A Very Active Atlantic
Well, it's late August, and we are fast approaching the climatological peak of the Atlantic Hurricane Season. As you might expect, the tropics are pretty active. We have one active named storm, one that was declared post-tropical, and another that has a high chance of becoming a tropical cyclone.
Post-Tropical Cyclone Fiona
Not, not that Fiona.
THIS is The Fiona we're talking about. The National Hurricane Center (NHC) has issued its last advisory on Fiona as of 10 AM CDT. The satellite loop is as of 9:45 PM this evening, and there really isn't much left of it.
Tropical Storm Gaston
Again, no, not this Gaston.
We are talking about THIS Gaston. As of 10 PM CDT, here were the specs for Tropical Storm Gaston:
Location: 14.7°N., 37.1°W., or about 875 miles west of the southernmost Cabo Verde Islands
Moving WNW at 17 mph
Maximum sustained winds: 65 mph
Minimum central pressure: 1002 mb
Thaankfully, the NHC's projected path takes it away from any land, and well to the east of Bermuda. Gaston is forecast to become a hurricane but will remain over open waters
Model guidance agrees that Gaston will become a hurricane, and most do bring it up to Category 2 Intensity. There are a few that do bring it up to a Category 3, which would make it a major hurricane. We will see what happens with Gaston over the next few days, but it remains an interest only for the ships and fish.
Now, this is the one that will have impacts to land. Right now, it's rather disorganized.
The NHC has indicated that there is a broad area of low pressure associated with these showers and thunderstorms. It will move west-northwestward during the coming days toward the Leeward Islands, the U.S. Virgin Islands, Puerto Rico, Hispaniola, and the Bahamas. Environmental conditions are only marginally favorable for development, but they will be better once the system reaches the Bahamas. The NHC gives 99L a 50% chance of formation during the next 2 days, and a 70% chance during the next 5 days.
Now, let's look at some model guidance. And that's all it should be taken as: guidance. This is not gospel truth. This can and will change easily, especially with an ill-defined system.
The models are in decent agreement that 99L will move toward the west-northwest eventually impacting the Bahamas in about 5 days, just as the NHC had shown. Now, after 5 days, most of the models agree on 99L crossing over south Florida into the southern Gulf of Mexico. Where it goes from there is anyone's guess. In fact, two of the most reliable models show very different solutions: GFS and ECMWF.
This is the 00Z (7 PM CDT) run of the GFS model valid for 7 PM next Tuesday. The GFS shows what appears to be a weak tropical depression over the Florida Peninsula, very near Orlando. You can also see what would be a large Hurricane Gaston well to the east of Bermuda. But again, this is just one run of one model. Now, let's look at the ECMWF.
Okay, so now, this is a bit different, and by a bit, I mean a lot. This is the 12Z (7 AM CDT) ECMWF run valid for 7 AM Tuesday. (The ECMWF runs only twice a day, whereas the GFS runs 4 times a day, hence the different runs pictures here.) The first notable difference is its intensity. The GFS had a weak tropical depression; the ECMWF has a major hurricane. The other notable difference is its location. The GFS had it over central Florida; the ECMWF has it south of northwest Florida. But also note what it does with Gaston. It makes it a much more intense, yet more compact, hurricane than the GFS. But this, yet again, is just one run of one model.
And, if you thought that the discrepancy was bad between the GFS and the ECMWF, look at the uncertainty in intensity forecasts. Literally, from nothing up to a Category 4 Hurricane. Intensity forecasting, in general, still has a long way to go. Frankly, we aren't that good at forecasting intensity, especially with all of the factors that go into it. Really, we just won't have a good idea until this gets a well-defined center and gets away from the Caribbean islands, and even then, there likely will still be a good degree of uncertainty.
So, what is the takeaway from all of this? We have two very reliable models that show two very different solutions for the same system. The first takeaway is that the models at least agree on bringing the system toward the Bahamas and southern Florida in about 5 days. The models also somewhat agree that the system will eventually end up in the Gulf of Mexico. Those really are our only takeaways that we have. Intensity-wise, we don't have a clue. Where it will end up making a final landfall, we don't know that either.
Now, before you think that this is all, let me throw 2 more wrenches into this mess.
What about possible center reformations? This happens especially with disorganized or sheared systems, like 99L is right now. It keeps spitting out little low level vortices that eventually decay and form with a new convective flare up. These center reformations are not predicted very well by the models, and they could have a pretty substantial impact on where it eventually goes and what/how steering mechanisms impact it.
What about Hispaniola? Hispaniola is home to the highest mountains in the Caribbean (around 10,000 feet). Tropical cyclones hate mountains. The mountains can completely shred a circulation to pieces. If 99L were to have its center form a bit to the south, the future track could also shift south and bring it over Hispaniola, which could destroy 99L.
Now, if there is one thing I want you to take away from this post, it's this: Regardless of what this becomes and where it goes, you should be prepared. It can't hurt to prepare for this system. If it hits you, you're prepared. If it misses you, great, you're prepared for the next one.
Model guidance agrees that Gaston will become a hurricane, and most do bring it up to Category 2 Intensity. There are a few that do bring it up to a Category 3, which would make it a major hurricane. We will see what happens with Gaston over the next few days, but it remains an interest only for the ships and fish.
INVEST 99L
Now, this is the one that will have impacts to land. Right now, it's rather disorganized.
The NHC has indicated that there is a broad area of low pressure associated with these showers and thunderstorms. It will move west-northwestward during the coming days toward the Leeward Islands, the U.S. Virgin Islands, Puerto Rico, Hispaniola, and the Bahamas. Environmental conditions are only marginally favorable for development, but they will be better once the system reaches the Bahamas. The NHC gives 99L a 50% chance of formation during the next 2 days, and a 70% chance during the next 5 days.
Now, let's look at some model guidance. And that's all it should be taken as: guidance. This is not gospel truth. This can and will change easily, especially with an ill-defined system.
The models are in decent agreement that 99L will move toward the west-northwest eventually impacting the Bahamas in about 5 days, just as the NHC had shown. Now, after 5 days, most of the models agree on 99L crossing over south Florida into the southern Gulf of Mexico. Where it goes from there is anyone's guess. In fact, two of the most reliable models show very different solutions: GFS and ECMWF.
This is the 00Z (7 PM CDT) run of the GFS model valid for 7 PM next Tuesday. The GFS shows what appears to be a weak tropical depression over the Florida Peninsula, very near Orlando. You can also see what would be a large Hurricane Gaston well to the east of Bermuda. But again, this is just one run of one model. Now, let's look at the ECMWF.
Okay, so now, this is a bit different, and by a bit, I mean a lot. This is the 12Z (7 AM CDT) ECMWF run valid for 7 AM Tuesday. (The ECMWF runs only twice a day, whereas the GFS runs 4 times a day, hence the different runs pictures here.) The first notable difference is its intensity. The GFS had a weak tropical depression; the ECMWF has a major hurricane. The other notable difference is its location. The GFS had it over central Florida; the ECMWF has it south of northwest Florida. But also note what it does with Gaston. It makes it a much more intense, yet more compact, hurricane than the GFS. But this, yet again, is just one run of one model.
And, if you thought that the discrepancy was bad between the GFS and the ECMWF, look at the uncertainty in intensity forecasts. Literally, from nothing up to a Category 4 Hurricane. Intensity forecasting, in general, still has a long way to go. Frankly, we aren't that good at forecasting intensity, especially with all of the factors that go into it. Really, we just won't have a good idea until this gets a well-defined center and gets away from the Caribbean islands, and even then, there likely will still be a good degree of uncertainty.
So, what is the takeaway from all of this? We have two very reliable models that show two very different solutions for the same system. The first takeaway is that the models at least agree on bringing the system toward the Bahamas and southern Florida in about 5 days. The models also somewhat agree that the system will eventually end up in the Gulf of Mexico. Those really are our only takeaways that we have. Intensity-wise, we don't have a clue. Where it will end up making a final landfall, we don't know that either.
Now, before you think that this is all, let me throw 2 more wrenches into this mess.
What about possible center reformations? This happens especially with disorganized or sheared systems, like 99L is right now. It keeps spitting out little low level vortices that eventually decay and form with a new convective flare up. These center reformations are not predicted very well by the models, and they could have a pretty substantial impact on where it eventually goes and what/how steering mechanisms impact it.
What about Hispaniola? Hispaniola is home to the highest mountains in the Caribbean (around 10,000 feet). Tropical cyclones hate mountains. The mountains can completely shred a circulation to pieces. If 99L were to have its center form a bit to the south, the future track could also shift south and bring it over Hispaniola, which could destroy 99L.
Now, if there is one thing I want you to take away from this post, it's this: Regardless of what this becomes and where it goes, you should be prepared. It can't hurt to prepare for this system. If it hits you, you're prepared. If it misses you, great, you're prepared for the next one.
- Make sure your readiness kit is stocked: flashlights, batteries, radios, 3 days supply of food and water per person, first aid kit, etc.
- Know your evacuation zones, and know your evacuation routes.
- Make sure you have a plan for your pets should you need to evacuate. Remember that some shelters do not take pets.
- Know where your shelters are located.
Really, you should be prepared for a disaster at all times, but especially during the peak of hurricane sseason.
So, in summary (tl;dr):
- Fiona has fizzled.
- Gaston will become a hurricane but will have no impact to land.
- 99L has a good chance of developing.
- 99L will likely move toward the Bahamas and southern Florida this weekend.
- 99L could move into the Gulf of Mexico early next week.
- We do not know where it will go once it reaches the Gulf of Mexico as there is much disagreement among the models.
- We do not know how strong the system will be, period.
- We do not know how much of a role center reformations and/or Hispaniola will play into 99L's future.
- The models WILL change.
- No matter what, you should always be prepared.
- Avoid the hype. If anyone tells you that this is THE forecast for 99L, do not believe them, especially while this still isn't even a tropical depression yet.
Don't worry, stay safe, stay informed, be prepared, and know your sources.
By the way, the next name on the list is Hermine (her-MEEN), not Hermione. Sorry.
Most of the forecast graphics came from Levi Cowan's amazing website. Check it out here.
By the way, the next name on the list is Hermine (her-MEEN), not Hermione. Sorry.
Most of the forecast graphics came from Levi Cowan's amazing website. Check it out here.
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