Monday, October 10, 2016

Former Hurricane Matthew and Tropical Storm Nicole: October 9, Update A

From what I hear, most people on the east coast are breathing a sigh a relief that Matthew is over and they can get on with life again... is it time for a nice cuppa tea yet? 

Former Hurricane Matthew
He is no longer officially a storm, although there are remnant bits of him floating out there in the Atlantic and some of his convection is now over New England and Canada, it is definitely more of a front than a tropical storm:

He reached the Carolinas yesterday as a very weak cat 1, with winds officially at 75mph (cat 1: 74-95mph). But it wasn't really the winds that were the biggest issue - it was the water. Almost always, it's the water. In looking at the Tidesonline data, it looks like Charleston has had the highest surge on the eastern seaboard, with data showing ~6ft storm surge - that is 6ft above normal tidal fluctuations: 

Add to that the rain, which exceeded 10 inches in some places, and you have a lot of water to wade through - certainly higher than your regular old wellington boots! It looks like North Carolina got the worst of this as far as flooding goes. 

As we now know, the track is not going to loop back around and he won't be revisiting the Bahamas or Florida or anywhere else. There was a huge amount of uncertainty in the models as I mentioned, and the pressure fields were quite complex. However, this also shows that the models have a long long way to go before their 3-5 days forecasts are close to reality! Fortunately, their 1 and 2 day forecasts are much better.

Aftermath Part "I lost count": 
This is the last time you will encounter a Hurricane Matthew (or even a Tropical Storm Matthew) - given the destruction he has caused, I expect that the name 'Matthew' will be retired from the naming list. Any storm that causes this level of damage is removed, otherwise, you see names repeat every 6 years. 

The latest from Haiti: 1000 dead, 1.5 million need humanitarian aid and are in shelters.

The latest from the US: 19 dead, 3000 in shelters, 2 million buildings without power. 

As he is now post-tropical, the NHC stopped giving updates on him. This is also my last update on Matthew. 

Phew... and moving right along, now Nicole!

Tropical Storm Nicole
She is currently at 24.4N, 65.3W, moving N at a whopping 2mph! Still almost stationary because she is still stuck with high pressure all around her - there is no easy path for her to take. The longer she stays stationary, the more unpredictable her future path becomes because the pressure fields around her shift. We can see this because again, her cone of uncertainty is quite large after 2 days... currently, she is scheduled to arrive in Bermuda in 4 days, on Thursday:

Dear Bermuda, I would definitely get the wellies out and dust down the rain jackets and get the wine and ice cream stocked up, but at 4 days out, and with that large cone, don't be too surprised if that forecast track does not quite pan out. Hopefully you can have the day off anyway and play golf or something instead! ;-) 

She is currently at strong Tropical Storm with winds of 65mph, central pressure 989mb (TS range: 39-73mph). The forecast is for her to increase to a hurricane on Tuesday. Her circulation is good in the lower half of the troposphere, but not in the upper troposphere - up there, she is actually part of a front. This is the structure of a Tropical Storm, not a Hurricane, so I agree with the NHC assessment that she is a Tropical Storm. As she moves northwards (eventually), she will move away from this front. 

Her convection is pretty messy right now (clearly she put her make-up on in the dark!): 

You can sort of see the center of circulation, and pretty much all the convection is to the east of that, which indicates that she is under some very strong wind shear. The wind shear is around 30-40 knots, which is strong (for such a weak storm), and it looks like it will continue at that sort of level for another day - possibly much more. 

There are a couple of things keeping her from becoming a hurricane now. First, of course there is the wind shear. But second, there is a lot of dry air to her north:
The sea surface temperatures are certainly warm enough to keep her going - from her current location to Bermuda, the coolest surface temperatures are 27 deg C. The upper 75m of the water column are also above 26.5 deg C at the moment, which will allow her to intensify. 

I am not sure yet whether that dry air will be enough to keep her in check if the wind shear dies down. Ultimately, it is the shear that I will be keeping an eye on. 

I'll be back tomorrow.

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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