Hurricane Sandy / Courtesy: WeatherTap
The northeast is facing a serious threat from Hurricane Sandy with the potential for a devastating impact somewhere in the storm’s path. The exact track is still uncertain as we are about 96 hours out before the brunt of Sandy will approach.
Hurricane preparations should begin for people living in Connecticut tonight or tomorrow. You will have Friday, Saturday and most of Sunday to prepare. Threats include serious coastal flooding, inland flooding, wind damage, and prolonged power outages. The extent of any of these threats is too early to know but it’s important to be prepared for any event.
I do think, however, that this storm will be an historic event for someone in the northeast. Too early to say if it’s New England or Washington, D.C.
This is the 5 p.m. forecast from the hurricane center. The forecast shows Sandy jogging east of North Carolina (over the Gulf Stream, by the way) and then hooking left toward the northeast. This type of track is virtually unprecedented for a New England hurricane (accurate records back into 1800s) yet is forecast by virtually every tool at our disposal.
The NHC keeps the storm a hurricane up until landfall and then transitions it to a “post-tropical” low that still contains powerful 65 mph sustained winds (which is what Irene was at landfall in New York).
Our computer models are in remarkable agreement with a track that takes the storm into New England or the northern Mid Atlantic. There are a few outliers, such as the 12z op Euro, that bring the hurricane into the southern Delmarva penninsula but that seems unlikely to me. It would be extremely difficult to get a hurricane to take such a hard left hook to start moving due west of event south of west like the Euro shows.
While the vast majority of these tracks would produce a signifcant impact in Connecticut the exact track may mean the difference between a full fledged hurricane and what would seem similar to a more typical fall-like nor’easter.
The question becomes what will the intensity of Sandy be at landfall and will she still be a hurricane? The answer to the second question is, in my opinion, yes. As I discussed yesterday the models keep Sandy as a warm core system during its slow extratropical transition. That continues today per Bob Hart’s cyclone phase space diagrams.
With Sandy expected to maintain a warm core and feature an expanding wind field the concern for serious impacts is quite high. Our computer models indicate that the hurricane may actually strengthen as it approaches the northeast. With colder waters to our south how is that possible? The answer is that the models show a remarkable amount of synoptic scale lift that will make strengthening of the storm possible as it heads to our latitude.
We always talk about the jet stream and how it influences our weather. Local maxima in the jet stream, called jet streaks, are what lead to really fun kinds of weather.
From quasigeostrophic theory it’s easy to come figure out which areas of a jet streak feature rising air or sinking air. It can be done with PV thinking too (which I actually think is a cooler way of demonstrating) but here’s the deal with QG.
Jet Streak Schematic / Courtesy NC State
108 Hour GFS 250mb height/isotach Forecast
In a jet streak you have rising motion in the right entrance region and left exit regions. In Sandy’s case you can see 2 powerful jet streaks in the eastern U.S. There’s also a smaller (easterly) jet streak over Newfoundland and a second jet out over the north Atlantic southeast of Nova Scotia.
I labeled the favored areas of the jet stream for QG upward motion with LFQ for left front (exit) quad and RRQ for rear right (entrance) quad. I’ve never seen a coupled jet structure like this in my life over this part of the Atlantic. The “Boom!” indicates what will happen in between the 4. Even if there wasn’t a hurricane coming north we would probably still see a sizable nor’easter given this setup near the tropopause.
All of this results in an extremely large area of upper level divergence that will be located over Sandy. This divergence will help keep the storm intense and possibly, depending on how the Sandy’s extratropical transition goes, intensify the hurricane.
All of this means we need to be prepared for a direct hit from a hurricane. While it’s certainly possible that this storm will just miss us to the east or west the wind, rain, and coastal flooding from Sandy will stretch far from the actual landfall location. It looks like Sandy will be quite a storm for someone… let’s hope it’s not here!