Eastern Pacific Basin Tropical Cyclones

Tropical Depression Nine-E Forecast Discussion


480 
WTPZ44 KNHC 071441
TCDEP4

Tropical Depression Nine-E Discussion Number   5
NWS National Hurricane Center Miami FL       EP092022
900 AM MDT Sun Aug 07 2022

The depression remains disheveled this morning, with the center of 
the system still partially exposed to the southwest of the deepest 
convective activity. This structure is primarily due to dry air 
being imported to the center by moderate southwesterly vertical wind 
shear (VWS). Subjective Dvorak intensity estimates were T2.5/35 kt 
from TAFB, T2.0/30 kt from SAB, while the latest objective estimate 
from UW-CIMSS ADT was T2.5/35 kt. Given the lackluster satellite 
presentation, the initial intensity was held at 30 kt for this 
advisory.

The depression is now moving northwest as a slightly slower pace,
estimated at 315/10 kt. A mid-level ridge located northeast of the
system is expected to steer it generally northwestward over the next
few days. One interesting note in the immediate future is there is a
weakness in this ridge to the north, partially related to an
upper-level trough currently shearing the depression. If the system
is able to become better aligned vertically, this could lead to a
rightward shift in the short-term track. The NHC track forecast
accounts for this possibility by being located on the right side of
the track guidance envelope over the next 12-36 hours. This track is
just a bit northeast of the previous one, though it blends back
towards the consensus aids by the end of the forecast, when the
system will likely be steered by the low-level trade wind flow.

A weak upper-level trough located northwest of the depression is the 
primary feature maintaining southwesterly VWS over the system. Over 
the next day or so, both the GFS and ECMWF suggest this feature 
should decay and shift southwest, perhaps related to convection 
building up-shear around the depression while helping to align its 
low and mid-level centers. Should this process occur, 
intensification still appears possible. One alternate solution is 
that convective outflow is not able to displace the upper-level low 
and some amount of shear is maintained over the system. For now, the 
latest NHC intensity forecast will maintain a peak of 45 kt in 36-48 
hours, right around the time the system will be crossing the 26 C 
sea surface temperature (SST) isotherm. After that time, weakening 
is expected over even cooler SSTs and a more stable environment. The 
system is still expected to become a post-tropical remnant low at 
the end of the forecast period. This intensity forecast is on the 
high side of the guidance envelope overall, but is close to the 
latest HCCA consensus aid.


FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 16.8N 109.9W   30 KT  35 MPH
 12H  08/0000Z 17.9N 111.1W   35 KT  40 MPH
 24H  08/1200Z 19.4N 112.6W   40 KT  45 MPH
 36H  09/0000Z 20.7N 114.2W   45 KT  50 MPH
 48H  09/1200Z 21.7N 115.9W   45 KT  50 MPH
 60H  10/0000Z 22.5N 117.7W   40 KT  45 MPH
 72H  10/1200Z 23.1N 119.3W   35 KT  40 MPH
 96H  11/1200Z 24.0N 122.5W   30 KT  35 MPH
120H  12/1200Z 24.0N 125.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Papin




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