TD9 was essentially stationary overnight. There’s not much change to the forecast track. We’re close enough to landfall (around 36 hours) that it’s time to echo the NHC’s reminder:
It is important not to focus on the forecast landfall point of this system. Among other reasons, dangerous storm surge flooding is likely to extend along the Gulf coast well to the east and south of the path of the center.
This is also important for those of us on the west side of the forecast track. Small movements in the track could easily mean the difference between a little bit of rain and a direct hit from a tropical storm (or somewhat unlikely, hurricane).
I’m going to use a different spag because I think it’s more clear. It doesn’t have all the models the other one does, but it’s easier to understand, I think:
The grey lines are the GFS ensemble – that’s a single model that they run multiple times with slightly differing initial parameters. It’s in pretty good agreement, although you can see that the difference between the western most and eastern most will make a huge difference as to who sees winds and who sees nothing from this system.
The color lines are the various models added to this plot. Each of them could have their own ensemble, but it’s not included here. This is a good compromise spag plot – it shows ensemble for GFS as well as a few other models.
So the most likely track will be taking the system just offshore from Apalachicola and landfall in the Big Bend. However, points east and west must still be vigilant.
That’s the best information we have at this time. As always, I close with the NHC Forecast Discussion product because it’s what I use to help me interpret all the graphics:
TROPICAL DEPRESSION NINE DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 1000 AM CDT WED AUG 31 2016 The system is producing vigorous deep convection, but there is little organization to the overall cloud pattern. Using the Dvorak rules, a bursting but disorganized convective pattern would indicate little change in strength. The intensity is held at 30 kt pending new observations from a NOAA Hurricane Hunter aircraft in a few hours. The tropical cyclone should be in a moderate shear environment, and over very warm water, for the next 36 hours or so. Therefore, strengthening is forecast and the official forecast remains close to the intensity model consensus. Given the reasonably favorable environment, it is appropriate to maintain the hurricane watch for the northeast Gulf coast at this time. The intensity forecast after 48 hours is problematic since the system will be in a decidedly baroclinic environment and under strong upper-level southwesterly flow. This means that any intensification that occurs in 2-3 days will likely have a contribution from baroclinic processes. By 96 hours, the global models depict the system as embedded in a frontal zone, so extratropical transition is forecast to occur by that time. The center is very difficult to locate, but observations from a ship suggest that there has been little motion since earlier this morning, so the initial motion estimate is stationary. There has been little change to the track forecast guidance. A 500-mb trough over the southeastern United States should cause the cyclone to move north-northeastward to northeastward across northern Florida and southeastern Georgia during the next couple of days. Later in the forecast period there is uncertainty as to how far offshore the center will move, with some of the global models such as the GFS and the U.K. Met being close to the northeastern states, and the ECMWF somewhat farther east. The official track forecast lies between these two possibilities. It is important not to focus on the forecast landfall point of this system. Among other reasons, dangerous storm surge flooding is likely to extend along the Gulf coast well to the east and south of the path of the center. FORECAST POSITIONS AND MAX WINDS INIT 31/1500Z 24.6N 88.0W 30 KT 35 MPH 12H 01/0000Z 25.9N 87.4W 40 KT 45 MPH 24H 01/1200Z 27.3N 86.5W 45 KT 50 MPH 36H 02/0000Z 29.0N 85.0W 55 KT 65 MPH 48H 02/1200Z 30.9N 82.4W 50 KT 60 MPH...INLAND 72H 03/1200Z 35.0N 75.0W 55 KT 65 MPH...OVER WATER 96H 04/1200Z 38.0N 70.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 05/1200Z 40.0N 69.0W 55 KT 65 MPH...POST-TROP/EXTRATROP