- Newly-formed Tropical Depression 18 will become a hurricane before moving over Cuba and may become a strong hurricane over the Gulf of Mexico, but it will weaken as it encounters cool waters and vertical wind shear over the northern Gulf of Mexico.
- Early indications are that the only effect South Carolina will see from this storm is needed rain later this week into this weekend.
- There is enough uncertainty in the forecast that we will have to monitor it for more significant impacts should it track more to the right than the current forecast.
A new tropical depression formed in the western Caribbean Sea this morning in the area of concern outlined back on Friday. Meet Tropical Depression 18:
This loop of visible satellite images shows newly-formed Tropical Depression 18 causing thunderstorms over the western Caribbean Sea.
Image Source: University of Wisconsin RealEarth
The National Hurricane Center's forecast takes it across western Cuba as it strengthens into a hurricane. The next name on our list for this year is Rafael, and the depression likely gains that name tonight.
After crossing Cuba, it will move over warm water in the southeastern Gulf of Mexico and will likely strengthen further during this time. However, we're not in the peak of hurricane season any more. The waters over the northern Gulf of Mexico are cooler now that we're in November. The prevailing westerly jet stream level winds will cause strong vertical shear once Rafael-to-be reaches this area. So, it will likely weaken on its approach to the central Gulf Coast region.
There is a good bit of uncertainty in the track once we get to the end of this week. Computer models disagree on whether the storm will slow down and wander over the Gulf of Mexico on Thursday through this weekend or whether it will keep marching northward and push through the southeastern states during this time.
So, we can't say with full confidence that this feature will sidestep us. We have more confidence in saying that impacts to South Carolina will likely be minimal. Even if it were to go along the east edge of the forecast cone and move faster than forecast, it would hit cool water and wind shear that weakens it before it reaches us.
We'll likely see some rain from it starting later this week. That's good; we need it! Even if it stays far from us, it will steer tropical moisture into areas near the Southeast Coast, which will interact with a cold front arriving at the end of the week to produce some rain. If it tracks northward into the Southeast this weekend, some heavier rains will fall here.
Other effects are unlikely and would only occur if the storm center tracks on the east side of the uncertainty cone. They include a tornado risk and flash flooding from heavy rain.
We continue to monitor other features elsewhere in the tropics:
- If you're wondering where the 'P' storm went, that name was used by the feature that was over the Azores back on Friday. It became Tropical Storm Patty, which today is no longer tropical and is heading toward Portugal and Spain.
- A weak disturbance just north of Cuba now (it was near Puerto Rico on Friday) will likely be absorbed by Rafael-to-be over the next few days.
- A decaying stationary front north of the Lesser and Greater Antilles may generate a tropical cyclone near the Bahamas this weekend. If it does, the storm could move toward Florida and then our way. It will be something to watch.
- A tropical wave (possibly the last one of the season) east of the Windward Islands will be a feature to watch for possible development starting later this week.
This wide-angle view of visible satellite images shows the weather features of interest across the Atlantic Basin.
Image Source: University of Wisconsin RealEarth
The current active spell in the Atlantic will last another 10-15 days while the Madden-Julian Oscillation remains favorable for activity on this side of the world.
Updates for T. D. 18/Rafael will come only if the likelihood of significant impacts in South Carolina increase.
