More Than 70K Without Power After Strong Southerly Gale

It was hard for me to sleep through the whipping southerly winds last night that gusted between 55 and 65 m.p.h. Others probably had a hard time waking up without an alarm clock as power was knocked out to more than 70,000 CL&P customers due to the weather. Dozens of school districts delayed their opening this morning and some closed all together.

8 a.m. CL&P Outage Map

8 a.m. CL&P Outage Map

The observations from last night were impressive. 53 knot gusts were recorded at Sikorsky and Tweed Airports overnight.

KDXR 310937Z AUTO 22030G46KT 1 1/2SM RA BR BKN015 OVC033 15/13 A2911 RMK AO2 PK WND 21046/0935 P0033

KBDL 311016Z 20031G40KT 4SM R06/6000VP6000FT -RA BR SCT014 BKN021 OVC026 16/14 A2902 RMK AO2 PK WND 20048/0954 P0012

KHFD 310943Z AUTO 19029G47KT 2SM +RA BR BKN017 OVC024 16/14 A2902 RMK AO2 PK WND 17047/0941 PRESFR P0024

KMMK 311005Z AUTO 20027G49KT 2 1/2SM +RA BR OVC012 16/14 A2910 RMK AO2 PK WND 21049/1002 PRESRR P0009 TSNO

KIJD 310852Z AUTO 20027G46KT 8SM -RA OVC014 16/13 A2918 RMK AO2 PK WND 19050/0814 SLP882 P0003 60006 T01610133 58075

KBDR 310952Z AUTO 21031G44KT 2 1/2SM -RA BR BKN014 BKN018 OVC023 13/13 A2909 RMK AO2 PK WND 18053/0928 RAB35 PRESRR SLP852 P0024 T01330128

KHVN 310936Z AUTO 19033G46KT 1 3/4SM R02/4500VP6000FT +RA BR BKN017 OVC022 14/12 A2909 RMK AO2 PK WND 18053/0916 PRESFR P0007 $

KGON 311103Z AUTO 22031G47KT 3/4SM R05/4000VP6000FT +RA BR SCT006 BKN012 OVC018 14/14 A2914 RMK AO2 PK WND 22047/1059 P0013

Last night I posted about the low level jet that was progged to develop over Connecticut during the wee hours of the morning. That most certainly happened! Here’s the 3-hour 6Z NAM forecast for 9 UTC. You can see a small sliver of 100+ knot winds at 850mb over W CT. The core of the jet was overhead and strengthening between 9Z and 11Z as it moved from west to east.

Screen shot 2013-01-31 at 8.27.06 AM

While the NAM frequently is generating 100 knot LLJ in the 24-48 hour window it’s unusual to see it actually verify overhead. Even though we’re used to seeing jets of the speed on prognostications check to see how often they actually happen! Here’s the KBOX Vad Wind Profile from 10:39 UTC to 11:26 UTC to show just how close NAM’s 3-hour wind forecast was to reality.

Screen shot 2013-01-31 at 8.32.07 AM

There are several 105 knot isotachs there!!! Some of them are only 4kft AGL. It’s not much of a surprise that Blue Hill Observatory with its wide open exposure at 635ft AGL outside of Boston was able to gust over hurricane force with this kind of wind profile!

KMQE 311154Z AUTO 20041G56KT 14/13 A2905 RMK AO1 PK WND 18070/1123 SLP847 P0015 60036 70049 T01440133 10150 20139 55043 $

I bet West Peak in Meriden was able to get a gust between 70 and 80 knots during the peak of the winds overnight with their open southerly exposure to the sound and 1,000 foot elevation. If you wanted to fly like a bird off Castle Craig this was your morning to try it!

Besides the low level jet that was anomalously strong we also had another factor that helped winds at the surface. Some turbulent mixing was able to mix down a sliver of the core of the LLJ but a strong isallobaric wind component at the surface helped increase the winds above what you’d expect from the already tight gradient.

KHFD 310653Z AUTO 19018G30KT 2SM -RA BR BKN013 OVC019 15/14 A2929 RMK AO2 PK WND 18032/0607 SLP919 P0015 T01500139
KHFD 310953Z AUTO 19030G46KT 2SM +RA BR BKN015 OVC023 16/14 A2901 RMK AO2 PK WND 17047/0941 SLP825 P0029 T01610144

The isallobaric wind was ripping as pressures were dropping rapidly. There was no shortage of PRESFR remarks in overnight METARs. In Hartford between 653 UTC to 953 UTC the pressure dropped from 991.9mb to 982.5mb or 9.4mb! That’s a very impressive 3-hour drop.

I didn’t see any evidence of inertial gravity waves on the pressure traces I looked at but the combination of the powerful LLJ, scattered convection and associated turbulent mixing, and a strong isallobaric wind was enough to produce a period of damaging winds this morning.


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