Invest area 97L poised to become a tropical depression as it nears the eastern Caribbean this week.
It is remarkable how well the GFS model in particular has “advertised” what we are seeing now and will see in the coming days. I first mentioned the possibility of something emerging from Africa back on September 21 and ever since then, the GFS has been locked on. Now, several days later, we have invest area 97L with a 90% of becoming a tropical depression or stronger over the next five days.
Right now, the system is still gathering itself over the deep tropics. It has a large area of energy and plenty of moisture to work with. Water temps are warm and the upper level winds are favorable. All of the intensity guidance eventually strengthens this system in to a hurricane but not until the eastern Caribbean Sea.
First up will be impacts for the Windward Islands. While it’s impossible to know exactly where the center will track let’s not focus entirely on that right now. Instead, let’s look at the hazards that are likely headed towards areas such as Martinique, Saint Lucia, Barbados, Grenada and Trinidad and Tobago. At the very least, squally weather will build in by early Wednesday morning it looks like. Heavy rain with gusty winds along with rough surf and larger waves will accompany the system no matter how strong it is at that point. It would not surprise me at all to see tropical storm conditions for portions of the Windward Islands as it appears that the low pressure area will be strengthening as it passes by. This is what people need to be ready for and not focusing on the center of circulation once it develops. The effects will extend well beyond the center – I know most people should know this but a friendly reminder never hurts.
After entering the eastern Caribbean Sea, what should be TS Matthew at that point is likely to intensify and become a hurricane as the week progresses. Upper ocean heat content will increase dramatically for the system meaning that there is ample fuel for it to become a formidable hurricane.
So what happens next? Obviously a lot of people want to know the answer to that question. I simply don’t know at this point. We are faced with yet another challenging forecast period with all kinds of variables thrown in from the possible interaction with northern South America to upper level low pressure areas digging in like we saw last year with Joaquin and almost every other scenario in between.
The model guidance beyond five days has been interesting to say the least. I won’t pretend that people can’t see the output from various social media and other hurricane related websites. One run of a model will show a hurricane moving in to the Gulf of Mexico. Twelve hours later, that same model has it turning north near Hispaniola. Let me make this very clear: we are talking about predicting the movement of a very complex weather system that will be interacting with equally complex pieces of energy, land masses and other unknowns that will ultimately shape the outcome. To think that we will have the solution six to ten days out is not a good idea. The wild swings from the various global models will be very interesting to watch but beyond five days exceeds the grasp of most in the weather community, especially when talking about a potentially powerful hurricane.
For now, let’s see how things develop over the next 48-72 hours and for interests in the Windward Islands especially, it’s time to pay close attention and be ready for impacts by mid-week.
As for how the story ends? I guess we will all find out together.
I’ll have more here later today with my video discussion followed by another blog post late tonight.
M. Sudduth 6:30 AM ET Sept 26