99L about to become a tropical depression in the Caribbean Sea
There are very few instances when I have posted a headline like the one in this blog. Hype is not a tool I use to get the attention of my audience unless it is warranted and I feel it could help to save lives and property. What I am seeing in some of the global models is worthy of getting your attention and if it’s hype, then all the better in the long run.
There is a storm brewing in the Caribbean that will soon get a name: Sandy. Right now we know it as 99L, an area of investigation with potential to develop. Within the next 10 days, we may remember it as one of the great ocean storms of recent memory. Before all of that, it will be a problem for the Caribbean and that much is certain.
So far, development of 99L has been slow. It now looks as though things are coming together in the western Caribbean, a few hundred miles south of Jamaica. Water temps are as warm as could be and upper level winds are becoming more and more favorable. The NHC gives the area an 90% chance of becoming a tropical cyclone within 48 hours. I think it’s as good as done at this point and we’ll soon have TS Sandy to track.
72 hour ECMWF showing "Sandy" over Jamaica
People with interests in Jamaica need to be watching this system closely. It will bring periods of heavy rain and an increase in wind as it moves slowly towards the northeast with time. This slow forward motion is going to be a problem as the tropical rains will have a lot of time to fall over the same area for a couple of days or more. I would also not be surprised to see this become a hurricane before it reaches Jamaica. Intensity prediction is very poor even in this day of high-end computer models. Hopefully we’re only talking about a weak tropical storm in a few days but remember that hope is not a good planning tool. Being prepared is far better.
After Jamaica, the threat shifts to Cuba, Hispaniola and the Bahamas. Here too, the main issue will be excessive rain from what is surely to be “Sandy” by mid to late week. How strong it is depends on how quickly it can develop a solid inner core. Interests in the region should be paying close attention to what happens as this feature grows. We are not talking about an “in and out” system that gets kicked in to the Atlantic in a day or so. I think the big story will be the heavy rain even if this does become a hurricane in the Caribbean.
It’s what happens after the Caribbean that has the potential to make this storm one that people talk about for a long, long time.
Day five of the ECMWF showing "Sandy" after moving through the Bahamas
To put it in simple terms, some of the global models are indicating that this storm will get caught in the southwest Atlantic and grow in to a hybrid mix of a hurricane and a Nor’easter the likes we have not seen since as far back as 1991 with the “Perfect Storm”. The closest event I can recall is “Nor-Ida” in 2009 which took the tropical leftovers of hurricane Ida from the Gulf of Mexico and transitioned it in to an epic ocean storm that blasted the North Carolina coast and points north. I was in that one and will never forget it. This storm could make that one look like a day in the park.
It all seems to have begun yesterday when some of the global models began to change their track for 99L from an out to sea event to one that may affect people from Florida to Maine. The Canadian was one of the first to show it. Then the American based GFS and finally, the very reliable ECMWF or Euro. People began talking about it within the weather blogs as if sniffing out something that movies are made out. It was incredible to read what people were saying could happen if this came to pass. Surely it was a one time fluke in the models and things would return to normal a mere 12 hours later. Not so much.
The overnight run of the Canadian global model shows pretty much the same scenario as yesterday. It takes what would be Sandy and turns it in to this enormous ocean storm that would cause coastal flooding, high winds and heavy rains for a large portion of the U.S. East Coast.
Day 8 of the ECMWF which shows a powerful coastal storm impacting the Mid-Atlantic region
Looking at the latest Euro run, it too continues its forecast of developing a very large and powerful storm as the tropical energy from what would be Sandy gets pulled in to a deep trough digging in. This entrainment and phasing is rare but when it happens, it can lead to very powerful hybrid storms that have both tropical and non-tropical characteristics. The Perfect Storm in 1991 was just such an example. The overnight run of the Euro is jaw-dropping, there is no other way to describe it.
On the other hand, the GFS has all but abandoned this idea and simply sheds off the energy from the tropics in to a separate ocean storm way out in the open Atlantic. The result is….nothing. No big storm once 99L/Sandy leaves the Caribbean. It is remarkable to see such vast differences in the models and goes to show how complex the situation is. We are talking about an event that is forecast by some of the models to take place more than a week away. I debated whether or not I should even discuss it since it’s so far out in time. But I figured that rational people who read my blog would understand and appreciate the heads up if this in fact comes to pass….the bad storm that is. Maybe it’s all just a fantasy by the models that show it and the only concern, albeit a very legitimate one, will be for the Caribbean and the Bahamas. If not, and this storm happens the way the Euro shows it and the GFS showed it yesterday for a time, then we will be talking about this well past the hurricane season.
For now, we wait and go with the short term which is that we see what is a developing tropical depression in the western Caribbean. The first impacts will be felt in Jamaica and eastern Cuba. From there, we will just have to see how things turn out. The next several days could be very interesting if not very important in shaping how the hurricane season comes to an end.
I’ll post another short update this evening to go over the latest on the situation in the Caribbean. I’ll also have the video blog posted to our iPhone app by early this afternoon and it will incorporate the overnight model runs as well as the early morning or 12Z model runs to compare. If you don’t have our app, you’re missing out on a great tool in the daily video blog. It brings this discussion to life with numerous graphics, satellite shots and an in-depth explanation of what’s going on in the tropics now and what’s forecast several days out.