Tropical Cyclone Discussion

656
WTPA44 PHFO 091433
TCDCP4
 
Tropical Storm Pena Discussion Number  12
NWS Central Pacific Hurricane Center Honolulu HI   CP042026
Issued by NWS National Hurricane Center Miami FL
500 AM HST Mon Nov 09 2026
  
Since the previous advisory, Pena appears to have become less 
organized. An ASCAT-B scatterometer pass sampled the system around 
0830 UTC, finding peak winds to around 35 kt, but indicating the 
low-level circulation has opened up into a trough. A 1044 UTC 
OSCAT-3 overpass, which often inflates surface wind speed 
significantly in heavy rain, also reported peak winds to 35 kt. A 
just-received AMSR3 microwave pass, which sampled Pena around 1204 
UTC, appears to confirm the findings from ASCAT-B that Pena may have 
opened into a trough and is losing convective organization. Based on 
these data, and the possibility of Pena being poorly defined at the 
surface, the initial intensity is lowered to 35 kt for this 
advisory.
 
The initial motion is analyzed as 265/8 kt, just south of due west. 
Pena is forecast to continue generally westward over the next couple 
of days as it is steered by a low- to mid-level ridge to the north. 
Beyond 48 h, the cyclone should turn gradually toward the 
west-northwest and accelerate as a weakness develops in the ridge 
due to a shortwave trough moving across the northwestern Pacific. 
The track guidance continues to remain in good agreement on this 
scenario, and no significant changes were made to the track 
forecast.
 
The intensity guidance is finally converging on a solution that is 
reflected in the new official forecast: Pena could intensify a 
little by 36 h, but it is not forecast to intensify at all 
thereafter. Some intensity guidance still shows weakening and 
dissipation during the next couple of days. It is unclear why, in a 
generally favorable environment, Pena has struggled to intensify, 
except for low-level and vertical structural challenges. Toward the 
end of the forecast period, vertical wind shear is expected to 
increase out of the west-southwest, which, combined with 
increasingly dry mid-level air, should allow Pena to weaken. The 
latest NHC intensity forecast is very similar to the last forecast 
and lies near the middle- to upper-end of the guidance envelope.
 
Given multiple independent data sources suggest that Pena is no 
longer well-organized at the surface, it is possible that Pena 
dissipates as soon as later today.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 11.4N 159.5W   35 KT  40 MPH
 12H  10/0000Z 11.4N 161.6W   35 KT  40 MPH
 24H  10/1200Z 11.3N 163.6W   35 KT  40 MPH
 36H  11/0000Z 11.1N 165.6W   40 KT  45 MPH
 48H  11/1200Z 11.1N 168.0W   40 KT  45 MPH
 60H  12/0000Z 11.4N 170.7W   40 KT  45 MPH
 72H  12/1200Z 12.0N 173.8W   40 KT  45 MPH
 96H  13/1200Z 13.4N 180.0E   35 KT  40 MPH
120H  14/1200Z 14.7N 175.3E   35 KT  40 MPH