Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
858 PM AST Fri Dec 2 2016
Update...scattered to numerous showers embedded in the trade
wind flow moved across eastern, northern and northwest sections of
Puerto Rico and across the surrounding waters during the
afternoon and early evening hours. Several flood advisories were
issued for municipalities across northwest, southeast and eastern
sections of Puerto Rico. Showers activity diminished rapidly over
land areas after sunset. For the overnight and early Saturday
morning, showers will continue to develop over the local waters
with few of them moving onshore affecting the eastern half of PR,
Vieques, Culebra and parts of the U.S. Virgin Islands. For
Saturday afternoon, another round of diurnally induced showers are
expected mostly across central interior and western sections of
Aviation...VFR conditions expected at all taf sites with
vcsh possible overnight at the leeward and USVI terminals as well as
jsj. Light and variable winds overnight, increasing to 10 to 15
knots after 03/13z from the east-southeast.
Marine...seas will continue to subside tonight and Saturday with
seas up to 5 and winds at 10 knots or less overnight.
Previous discussion... /issued 127 PM AST Fri Dec 2 2016/
Discussion...during early morning hours showers began to affect
the eastern portions of Puerto Rico and between 6 and 8 am showers
intensified over the southeast portions of Puerto Rico. These
showers generated major ponding of water across roadways and
tributaries out of their banks. Before mid morning most o these
showers dissipated. After mid morning passing showers affected the
eastern portions of PR including the San Juan metropolitan area.
Tonight...showers will continue to develop over the local waters
with a few moving on shore affect the eastern half of PR and all
local islands. These showers will become more frequent through the
overnight hours. Surface winds are forecast to become from the
east during the weekend. On Saturday an increase on showers is
expected as a weak perturbation is forecast to move across the
area. This weather feature will support early morning showers
across the east half of Puerto Rico and adjacent islands. On
Saturday afternoon...showers will develop mainly over the interior
and west sections of PR with limited shower activity elsewhere.
Beginning on Sunday and into early next week the upper ridge is
to erode and prevailing winds are to become more northeasterly
while increasing once again, as another area of high pressure will
build across the western Atlantic. This prevailing moderate
northeast wind flow will increase the chance early morning
cloudiness and quick passing showers along the north and east
coastal section of the islands.
Aviation...cloudiness is expected to increase over the interior/northwest
PR as well as downwind from El Yunque, with brief periods of MVFR
conditions in rain showers/+shra impacting tjmz/tjbq, as well as vcsh at
tjsj until 02/22z. Surface winds are expected to continue mainly
from the southeast at around 15 kt but locally higher in/near showers.
Marine...seas will continue to subside during the rest of today
and tonight. Seas up to 5 with winds at around 10 knots. The next
significant swell event is forecast for late Monday as a northerly
swell will reach the local Atlantic waters.
Preliminary point temps/pops...
sju 76 89 76 86 / 50 50 20 20
stt 77 85 75 85 / 50 50 20 20