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| #1148879 (Received by flhurricane at: 5:12 AM 22.Aug.2023) TCDAT3 Tropical Storm Franklin Discussion Number 7 NWS National Hurricane Center Miami FL AL082023 500 AM EDT Tue Aug 22 2023 Although deep convection has increased overnight in areal extent with frigid cloud top temperatures of -84 Celsius, Franklin remains a somewhat disorganized tropical cyclone. Unfortunately, neither the METOP-B and C scatterometer passes (both misses) or microwave data were helpful in determining with confidence the center of circulation. Best estimate is near the new deep convective bursts near the northwest edge of the convective overcast. The initial intensity is held at 45 kt for this advisory and is supported by the TAFB and SAB satellite intensity estimates, and a blend of the latest UW-CIMSS objective techniques. The deep-layer flow southeast of a mid-Atlantic trough to the northwest of Franklin is producing moderate southwesterly vertical wind shear over the cyclone. Statistical-dynamical ECMWF and GFS SHIPS guidance indicate that Franklin will remain in a harsh shear environment for next several days, and interaction with the higher mountainous elevations as it traverses Hispaniola should further disrupt the storm`s circulation. By the weekend, however, the global models are in good agreement that the upper wind pattern will become more conducive for strengthening and the official forecast shows Franklin become a hurricane over the southwest Atlantic by day 4. The initial motion is estimated to be an uncertain northwestward drift at 325/3 kt. Intermittent deep bursts of convection due to a moderate deep-layer wind shear environment can induce surface center reformation, particularly where the coldest cloud top temperatures and the mid-level circulation center resides. Franklin should remain in a weak synoptic steering current due to the previously mentioned high amplitude mid-atlantic trough in the western Atlantic for the next 12 hours or so. A subtropical high eventually builds in to the east of Franklin, which should induce a northward motion, and then a northeastward track after the 48 hour period. Toward the end of the forecast period, Franklin is expected to turn generally northward as a mid-latitude shortwave pulse moves off of the eastern seaboard on Sunday and strengthens the weakness over the western Atlantic. The forecast track lies between the TVCA simple multi-model consensus the the HFIP corrected consensus aid, and is slightly faster (along-track spread) than the previous advisory between the 48 and 72 hour periods. KEY MESSAGES: 1. Heavy rainfall from Franklin is expected across portions of Puerto Rico and Hispaniola into Thursday. The heavy rainfall may produce areas of flash and urban flooding as well as river rises and mudslides. Across Hispaniola, significant and potentially life-threatening flash flooding is possible today into Wednesday. 2. Franklin is expected to bring tropical storm conditions to portions of the Dominican Republic and Haiti beginning today where Tropical Storm Warnings are in effect. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 14.8N 70.3W 45 KT 50 MPH 12H 22/1800Z 15.7N 70.5W 50 KT 60 MPH 24H 23/0600Z 17.3N 70.5W 55 KT 65 MPH 36H 23/1800Z 19.3N 69.7W 40 KT 45 MPH...ALONG COAST 48H 24/0600Z 21.6N 68.8W 45 KT 50 MPH 60H 24/1800Z 22.7N 67.7W 50 KT 60 MPH 72H 25/0600Z 23.2N 66.3W 55 KT 65 MPH 96H 26/0600Z 23.6N 64.3W 65 KT 75 MPH 120H 27/0600Z 26.3N 64.6W 70 KT 80 MPH $$ Forecaster Roberts/Pasch |
