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11pm AST Tuesday NHC Discussion

Posted by Chris in Tampa on 9/19/2017, 11:27 pm

Hurricane Maria Discussion Number  16
NWS National Hurricane Center Miami FL       AL152017
1100 PM AST Tue Sep 19 2017

Since the previous advisory, WSR-88D radar data from San Juan
Puerto Rico has shown the development of concentric eyewalls and
a double-wind maximum.  This has led to an increase in the size of
the 50- and 64-kt wind radii.
 An earlier Air Force Reserve
reconnaissance aircraft measured a peak flight-level wind of 157 kt
and a few SFMR winds of 149-152 kt in the small inner eyewall
between 2200 and 0000 UTC this evening.  Based on these data, the
initial wind speed was increased to 150 kt.  The minimum pressure
estimated from earlier dropsonde data is 909 mb, which is the tenth
lowest minimum pressure recorded in an Atlantic basin hurricane.
Since the outer eyewall has become better defined and the winds are
increasing within the outer eyewall, it is likely that Maria's
intensification will finally cease.  However, Maria is expected to
remain an extremely dangerous category 5 hurricane until landfall in
Puerto Rico early Wednesday
.  The passage of the core over Puerto
Rico should cause some weakening, but Maria is likely to remain a
major hurricane for several more days. Increasing shear and cooler
waters over the western Atlantic in the wake of hurricanes Irma and
Jose will likely lead to additional weakening late in the period.

Maria is moving between west-northwest and northwest at about 9 kt.
A weak ridge over the western Atlantic is expected to steer the
hurricane on this general heading over the next couple of days.
This track will bring the center of Maria over Puerto Rico and just
north of the eastern Dominican Republic over the next day or so.
After that time, a break in the ridge should cause Maria to turn
north-northwestward, then northward by late in the week.  The track
guidance is tightly clustered through 72 hours, yielding fairly high
confidence in the track forecast through that time.  There is some
increase in the spread of the models at days 4 and 5, with the GFS
and HWRF farther west and faster, while the ECMWF is along the
eastern edge of the guidance and slow.  For now, the NHC track
forecast is between the various consensus models at 96 and 120 h.

KEY MESSAGES:

1. Maria's core will pass near or over St. Croix within the next
few hours and will approach the southeastern coast of Puerto Rico
early Wednesday, bringing life-threatening wind, storm surge, and
rainfall impacts to portions of those islands.  Everyone in these
areas should follow advice from local officials to avoid
life-threatening flooding from storm surge and rainfall.

2. Wind speeds atop and on the windward sides of hills and mountains
and on high-rise buildings could be much stronger than the
near-surface winds indicated in this advisory.


3. A Hurricane Warning is also in effect for the remainder of the
Virgin Islands and the northern coast of the Dominican Republic,
where Maria is expected to bring dangerous wind, storm surge, and
heavy rainfall.

4. A Hurricane Watch is in effect for the southeastern Bahamas and
the Turks and Caicos, where Maria could bring hurricane conditions
on Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT  20/0300Z 17.3N  64.7W  150 KT 175 MPH
12H  20/1200Z 18.0N  65.8W  145 KT 165 MPH
24H  21/0000Z 18.9N  67.3W  125 KT 145 MPH
36H  21/1200Z 19.9N  68.6W  120 KT 140 MPH
48H  22/0000Z 20.9N  69.7W  115 KT 130 MPH
72H  23/0000Z 23.3N  71.4W  110 KT 125 MPH
96H  24/0000Z 26.2N  72.2W  105 KT 120 MPH
120H  25/0000Z 29.5N  72.5W   90 KT 105 MPH

$$
Forecaster Brown

61



In this thread:

11pm AST Tues: 175mph; Eye of potentially catastrophic cat 5 hurricane Maria nearing St. Croix - Chris in Tampa, 9/19/2017, 11:25 pm
    • 11pm AST Tuesday NHC Discussion - Chris in Tampa, 9/19/2017, 11:27 pm

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