Invest 92L is now Potential Tropical Cyclone 9, what does this mean. Well, a few years ago, the Hurricane Center started Potential Tropical Cyclone advisories; this is the system that is nearly developed but does not have a closed center. This allows the Hurricane Center to put Tropical Storm Watches and Warnings up to alert folks in the track earlier. So that's what they did, it is expected to become Tropical Storm Isaias later today or tonight. This forecast is a nightmare beyond 3-4 days so don't look far past Thursday on the cone, below this paragraph is my update from this morning that goes into detail. A Tropical Storm Warning is in effect for... * Puerto Rico, Vieques, Culebra * U.S. Virgin Islands * British Virgin Islands * Antigua, Barbuda, Montserrat, St. Kitts, and Nevis * Guadeloupe, Martinique, and St. Martin * Saba and St. Eustatius * St. Maartin
The National Hurricane Center says "It cannot be stressed enough that since the system is still in the formative stage, greater than average uncertainty exists regarding both the short-term and longer-term track and intensity forecasts."
BEHIND THE FORECAST (THIS IS EVERYTHING YOU NEED TO KNOW) The talk of the past few days has been 92L, a Tropical Wave located to the east of the Caribbean Islands now PTC9. Below, I'll explain why we need to watch but not panic. Since yesterday, the system has become better organized and appears to be on the way of becoming a Tropical Depression or Tropical Storm Isaias later today or tomorrow. The wave is located in the Atlantic Ocean Main Development Region, this is the area where the stronger and more long tracked systems develop, but not always. This morning, The National Hurricane Center increased the odds of the system becoming a Tropical Depression or Storm to 90%. Based on the presentation on Satellite, I believe it will become an official system later today when the Hurricane Hunters head into the system or tomorrow. Cape Verb waves are usually the ones to watch for a United States hit, although though this system is still 6-9 days out from any US state. No one has a clue where this system will be then, especially since there's no center. We can all agree in about 2 days, this system will be near Puerto Rico, but we can't say what will happen after that it is all a guessing game at this point. So, don't freak out if you see posts warning of a significant threat to the United States east coast, there's a lot of things that can happen between now and then. The system could make landfall on one of the Caribbean and get destroyed by mountains. I'll try and lead you through step by step below, so please read it.
1) The system has become better organized since yesterday but is still weak. The latest buoy data suggests the system is producing Tropical Storm force wind gusts, but there was not much a wind shift when the system passed over it.
2) On image 2, you can still see the dry air to the north of the system, which has been with it since the beginning. This is slowing the development of the system and will be with it for a while.
3) Where does the system go, what is the track, how strong is it. What happens with land interactions dry air, these are all unanswered questions that we just don't know. I'll explain my thinking below.
MODELS: The spaghetti models above, these are numerous computer models that focus on the development of a Hurricane/ Tropical Storm. So what are these lines saying? Well, there's overwhelming agreement that the system will travel west to the Lesser Antilles Puerto Rico; the agreement spreads out after that. Interests in the Lesser Antilles should monitor the progress of this system. What happens after that point, there's a section of models that keep it weak, and thus it can't get connected to the High Pressure and drops south through the Caribbean islands likely getting destroyed by the high mountains of the islands. The other section of models to the north, more concerning for the US East Coat keep the system strong and pull it north-northeast toward the US. However, there are still many uncertainties if it heads toward Florida, Carolina's, or out to sea all three options or on the table right now, and none can be written off or decided yes that's the one to watch. Model data is very unreliable until the system actually develops a center, we are also missing a bunch of flight data this year.
What about the strength of the system, how strong will it be Hurricane/ Tropical Storm? Well, this is one of the biggest questions marks with this system. A few models rush the system to a Hurricane off the East coast, while many keep the system weak low-end tropical storm or only develop it for a few days before destroying it. Why is the data so jumpy? Well, this is because we are missing critical upper air data, so we just don't know. What are some possibilities, all options are on the table at this point?
The Bottom Line is, we are watching a wave with more concern for potentially being a threat somewhere from the Gulf to the east coast or just out to sea over the next 6-9 days, but there's nothing to do right now, other than just watch it. One thing you can do is make sure you have a Hurricane Plan built and supplies in your Hurricane kits. The only other thing you can do is stay tuned for updates from trusted sources like here; you will only get the real truth, not a dramatic panic hype. Stay tuned.