Tropical weather analysis - October 28, 2012

By: KoritheMan , 7:23 AM GMT on October 28, 2012

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Sandy

Hurricane Sandy continues moving toward across the western Atlantic. As of the latest NHC advisory, the following information was available on Sandy:

Wind: 75 mph, with higher gusts
Location: 31.5°N 73.7°W
Movement: NE at 14 mph
Pressure: 960 mb
Category: 1 (Saffir-Simpson Hurricane Scale)

After a burst of convection earlier this evening, the thunderstorm activity with Sandy has become a little thin. However, a fresh burst has recently occurred about 50 miles north of the center, which suggests that Sandy is still clinging to tropical cyclone status; an AMSU microwave pass near 2100 UTC also suggested that the cyclone still possessed a warm core.



Figure 1. Latest infrared satellite image of Hurricane Sandy. Image credit: NOAA

Having said that, Sandy is certainly not a typical hurricane. It is interacting with a rather vigorous mid autumn cold front, with coastal radars suggesting that the heaviest rains are in a band well to the west of the center. In addition, water vapor imagery and various microwave data indicate that the hurricane remains embedded in a tongue of very dry air, which is at least partially responsible for the lack of deep convection within the eastern half of the storm. All of this suggests that Sandy is deriving at least a portion of its energy from baroclinic processes.

Interestingly, the vertical shear over Sandy appears to have decreased a little, which I admit was well forecast by the GFS. While this could argue for some restrengthening through tropical processes, sometimes it is better to use one's personal experience and intuition rather than blindly trust a computer model forecast. The environment around Sandy is at the bottom end of the tropical spectrum, with the western side actually more tropical than the eastern half due to that portion of the circulation being more embedded within the warm front associated with the eastern United States cold front. Indeed, the eastern side of the cyclone center appears to be pulling in the cold airmass over Florida and the Gulf Coast states in the wake of the trough. Further corroboration to this is given by areal dew point readings in the upper 50s to lower 60s across coastal sections of South and North Carolina.

My doubts notwithstanding, perhaps there is some truth to the GFS/SHIPS forecast of lower shear: as I said above, the mean vertical shear over the hurricane does appear to have decreased compared to 24 hours ago, and I think dry air is more the reason Sandy is not developing a core again than wind shear. Since there appears to be more baroclinicity than not, I am not forecasting any restrengthening as a tropical cyclone. However, it remains an outside possibility.

In about 24 hours, the global and dynamical models suggest that Sandy will enter a highly baroclinic environment characterized by strong southwesterly flow aloft, progressively cooler water, and cold air advection on the backside of the upper trough. These factors are anticipated to reinvigorate the cyclone a bit, and Sandy is forecast to be of hurricane strength when it makes landfall. Subsequent to moving inland, the storm is forecast to steadily weaken as it moves away from the core of baroclinic forcing. To maintain some continuity with the previous forecast, I still have Sandy as a tropical entity at landfall, although it will clearly not be a very typical one, if that verifies at all.

Coastal buoy observations suggest that Sandy is producing sustained winds to about 35 kt, minimal tropical storm force, across coastal sections of North Carolina. Duck, North Carolina, located in far eastern North Carolina right on the Outer Banks recently reported a sustained wind of 41 mph. Surface observations suggest that these winds have not really penetrated inland, although there have been several reports of tropical storm force wind gusts along the far outer fringes of Sandy's large circulation. These winds are slowly spreading spread northward as Sandy moves in tandem with the upper trough/cold front.

Due to the likelihood of Sandy losing tropical characteristics shortly before landfall, it was decided as a course of least regret by the National Hurricane Center not to issue hurricane watches or warnings north of the tropical storm warning, as the abrupt change in the status of the cyclone would result in an equally abrupt change in the watches and warnings. Instead, high wind watches and warnings have been issued in place of the hurricane bulletins. For forecasts specific to your area, please monitor forecasts issued by your local National Weather Service forecast office. I want to accentuate the threat Sandy poses, and that the status of the warnings are irrelevant. This will deliver significant impacts across virtually all of New England given the enormous wind field, which eclipses even that of Katrina and Ike. I cannot stress enough how seriously people need to take this storm. If things as verify as forecast, Sandy will be worse than Irene or Lee by far.

Widespread and prolonged power outages, possibly up to two weeks in some select locations, heavy rain/inland flooding, significant coastal flooding, and snowfall on the backside of the cyclone are likely across the affected areas. The snows could be particularly heavy over the mountains of West Virginia. Given the marginal thermodynamic environment/stable boundary layer, the attendant threat for tornadoes appear rather low at the moment.

The track forecast remains straightforward, as the model consensus remains tightly clustered. Sandy is accelerating toward the northeast as it moves along the deep-layer southwesterly flow associated with the eastern United States trough. This motion is forecast to continue for another 24 hours or so, after which time the hurricane is forecast to turn northward, northwestward, and finally west-northwestward in an unusual beeline for the New England coast. This occurs underneath a building mid-level ridge over Atlantic Canada as the trough lifts out to the northeast. The consensus has barely budged, and my forecast is only a little north of yesterday's, in best agreement with the TVCE consensus at 0z. This is along the left edge of the dynamical model suite.

Residents living in the affected areas should be making preparations now, as weather conditions will begin to go downhill as early as Sunday night. Landfall is expected Tuesday morning around 3 or 4 in the morning.

5-day intensity forecast

INITIAL 10/28 0600Z 65 KT 75 MPH
12 hour 10/28 1800Z 65 KT 75 MPH
24 hour 10/29 0600Z 65 KT 75 MPH
36 hour 10/29 1800Z 70 KT 80 MPH
48 hour 10/30 0600Z 70 KT 80 MPH...NEAR NEW ENGLAND
72 hour 10/31 0600Z 45 KT 50 MPH...INLAND POST-TROPICAL/EXTRATROPICAL
96 hour 11/01 0600Z 30 KT 35 MPH...POST-TROPICAL/EXTRATROPICAL
120 hour 11/02 0600Z 25 KT 30 MPH...POST-TROPICAL/EXTRATROPICAL

5-day track forecast



Figure 2. My 5-day forecast track for Sandy.

Watches and warnings

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* SOUTH SANTEE RIVER SOUTH CAROLINA TO DUCK NORTH CAROLINA
* PAMLICO AND ALBEMARLE SOUNDS
* BERMUDA

IN ADDITION...HIGH WIND WATCHES AND WARNINGS...ALONG WITH
OTHER WATCHES AND WARNINGS...ARE IN EFFECT FOR THE MID-ATLANTIC
STATES AND MUCH OF NEW ENGLAND. SEE STATEMENTS FROM LOCAL NATIONAL
WEATHER SERVICE FORECAST OFFICES.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE
THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.

Storm surge values

Here are the storm surge values for the affected areas as predicted by the National Hurricane Center.

NC SOUTH OF SURF CITY...1 TO 3 FT
NC NORTH OF SURF CITY INCLUDING PAMLICO/ALBEMARLE SNDS...4 TO 6 FT
SE VA AND DELMARVA INCLUDING LOWER CHESAPEAKE BAY...2 TO 4 FT
UPPER AND MIDDLE CHESAPEAKE BAY...1 TO 2 FT
LONG ISLAND SOUND AND RARITAN BAY...5 TO 10 FT
ELSEWHERE FROM OCEAN CITY MD TO THE CT/RI BORDER...4 TO 8 FT



Invest 98E

An area of low pressure centered roughly 600 miles southwest of Manzanillo is gradually showing signs of organization.



Figure 3. Latest infrared satellite image of Invest 98E. Image credit: NOAA

The upper tropospheric shear looks light, and the biggest impediment appears to be that the system is still largely embedded in the Intertropical Convergence Zone (ITCZ). The global models do not appear to be resolving this situation particularly well, as they show a quasi-stationary system that moves erratically for the next five days in response to several competing gyres within a convectively active ITCZ. For this reason, I am little more conservative than the NHC in regards to development potential.

In addition, the GFS forecasts strong northwesterly shear north of about 16N beginning in about 72 hours, which could arrest any strengthening beyond that time. The farther south the system remains, the better the surrounding environment will be.

This low is expected to move slowly toward the west-northwest, but it is possible that motion could be erratic.

Probability of development in 48 hours: 40%

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5. WunderAlertBot (Admin)
6:44 AM GMT on October 29, 2012
KoritheMan has created a new entry.
4. KoritheMan
7:44 AM GMT on October 28, 2012
Quoting trHUrrIXC5MMX:
nice...btw 98E has a 50% chance now...


I know.
Member Since: March 7, 2007 Posts: 602 Comments: 21303
3. KoritheMan
7:44 AM GMT on October 28, 2012
Quoting NOLA2005:
Good analysis, Kori. Been trying to convince friends in coastal CT & RI that this is a bad situation.


I seriously think this could be comparable to a major hurricane.
Member Since: March 7, 2007 Posts: 602 Comments: 21303
2. NOLA2005
7:40 AM GMT on October 28, 2012
Good analysis, Kori. Been trying to convince friends in coastal CT & RI that this is a bad situation.
Member Since: August 18, 2007 Posts: 0 Comments: 209
1. trHUrrIXC5MMX
7:39 AM GMT on October 28, 2012
nice...btw 98E has a 50% chance now...
Member Since: April 23, 2011 Posts: 104 Comments: 14873

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About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.

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