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Potential Tropical Cyclone Two Forecast Discussion Number 3
2019-07-11 04:45:51| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Wed Jul 10 2019 000 WTNT42 KNHC 110245 TCDAT2 Potential Tropical Cyclone Two Discussion Number 3 NWS National Hurricane Center Miami FL AL022019 1000 PM CDT Wed Jul 10 2019 The system is becoming better organized, and it is almost a tropical depression. Satellite images show a persistent area of deep convection near the estimated center with loosely organized bands surrounding that feature. Earlier, the NOAA Hurricane Hunters found that the pressure has dropped a little to 1009 mb, although the center is not yet well defined. The estimated initial intensity is still 25 kt based on surface observations and the NOAA dropsonde data. The broad low is moving west-southwestward at about 8 kt. The track models are in general agreement that a mid-level ridge centered over the Rockies should cause the system to move slowly westward on Thursday and west-northwestward on Friday. After that time, however, the models diverge considerably with some solutions showing an abrupt northward turn toward a weakness in the ridge and others showing a more gradual one. The latest GFS run has shifted to the west of its previous track, closer to the previous NHC forecast, while the HWRF model has shifted to the right. Based on the overall guidance spread, this track forecast is nudged to the east of the previous forecast to be closer to the various consensus models, which typically are the most reliable. However, this forecast is still near the western edge of the model envelope. 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. Since the system is still in the formative stage, only slow strengthening is likely during the next 12 hours or so. However, after that time more significant strengthening is likely due to very warm SSTs across the northern Gulf of Mexico, a fairly moist atmosphere, and a favorable upper-level pattern over the system. The NHC intensity forecast is largely an update of the previous one and shows the system becoming a tropical storm on Thursday and a hurricane by late Friday. Additional strengthening is likely beyond the 48-hour point and the time it makes landfall, which is predicted to occur in a little less than 3 days. This forecast is fairly close to the IVCN and HCCA models. Key Messages: 1. A tropical depression is expected to form on Thursday 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 on Thursday. 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 needed on Thursday. 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 11/0300Z 27.7N 88.0W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 11/1200Z 27.6N 88.6W 30 KT 35 MPH...TROPICAL CYCLONE 24H 12/0000Z 27.6N 89.5W 40 KT 45 MPH 36H 12/1200Z 27.9N 90.5W 50 KT 60 MPH 48H 13/0000Z 28.3N 91.3W 65 KT 75 MPH 72H 14/0000Z 30.2N 92.1W 60 KT 70 MPH...INLAND 96H 15/0000Z 32.8N 92.3W 35 KT 40 MPH...INLAND 120H 16/0000Z 35.5N 92.3W 20 KT 25 MPH...INLAND $$ Forecaster Cangialosi
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