Monday, November 30, 2020 Heavy Rain, Strong Winds, and Severe Convection

[Whineminster]

Looks heavy.  A lot heavier than people are giving it credit I think.  Just like y'all poopoo'd the October derecho

[USCAPEWEATHERAF]

Would not be surprised to see a few tornado warnings across SNE tonight!

[USCAPEWEATHERAF]

Heavy rains will move into Southern New England from south to north in the next few hours and especially overspread RI and Eastern MA just before 11 am EST (16z) this morning.  Winds will begin to increase from the south and southeast right after midday and then escalate further throughout the rest of the afternoon and evening.  A large and massive in size extra-tropical cyclone with a center of 999mb currently over VA will move northward and begin to occlude later today after deepening another ten millibars to around 989mb near BUF.  Models are converging on an intense low level jet overspreading the RI and SE MA area this afternoon with a peak in winds after 9pm EST especially the further east one is located.  These winds could max out over hurricane force, and maybe some gusts over 90-mph.  Again, with southeast winds off the marine influence of the Atlantic Ocean, there is some data that suggests an inversion will keep the winds off the surface and at 1000 feet above ground level.  If convection develops, echo tops should be generally between 25-30 thousand feet, enough to transfer the extreme winds to the surface in any drag processes such as microbursts enhanced by heavy down pours.  An intense situation is developing east of Myrtle Beach, SC with a line of intense thunderstorms developing and moving northward towards Hatteras, NC.  These could produce waterspouts, damaging wind gusts and potentially tornadoes.  This area will move up the East Coast throughout the day in line with the best helicity over 600 m/s towards eastern MA and RI this evening.  This will provide the atmosphere with turning of the winds with height, ie shear, and enough to produce mesocyclones.  I believe the SPC will upgrade our region to a slight risk.  Tornadoes should be positioned at 5 percent risk.  Model soundings from CHH suggest a veering wind profile or turning of wind with height in a cyclonic circulation.  Winds at the surface from the SE to west in the upper levels over 90 degrees of turning, suggests tornado profile!  Stay alert!

[CoastalWx]

He awakens.

[TauntonBlizzard2013]

4 minutes ago, CoastalWx said:

He awakens.

[USCAPEWEATHERAF]

seems like the 11z HRRR model run shows the height of severe weather impacts on Cape Cod will be around midnight!

[Damage In Tolland]

24 minutes ago, USCAPEWEATHERAF said:

Heavy rains will move into Southern New England from south to north in the next few hours and especially overspread RI and Eastern MA just before 11 am EST (16z) this morning.  Winds will begin to increase from the south and southeast right after midday and then escalate further throughout the rest of the afternoon and evening.  A large and massive in size extra-tropical cyclone with a center of 999mb currently over VA will move northward and begin to occlude later today after deepening another ten millibars to around 989mb near BUF.  Models are converging on an intense low level jet overspreading the RI and SE MA area this afternoon with a peak in winds after 9pm EST especially the further east one is located.  These winds could max out over hurricane force, and maybe some gusts over 90-mph.  Again, with southeast winds off the marine influence of the Atlantic Ocean, there is some data that suggests an inversion will keep the winds off the surface and at 1000 feet above ground level.  If convection develops, echo tops should be generally between 25-30 thousand feet, enough to transfer the extreme winds to the surface in any drag processes such as microbursts enhanced by heavy down pours.  An intense situation is developing east of Myrtle Beach, SC with a line of intense thunderstorms developing and moving northward towards Hatteras, NC.  These could produce waterspouts, damaging wind gusts and potentially tornadoes.  This area will move up the East Coast throughout the day in line with the best helicity over 600 m/s towards eastern MA and RI this evening.  This will provide the atmosphere with turning of the winds with height, ie shear, and enough to produce mesocyclones.  I believe the SPC will upgrade our region to a slight risk.  Tornadoes should be positioned at 5 percent risk.  Model soundings from CHH suggest a veering wind profile or turning of wind with height in a cyclonic circulation.  Winds at the surface from the SE to west in the upper levels over 90 degrees of turning, suggests tornado profile!  Stay alert!

Can envision 7-10 Tors ripping across the Cape tonight under the cover of darkness. By 6:00 PM, you should be under a king sized mattress in the tub 

[CoastalWx]

11 minutes ago, Damage In Tolland said:

Can envision 7-10 Tors ripping across the Cape tonight under the cover of darkness. By 6:00 PM, you should be under a king sized mattress in the tub 

Looking west down rt 6, I expect to see several TORs at once backlit by the flashes of LTG. Both bridges destroyed. 

[dryslot]

This could be biblical.

[Baroclinic Zone]

9 minutes ago, dryslot said:

This could be biblical.

@kdxken  will appreciate the rains

[Damage In Tolland]

20 minutes ago, CoastalWx said:

Looking west down rt 6, I expect to see several TORs at once backlit by the flashes of LTG. Both bridges destroyed. 

Coming in waves. As soon as two dissipate.. three more drop down in tandem. It continues like this for many, many hours . Just on the cape 

[Baroclinic Zone]

Nice solid 1-2"+ coming.  Fill that groundwater up.

[weatherwiz]

Forecast 3km CAPE for I think 19z today. Want to watch how that progresses moving into SNE. Also a push of MLCAPE of 250-500 J. Going to be an active day

[Baroclinic Zone]

12 hours ago, Baroclinic Zone said:

Latest map.

[weatherwiz]

Think we could see an enhanced risk with next SPC update with SLIGHT into SNE. 

[ineedsnow]

8 minutes ago, Baroclinic Zone said:

Latest map.

Meh

[CoastalWx]

Although LLJ is strongest on the Cape, they sometimes are a bit inverted with being near 50F water. It will probably be best just away from the S facing shores... just inland in SE MA especially. 

[USCAPEWEATHERAF]

2 minutes ago, CoastalWx said:

Although LLJ is strongest on the Cape, they sometimes are a bit inverted with being near 50F water. It will probably be best just away from the S facing shores... just inland in SE MA especially. 

I think there may be more of a tornado then damaging gust threat given the marine influence!

[weatherwiz]

3 minutes ago, CoastalWx said:

Although LLJ is strongest on the Cape, they sometimes are a bit inverted with being near 50F water. It will probably be best just away from the S facing shores... just inland in SE MA especially. 

agreed. 

[USCAPEWEATHERAF]

1 minute ago, weatherwiz said:

agreed. 

I think the slight risk should be expanded where the marginal risk is right now, for the 5 percent tornado risk.  It is becoming clear that there is a strong threat for slight risk worthy graphics over the southern half of southern New England!

[weatherwiz]

6 minutes ago, USCAPEWEATHERAF said:

I think the slight risk should be expanded where the marginal risk is right now, for the 5 percent tornado risk.  It is becoming clear that there is a strong threat for slight risk worthy graphics over the southern half of southern New England!

There could be a second window across the Cape...like sunrise surprise window.

[USCAPEWEATHERAF]

Just now, weatherwiz said:

There could be a second window across the Cape...like sunrise surprise window.

Winds or Tornado threat?

[weatherwiz]

Just now, USCAPEWEATHERAF said:

Winds or Tornado threat?

both.

Although the TOR potential with this setup is a bit odd...probably moreso along the lines of cells merging 

[Typhoon Tip]

Blue Hill over to the cap of The Pru'  ... 

Not an altogether impressively - by interior OV/NE ...EC standards - cyclonic depth.  But the synoptic layout in general.. it's a big low pressure 'area' - it's almost entirely where it's anomaly/ISE is/are oriented, that/those being just the girth of this thing alone... 

Be that as it may, it'll be hauling a llv jet up and crucially as to whether that wind is realized closer to/on the ground comes down to lapse rate.   

What is the actual anomaly calculation for this warm conveyor belt velocity where it is max, and is that located in front or beneath the warm intrusion latitude?

I think we've seen some big modeled wind belts in the past ...fail to really materialize, and then others seemed more paltry but ended up over producing.. It really comes down to whether the SFC to 900 mb level pressure gradient crosses up with steepening lapse rates.  If yes, snap crackle and pop.. If no, really really fast cloud motion with just some white noised turbine sounds but unmemorable.  

As far as convection ...typical modulator ... I think there is limited/less resistance to warm boundary displacement N up the the coastal plain of the EC - can see the current warm placement near the VA Capes as amorphous if not repositioning closer to the south coast getting there in an "air" or rapidity. But even N of that axis,...I can imagine there may be some ribbon echo line sinuously side-winding west to east amid a shreds of other rad shrapnel racing NNE at ludicrous speeds...  That's a different momentum concern than the mixing the LLJ aspect outlined further above.  

So, multi faceted result of the first in the +PNA modal load ...  We'll see if the 108 hr ...then again ... 180 to 200 hr periods also get their 'synergistic' sort of feed-back and correct more prevalent in future runs. I think there's a chance they may - 

[HIPPYVALLEY]

24 minutes ago, ineedsnow said:

Meh

Unless you are on a hilltop, W MA is where wind goes to die. 

[USCAPEWEATHERAF]

3 minutes ago, Typhoon Tip said:

Blue Hill over to the cap of The Pru'  ... 

Not an altogether impressively - by interior OV/NE ...EC standards - cyclonic depth.  But the synoptic layout in general.. it's a big low pressure 'area' - it's almost entirely where it's anomaly/ISE is/are oriented, that/those being just the girth of this thing alone... 

Be that as it may, it'll be hauling a llv jet up and crucially as to whether that wind is realized closer to/on the ground comes down to lapse rate.   

What is the actual anomaly calculation for this warm conveyor belt velocity?   I think we've seen some big modeled belts in the past ...fail to really materialize, and then others seemed more paltry but ended up over producing.. It really comes down to whether the SFC to 900 mb level pressure gradient crosses up with steepening lapse rates.  If yes, snap crackle and pop.. If no, really really fast cloud motion with just some white noised turbine sounds but unmemorable.  

As far as convection ...typical modulator ... I think there is limited/less resistance to warm boundary displacement N up the the coastal plain of the E . ...I can imagine there may be some ribbon echo line sinuously side-winding west to east amid a shreds of other rad shrapnel racing NNE at ludicrous speeds...  That's a different momentum concern than the mixing the LLJ down.  

So, multi faceted result of the first in the +PNA mode onset ...  We'll see if the 108 ...then again ... 180 to 200 hour periods also get their 'synergistic' sort of feed-back and correct more prevalent in future runs. I think there's a chance they may - 

I think the weekend threats may end up more south than they are currently progged.  the NAO is tanking Negative by the 5th and so is the AO, if they coincide, we are getting blanketed by cirrus and snow clouds, while DC and NYC are enjoying their early DEC snows!

[Typhoon Tip]

12 minutes ago, USCAPEWEATHERAF said:

I think the weekend threats may end up more south than they are currently progged.  the NAO is tanking Negative by the 5th and so is the AO, if they coincide, we are getting blanketed by cirrus and snow clouds, while DC and NYC are enjoying their early DEC snows!

NAO drop does suggest suppression along the Coast ... "eventually"  

I am not sure - by this weekend ... - that sort of suppressive exertion by a -NAO is sufficiently garnered/ large enough, however.  It may ...but that's probably not the case in my mind?  This NAO index decline is a gradual drop off... It is not really "jolting" the hemisphere with any sort of usurping force when it takes 10 days to abrate 1.5 SD ... ending in a mop ended fray out there week 2 or so...  Also, the "west" vs "east" biased blocking in the super-synoptic layout of the geopotential height medium plays an important role in the amount suppression over eastern North American longitudes...  East imposes less and vice versa

In other words, if I were asked ...I would be inclined to suggest that the weekend impulse probably rides up the geopotential interface ... prior to any -NAO exertion setting in... and that the Euro run is typically too far S on D6 with it's almost due east escape off the Va Capes like that... It's fiddling with perspectives admittedly ... I think it is worth watching that little guy though, ... I mean...nothing major or very noteworthy but .. folks around here really want snow in the air - or at least the cinema of the chance for it in the models ... - and failing that, many of them lose out on happiness.  Lol... 

[PowderBeard]

This one is likely to surprise.

[Baroclinic Zone]

Mix these down.

 

[weatherwiz]

16 minutes ago, Typhoon Tip said:

Blue Hill over to the cap of The Pru'  ... 

Not an altogether impressively - by interior OV/NE ...EC standards - cyclonic depth.  But the synoptic layout in general.. it's a big low pressure 'area' - it's almost entirely where it's anomaly/ISE is/are oriented, that/those being just the girth of this thing alone... 

Be that as it may, it'll be hauling a llv jet up and crucially as to whether that wind is realized closer to/on the ground comes down to lapse rate.   

What is the actual anomaly calculation for this warm conveyor belt velocity where it is max, and is that located in front or beneath the warm intrusion latitude?

I think we've seen some big modeled wind belts in the past ...fail to really materialize, and then others seemed more paltry but ended up over producing.. It really comes down to whether the SFC to 900 mb level pressure gradient crosses up with steepening lapse rates.  If yes, snap crackle and pop.. If no, really really fast cloud motion with just some white noised turbine sounds but unmemorable.  

As far as convection ...typical modulator ... I think there is limited/less resistance to warm boundary displacement N up the the coastal plain of the EC - can see the current warm placement near the VA Capes as amorphous if not repositioning closer to the south coast getting there in an "air" or rapidity. But even N of that axis,...I can imagine there may be some ribbon echo line sinuously side-winding west to east amid a shreds of other rad shrapnel racing NNE at ludicrous speeds...  That's a different momentum concern than the mixing the LLJ aspect outlined further above.  

So, multi faceted result of the first in the +PNA modal load ...  We'll see if the 108 hr ...then again ... 180 to 200 hr periods also get their 'synergistic' sort of feed-back and correct more prevalent in future runs. I think there's a chance they may - 

Bingo

One thing to watch too is where this axis of higher theta-e traverses. Does appear this clips at least parts of CT/RI/SE MA