Sunday, September 17, 2017

Hurricanes Jose and Maria, Tropical Depression Lee: September 17, Update A

A sunday afternoon cheese and wine o’clock update, which may take a little time as there is so much going on!

Hurricane Jose
A plane went into Jose today and found that his winds had increased to 90mph and central pressure is 972mb, which makes him a strong cat 1 storm (cat 1 range: 74-95mph). His convection is actually about the same as yesterday, with no clear eye:

I would say he is marginally weaker than 90mph, because we should start to see an eye trying to develop and we aren’t seeing that yet. But it’s close enough to within a few mph and he is a cat 1 storm, which I do agree with. He is quite a big boy though, with outer bands covering the length a large portion of the US eastern seaboard:
Like yesterday, you can see the clouds streaming off to the northeast because of wind shear, which of course puts Bermuda in the path of some of those rain-bands. No golf today. 

He is currently at 31.9N, 71.8W, heading N at 9mph. This center is to the south of the main area of convection, again because of that wind shear. The track is also pretty much the same and he will stay in the Atlantic, east of most of the US, but possibly clipping the New England area on Wednesday:
There is quite a lot of uncertainty in this because we aren't sure quite where he will turn to the northeast. I think his structure is a little weaker than yesterday, with slightly smaller vorticity (circulation) in the upper troposphere. It is also offset from the circulation in the middle and lower troposphere, again because of wind shear. You can see this in the vorticity maps. Here are the maps for the lower (850mb), middle (500mb), and upper (200mb) troposphere:

The wind shear looks like it will continue to remain strong (inhibiting too much development) until he gets to around the latitude of DC. But he is passing over warm water with sea surface temperatures of over 29 deg C, and the upper ~75m warmer than 26 deg C, which will work against the wind shear. Overall, a cat 1 storm for the next couple of days seems likely.  

From Tides Online, it looks like the water levels along the coast are generally between 0.5-1ft above normal all the way up to Chesapeake Bay, where water levels are currently 1ft above normal.

<Technical Alert!> A useful source of general marine and coastal data (until he passes North Carolina) is the SECOORA – the Southeast Coastal Ocean Observing Regional Association – website.  You can go to their Marine Weather Portal and click on any of the blue dots, which will show you the measurements at that location. I clicked on the one closest to Jose – a NOAA NDBC (National Data Buoy Center) mooring, which shows that the wind speed was around 23.2 knots (almost 27mph)
SECOORA is part of that US-wide ocean observing network (US IOOS) I mentioned when Harvey was approaching Texas. In the Gulf, you saw data from a buoy through GCOOS - the Gulf of Mexico Coastal Ocean Observing System. There are also observations available for the Caribbean – the CARICOOS, the mid-Atlantic Bight – MARACOOS, and the Northeast Atlantic – NERACOOS, but more on those when needed! &End Technical Alert!>

Hurricane Maria
Again, a plane went into this system and returned data to say that she is now a hurricane. Currently she is a mid-sized cat 1 storm with winds of 80mph (cat 1 range: 74-95mph) and a central pressure of 982mb:
Her convection has certainly picked up today, and given that her circulation is strong (which we can see from the vorticity maps above), I would say she is stronger than this – maybe with wind speeds of around 85mph (no higher than 90 mph as there is no visible eye yet). However, I would agree that she is a cat 1 storm. She continues to move over warm water of course, with the sea surface waters over 29 deg C, and she is now in an area where the upper ~100m of the water column is warmer than 26 deg C which means she will continue to grow. There is very little wind shear ahead of her, and although there was some dry air that was entering the system earlier, that is now also diminishing, which we can see from the improvement in convection. This all points to a mid-sized cat 1 storm at the moment, steadily increasing to a stronger cat 1 overnight, and possibly a weak cat 2 tomorrow (depending on her interactions with the islands) – which we will see if she has an eye.

She is at 14N, 57.9W, heading WNW at 15mph. The track has shifted slightly southwards, primarily because of the data that the plane returned which put the center a little more to the south than they initially thought:
I think she will continue WNW, but may stay a little more on the southern side of that cone, passing through to the Caribbean tomorrow evening/early Tuesday close to Martinique (maybe between Martinique and St. Lucia). If her center passes over any of these islands, they will take her down a notch.

Tropical Depression Lee
Lee was downgraded to a Tropical Depression today with winds officially at 35mph, central pressure at 1007mb (TD range: 17-38mph). The good news is that he got caught in the last vestiges of the Saharan Air Layer:
and as a result, his convection took a bit of a wallop earlier today:
However, it is returning because he is still over warm water and I would place him still as a weak Tropical Storm. This is a battle between the dry and dusty atmosphere, and the warm and wet ocean! He is currently at 13.2N, 37.3W, and continues to head W at 8mph. I think he will continue a little more on the southern edge of the cone in the NHC track:
But he is not a very well developed storm now at all. His structure is quite poor - the lower troposphere circulation is now disjointed from the mid-troposphere circulation (which you can see in the vorticity maps above), so it is a little tricky to pinpoint a good center. He has recently entered an area of wind shear to the north, which you can see as more clouds are streaming off to the northeast. If he continues more westward, he will remain generally south of the shear and continue to remain a little stronger. If he moves on the NHC track, then I agree with them that he will get hit by that wind shear and not get too far. Given the NHC tracks have been pretty good, I will go with their version.

More 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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