Tropical Storm Franklin A Potential Long-Range Threat Update Four

000

WTNT33 KNHC 260248

TCPAT3

BULLETIN

Tropical Storm Franklin Advisory Number  22

NWS National Hurricane Center Miami FL       AL082023

1100 PM AST Fri Aug 25 2023

...FRANKLIN STRENGTHENS...

SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION

-----------------------------------------------

LOCATION...22.4N 66.2W

ABOUT 320 MI...515 KM ENE OF GRAND TURK ISLAND

ABOUT 690 MI...1110 KM S OF BERMUDA

MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H

PRESENT MOVEMENT...ENE OR 60 DEGREES AT 8 MPH...13 KM/H

MINIMUM CENTRAL PRESSURE...996 MB...29.42 INCHES

WATCHES AND WARNINGS

--------------------

There are no coastal watches or warnings in effect.

DISCUSSION AND OUTLOOK

----------------------

At 1100 PM AST (0300 UTC), the center of Tropical Storm Franklin was 

located near latitude 22.4 North, longitude 66.2 West. Franklin is 

moving toward the east-northeast near 8 mph (13 km/h). A sharp turn 

toward the north is expected on Saturday, followed by a northward to 

north-northwestward motion over the western Atlantic through early 

next week.

Maximum sustained winds have increased to near 60 mph (95 km/h) with 

higher gusts. Gradual strengthening is forecast during the next day 

or so, followed by more significant strengthening on Sunday and 

Monday. Franklin is forecast to become a hurricane by early next 

week.

Tropical-storm-force winds extend outward up to 115 miles (185 km)

from the center.

The estimated minimum central pressure based on dropsonde data from 

the Air Force Hurricane Hunters is 996 mb (29.42 inches).

HAZARDS AFFECTING LAND

----------------------

None.

NEXT ADVISORY

-------------

Next complete advisory at 500 AM AST.

$$

Forecaster Reinhart

932 

WTNT43 KNHC 260249

TCDAT3

Tropical Storm Franklin Discussion Number  22

NWS National Hurricane Center Miami FL       AL082023

1100 PM AST Fri Aug 25 2023

Westerly shear continues to affect Franklin tonight, as evidenced by 

the sharp edge to its cold cloud tops on infrared satellite images. 

However, the low-level center that was exposed earlier today appears 

to have moved under the western edge of the convective canopy. An 

Air Force Reserve Hurricane Hunter aircraft flew the storm at 700 mb 

this evening and reported peak flight-level winds of 56 kt, with 

believable SFMR winds in the 45-55 kt range. These data warrant a 

slight increase to the initial intensity (50 kt), especially given a 

recent dropsonde that suggests the surface pressure has fallen to 

996 mb tonight. A recent ASCAT-B pass over Franklin further supports 

this, with peak wind vectors slightly above 45 kt. Note that the 

initial intensity of Franklin is more uncertain than normal, with 

there being a large spread between some of the aircraft data and the 

various objective and subjective satellite estimates.

The intense convection closer to the center of Franklin appears to 

have drawn the surface center more northeastward, and the initial 

motion is an uncertain 60/7 kt. A high pressure ridge building to 

the east of Franklin is expected to steer the cyclone more northward 

and north-northwestward this weekend and into early next week. Then, 

a deep-layer trough is forecast to move across the northeastern U.S. 

and eastern Canada by midweek. This should cause Franklin to 

accelerate northeastward deeper into the mid latitudes through the 

end of the forecast period. The updated NHC track forecast lies to 

the east of the previous one during the first 60-72 h of the period, 

mainly a result of the eastward adjustment to the initial position 

of Franklin. There are some notable forward speed differences beyond 

72 h, with the GFS significantly faster than the rest of the global 

and regional models. With the NHC forecast remaining near the 

multi-model consensus aids, no notable changes were made to this 

portion of the track forecast.

The westerly shear that has plagued Franklin for the past couple of

days is expected to decrease during the next 24-36 h. So while only

modest strengthening is forecast in the near term, more significant

strengthening seems likely thereafter as the cyclone moves over

very warm SSTs (29-30 deg C) and within a more favorable dynamic

environment. The updated forecast shows Franklin becoming a

hurricane by 48 h and peaking near major hurricane intensity in

72-96 h, in good agreement with the latest HCCA and IVCN aids. As

Franklin accelerates to higher latitudes, cooler waters and

increased deep-layer shear will induce weakening and eventually

extratropical transition beyond the end of the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  26/0300Z 22.4N  66.2W   50 KT  60 MPH

 12H  26/1200Z 23.0N  66.0W   55 KT  65 MPH

 24H  27/0000Z 23.9N  66.3W   55 KT  65 MPH

 36H  27/1200Z 25.3N  67.0W   60 KT  70 MPH

 48H  28/0000Z 27.0N  67.9W   70 KT  80 MPH

 60H  28/1200Z 28.8N  68.4W   80 KT  90 MPH

 72H  29/0000Z 30.5N  68.4W   95 KT 110 MPH

 96H  30/0000Z 34.7N  66.5W   95 KT 110 MPH

120H  31/0000Z 40.0N  60.0W   75 KT  85 MPH

$$

Forecaster Reinhart

12:02 PM ADT Friday 25 August 2023

Tropical Cyclone Information Statement (Franklin) in effect for:

Marine Zone

Maritime Waters

East Scotian Slope

Laurentian Fan

Newfoundland Waters

Southeastern Grand Banks

Southwestern Grand Banks

For Tropical Storm Franklin.

This is the first official CHC bulletin on Tropical Storm Franklin expected to become a strong category-2 hurricane tracking west of Bermuda next week. We have been posting general outlooks on our Twitter/X account @ECCC_CHC since Monday.  Computer models can now simulate hurricanes out to 10 days into the future but the scenarios that they depict can be far from reality and generate great speculations.    

Now that we are within about 5 days of Franklin entering Canadian offshore waters, we have a somewhat better idea of how the storm may affect our weather around the middle of next week.  The most likely track as of now is for Franklin to pass well south of Nova Scotia and close to southeastern Newfoundland with the windiest part of the storm staying offshore.  This could certainly change, so check back on this bulletin Saturday and Sunday when it will be updated with the latest forecast discussion. Six-hourly updates are planned to begin early Monday.

Rainfall may be the main aspect of the storm to contend with.  The southern portions of the Atlantic Canadian marine district will have a greater probability of strong winds and high seas.  There will also be non-tropical weather systems well northwest of the hurricane that will be affecting Atlantic Canada during that timeframe (middle of next week). Whenever there is a possible interaction between non-tropical weather systems and a tropical system there is an increased threat for heavy rain.

The next bulletin from the CHC is planned for Saturday afternoon. 

Forecaster: Fogarty

Please continue to monitor alerts issued by the Canadian Hurricane Centre and forecasts issued by Environment Canada.