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NOAA NOAA United States Department of Commerce

Tropical Depression SIXTEEN


400 AM EST MON NOV 21 2016

The cloud pattern associated with the low pressure system located
over the southwestern Caribbean Sea has become better organized over
the past 12 hours, including the development of some banding
features. An Air Force Reserve reconnaissance aircraft yesterday
between 1900-2000 UTC indicated that the low had a well-defined
circulation center, along with flight-level winds of 38 kt and SFMR
surface winds of 32-34 kt in no-rain areas. Since that time, an
intense convective burst with cloud tops of -88C developed near the
center between 0400-0500 UTC, which likely helped to spin up the
inner-core circulation a little more. In addition, ship C6VG7
located 90-100 nmi southeast of the center has been reporting winds
as high 38 kt at an elevation of 34 meters, which adjusts to a
10-meter wind of 30-32 kt. Although cloud tops have warmed since
that earlier strong convective burst occurred, the overall
convective cloud pattern has improved since the recon flight
yesterday. Therefore advisories are being initiated on this system
as a 30-kt depression, which could be conservative.

The depression has been meandering in the same general area for the
past 12 hours or so, and little motion is expected today and early
Tuesday while the cyclone remains trapped within a blocking ridge
pattern. By 36-48 hours, an east-west oriented ridge is forecast by
the global models to develop across the Greater Antilles and the
Bahamas, which is expected to nudge the depression in a slow
westward direction for the remainder of the forecast period, with
landfall possibly occuring after 72 hours. The system is expected to
move across Central America and into the eastern North Pacific by
120 hours as a remnant low. The NHC official forecast track lies
close to the various consensus model forecasts.

Marginal environmental conditions are only expected to support slow
strengthening for the next 36 hours or so. After that, the moderate
vertical wind shear currently affecting the cyclone is forecast to
decrease to less than 10 kt while mid-level humidity values increase
to more than 70 percent. This should allow for the depression to
strengthen into a hurricane by 72 hours before landfall occurs. By
96 hours, the cyclone is expected to be inland over Central America
and undergoing rapid weakening due to the interaction with the
mountainous terrain of that region. The intensity forecast closely
follows the consensus intensity model IVCN.


INIT  21/0900Z 11.5N  79.4W   30 KT  35 MPH
 12H  21/1800Z 11.4N  79.4W   35 KT  40 MPH
 24H  22/0600Z 11.4N  79.5W   40 KT  45 MPH
 36H  22/1800Z 11.4N  79.8W   45 KT  50 MPH
 48H  23/0600Z 11.3N  80.5W   55 KT  65 MPH
 72H  24/0600Z 11.3N  82.0W   65 KT  75 MPH
 96H  25/0600Z 11.3N  84.7W   45 KT  50 MPH...INLAND
120H  26/0600Z 11.0N  88.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

Forecaster Stewart