Good morning. Maria has continued to gradually organize overnight and as of the 11 am advisory is now a tropical storm with sustained winds of 55 mph. Environmental conditions are conducive to further (possibly rapid) development and there is every reason to expect that it will affect the southern leeward islands as a significant if compact hurricane, most likely category 2. Mid-week, it (I’m trying hard to stick with “it” here, but I hope you’ll forgive me if I fall into old habits of “she” for Maria and “he” for Jose) is very likely to pass close to or over the US Virgin Islands and Puerto Rico as a major hurricane, most likely category 3 but category 4 is not out of the question. A basic rule of thumb is to always prepare for one category higher than you are forecast to get. The Virgin Islands in particular are very vulnerable, having been severely impacted by Irma. Puerto Rico’s infrastructure is also far from up to dealing with this kind of impact. The same is true for the Dominican Republic.
Here are the ECMWF ensembles from the overnight run:
And here are the GFS ensembles from this morning’s run:
The model guidance is quite tightly clustered through day 4, taking Maria somewhere in the vicinity of Puerto Rico or eastern Dominican Republic. It’s fair to say that there is high confidence in the track forecast to that point.
After that, things diverge quickly and are highly dependent upon what happens with Hurricane Jose. Jose is currently moving north in the direction of New England but is almost certain to turn east well before landfall, while weakening to a tropical storm in the face of colder waters and increased shear. After that, it appears Jose will be trapped by a blocking ridge and turn south into yet another cyclonic loop. (The ECMWF has a small window for Jose to escape, more about that later.)
The GFS insists on strengthening Jose back into a significant hurricane over the cold waters of the north Atlantic. To put it mildly, I struggle mightily to take that solution as even remotely credible. At any rate, a strong Jose creates a weakness that allows Maria to turn north in the vicinity of Hispaniola and then escape out to sea.
The ECMWF portrays a weak remnant of Jose moving south then west into the NE states or Canada. This is substantially more credible but still a very uncertain solution in my mind. That solution provides less of a weakness than the GFS solution but still allows Maria to move north, possibly to landfall somewhere from North Carolina up.
A third possibility not currently depicted by either GFS or ECMWF but favored by a couple of other global models has Jose either dissipating off of Nova Scotia or escaping out to sea, in which case we would get a stronger ridge that would force Maria towards the southeast US coast.
Bottom line is it will be a few days before we can have any confidence regarding possible US mainland landfall.
But what is already a fairly confident forecast is bad enough. We are likely to see the third US landfall of a major hurricane when Maria reaches the US Virgin Islands and Puerto Rico. And folks still barely beginning their recovery from Irma are likely to be hit again.
I will be updating this diary during the afternoon with additional model output and any other news of significance.
Sunday, Sep 17, 2017 · 5:51:42 PM +00:00
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jrooth
An Air Force reconnaissance plane is inbound into Maria at this time. We should have the first center fix and central pressure reading in about 10 minutes. So far the maximum winds seen are 56 kt at flight level, 50 kt SFMR (a side-looking radar measurement of surface wind)
Sunday, Sep 17, 2017 · 6:20:38 PM +00:00
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jrooth
First center fix:
URNT12 KNHC 171811
VORTEX DATA MESSAGE AL152017
A. 17/17:53:10Z
B. 13 deg 38 min N
056 deg 57 min W
C. 700 mb 2992 m
D. 64 kt
E. 346 deg 7 nm
F. 079 deg 59 kt
G. 336 deg 11 nm
H. 986 mb
I. 10 C / 3046 m
J. 16 C / 3038 m
K. 9 C / NA
L. CLOSED
M. E09/28/16
N. 12345 / 07
O. 0.02 / 1.5 nm
P. AF303 0115A MARIA OB 08
MAX FL WIND 59 KT 336 / 11 NM 17:49:30Z
CNTR DROPSONDE SFC WIND 085 / 3 KT
64 knots is the threshold for a category 1 hurricane.