000 WTPZ42 KNHC 181442 TCDEP2 TROPICAL DEPRESSION TWELVE-E DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP122014 800 AM PDT MON AUG 18 2014 The unusually large depression, at least 800 nmi in diameter, has changed little since the previous advisory. A 1047 UTC SSMI microwave overpass indicated that the depression has a well-defined but fully exposed low-level circulation center, with a smaller secondary circulation located about 120 nmi east of the main center. Deep convection has been unable to develop and persist near the main low-level center, possibly due to the aforementioned secondary swirl and modest east-northeasterly mid- to upper-level shear undercutting the otherwise favorable outflow pattern. A blend of the TAFB, SAB, and ADT satellite intensity estimates supports maintaining the initial intensity at 30 kt. Recent passive microwave fix data suggest that the depression has turned toward the west-northwest and is now moving 290/07 kt. The cyclone is expected to turn northwestward later today as the depression moves around the southwestern periphery of a deep-layer ridge located over the southwestern U.S. and northwestern Mexico. A mid-latitude trough/low currently digging south-southeastward along the U.S. west coast is expected to erode the ridge on Tuesday and Wednesday, allowing the cyclone to move more northward. However, the trough is forecast to shift eastward by late Wednesday, which will allow the ridge to build back in to the north of the cyclone and forcing it back on a northwesterly track toward colder water through Days 4 and 5. The new forecast track is similar to the previous advisory track, and lies in the middle of the NHC guidance envelope and close to the consensus model TVCE. The large circulation and associated radius of maximum winds, plus modest easterly shear, are expected to hinder the intensification process for the next 72 hours or so despite the favorable outflow regime. After that, the system is forecast to move over sub-26C and progressively cooler waters, which should induce slow weakening. The intensity forecast closely follows the ICON consensus model through 72 hours, but is a little above ICON after that due to the large cyclone requiring more time than normal to spin down. Although the cyclone is forecast to remain well offshore of the southwestern United States, a northward surge of moisture partly associated with this system could move into that region by late Wednesday and Thursday. Please monitor products issued by your local National Weather Service office for more details on a possible heavy rainfall threat. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 16.7N 117.7W 30 KT 35 MPH 12H 19/0000Z 17.1N 118.7W 35 KT 40 MPH 24H 19/1200Z 17.7N 119.8W 40 KT 45 MPH 36H 20/0000Z 18.3N 120.3W 45 KT 50 MPH 48H 20/1200Z 18.9N 120.5W 50 KT 60 MPH 72H 21/1200Z 20.4N 121.0W 50 KT 60 MPH 96H 22/1200Z 22.8N 122.6W 45 KT 50 MPH 120H 23/1200Z 25.5N 125.0W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Stewart