Severe Thunderstorm Watch #507

[CanisLupusArctos]

NOAA/SPC has upgraded New England's severe weather risk to moderate for today. Damaging wind and hail are the main threats for this afternoon. Storms are starting to pop up throughout NY state and are moving east. Severe thunderstorm watch issued at 1130 am effective until 8 pm. Storms may last longer than that, though they may not be officially "severe."


URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 507
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM EDT WED JUL 21 2010

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

NORTHERN CONNECTICUT
WESTERN MASSACHUSETTS
WESTERN MAINE
NEW HAMPSHIRE
NEW YORK
NORTHERN PENNSYLVANIA
VERMONT
LAKE ERIE
LAKE ONTARIO
COASTAL WATERS

EFFECTIVE THIS WEDNESDAY MORNING AND EVENING FROM 1130 AM UNTIL
800 PM EDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 75
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 90
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES NORTH
NORTHWEST OF BRADFORD PENNSYLVANIA TO 45 MILES NORTH NORTHEAST OF
AUGUSTA MAINE. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...WIDESPREAD STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED
THIS AFTERNOON ACROSS MUCH OF THE NORTHEAST UNITED STATES...AHEAD OF
APPROACHING UPPER TROUGH. COOL TEMPERATURES ALOFT...INCREASINGLY
STRONG WESTERLY FLOW ALOFT...STEEP LAPSE RATES...AND MODERATE
INSTABILITY WILL CONTRIBUTE TO THE RISK OF LARGE HAIL AND DAMAGING
WINDS. MULTIPLE BANDS OF STORMS WILL LIKELY AFFECT THE WATCH AREA
THROUGH THE DAY.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 28035.


...HART

[NHKathy]

how were the storms up there? how about in Moultonborough??

[ITD]

Pretty intense, lightning strike nearby took out some of my electronics, bummer. No damage to trees that I can see though, Moultonboro/center harbor area.

[ApS]

Thanks for the severe-weather warning. :look: Tuning in to AM-radio disclosed a continuous stream of lightning crackles—this was going to be serious.

The west part of Wolfeboro got pelted by some decent-sized hail, which quickly melted. Much cloud-to-cloud lightning—a few strikes to ground nearby. :eek2: Haven't checked for any "windfalls" as yet, but didn't hear any.

(Any windfall can open up the woods to successive (serial) windfalls in storms later).

The strong wind that preceeded the worst part of the storm made my deep woods sound like a train passing by. :eek: A very few boats (including a tuber) ran for cover just minutes before the storm struck here. :rolleye2:

The lake's surface turned white before waves had a chance to form!

[Formula]

These trees just missed the boat house and the other boats. I would guess that they are about 30-50 footers. not much damage elsewhere.

[CanisLupusArctos]

The National Weather Service storm survey has confirmed tornado damage in the Portland Maine area from Wednesday's storms. The tornadoes originated from thunderstorms that developed strong rotation as they approached Lake Winnipesaukee, triggering the NWS to issue a tornado warning for Moultonborough eastward to the Maine border (it was later extended to Portland.)

There was extensive damage to trees & power poles in Sandwich NH at about the same time the tornado warning was issued for this area.

When the lakes region storms (rotating) reached the Portland area, they finally produced their tornadoes. Three EF-1 twisters were confirmed by damage survey: Limerick, Gorham, and Alfred.

This time lapse from the WeatherCam (http://www.youtube.com/blackcatnh#p/a/u/0/UcPMFAJwS4M) begins just before the tornado warning was issued in Moultonborough and is also posted in the "scenes" section of the newly-redesigned WeatherCam website (http://www.blackcatnh.com).

There was also extensive tree/pole damage from the Vermont border eastward to Plymouth as those storms approached the Lakes Region (before they developed rotation.) The NWS confirmed that damage to be from a microburst, NOT tornado. Tornadoes offer a "rotary vacuum/lawnmower effect" while a microburst offers a "flattening" effect like an invisible foot stomping on the ground, treating the trees as if they were nothing more than tall grass underneath the giant foot.