Tropical Cyclone Discussion

095
WTNT43 KNHC 282043
TCDAT3
 
Tropical Storm Hanna Discussion Number   2
NWS National Hurricane Center Miami FL       AL082026
500 PM AST Mon Sep 28 2026
 
Since this morning, Hanna's convective structure has become a little 
more disheveled with the tropical storm is affected by 20-25 kt of 
westerly vertical wind shear. There has not been an appreciable 
change in the subjective or objective intensity estimates this 
afternoon, and the initial intensity is held at 40 kt.

The initial motion of Hanna is east-southeastward at 115 degrees at 
15 kt. Hanna is embedded in the flow in between a longwave trough to 
its northeast, and a larger subtropical ridge to its south. This 
synoptic pattern should result in a continued east-southeastward 
motion over the next 24-36 hours with some gradually slow down in 
the track as the mid-latitude trough leaves Hanna behind. Much of 
the track guidance then shows a slow east-northeastward motion 
after the cyclone becomes more vertically shallow and becomes 
influenced by a low-level ridge centered south of the Azores. The 
NHC track forecast is very similar to the previous one, roughly in 
between the simple (TVCN) and corrected consensus (HCCA) aids.

Vertical wind shear over Hanna is expected to persist in over the 
next 48-72 h, though because the tropical storm is currently moving 
in the same direction as the shear vector, bursts of deep convection 
down-shear of the center may allow for some slight intensification, 
which is reflected in the HCCA intensity guidance. However, when 
Hanna slows down and turned more east-northeastward, the shear is 
expected to shift more out of the north, importing very dry 
tropospheric air into the circulation. Simulated satellite imagery 
from the ECMWF and hurricane-regional models still show convection 
ceasing over the storm in around 60 h, marking its transition to a 
post-tropical cyclone in the forecast. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/2100Z 36.5N  48.7W   40 KT  45 MPH
 12H  29/0600Z 35.5N  46.1W   45 KT  50 MPH
 24H  29/1800Z 34.3N  44.3W   45 KT  50 MPH
 36H  30/0600Z 33.9N  43.4W   40 KT  45 MPH
 48H  30/1800Z 34.2N  42.5W   35 KT  40 MPH
 60H  01/0600Z 34.8N  41.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  01/1800Z 36.0N  38.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  02/1800Z...DISSIPATED