produce anything

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Just now, sbos_wx said:

There is not even a remote chance these produce anything

And why is that Jay, they are along a warm front.

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Just now, sbos_wx said:

There is not even a remote chance these produce anything

Would you say 7/23/19 is an analog?

  • Haha 4

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7 minutes ago, USCAPEWEATHERAF said:

And why is that Jay, they are along a warm front.

They are literally thunder showers, maybe a bit more heavy once they cross into NNE.

Did you read the AFD?

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1 minute ago, sbos_wx said:

They are literally thunder showers, maybe a bit more heavy once they cross into NNE.

Did you read the AFD?

yes of course I did, I know they aren't the main show.

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Once you get a couple TORS once in 100 yrs, Now there going to be the norm with every CF.

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1 minute ago, USCAPEWEATHERAF said:

yes of course I did, I know they aren't the main show.

So why on god's green earth would you think a tornado would pop out of one of them?

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Looks interesting. The cells coming   from the southwest are gaining strength. Could be mostly W/MA but the stuff from CN an RI could be performing for round 1.

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12 minutes ago, weatherwiz said:

I think there is a typo in there...they say mlvl lapse rates 6.5-7 C/KM...if that were the case this would be a much bigger event 

That is after the evening hours Paul, it develops later on in the evening.

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42 minutes ago, dryslot said:

Once you get a couple TORS once in 100 yrs, Now there going to be the norm with every CF.

Like how every noreaster is a potential 1/22/05 or 1/15 due to the gulf stream

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47 minutes ago, sbos_wx said:

So why on god's green earth would you think a tornado would pop out of one of them?

Do you really need to ask James?  Ha.  

Cape Cod climo is hurricanes, tornadoes and blizzards.

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