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Tropical Storm Douglas Forecast Discussion Number 6
2020-07-21 22:37:50| National Hurricane Center (East Pacific)
Issued at 1100 AM HST Tue Jul 21 2020 000 WTPZ43 KNHC 212037 TCDEP3 Tropical Storm Douglas Discussion Number 6 NWS National Hurricane Center Miami FL EP082020 1100 AM HST Tue Jul 21 2020 Douglas appears to have been trying to scour out a little bit of dry air on its western side during the day, although recent visible images suggest that deep convection is attempting to wrap entirely around the center. Because the convective pattern didn't change much from earlier, Dvorak classifications from TAFB and SAB remain T3.5/55 kt, so the initial intensity is held steady on this advisory. Strong ridging to the north of Douglas continues to impart a west-southwestward motion of the cyclone, or 255/13 kt. As mentioned this morning, the ridge is likely to take on a more east-west orientation as a mid-/upper-level low northeast of the Hawaiian Islands retrogrades westward, and this pattern evolution will allow Douglas to turn westward by tonight and then west-northwestward by late Wednesday. That general motion is forecast to continue for the remainder of the 5-day forecast period. The track guidance still showcases a faster ECMWF and slower GFS and HWRF solutions, and the overall envelope and model consensus aids have again nudged northward. The updated track forecast is therefore a little north of the previous one, mainly after 48 hours through day 5. Once deep convection can isolate Douglas's center from the ambient environment, low shear and warm sea surface temperatures of 28-29 degrees Celsius should allow intensification to resume. Despite this morning's hiatus in strengthening, the SHIPS Rapid Intensification (RI) guidance continues to key in on a significant chance of RI during the next day or two. Therefore, the intensity forecast from this morning has been left unchanged, and it still generally lies between the HCCA and Florida State Superensemble, closer to the higher end of the guidance envelope. Douglas should reach its peak intensity in about 48 hours, after which time oceanic heat content values drop to zero, which should cause some gradual weakening. Based on a partial ASCAT-A pass, Douglas's tropical-storm-force wind radii were increased on the northern side. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 12.1N 125.4W 55 KT 65 MPH 12H 22/0600Z 11.9N 127.1W 70 KT 80 MPH 24H 22/1800Z 12.1N 129.5W 80 KT 90 MPH 36H 23/0600Z 13.0N 131.9W 85 KT 100 MPH 48H 23/1800Z 14.4N 134.5W 90 KT 105 MPH 60H 24/0600Z 15.7N 137.3W 85 KT 100 MPH 72H 24/1800Z 16.9N 140.2W 75 KT 85 MPH 96H 25/1800Z 18.5N 146.0W 65 KT 75 MPH 120H 26/1800Z 19.0N 151.5W 55 KT 65 MPH $$ Forecaster Berg
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