Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
312 PM AST Wednesday Jul 23 2014
Discussion...Tropical Depression Two has been downgraded to a
wave but will remain a strong wave entering the Caribbean. 12z GFS
maintains 40 knot winds at 4 kft only 60 nm south of St. Croix and
south PR coast on Thursday/18z which might be a little overdone though
GFS moves it along at 20 knots entering the Caribbean. Increasing
showers and thunderstorms entering northeast Caribbean Thursday morning
and precipitable water maintaining 2.4 inches while it does. Grids
were upgraded for this which appears likely as it will not
effectively leave the inter-tropical convergence zone during this period. However...the wave
is still not likely to redevelop into a depression especially as
it begins to encounter the low level Caribbean jet late Thursday...
which will absorb the wave. Flooding may not be a substantial
threat since it will be moving so quickly but will have to see how
intense the showers become.
Aviation...shra/tsra ov west PR will decr late after but IFR a threat at
tjmz for next couple of hours. Otw isolated rain showers thruout area into
tonite. Rain showers/thunderstorms and rain increase on Thursday from tropical WV along WI IFR/MVFR all
taf sites and obscured mountains wind below fl150 east 15-25 knots increase 20-30 knots
Marine...increasing showers and thunderstorms on Thursday bring
the threat of lightning...gusty wind and locally higher seas which
may continue through Friday. Increasing trade winds will also
boost seas to 7 feet or so on the Caribbean offshore waters by late
Friday. GFS maintains strength of the wave while passing south of St.
Croix and PR on Thursday. Small Craft Advisory may be necessary for
Caribbean waters tomorrow if this appears likely. Strong wind
gusts in convection at least seems a good bet.
Preliminary point temps/pops...
sju 79 91 79 90 / 40 50 40 40
stt 81 91 80 91 / 40 50 50 50