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Tropical Storm Franklin Discussion Number   1
NWS National Hurricane Center Miami FL       AL082023
500 PM AST Sun Aug 20 2023
 
This afternoon we have received a wealth of data from both a NOAA
reconnaissance mission and satellite imagery near the area of low
pressure located in the eastern Caribbean Sea. Earlier visible
satellite imagery showed the system had likely formed a tight
low-level vortex based on the earlier cloud motions before a
convective burst obscured the center. Scatterometer data that
clipped the system on the east side also showed winds near tropical
storm intensity. The NOAA aircraft flew through the system shortly
thereafter, and found the system had indeed formed a well-defined
center, with 950-mb flight level winds of 51 kt just to the
northeast of the center. All this information confirms that
Tropical Storm Franklin has formed this afternoon, with an initial
intensity set at 40 kt.
 
The initial motion is off to the west-northwest at 290/12 kt. Over 
the next 24 hours this general motion should continue while the 
system remains steered by a narrow mid-level ridge. Thereafter, a 
large mid-ocean trough over the western Atlantic will produce a 
pronounced weakness in this ridging, likely causing the tropical 
storm to make a sharp turn northward, bringing the storm near or 
over the large island of Hispaniola in about 48-60 h. Afterwards, 
another mid-latitude trough is forecast to amplify southward, 
maintaining this weakness, and resulting in Franklin turning 
northeastward towards the end of the forecast period. There is a 
decent amount of spread in the track guidance, related to just when 
Franklin will make the initial northward turn. For this initial 
forecast, the NHC track forecast will stick close to the track 
consensus TVCN, which favors a track in between the latest ECMWF and 
GFS solutions, favoring the GFS a bit more.
 
Intensity wise, Franklin may have to deal with a bit of westerly
wind shear in the short-term, limiting more robust intensification
early on. However, this shear drops off as the system makes its turn
northward towards Hispaniola a bit more intensification is shown
with a 55-kt intensity peak as Franklin approaches the coast. The
intensity forecast then is complicated by the fact that Franklin
will likely pass near or over the island sometime in the 2-3 day
time period, and some weakening is shown during this time.
However, the forecast environment after the system re-emerges into
the Western Atlantic looks mostly favorable, with reintensification
likely as long as the system is not too disrupted by the higher
terrain of Hispaniola. The NHC intensity forecast is in good
agreement with the consensus aids, and lies closest to the HFIP
corrected consensus approach through the forecast period.
 
Based on the current track forecast, a tropical storm watch has
been issued for the entire southern coastline of Haiti and the
Dominican Republic.
 
 
KEY MESSAGES:
 
1. Franklin is forecast to approach Hispaniola late on Tuesday and
move across the island on Wednesday as a tropical storm, bringing a
risk of flooding from heavy rainfall, strong winds, and dangerous
waves along the coast.
 
2. Heavy rainfall from Franklin is expected across portions of
Puerto Rico and Hispaniola through the middle of the week. The heavy
rainfall may produce areas of flash and urban flooding as well as
river rises and mudslides. Across Hispaniola, significant and
potentially life-threatening flash flooding is possible Tuesday into
Wednesday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  20/2100Z 14.6N  67.1W   40 KT  45 MPH
 12H  21/0600Z 15.0N  68.9W   45 KT  50 MPH
 24H  21/1800Z 15.4N  70.7W   45 KT  50 MPH
 36H  22/0600Z 15.8N  71.5W   50 KT  60 MPH
 48H  22/1800Z 17.2N  71.5W   55 KT  65 MPH
 60H  23/0600Z 19.1N  71.1W   50 KT  60 MPH...INLAND
 72H  23/1800Z 21.0N  70.6W   55 KT  65 MPH...OVER WATER
 96H  24/1800Z 23.9N  67.5W   65 KT  75 MPH
120H  25/1800Z 25.4N  65.0W   75 KT  85 MPH
 
$$
Forecaster Papin
 
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