Tropical Storm Franklin Forecast Discussion Number 5

By | August 21, 2023

WTNT43 KNHC 212049

Tropical Storm Franklin Discussion Number   5
NWS National Hurricane Center Miami FL       AL082023
500 PM EDT Mon Aug 21 2023

Franklin is not an especially well-organized tropical cyclone this 
afternoon. The NOAA reconnaissance mission has been sampling the 
storm for a large part of the afternoon, and found a center 
to the south of where the position was estimated earlier today. In 
addition, the winds on the southwest side of the circulation are 
more diffuse, and overall the circulation is a bit more elongated 
than what the plane found yesterday at this time. Peak 850-mb flight 
level winds were at 48 kt just to the northwest of the circulation, 
which supports an intensity between 40-45 kt after using a standard 
reduction. The initial intensity will remain at 45 kt for this 
advisory, which is also in between the higher TAFB and lower SAB 
intensity estimates. 

The tropical storm has been meandering today, and my best guess at 
an initial motion is a drift south of due west at 265/4 kt. Given 
the current elongated nature of the surface circulation, the short- 
term track forecast is tricky, ranging from the GFS on the east side 
of the guidance envelope that has a center reformation to the 
northeast, and the CMC and ECMWF which are on the western side of 
the guidance envelope. The steering currents are also poorly defined 
currently due to a large mid-oceanic trough in the western Atlantic 
disrupting the flow pattern. Mid-level ridging eventually builds in 
to the east of Franklin, which should ultimately induce a northward 
motion by 24-36 h, and then northeastward between 48-96 h, as a 
mid-latitude trough reinforces the weakness to the north of the 
storm. The track guidance has slowed down again compared to the 
previous cycle, prolonging the time the system will remain over the 
Caribbean Sea before it moves over Hispaniola. The NHC track 
forecast is once again slower than the previous cycle and has also 
been nudged a touch westward compared to the previous one, but is 
now a bit east of the simple and corrected consensus aids. 

Given Franklin's current structure, I am somewhat skeptical there 
will be a lot of meaningful near-term intensification, especially 
while moderate vertical wind shear continues to disrupt the 
convective structure. However, both the GFS- and ECMWF-based SHIPS 
guidance indicate that the shear will briefly drop under 10 kt in 
about 24 hours, and when combined with warm 29 C sea-surface 
temperatures, it still seems prudent to show some intensification 
before Franklin moves inland over Hispaniola. Significant land 
interaction over the higher terrain will then lead to weakening, 
which could be underdone here given the current track over some of 
the most mountainous terrain. After Franklin emerges into the 
western Atlantic, another round of southwesterly shear may slow the 
rate of reintensification, and the latest NHC intensity forecast is 
a bit more subdued than the previous one, once again electing to 
follow the HCCA consensus aid. Given the complex intensity factors 
mentioned above, this is a low confidence forecast. 


1. 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 

2. Franklin is expected to bring tropical storm conditions to 
portions of the Dominican Republic and Haiti beginning on Tuesday 
where Tropical Storm Warnings are in effect.


INIT  21/2100Z 14.3N  70.1W   45 KT  50 MPH
 12H  22/0600Z 14.3N  70.9W   45 KT  50 MPH
 24H  22/1800Z 15.3N  71.3W   50 KT  60 MPH
 36H  23/0600Z 17.2N  71.2W   55 KT  65 MPH
 48H  23/1800Z 19.1N  70.8W   40 KT  45 MPH...INLAND
 60H  24/0600Z 20.6N  70.3W   45 KT  50 MPH...OVER WATER
 72H  24/1800Z 22.2N  68.7W   50 KT  60 MPH
 96H  25/1800Z 23.6N  66.0W   60 KT  70 MPH
120H  26/1800Z 25.6N  65.5W   70 KT  80 MPH

Forecaster Papin

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