Hermine – What an Odd Storm

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Well, Hermine is finally here. My hair is about 5-10 percent grayer than it was before this storm appeared on our “radar”! From the beginning Hermine was an enigma and was a real pain to forecast. Forecasts from our computer models and the National Hurricane Center were exceptionally poor and there’s no doubt a lot of people annoyed at the shifting forecasts for the Labor Day weekend.

I can’t think of one model that performed well and I really can’t think of a tropical/post-tropical storm up here where the models performed worse. It was an ugly storm for numerical weather prediction.

It’s important to remember that here in Connecticut we never expected a major storm and didn’t really expect any serious impacts. For days we were mentioning that a “glancing blow” was the most likely scenario with some isolated power outages and some coastal flooding on the Sound – but nothing worse than a typical nor’easter.

CrXHPOqWIAAUrcGYou wouldn’t get that same impression reading statements from the National Weather Service, however! The initial wording on the tropical storm watch issued days ahead of the storm was beyond ridiculous (and apparently in error).

A 15-25 mph wind with gusts to 35 mph requires “hiding from the wind” and the need to adequately shelter? To me it sounds like a breezy day. I hope anyone who hid on Thursday has emerged from their hiding space to enjoy the beautiful weekend weather.

Even after the threat continued to diminish statements coming from the National Weather Service on Long Island were indicating the kind of damage one would expected to see from a storm like Tropical Storm Irene and not Hermine’s remnant gusts. This statement issued at 1:37 p.m. Sunday seemed way over the top to me.

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We’ve been expecting a “minor” impact from days. Wind gusts in the 40-50 mph range in southeastern Connecticut just doesn’t do this kind of damage.

On Saturday night at 11:50 p.m. the National Weather Service was talking about a “life-threatening storm surge” on Long Island Sound when it seemed clear we would be dealing with mainly offshore winds – and most storm surge guidance was showing minor to low-end moderate coastal flooding at worst.

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This to me is a case of impact based statements gone bad. From the beginning the messaging with Hermine coming from some places has been only “worst case scenario” and not what the most likely scenario was. Getting people to prepare for a worst case scenario is important but we aren’t doing ourselves any good only talking about a scenario that has a 10% chance of occurring.

It struck me as odd that if someone was listening to our newscast at 11 p.m. Saturday that they would have taken away a message of, “minor coastal flooding and some minor wind issues – nothing to be overly worried about” yet if they read the Hurricane Local Statement from the NWS they would have though Irene 2.0 was on its way. We need to do a better job as a weather community communicating actual risk and changing the message when the threat evolves. I’m not sure where this breakdown occurred and why there was such disparate messaging coming out.

This storm was poorly forecast, poorly communicated, and a bust. Unfortunately, this isn’t entirely new – Joaquin last year wasn’t exactly a treat. I wonder what storm in 2017 we can muster up to drive me crazy.

Hermine Makes Landfall

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Hermine made landfall in Florida last night and is moving northeast fairly rapidly. What makes Hermine unusual is that its forward motion will slow off the Mid Atlantic coast and it will stall for several days south of New England. This morning, however, there is some good news for Connecticut. It appears that the “stall” will happen far enough south and east to spare us a major impact Sunday and Monday.

Here’s the overnight GFS and Euro models which show great agreement with a stall east of Delaware/Maryland on Sunday.

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While this will bring some wind and some rain to Connecticut later Sunday and Monday the impact will be limited. At this point I’m not expecting inland flooding or wind damage – though minor coastal flooding is likely on Long Island Sound with prolonged easterly winds. You can see the spike in the tide level Sunday night at Bridgeport on this forecast below. This is not an alarming spike – it is something we see fairly often with storms to our south.

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What’s less clear is what Hermine does after its Labor Day vacation sitting over the Atlantic off of Delaware. Does it come north to New England or scoot out to sea? At this point the latter seems more likely but we certainly don’t know for sure.

The bottom line is at this point Hermine’s impact here appears to be fairly small. Some wind and some rain – enough to ruin beach plans – but not enough to cause widespread damage. There is still a small chance we see a bump north with Hermine’s stall which would increase the wind and rain intensity so we will need to watch it closely. Farther south, the most significant impact from Hermine may be on the Jersey Shore and parts of the Delmarva Penninsula where major coastal flooding and beach erosion is likely.

Hermine Strengthens and Comes North

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It’s becoming more clear tonight that Hermine will have some impact on our weekend weather. What impact that is, however, remains to be seen. Our computer models agree that Hermine will lift north through Florida and track inland through Georgia and the Carolinas.

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The GEFS (shown immediately above) bring the storm very close to Long Island Sunday and Monday while some of the other tropical models and the European ensembles keep the storm a bit farther south. Most of the tropical models (shown above) keep the storm off of Delaware/Maryland as opposed to the Jersey Shore. How far north the storm gets will make a huge difference locally.

The GEFS/GFS (north) solution would be similar to a moderate/strong nor’easter for Connecticut. Rain, gusty winds, and minor to moderate coastal flooding. Certainly not an Irene or Sandy but a pretty nasty storm nonetheless. A reasonable worst case scenario is sporadic power outages, locally heavy rain, and some coastal flooding on the Sound. If a farther south solution verifies then we would see only minimal impacts with clouds, a bit of a breeze, and a few showers.

By the time the storm gets close to our latitude it will be non-tropical. It will be more nor’easter-like than tropical storm-like. Instead of getting it’s energy from warm ocean waters this storm will be maintaining itself through extratropical processes (it will get its energy from baroclinic processes – meaning the storm will have fronts and be interacting with the jet stream).

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So we’re relatively confident this storm won’t pass harmlessly out to sea. Someone in either the Mid Atlantic or southern New England will get a pretty nasty coastal storm for Labor Day weekend from what’s left of Hermine – what we need to figure out is which specific areas will get hit the hardest. Stay tuned!

Tropical Depression 9 – We’re Watching It

The kiss of death for a TV meteorologist is guaranteeing sunshine, low humidity, and comfortable temperatures for a holiday weekend. Something always seems to go wrong. This year Tropical Depression 9 is threatening to ruin the party.

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Tropical Depression 9 is looking better organized this evening and has a decent shot of becoming a strong tropical storm or even a hurricane before making landfall in Florida. What happens after that is much less certain. Here’s the forecast from the National Hurricane Center which brings the storm along the Carolina coast and then slows it down and begins to hook it left in the general direction of New England.

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So what the heck is going on? Why the stall and left hook? Many of our computer models show a somewhat odd evolution including most of the GFS ensemble members and some of the European ensemble members. When this thing gets to our latitude there’s a whole lot of weirdness going on.

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The reason why we’re seeing a bit of a stall/bend back to the west is that TD9 appears will miss it’s one way ticket out to the Atlantic Ocean. The westerlies/jet stream may avoid picking this storm up causing it to meander around our latitude. That allows all sorts of funky things to happen including loop-de-loops, total stalls, movement in odd directions (due west), etc.

The jet stream effectively retreats to the north here with a building ridge to our north and east. This closes the escape hatch most storms love to take.

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It’s important to note that getting a direct hit from a major tropical storm or hurricane with this kind of setup is tough to do. A large blocking downstream ridge helped Sandy get flung west (but more importantly a large cut-off low to the west effectively sucked the storm in). Hurricane Esther in 1961 has a fun looking path from a funky weather pattern.

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But it’s really hard to come up with examples of storms that stalled or had such an odd evolution off the coast that had a major impact here. Sure it’s possible but it’s definitely not likely.

The most likely scenario is a miss or little/no impact in Connecticut. This is still 5 days away and the storm isn’t even a storm yet – just a depression. There’s a small risk (say less than 1 in 4) that these closer to the coast or nearby stall scenarios will verify which would give us a more moderate impact storm (think out of season nor’easter with rain instead of snow). It’s extremely unlikely that we’d see a serious/major impact at this point from a more powerful tropical cyclone- though I can’t rule it out entirely.

So there you have it. We’ll watch this storm every step of the way and keep you posted. The good news is (for the time being) that the most likely scenario is still a sunny and warm Labor Day weekend. Let’s hope it doesn’t change – although we do need the rain!

Concord, MA Tornado

Courtesy: NECN
Courtesy: NECN

Of all the tornado warnings that are issued in southern New England – it’s hard to think of one more perfectly executed than the one issued Monday morning on August 22nd for Middlesex County, Massachusetts by Hayden Frank at the National Weather Service in Taunton.

This was a classic low probability/high impact severe weather event that we deal with with some regularity over the summer. What the models did show was some minor instability and a moderately sheared environment in the lowest levels of the atmosphere. With very low cloud bases (low LCLs) and a moist flow off the ocean (where sea surface temperatures are at their climatological maximum) these are always worth watching but frequently don’t produce much of anything.

The meteorologists at Taunton mentioned this possibility in their 4 p.m. Sunday forecast discussion.

there is a very low
probability of a brief tornado or waterspout developing.  However,
this is a very low probability.

Hayden mentioned it again on NWS Chat to media and Emergency Managers later in the evening.

The 12z models on Sunday weren’t overly impressive – but they were enough to keep things interesting. Here’s the 12z 4km NAM which shows an impressively veered wind profile and a bit of surface-based instability (about 500 j/kg of CAPE).

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The 00z 4km NAM had a similar story to tell with some surface-based CAPE and a similarly impressive veered wind profile in the lowest part of the atmosphere. What is most impressive here is that there’s over 200 m2/s2 of SRH in the 0-1km layer!

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On radar you can see a hint of an MCV that forms just north of Worcester and tracks northeast toward the New Hampshire Seacoast. It’s certainly conceivable that low level shear was enhanced even further near this system. The storm began to look interesting around Marlborough.

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KBOX 0654 BR/BV/CC/NROT

A line of higher reflectivity echoes is moving northeast and there appears to be several embedded mesocyclones. None are particularly tight but the one on the Marlborough/Southborough line is concerning with ~59 knot of Low Level Delta V (LLDV) and nROT > 1.00. These values are higher than the median for recent northeast tornadoes – though the LLDV is not gate-to-gate and is relatively broad.

At 701 UTC some of these embedded mesocyclones persisted and the first Tornado Warning of the morning was issued. nROT continued around 1.00 as the line moved northeast with several mesocyclones appearing and disappearing until one really went to town over Concord. nROT peaked at 1.40 and LLDV peaked at 73 knots.

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KBOX 0717 BR/BV/CC/NROT
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For a night where there was no tornado outlook from SPC (they did mention the threat for an isolated rotating storm, however) and an uncertain evolution this was a very impressive warning performance by the NWS. The warning was issued at 3:01 a.m. and the tornado hit Concord, MA at 3:20 a.m. That’s an impressive 19 minutes of lead time!

Kudos to the NWS to recognizing the threat and watching the radar so closely during the overnight shift. A job well done and a good reminder to watching things very, very closely this time of year when you have strong 0-1km shear, low LCLs, and even a small amount of instability.