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Tropical Storm Franklin Discussion Number   7
NWS National Hurricane Center Miami FL       AL082023
500 AM EDT Tue Aug 22 2023
 
Although deep convection has increased overnight in areal extent 
with frigid cloud top temperatures of -84 Celsius, Franklin remains 
a somewhat disorganized tropical cyclone.  Unfortunately, neither 
the METOP-B and C scatterometer passes (both misses) or microwave 
data were helpful in determining with confidence the center of 
circulation.  Best estimate is near the new deep convective bursts 
near the northwest edge of the convective overcast.  The initial 
intensity is held at 45 kt for this advisory and is supported by 
the TAFB and SAB satellite intensity estimates, and a blend of the 
latest UW-CIMSS objective techniques.  
 
The deep-layer flow southeast of a mid-Atlantic trough to the
northwest of Franklin is producing moderate southwesterly vertical
wind shear over the cyclone.  Statistical-dynamical ECMWF and GFS 
SHIPS guidance indicate that Franklin will remain in a harsh shear 
environment for next several days, and interaction with the higher 
mountainous elevations as it traverses Hispaniola should further 
disrupt the storm's circulation.  By the weekend, however, the 
global models are in good agreement that the upper wind pattern
will become more conducive for strengthening and the official
forecast shows Franklin become a hurricane over the southwest
Atlantic by day 4.
 
The initial motion is estimated to be an uncertain northwestward 
drift at 325/3 kt.  Intermittent deep bursts of convection due to a 
moderate deep-layer wind shear environment can induce surface 
center reformation, particularly where the coldest cloud top 
temperatures and the mid-level circulation center resides. Franklin 
should remain in a weak synoptic steering current due to the 
previously mentioned high amplitude mid-atlantic trough in the 
western Atlantic for the next 12 hours or so.  A subtropical high 
eventually builds in to the east of Franklin, which should 
induce a northward motion, and then a northeastward track after the 
48 hour period.  Toward the end of the forecast period, Franklin is 
expected to turn generally northward as a mid-latitude shortwave 
pulse moves off of the eastern seaboard on Sunday and strengthens 
the weakness over the western Atlantic.  The forecast track lies 
between the TVCA simple multi-model consensus the the HFIP corrected 
consensus aid, and is slightly faster (along-track spread) than the 
previous advisory between the 48 and 72 hour periods.
  
 
KEY MESSAGES:
 
1. Heavy rainfall from Franklin is expected across portions of 
Puerto Rico and Hispaniola into Thursday. 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 today into Wednesday.
 
2. Franklin is expected to bring tropical storm conditions to
portions of the Dominican Republic and Haiti beginning today
where Tropical Storm Warnings are in effect.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/0900Z 14.8N  70.3W   45 KT  50 MPH
 12H  22/1800Z 15.7N  70.5W   50 KT  60 MPH
 24H  23/0600Z 17.3N  70.5W   55 KT  65 MPH
 36H  23/1800Z 19.3N  69.7W   40 KT  45 MPH...ALONG COAST
 48H  24/0600Z 21.6N  68.8W   45 KT  50 MPH
 60H  24/1800Z 22.7N  67.7W   50 KT  60 MPH
 72H  25/0600Z 23.2N  66.3W   55 KT  65 MPH
 96H  26/0600Z 23.6N  64.3W   65 KT  75 MPH
120H  27/0600Z 26.3N  64.6W   70 KT  80 MPH
 
$$
Forecaster Roberts/Pasch
 
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