Hurricane Maria Discussion Number 17
NWS National Hurricane Center Miami FL AL152017
500 AM AST Wed Sep 20 2017
Radar observations from the San Juan WSR-88D and wind data from an
Air Force Reserve Unit Hurricane Hunter aircraft indicate that
Maria has just about completed an eyewall replacement. Based on
the now-dominant outer eyewall, the eye diameter has increased from
10 n mi to 30 n mi. This has likely contributed to some weakening,
and based on the latest observations from the Hurricane Hunters, the
intensity is set at 135 kt which is at the top of category 4 range.
Although there has been a slight reduction of intensity, Maria
remains an extremely dangerous hurricane. Some weakening is
likely while the system crosses Puerto Rico. Later in the forecast
period, less favorable upper-level winds should cause further
weakening, but Maria is likely to remain a large and powerful
hurricane for the next 5 days. The official intensity forecast is
near or a little above the model consensus.
Maria continues to move between west-northwest and northwest at
about 9 kt. The flow on the south side of a weak mid-level 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 across Puerto Rico and just north of the eastern
Dominican Republic over the next day or so. After that time a
break in the ridge, partially associated with Tropical Storm Jose,
should cause Maria to turn north-northwestward, then northward by
the end of the forecast period. The track guidance remains tightly
clustered through 72 hours, giving 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 latest ECMWF
prediction near the western edge of the guidance envelope but with
all of the reliable models well offshore of the southeast U.S. at
the end of the period. The official forecast is very close to the
latest FSU Superensemble track.
bkmk