000 WTPZ43 KNHC 061453 TCDEP3 Tropical Depression Eighteen-E Discussion Number 9 NWS National Hurricane Center Miami FL EP182021 1000 AM CDT Sat Nov 06 2021 After struggling to produce much in the way of deep convection yesterday, a large nocturnal deep convective burst, with overshooting cloud tops as cold as -85 C, occurred near the estimated center of the depression, though this activity is beginning to wane. An 0815 UTC AMSR2 microwave pass also suggested modest organization under the cirrus, with some banding features present in the deep convection. While last night's scatterometer derived winds only topped out at 27 kt, the most recent subjective Dvorak intensity estimate from TAFB is at T2.0/30 kt. The latest objective UW-CIMSS ADT estimate is even higher at T2.5/35 kt. These estimates support bringing the intensity back up to 30 kt for this advisory. Using both scatterometer and microwave fixes, the depression has maintained a south of due west heading over the past 12-24 hours, with the latest motion estimated at 260/12 kt. This general heading is expected to continue for the next several days with a gradual bend poleward in the latter half of the forecast period as the cyclone rounds the southern side of a expensive mid-level ridge centered over Mexico. The latest NHC track forecast has been adjusted just a bit faster, blending the tightly clustered consensus aids TVCE and HCCA. The depression's overnight convective burst was well anticipated by the both the GFS and ECMWF simulated IR brightness temperature and both models show more persistent activity continuing through the forecast period. Despite this factor, neither model shows much, if any, additional strengthening. This result is interesting, since both the GFS- and ECMWF-based SHIPS guidance indicate low 200-850 hPa vertical wind shear, 27-28 C sea-surface temperatures, and a fairly moist mid-level environment. One factor possibly limiting the intensity forecast is the possibility of higher westerly mid-level shear undercutting the more favorable deep-layer shear. In addition, the tropical cyclone is forecast to remain at fairly low-latitude which can sometimes limit vortex spin-up in a lower Coriolis environment. Even the overzealous HWRF model has come back down to earth, showing only a peak intensity as a more modest tropical storm. The latest NHC intensity forecast does still show TD18-E eventually becoming a tropical storm in 36 h, but does not show any additional development. This forecast is a blend between the slightly higher intensity consensus aids (IVCN, HCCA) with the more pessimistic global model guidance (UKMET, GFS, ECMWF) which do not indicate any additional intensification over the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 8.4N 96.6W 30 KT 35 MPH 12H 07/0000Z 8.2N 98.3W 30 KT 35 MPH 24H 07/1200Z 8.1N 100.7W 30 KT 35 MPH 36H 08/0000Z 8.4N 103.2W 35 KT 40 MPH 48H 08/1200Z 8.9N 105.5W 35 KT 40 MPH 60H 09/0000Z 9.5N 108.0W 35 KT 40 MPH 72H 09/1200Z 10.0N 110.4W 35 KT 40 MPH 96H 10/1200Z 10.5N 115.5W 35 KT 40 MPH 120H 11/1200Z 10.7N 121.2W 35 KT 40 MPH $$ Forecaster Papin