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Hurricane Maria Discussion Number  19
NWS National Hurricane Center Miami FL       AL152017
500 PM AST Wed Sep 20 2017

An Air Force Reserve reconnaissance aircraft found that Maria's
center moved off the northwestern coast of Puerto Rico just before
1800 UTC, but the hurricane appears to have taken quite a hit from
the high mountains of the island.  The aircraft measured a maximum
flight-level wind of 106 kt to the east of the center and SFMR
surface winds as high as 91 kt.  The initial intensity is therefore
set to 95 kt.  The central pressure has also risen considerably, and
the latest report from the airplane is 957 mb.

Maria may have taken a temporary jog west-northwestward across
Puerto Rico, likely due to topographic effects, but the longer-term
motion remains northwestward, or 305/10 kt.  Maria should maintain
a northwestward motion for the next 36 hours while it remains on
the southwestern periphery of a mid-level high over the western
Atlantic.  After 36 hours, Maria is expected to turn northward
between the high and a broad trough extending from Tropical Storm
Jose southwestward into the Gulf of Mexico.  The updated track
guidance remains in excellent agreement on this scenario, and the
overall guidance envelope has shifted a bit eastward on this cycle.
The new NHC forecast is therefore nudged a little east of the
previous forecast toward the various consensus aids.

It may take some time for Maria's structure to reorganize itself
now that it is back over water.  Although the intensity models are
not all that enthusiastic about strengthening, the environment
looks conducive for intensification, and the NHC forecast lies at
the upper bound of the guidance, closest to the HWRF solution.  It
would not be surprising, however, if Maria eventually strengthens
more than shown here.  Some weakening is expected by days 4 and 5
due to increased shear, as well as Maria possibly moving over the
cold wake of Tropical Storm Jose to the east of the Carolinas.

We would like to thank the crew of the latest Air Force Reserve
mission for their incredible service today.  After beginning their
mission this morning before the center first moved onshore, the crew
went above and beyond, returning to Curacao to refuel, and then
heading back to Puerto Rico to catch Maria's center when it first
moved back off the coast.  The data collected by the crew was
incredibly important for us to analyze Maria's intensity and
structure after moving across the island, and we are grateful for
their effort.

KEY MESSAGES:

1. Maria's core is moving away from the northwestern coast of Puerto
Rico, and strong winds and storm surge flooding should subside
through early Thursday.  However, heavy rainfall is expected to
continue, and catastrophic flash flooding is occurring on the
island, especially in areas of mountainous terrain.  Everyone in
Puerto Rico should continue to follow advice from local officials to
avoid these life-threatening flooding conditions.

2. A Hurricane Warning is in effect for the northern coast of the
Dominican Republic, the Turks and Caicos Islands, and the
southeastern Bahamas, where Maria is expected to bring dangerous
wind, storm surge, and heavy rainfall.


FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 18.8N  67.3W   95 KT 110 MPH
 12H  21/0600Z 19.5N  68.2W   95 KT 110 MPH
 24H  21/1800Z 20.5N  69.3W  100 KT 115 MPH
 36H  22/0600Z 21.6N  70.3W  105 KT 120 MPH
 48H  22/1800Z 22.9N  71.1W  105 KT 120 MPH
 72H  23/1800Z 25.8N  72.2W  100 KT 115 MPH
 96H  24/1800Z 29.0N  72.5W   90 KT 105 MPH
120H  25/1800Z 31.5N  72.0W   80 KT  90 MPH

$$
Forecaster Berg

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