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Potential Tropical Cyclone Two Forecast Discussion Number 4
2019-07-11 10:46:54| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Thu Jul 11 2019 000 WTNT42 KNHC 110846 TCDAT2 Potential Tropical Cyclone Two Discussion Number 4 NWS National Hurricane Center Miami FL AL022019 400 AM CDT Thu Jul 11 2019 The convective activity associated with the broad area of low pressure is still spread out, and the center of circulation is not well defined at this time. Both surface and scatterometer data indicate that the winds remain near 25 kt. The modest northerly shear affecting the system should not hamper further development. Overall, the environmental conditions still favor the formation of a tropical depression or a tropical storm later today, and as the system moves over warm waters, strengthening is indicated. The intensity models are not as aggressive as they were in previous runs, but still bring the disturbance to hurricane status in about 48 hour or so, as the disturbance approaches the coast. During the past several hours, the low pressure area has barely moved due to weak steering currents. However, a westward or 260 degrees drift at about 4 kt should begin soon. The system is heading toward a weakness in the ridge, and this pattern should induce a slow turn toward the west-northwest and then north during the next 3 to 5 days. The NHC track forecast continues to be located on the western edge of the guidance envelope, and it has been adjusted slightly eastward to be more consistent with the multi-model ensemble TVCA. It should be noted that track errors are typically larger for potential tropical cyclones than more mature systems. In addition, the run-to-run consistency in the track models has been poor, so confidence in the details of the forecast is not high at the moment. Key Messages: 1. A tropical depression is expected to form later today over the northern Gulf of Mexico. Conditions appear favorable for this system to strengthen to a hurricane that will bring storm surge, rainfall, and wind hazards to the central Gulf Coast. 2. A dangerous storm surge is possible in portions of southern and southeastern Louisiana where a Storm Surge Watch is in effect. Additional storm surge watches may be needed later today. Residents in these areas should monitor the progress of this system and listen to any advice given by local officials. 3. A Hurricane Watch is in effect for much of the Louisiana coast and additional tropical storm or hurricane watches and warnings could be required. Residents in the watch area should ensure they have their hurricane plan in place. 4. The slow movement of this system will result in a long duration heavy rainfall threat along the central Gulf Coast and inland through the lower Mississippi Valley through the weekend and potentially into early next week. Flash flooding and river flooding will become increasingly likely, some of which may be significant, especially along and east of the track of the system. FORECAST POSITIONS AND MAX WINDS INIT 11/0900Z 27.5N 88.2W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 11/1800Z 27.5N 88.7W 30 KT 35 MPH 24H 12/0600Z 27.7N 89.5W 40 KT 45 MPH 36H 12/1800Z 28.0N 90.3W 50 KT 60 MPH 48H 13/0600Z 28.5N 91.1W 65 KT 75 MPH 72H 14/0600Z 31.0N 91.7W 45 KT 50 MPH...INLAND 96H 15/0600Z 33.5N 92.0W 30 KT 35 MPH...INLAND 120H 16/0600Z 36.0N 90.9W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Avila
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