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Let's kick off severe wx season!

weatherwiz

By weatherwiz,
in New England

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weatherwiz

weatherwiz

Posted
Posted

Well yesterday was the beginning of what has the potential to be very active as far as convection and severe weather chances are concerned. As massive ridge has been building here in the east, finally allowing the sub-tropical jet stream to lift northward through the area. This has allowed for much warmer and more humid air to work it's way into the region. At the same times there has been a fairly persistent trough across much of the western and portions of the central US. This pattern is actually somewhat similar to that of April, however, given the time of year the axis of the ridge really didn't get this far north and this pattern was also responsible for the historic month of April as far as tornadoes go and also has been responsible for the very active week out across the Plains and into the Ohio/Tennessee River Valleys. Now that we are getting later into the spring and approaching the summer season it's becoming much easier for these ridges to build further northward. While there are some model differences for the upcoming week the general idea is we here in the Northeast will be just about on the crest of the ridge. What does this mean?

While the brunt of the heat will not really work into the region we will still see temperatures just above-average for most, some days even getting much higher than average depending on wind flow. Dewpoints will be rather high, 60's to near 70F at times, due to a persistent southerly/southwesterly flow. The two most important aspects here though is being on the crest of the ridge allows for much steeper mid-level laspe rates and it also allows for the potential for sufficient shear, especially with an active jet which is what we have now. It also allows the potential for the development of extreme instability.

As we move towards the early stages of next week and then into mid-week the potential setup will give us a northwest flow aloft...while it may not end up being a true northwest flow aloft in most of our major severe weather outbreaks have occurred in a northwest flow aloft. It is this type of flow that can advect those EML's into our region (though they are very rare here) and they also help to produce some directional shear.

A cold front, which has been stationary at times, will finally sag south of the region sometime this weekend, )actually a backdoor cold front may also work in from the east or northeast across parts of eastern MA), due to the strong ridging offshore the front should diffuse and then become a warm front and lift back northward through the region Morning. Once this warm front works through the low-level airmass will once again quickly warm and higher dewpoints will once again overspread the region. 925mb temps get to around +20C to +23C throughout the region with 850mb temps nearing +17C to +20C...with excellent mixing and full sun this would support temperatures well into the middle and upper 80's...even 90's in the torch spots. Dewpoints look to increase to the mid to perhaps even upper 60's. It's also interesting to note where some of the models want to advect in an EML into the region as 700mb temperatures rise to +7C to perhaps +10C...it will be very interesting to see if this does hold. For those wondering what an EML is (since some have asked about it) and EML is an "Elevated Mixed-Layer"...it's also a capping inversion as it's associated with a tongue of very warm and very dry air aloft (usually in the 700-800mb though it could extend a bit lower and a bit higher). An EML is very important for large-scale severe weather and tornadoes b/c 1. It's associated with very steep mid-level lapse rates which can lead to extreme amounts of instability 2. Since it's a capping layer it prevents clouds from building too early, which gives the better potential for maximized solar heating 3. It can also keep aerial coverage of storms down which is perfect for supercells, especially long-lived ones b/c it prevents storms from choking each other's updrafts. Here is an example of an EML sounding:

As you can see the area of warming and extreming drying from about 850-700mb:

08309500zabrsnd.gif

Now this is a textbook case of an EML, and unfortunately when we are lucky enough for them to get here they usually aren't this well defined. Here is the 0z sounding from OKX last night, it has somewhat of an EML look with the jetting area of dry air and small area of warming.

OKX.gif

For Monday after some showers...maybe a rumble of thunder with the northward advancing warm front things should quickly clear out and this should allow for sufficient sunshine. Away from the coast temperatures should reach the mid 80's...perhaps near upper 80's if clouds burn off really fast. Along the south coast temperatures will be mid to upper 70's due to a flow off the ocean and up at Pete's house where solar radiation is much less. With a rich southerly flow once again, and a good deal of theta-e advection dewpoints should climb into at least the middle 60's...some models show 70' dewpoints but until there is any evidence of this actually occurring this is likely overdone.

With temperatures potentially getting into the 80's, dewpoints into the mid 60's and very steep mid-level lapse rates present (6.5-7.5 C/KM) all these ingredients together will have the potential to produce some extreme instability values...SBcape values between 2500-4000 J/KG, MLcape values between 1500-2500 J/KG, MUcape values between 3500-4500 J/KG, LI values between -6 and -8C, TT into the lower to mid 50's, and the SI index around -6 or so.

Looking aloft at shear it doesn't look overly impressive but it's not terribly bad, in fact the NAM tries to increase winds in the mid and upper-levels of the atmosphere as the day goes on as vertical shear values increase to perhaps as much as 35-45 knots.

Just have to watch and see how this unfolds...due to that EML potential with 700mb temps potentially as high as +7C to +10C we may be capped...the cold front sliding through won't be overly strong so it's probably going to need some decent mid and upper level support from either jet energy or a strong vort max rotating through aloft.

After Monday the next threat potential is Wednesday, and while it's far out there it does look fairly impressive right now as Wednesday could feature much more in the way of shear.

I also wanted to add for HA-HA's...there seems to be something about the 5/31 period for severe wx in the Northeast...some notable examples (there are others but these were biggies:

5/31/85

5/31/98

5/31/02

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Damage In Tolland

Damage In Tolland

Posted
Posted

I never said today...tomorrow what's left of it moves through, plus backdoor action tomorrow, it quickly lifts back northward Sunday night/early AM Monday.

There isn't any cold front that moves across SNE . That stays up in NNE.

The only small possibility is that NE Mass is backdoored.

Winds stay S thru Sunday then shift SW for us

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weatherwiz

weatherwiz

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There isn't any cold front that moves across SNE . That stays up in NNE.

The only small possibility is that NE Mass is backdoored.

Winds stay S thru Sunday then shift SW for us

eh whatever, some type of boundary moves through b/c low-level temperatures cool for a few days then we get right back into the warm sector.

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HoarfrostHubb

HoarfrostHubb

Posted
Posted

About to get whacked here...

SPECIAL WEATHER STATEMENT

NATIONAL WEATHER SERVICE TAUNTON MA

230 PM EDT SAT MAY 28 2011

MAZ004-010-011-026-NHZ011-015-281930-

CHESHIRE NH-EASTERN HAMPDEN MA-EASTERN HAMPSHIRE MA-NORTHERN

WORCESTER MA-NORTHWEST MIDDLESEX COUNTY MA-WESTERN AND CENTRAL

HILLSBOROUGH NH-

230 PM EDT SAT MAY 28 2011

AT 228 PM EDT NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

STRONG THUNDERSTORM CAPABLE OF PRODUCING SMALL HAIL 3 MILES NORTHEAST

OF WARE...OR ABOUT 18 MILES SOUTHEAST OF AMHERST...MOVING NORTHEAST

AT 25 MPH.

* SOME LOCATIONS AFFECTED INCLUDE...NORTH BROOKFIELD...NEW

BRAINTREE...HARDWICK...OAKHAM...BARRE...PETERSHAM...HUBBARDSTON...

PHILLIPSTON...TEMPLETON...WESTMINSTER...GARDNER...RINDGE...

WINCHENDON...FITCHBURG...ASHBY AND ASHBURNHAM.

FOR YOUR SAFETY...GET INSIDE WHEN THESE STORMS APPROACH. WINDS MAY BE

STRONG ENOUGH TO BRING DOWN SMALL BRANCHES. MINOR STREET FLOODING AND

PONDING OF WATER IN POOR DRAINAGE AREAS IS ALSO POSSIBLE.

THIS STORM WAS PRODUCING FREQUENT CLOUD TO GROUND LIGHTNING. GET

INDOORS OR INSIDE A VEHICLE NOW! IF YOU ARE CAUGHT OUTSIDE...STAY

AWAY FROM ISOLATED TALL OBJECTS SUCH AS TREES. AVOID OPEN AREAS SUCH

AS GOLF COURSES AND BALL FIELDS.

&&

LAT...LON 4281 7206 4269 7173 4217 7214 4224 7236

$$

DOODY

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