While threat in Southeast increases, not much change for us right now

Good afternoon.

Hurricane Matthew remains THE weather story, and not much has changed in terms of its intensity or structure. It is still a very well organized storm which is likely to result in severe devastation to several Caribbean islands. Models today have also been trending towards a more severe impact to the Southeast coast. As far as the Northeast threat, uncertainty remains very high as models are still split.

Important points to make

1) Any direct impact to the Northeast will not likely be before the end of the weekend. For the southern Mid-Atlantic, it will most likely be early this weekend.

2) Computer models shifted greatly today, and we need to watch for further trends. Confidence is quite low beyond late this week. Much of the energy involving the blocking ridges and incoming troughs is still over the Pacific where observations are extremely sparse. Some of it is coming ashore now and will be ingested in the 00Z models tonight, and more energy will be added to later models which should help increase the accuracy.

3) There have been multiple runs by NOAA’s Gulfstream IV aircraft dropping upper-level dropsondes across the western Atlantic and Caribbean Sea to help sample the atmosphere in areas of scarce data. Eastern offices have also launched extra weather balloons to sample the atmosphere more often, and more offices will join in this week.

4) This will likely be a devastating hurricane for Haiti and eastern Cuba, as it is expected to impact those islands as a major hurricane. In addition to a direct hit for the Tiburon Peninsula, heavy rain and wind will spread across nearly all of Hispaniola. The island – especially Haiti – is extremely prone to mudslides and flash flooding. Storm surge is another severe threat for southern Haiti.

5) Models today shifted westward in the medium term. As a result, the threat to Florida has increased greatly. Some of the ensembles actually bring the eye ashore in southeast Florida, while most other runs keep it just offshore later this week. Dangerous weather conditions are very possible on the east coast of Florida if current trends hold. Severe conditions are also likely in large parts of the Bahamas.

Current situation
Visible satellite imagery of Hurricane Matthew at 4:45 pm EDT October 3, 2016. It is currently a category 4 hurricane on a path towards the Tiburon Peninsula of Haiti.

Visible satellite imagery of Hurricane Matthew at 4:45 pm EDT October 3, 2016. It is currently a category 4 hurricane on a path towards the Tiburon Peninsula of Haiti.

Hurricane Matthew is currently located southeast of Jamaica and south of the western tip of Haiti. It is slowly moving north and will likely make landfall in the Tiburon Peninsula early Tuesday, and possibly near the eastern tip of Cuba sometime later in the day. It remains an extremely dangerous category 4 storm, with 140 mph sustained winds and a minimum central pressure near 940 mb.

I wouldn’t be surprised to see some strengthening in the next 12 to 24 hours. As a result, it could be near category 5 intensity when it reaches the coast of Haiti. Some weakening is likely afterward as it interacts with the high terrain of western Hispaniola and eastern Cuba. Nonetheless, it should remain an intense and dangerous hurricane at least for the next 3-4 days.


Longer term scenarios

Yesterday, I mentioned there were five plausible scenarios for the track and intensity of Matthew. Today, I will leave the scenarios intact but the probabilities will change. The greatest challenge is that there are several other features in the atmosphere which will drive Matthew over the next week. An outline below shows them in greater detail (based on 12Z GFS).

Explaining the atmosphere
Annotated 12Z GFS vorticity map for Friday night. Although the positions are not certain, the features are well defined.

Annotated 12Z GFS vorticity map for Friday night. Although the positions are not certain, the features are well defined.

The key features are:

A) The vortex representing Hurricane Matthew.

B) Steering ridge located to the east. Most models today have strengthened the ridge, forcing Matthew farther west. It is supposed to retreat eastward late in the week, allowing Matthew to at least go somewhat out to sea.

C) Invest 98L, a weak tropical low located well east of the Bahamas and likely to move northwest. If it develops into a tropical cyclone and reaches deep enough into the atmosphere, it may open up a pathway. The NHC gives it a 50% chance of development, although it is unlikely to strengthen significantly.

D) Late in the week, models suggest a new ridge will develop near the Gulf coast. If it builds in strong and the trough (E) cannot capture Matthew, it is conceivable that the storm could stall out near the southeast coast or offshore. The ridge would prevent a movement far inland.

E) A trough is expected to dig south through the Midwest and towards the east coast this weekend. If the trough is strong, it could capture Matthew and force it northward. Such would likely result in landfall in the Northeast, but if the trough is not as strong, it could just force Matthew out to sea at high latitudes. A weaker trough would likely not be able to capture Matthew.

Track scenarios

Basically, the five scenarios mentioned yesterday all remain the same. None of them can be eliminated at this time, but the probabilities are adjusted:

Florida landfall (Scenario 1) – 25% chance

  • Occurs if the eastern ridge (B) is strong enough to force Matthew farther west than expected. Weakening would be likely afterward depending on track.
  • Supported by some GFS ensembles, GFDL, NAVGEM and JMA

Carolina landfall (Scenario 2) – 30% chance

  • Occurs if the eastern ridge (B) is moderately strong, not enough to force it into Florida but strong enough to make landfall
  • Depending on the incoming trough (E) and the Gulf ridge (D), it could still move out to sea afterward and either Scenarios 3 or 4 below apply
  • Supported by most recent GFS and HWRF

Remains at sea, trough does not capture (Scenario 3) – 15% chance

  • Occurs if the eastern ridge (B) weakens and does not allow the coastal turn to take place while the incoming trough (E) is too weak to phase with Matthew, OR
  • Occurs if 98L (C) strengthens significantly to open a weakness in the eastern ridge (B), enough to recurve Matthew
  • Supported by CMC

Remains at sea initially, trough captures and sends storm north (Scenario 4) – 15% chance

  • Occurs in the same first setup as Scenario 3, except the incoming trough (E) is stronger and phases with Matthew offshore, forcing it north or north-northwest
  • Supported by earlier GFS runs

Stalls out near or off Southeast coast (Scenario 5) – 15% chance

  • Occurs if the Gulf ridge (D) rebuilds in time to prevent the incoming trough (E) from interacting with Matthew, and the eastern ridge (B) remains sufficiently strong and unbroken
  • Supported by earlier ECMWF runs and some ensembles

For the southeast coast from Florida to Cape Hatteras, the situation is a lot more ominous than it was yesterday. However, that does not mean the threat to the Northeast and Mid-Atlantic, at least at this time, is any greater. We are still too far out to specify what the trough will do and how the other features will interact once we get past 25°N latitude. There are so many pieces to the puzzle that we are no closer to reaching a conclusion. Regardless, for Haiti and eastern Cuba, this will likely be a catastrophic storm – we need to send our prayers to those who face imminent impact. Their lives may never be the same.

I will likely have another post tomorrow and hopefully we will know more and be able to narrow down the possibilities – ideally for the better, but we should also prepare for the worst.

Forecaster Craig Ceecee – @Ceecee_Wx

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