Jump to content

  • Member Statistics

    17,584
    Total Members
    7,904
    Most Online
    LopezElliana
    Newest Member
    LopezElliana
    Joined

Northeast Severe/Convective/Thunder thread II

Baroclinic Zone

By Baroclinic Zone,
in New England

Recommended Posts

  • Replies 1.1k
  • Created
  • Last Reply
NJwinter23

NJwinter23

Posted
Posted

Between Friday and today, the models have been atrocious with this warm shot advecting eastward (for the mid-Atlantic/Northeast Sunday-Tuesday). All over the place... I originally thought late last week it would have trouble making it into the Northeast, then every model bailed on that idea by Sunday and I had to change tune for warmer in the DC-NYC corridor. Now everything has trended back to a significant onshore flow early next week muting this potential burst of warmth.

Anyhow, the models are all in good agreement for some kind of thunderstorm complex dropping from southeast Canada into the Northeast Saturday night/early Sunday morning. Given the timing, i would guess the severe potential with this is limited.

Link to comment
Share on other sites
OceanStWx

OceanStWx

Posted
Posted

This seems like as good a place as any to put this, but I've been doing a little post-event review on last Tuesday's severe weather. We knew our CWA up this way had a very small window for severe, and we did end up getting some decent storms into the western zones for a time. However, the more interesting part of the day for me occurred over the waters.

We had morning convection which rolled across northern NH and western ME, some prompting a SMW near Portland early. The storms kept regenerating over the outer waters through the mid morning, creating some pretty good gravity waves and outflow. After the gravity waves passed each buoy, winds would kick up out of the NE, which was expected. Winds kept gusting near small craft, and late morning winds began to veer sharply and gust higher. So we were stuck in between a small craft or a more short fused marine statement considering it was convectively forced in nature. We decided to go with a small craft advisory with the numerous outflow boundaries visible on satellite.

Soon after that winds were southeast and gusting to near storm force at Matinicus Rock. No storms or recent outflow boundaries could explain it. In the moment I guessed at what it was, but the lack of real time data from the buoys made confirmation difficult. Hindsight being 20/20, I probably should have made the decision for us to issue some sort of marine weather statement or SMW on top of the small craft, but things were busy with the convective threat on land too.

From the satellite, you can see the old outflow boundary washing out and the new MCS emerging off the coast at 11 AM.

This is what we could see from the radar at the time. Strongest cells were well out to sea, with trailing stratiform precip.

Once I got around to researching the event, I only needed to see this to know what happened. We had a wake low form. In this pressure trace, you can see low pressures associated with the leading edge of convection. Then pressure rise after the leading edge passes Matinicus. Then pressure drops sharply (that's 9 mb in 2 hours) as the wake low develops.

This pressure difference drives the wind (from the high to the low). It develops in response to MCS dynamics. Rain will result in evaporational cooling as it falls into the relatively dry air below. At the same time the rapidly descending rear inflow jet results in adiabatic warming. The rain rates near the strongest convection are usually enough to offset this adiabatic warming. However, in the stratiform region the rain rates are much less and warming outweighs cooling by a large margin. In addition, the air may already be near saturated, so the evaporational cooling is much less. The increased warming creates a local low pressure. In this case the land/sea interface may have played a role as well. Inland heating may have just exacerbated the temperature difference. The process is fairly common with Midwestern/Plains MCSs, minus the land/sea issues of course. This is how you can have destructive easterly winds in the trailing stratiform region.

You can see even with the cold water temperatures modifying things, Matinicus did see temperatures rise with the wake low formation.

Here wind direction begins with northeasterly outflow, and quickly veers to southeast and then south as the wake low develops in strength.

Winds speeds and gusts, with a peak near 45 knots, coincident with the lowest pressure. I'm curious how winds would have responded if there wasn't such a sharp marine inversion in place.

In addition to the strong winds, here is another reason why this was important. Seas quickly jumped up nearly 2 feet in 2 hours. And looking at the wave period, these initial waves were steep in nature. Big problem for any early day boaters. And while winds 2 hours later were near calm, seas remained near 5 feet for the rest of the day.

I was familliar with the phenomenom in the middle of the country, but this was the first time I can remember seeing such a thing off of New England.

Link to comment
Share on other sites
free_man

free_man

Posted
Posted

Between Friday and today, the models have been atrocious with this warm shot advecting eastward (for the mid-Atlantic/Northeast Sunday-Tuesday). All over the place... I originally thought late last week it would have trouble making it into the Northeast, then every model bailed on that idea by Sunday and I had to change tune for warmer in the DC-NYC corridor. Now everything has trended back to a significant onshore flow early next week muting this potential burst of warmth.

Anyhow, the models are all in good agreement for some kind of thunderstorm complex dropping from southeast Canada into the Northeast Saturday night/early Sunday morning. Given the timing, i would guess the severe potential with this is limited.

Severe potential may be limited, but hopefully some widespread storms or at least a MCS can sustain itself in the overnight hours. At least there is a glimmer of hope there, though that threat, of course, may shift more towards WNE/NY/PA/NJ with time. (congrats in advance) ;)

Link to comment
Share on other sites
CoastalWx

CoastalWx

Posted
Posted

Wow, that's interesting. I know they had a strong wake low near MSP I believe a couple of weeks ago, but yeah..you rarely see that here. I wonder if there were some diabatic effects such as the inland heating to set it off like you said. I bet that happens a little more often than we think in that area.

What puzzles me, is how we can get such strong winds, with that inversion overhead. I almost can't even wrap my head around that. 45kts? Holy crap.

Wow, that's interesting. I know they had a strong wake low near MSP I believe a couple of weeks ago, but yeah..you rarely see that hear. I wonder if there were some diabatic effects such as the inland heating to set it off like you said. I bet that happens a little more often than we think in that area.

What puzzles me, is how we can get such strong winds, with that inversion overhead. I almost can't even wrap my head around that. 45kts? Holy crap.

Link to comment
Share on other sites
OceanStWx

OceanStWx

Posted
Posted

Wow, that's interesting. I know they had a strong wake low near MSP I believe a couple of weeks ago, but yeah..you rarely see that hear. I wonder if there were some diabatic effects such as the inland heating to set it off like you said. I bet that happens a little more often than we think in that area.

What puzzles me, is how we can get such strong winds, with that inversion overhead. I almost can't even wrap my head around that. 45kts? Holy crap.

I mean there is always some sort of an inversion present, but not typically this strong...

2012052912.74389.skewt.gif

If anything the adiabatic warming probably just increased the strength of the low level inversion, as temps below 850 increased. Since it was pressure induced wind we still got a response near the surface, but I imagine it would have been greater had this been a more traditional over-land MCS.

Definitely not something that most Northeast mets see very often. I'm going to try and work this up as a case study for future reference at the office here, because there was definitely a "could go either way" aspect to the type of headline to cover the threat.

Link to comment
Share on other sites
CT Rain

CT Rain

Posted
Posted

Nice discussion, Chris. Yeah it definitely looks like a wake low formation... classic MCS pressure trace (with temp spike as well during strongest pressure falls).

The land/sea interface is interesting too in helping to modify things somewhat.

Link to comment
Share on other sites
free_man

free_man

Posted
Posted

...PARTS OF THE NORTHEAST...

A FAIRLY POTENT SHORT-WAVE TROUGH DIGGING SEWD TOWARD NEW ENGLAND

COMBINED WITH MODEST AFTERNOON DESTABILIZATION SHOULD RESULT IN THE

DEVELOPMENT OF SHOWERS AND THUNDERSTORMS -- FROM ERN NY INTO MUCH OF

NEW ENGLAND. WITH THE STORMS DEVELOPING IN A FORECAST BACKGROUND

KINEMATIC ENVIRONMENT OF MODERATELY STRONG NWLY FLOW THROUGH A DEEP

LAYER...POTENTIAL FOR EVOLUTION OF ONE OR MORE FAST-MOVING BOWING

SEGMENTS APPEARS POSSIBLE. THUS...IT APPEARS THAT POTENTIAL FOR

DAMAGING WINDS -- DESPITE THE MODEST INSTABILITY -- WARRANTS

INCLUSION OF A SLIGHT RISK AREA. THE MAIN THREAT SHOULD EXIST FROM

MID AFTERNOON ONWARD...WITH STORMS EXPECTED TO APPROACH THE COAST

AND BEGIN WEAKENING DURING THE EVENING.

Link to comment
Share on other sites
scoob40

scoob40

Posted
Posted

...PARTS OF THE NORTHEAST...

A FAIRLY POTENT SHORT-WAVE TROUGH DIGGING SEWD TOWARD NEW ENGLAND

COMBINED WITH MODEST AFTERNOON DESTABILIZATION SHOULD RESULT IN THE

DEVELOPMENT OF SHOWERS AND THUNDERSTORMS -- FROM ERN NY INTO MUCH OF

NEW ENGLAND. WITH THE STORMS DEVELOPING IN A FORECAST BACKGROUND

KINEMATIC ENVIRONMENT OF MODERATELY STRONG NWLY FLOW THROUGH A DEEP

LAYER...POTENTIAL FOR EVOLUTION OF ONE OR MORE FAST-MOVING BOWING

SEGMENTS APPEARS POSSIBLE. THUS...IT APPEARS THAT POTENTIAL FOR

DAMAGING WINDS -- DESPITE THE MODEST INSTABILITY -- WARRANTS

INCLUSION OF A SLIGHT RISK AREA. THE MAIN THREAT SHOULD EXIST FROM

MID AFTERNOON ONWARD...WITH STORMS EXPECTED TO APPROACH THE COAST

AND BEGIN WEAKENING DURING THE EVENING.

That's for tomorrow.

Link to comment
Share on other sites
weatherwiz

weatherwiz

Posted
Posted

Instability too meh to get excited I think. Dynamics and shear look good... not sure we'll be able to generate enough CAPE to really rock though.

I wouldn't be too surprised if Cape is somewhat underdone...kind of usually tends to happen in these setups.

Anyways as long as we get around 500 J/KG of cape that will be good enough to produce widespread hailers...to probably get storms capable of >1'' hail we'd probably need 1000-1250 J/KG of cape.

Link to comment
Share on other sites
CoastalWx

CoastalWx

Posted
Posted

I wouldn't be too surprised if Cape is somewhat underdone...kind of usually tends to happen in these setups.

Anyways as long as we get around 500 J/KG of cape that will be good enough to produce widespread hailers...to probably get storms capable of >1'' hail we'd probably need 1000-1250 J/KG of cape.

I kind of like tomorrow's setup for parts of the area. It may be relegated to more of NNE, but it's interesting to me.

Link to comment
Share on other sites
CoastalWx

CoastalWx

Posted
Posted

Tomorrow actually looks impressive to me for transporting mid level wind down... Micro/macrobursting potential

Yeah it seems that way. I like the convergence of wind maxes moving into the area. IOW, 850-500 winds really ramp up quickly from SE-NW. Look at the winds at each of these levels by 21z tomorrow. Also, decent jet support. Could be a few good lines in NNE and probably spills into northeast parts of the area towards 00z Saturday? Maybe down into CT?

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...