Key Points:
- A tropical storm will likely form over the eastern Gulf of Mexico this weekend, which will likely track along or near the South Carolina coast early next week. The next name on this year's list is Debby.
- There remains considerable uncertainty about the track and especially the timing, which will clear up once the storm becomes organized this weekend.
- There is higher confidence about heavy rainfall and flooding affecting South Carolina than with the other risks usually brought by tropical cyclones. This will primarily affect the Coastal Plain but may impact more of the state.
- Other risks will depend on the track of the storm and how intense it is while affecting South Carolina, but the risk for hurricane-force winds is very low.
- Astronomical tides will be high early next week, as a new moon occurs on Sunday, but not as high as with a 'king tide' situation. Coastal flooding will likely occur with one or more high tides Monday into Tuesday.
A tropical wave we've been tracking all week remains poorly organized as it crosses Cuba today. However, the confidence is increasing with the forecast, and it's likely to bring impacts to South Carolina early next week. The National Hurricane Center (NHC) thought it best to begin issuing advisories for it as a Potential Tropical Cyclone. So, here's a look at Potential Tropical Cyclone Four as it marches across Cuba this morning:
This loop of visible satellite images shows Potential Tropical Cyclone Four marching across Cuba this morning (8:30 a.m. to 10:30 a.m EDT).
Source: University of Wisconsin RealEarth
Here is the forecast track and uncertainty cone from NHC:
Here's NHC's track forecast and cone of uncertainty for Potential Tropical Cyclone Four.
Remember that the uncertainty cone plot refers only to the potential center path and does not indicate there area where impacts will occur.
While there is a scattering of thunderstorms around this feature and a broad turning motion, we don't yet have a coherent surface circulation and a good concentration around that center. Until this occurs, we will have some level of uncertainty in the forecast for PTC4.
However, computer models have begun to cluster around a track forecast that takes it into the eastern Gulf of Mexico, then northward into Florida, then northeastward through southern Georgia and along the Carolina coastal areas, or just offshore during the first part of next week.
The plot of computer model tracks from the Automated Tropical Cyclone Forecast system are clustered near the South Carolina coast next week, but timing varies.
Image Source: WeatherBELL
Any of these possibilities would bring some impacts to the state, but the timing is in question, and the exact track would dictate what the impacts would be. One scenario is a track that's on the left side of the NHC forecast track. That would bring us a storm with less risk for damaging wind, but we'd see flooding rainfall and risk for tornadoes over much of South Carolina, and onshore winds would lead to coastal flooding at high tide. Another scenario is a track to the right, which would result in less of the state being impacted by wind and rain, but the storm likely would intensify as it moves parallel to the coast. There is also a small chance that the storm crosses Florida, moves over the Atlantic and stalls or wanders, has some time to intensify, and then moves back toward our coast or into North Carolina but close enough for more significant impacts to us.
Scenarios involving a track far enough to the west or east that South Carolina sees minimal effects have little chance of happening.
The main uncertainty right now is with timing. The upper-level feature that will steer the storm toward us, a trough forming over the eastern part of the country, will be a transient feature and will pull away to the northeast on Sunday into Sunday night, leaving the tropical feature with weak steering currents until another upper trough moves in at midweek and pulls the storm out of the Southeast. So, there's a chance the storm drifts slowly northeastward and could stall for a time. That might happen over Florida and Georgia, over us, or the Atlantic as mentioned above.
Thankfully, the most likely scenario is for this to be on the weaker side, a tropical storm instead of a hurricane. However, the rain and flooding may turn out to be significant. There may be some lower-end wind impacts, too. Should the center track along the coast or inland, our coastal areas will have a tornado risk. So, if you live along our coast, you should get ready this weekend. As always, if you need storm prep tips, hurricane.sc is there for you.
Elsewhere in the Atlantic Basin, there is one other feature to monitor, which is a tropical wave over the tropical Atlantic to the east of the Lesser Antilles along 43° west. Some models show eventual development from this feature, so it will be one to monitor in the coming days as it marches westward.
In the meantime, we have some worries this weekend ahead of the likely stormy situation next week. The upper trough settling into the eastern part of the country is sending another 'not as hot front' into South Carolina, which will trigger thunderstorms in the hot and steamy air mass present over us now. The storms can be locally severe this afternoon and evening, then again Saturday and Saturday evening. The risk will be for locally damaging wind. Outside of that, we have oppressive heat and humidity this afternoon, with highs in the middle to upper 90s across the state and heat index peaking in the 105-110 range, but the heat will ease slightly for Saturday. It will cool down more substantially for Sunday, which should have little severe storm risk, but with widespread showers and thunderstorms along the front, which should gradually dissipate Sunday into Sunday night along our coast.
So, there's this football ... uh ... match ... here in Columbia on the ... uh ... pitch ... at Williams-Brice Stadium Saturday evening. It looks like I'll be there doing weather stuff. If you plan to be there for the match and pre-match fun, keep in mind that our usual heat and humidity are things we know how to deal with, but visitors from all over might not. Be a good neighbor, watch for signs of heat-related illness, and help those in distress. Also, be mindful that gusty storms may affect the area, so be ready to duck into your car or a sheltered area of the "Willy B." should storms approach.
We're not sure how long it will take the likely Debby-to-be to move away next week. Once it does, we should see a day or two of typical midsummer heat, humidity, and stray afternoon thunderstorms. We might see another 'not as hot front' reach us next Friday or Saturday.
