Eastern Pacific Basin Tropical Cyclones

Tropical Depression Eighteen-E Forecast Discussion


000
WTPZ43 KNHC 062042
TCDEP3

Tropical Depression Eighteen-E Discussion Number  10
NWS National Hurricane Center Miami FL       EP182021
400 PM CDT Sat Nov 06 2021

The structure of TD18-E looks a bit ragged this afternoon. The
earlier convective burst has decayed during the diurnal minimum,
though new convective cells are redeveloping to the
southwest and northeast of the estimated center position. A 1549
UTC ASCAT-B pass had peak winds of 29-kt on the north side of the
circulation. The scatterometer wind data also revealed that the
circulation is more elongated from southwest-to-northeast than 24
hours ago with the ambiguities suggesting it is barely
closed. For now, the system will be kept as a tropical depression,
with maximum sustained winds of 30 kt, matching the T2.0/30 kt
subjective Dvorak estimates from TAFB and SAB this afternoon.

The depression continues to move just south of due west at 265/12 
kt. There has been little change to the forecast track reasoning, 
with a prominent mid-level ridge over Mexico steering the system 
generally westward. The depression could gain a bit of latitude 
from 24-72 hours as the ridge weakens a bit over Mexico, but 
afterwards another mid-level ridge takes its place west of the Baja 
California Peninsula. The latest NHC track forecast is very 
similar to the previous forecast, and lies closest to a blend 
between the GFS and ECMWF runs (GFEX) this cycle. 

While the depression this afternoon looks more convectively 
organized than 24 hours ago, the current elongated structure is not 
favorable for intensification in the short term, despite seemingly 
conducive environmental conditions (low shear, warm sea-surface 
temperatures, moist mid-level air). While the intensity consensus 
aids (ICON, HCCA) show a bit more intensification than before, I'd 
like to see if the fragile vortex is able to survive another 24-36 
hours traversing the low-latitudes before showing more significant 
intensification. In addition, the global models continue to show 
little if any strengthening. The latest NHC forecast is a carbon 
copy of the previous one and is closest in intensity to the latest 
ECMWF and LGEM guidance. 


FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z  8.3N  97.7W   30 KT  35 MPH
 12H  07/0600Z  8.2N  99.4W   30 KT  35 MPH
 24H  07/1800Z  8.3N 101.7W   30 KT  35 MPH
 36H  08/0600Z  8.8N 104.1W   35 KT  40 MPH
 48H  08/1800Z  9.2N 106.6W   35 KT  40 MPH
 60H  09/0600Z  9.8N 109.0W   35 KT  40 MPH
 72H  09/1800Z 10.2N 111.6W   35 KT  40 MPH
 96H  10/1800Z 10.4N 116.8W   35 KT  40 MPH
120H  11/1800Z 10.5N 122.5W   35 KT  40 MPH

$$
Forecaster Papin



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