TROPICAL STORM GASTON
This is a satellite view of Tropical Storm Gaston as of 3:45 PM CDT. It is a pretty well-organized system. Here is the information from the National Hurricane Center as of 4 PM CDT:
Location: 17.4 N, 40.6 W; about 1,100 miles west of the Cabo Verde Islands
Movement: NW at 16 mph
Winds: 70 mph
Pressure: 990 mb
This is the projected path from the National Hurricane Center for Gaston. It is forecast to weaken Thursday. This is because Gaston will encounter some strong wind shear. However, by Saturday, it looks like Gaston will restrengthen back to hurricane status. All in all, Gaston does not appear to affect any land areas for the next several days.
INVEST 99L
Before I begin: This is NOT a developed system. Since it is disorganized, there is a much higher degree of uncertainty. Take all models shown in this section as guidance. They are NOT truth. They WILL change. This all just provides a general idea of what could happen. Remember, my goal with this post is to inform and NOT to incite fear or panic. Keep all of this in mind while reading this section.
Now, this is likely the one you've been hearing about. Right now, it's rather disorganized, and conditions are only marginally favorable for it to develop right now.
As of 1 PM CDT, the National Hurricane Center gives 99L a 60% chance of becoming a tropical depression or a tropical storm over the next 2 days, but an 80% chance over the next 5 days. Conditions appear to be much more favorable as the system moves toward the Bahamas. The National Hurricane Center does note that: "this system could become a tropical storm or tropical depression at any time during the next couple of days."
Now, you can see that the red-hatched area is the area of expected motion and development. We are fairly confident that 99L will move west-northwestward toward the Bahamas and southern Florida. That's about 5 days out. And really, that's all we're somewhat confident about.
Let's look at the current stats on Invest 99L:
Location: 18.7 N, 65.4 W; generally north of the U.S. Virgin Islands and northeast of Puerto Rico
Winds: 45 mph
Pressure: 1009 mb
Now, these are the "spaghetti" plots for 99L as of 18Z (1 PM CDT). These are tracking where the center of the system will move. IMPORTANT: impacts can extend far beyond the center of the system. You can see that the majority of the models take the system toward the Bahamas in 5 days (120 hours). Then, the models try to take 99L (or what could be Hermine at this point in time) either into the eastern Gulf of Mexico or up the Florida Peninsula. There is still quite a spread at this point. Also...
There has been quite a bit of inconsistency with the models past the Bahamas. Anywhere from the central Gulf of Mexico to the spine of Florida has been the target of these models. I've also seen models taking it as far as Houston or missing Florida to the east.
Two of our most reliable models have been at odds with each other over the past several days: the GFS and the ECMWF. Let's start with a look at the GFS.
This is the 12Z (7 AM CDT) run of the GFS out 168 hours (1 week). Note that it really doesn't develop the system at all, and it moves it off the east coast of Florida. Now, there is a problem with this run: it's not all that reasonable.
Pictured above are the 500 mb and 850 mb (about 17,000 feet and 5,000 feet high, respectively) forecast maps in 4 days (96 hours). On both maps, the black "H" represents a high aloft. The bold arrows around the high are the steering flow around that high. Then, I have 99L marked where it would be according to the GFS with an arrow pointing up the east coast of Florida, showing the path the GFS is forecasting.
So, here is the problem. There is an upper level high to the north of 99L at this time forecast by the GFS. There is no weakness (no troughing) in the ridge to support this moving north, even if it is a shallow system (besides, stronger systems tend to feel weaknesses more than weaker systems). With the upper level high to the north, the steering flow should be driving 99L to the west, not the north. Thus, I am not considering the 12Z run of the GFS as a viable option.
Now, what about previous runs?
This animation shows the last 12 runs of the GFS all valid at 7 AM on Aug. 30 (next Tuesday). Note how the position of the low changes radically for all the previous forecasts: from the central Gulf, to the southern tip of Florida, to off the east coast of Florida. This tells me that the GFS is having issues with this system. Granted, it is a disorganized system right now.
But let's look at the other competing model: the ECMWF.
Now, this is typically the more reliable model, and in this case, it has the better idea: taking it across the southern tip of Florida due to the ridge to its north. But this one takes it along the west coast of Florida into the Big Bend. So, how has the ECMWF's consistency held up?
Better than the GFS, but still not where we'd like it. This is the last 6 runs of the ECMWF (this model only runs twice a day, the GFS runs 4 times a day) valid at 7 AM CDT Aug. 30 (next Tuesday). For all but one run, the ECMWF takes 99L into the Gulf of Mexico.
However, here's a major caveat: we still do not have a well defined center with 99L. Until we get that well-defined center, the models, no matter how good they are, will struggle to resolve it. Thus, the models will continue to spit out different solutions since it does not have a good starting point.
Now, let's answer a few questions that you probably have:
Let's look at the current stats on Invest 99L:
Location: 18.7 N, 65.4 W; generally north of the U.S. Virgin Islands and northeast of Puerto Rico
Winds: 45 mph
Pressure: 1009 mb
Now, these are the "spaghetti" plots for 99L as of 18Z (1 PM CDT). These are tracking where the center of the system will move. IMPORTANT: impacts can extend far beyond the center of the system. You can see that the majority of the models take the system toward the Bahamas in 5 days (120 hours). Then, the models try to take 99L (or what could be Hermine at this point in time) either into the eastern Gulf of Mexico or up the Florida Peninsula. There is still quite a spread at this point. Also...
There has been quite a bit of inconsistency with the models past the Bahamas. Anywhere from the central Gulf of Mexico to the spine of Florida has been the target of these models. I've also seen models taking it as far as Houston or missing Florida to the east.
Two of our most reliable models have been at odds with each other over the past several days: the GFS and the ECMWF. Let's start with a look at the GFS.
This is the 12Z (7 AM CDT) run of the GFS out 168 hours (1 week). Note that it really doesn't develop the system at all, and it moves it off the east coast of Florida. Now, there is a problem with this run: it's not all that reasonable.
Pictured above are the 500 mb and 850 mb (about 17,000 feet and 5,000 feet high, respectively) forecast maps in 4 days (96 hours). On both maps, the black "H" represents a high aloft. The bold arrows around the high are the steering flow around that high. Then, I have 99L marked where it would be according to the GFS with an arrow pointing up the east coast of Florida, showing the path the GFS is forecasting.
So, here is the problem. There is an upper level high to the north of 99L at this time forecast by the GFS. There is no weakness (no troughing) in the ridge to support this moving north, even if it is a shallow system (besides, stronger systems tend to feel weaknesses more than weaker systems). With the upper level high to the north, the steering flow should be driving 99L to the west, not the north. Thus, I am not considering the 12Z run of the GFS as a viable option.
Now, what about previous runs?
This animation shows the last 12 runs of the GFS all valid at 7 AM on Aug. 30 (next Tuesday). Note how the position of the low changes radically for all the previous forecasts: from the central Gulf, to the southern tip of Florida, to off the east coast of Florida. This tells me that the GFS is having issues with this system. Granted, it is a disorganized system right now.
But let's look at the other competing model: the ECMWF.
Now, this is typically the more reliable model, and in this case, it has the better idea: taking it across the southern tip of Florida due to the ridge to its north. But this one takes it along the west coast of Florida into the Big Bend. So, how has the ECMWF's consistency held up?
Better than the GFS, but still not where we'd like it. This is the last 6 runs of the ECMWF (this model only runs twice a day, the GFS runs 4 times a day) valid at 7 AM CDT Aug. 30 (next Tuesday). For all but one run, the ECMWF takes 99L into the Gulf of Mexico.
However, here's a major caveat: we still do not have a well defined center with 99L. Until we get that well-defined center, the models, no matter how good they are, will struggle to resolve it. Thus, the models will continue to spit out different solutions since it does not have a good starting point.
Now, let's answer a few questions that you probably have:
- Where is it going? Excellent question. In the short term, to the Bahamas. There is modest agreement that it will cross the southern part of Florida (ignoring the 12Z GFS). After that, we simply have no idea. Until this system gets better organized, we won't have a clear cut answer.
- How strong will it be? Another excellent question. Let's look at model guidance to see if it tells us anything.
Hmmm, nope. Once again, we don't have a well-defined system. Add on top of that, intensity forecasting is a science that we have not fully grasped yet. So, to answer your question, we simply have no idea. It depends on when it develops, the forecast track (when it gets a well-defined center), and many, many other things. Chances are we will know more as time goes on. - What should I do right now? Well, I have a two-part answer:
If you live in the Bahamas or southern Florida: monitor this system closely. You are now within 5 days of potential impacts. It's probably a good idea to go ahead and restock your emergency preparedness kit. You don't want to be caught off guard if this system develops. Go over your disaster preparedness plan. Do you know your evacuation routes? Do you know where your shelters are? What will you do about your pets? (Remember, some shelters do not allow pets.) What evacuation zone do you live in? Really, all of these questions should have been answered at the beginning of hurricane season, but you definitely should review now.
If you live elsewhere in Florida or along the northern Gulf Coast: keep an eye on this system. Right now, it is still about a week away from any impacts (if they are to occur). However, you should be checking your emergency preparedness kit as well. Ask yourself the same questions as above.
Regardless, this is not the time to panic and worry. But, it is hurricane season, and you should always be prepared with your plan, just in case anything were to happen. - So-and-so says that a hurricane is headed for my home. Should I believe them? Frankly, no. At least, not right now. Remember, this system doesn't even have a well-defined center, and it isn't even classified yet. Since it doesn't have a well-defined center, the models will struggle, and they will give you a different solution each time it runs. Make sure you always get your information from official sources (NWS, NOAA, NHC, etc.). If the official sources are saying something, you should believe them and heed their advice.
So, what's the takeaway from all of this?
- Gaston will not affect land, though it is likely to become a hurricane this weekend.
- 99L has a high chance of becoming our next named storm: Hermine (her-MEEN)
- 99L currently does not have a well-defined center, and until it does, it will not be classified as a tropical storm (even though it is producing tropical-storm-force winds).
- 99L will likely move toward the Bahamas and southern Florida, though intensity remains very uncertain.
- 99L may cross into the Gulf of Mexico. However, where it goes and how strong it will be is unknown.
- The models WILL change. That is something that we are certain about.
- If anyone, at this point, tries to give you an exact forecast, do not believe them!
- Stay alert of the tropics, but do not panic or worry.
- You should always be prepared just in case. It's never a bad idea to be over-prepared.
- Know your sources!
- Again, don't worry! Just be prepared. Have a plan, and be ready to put the plan into action if necessary.
Once again, all forecast model images come from Levi Cowan's amazing website. Check it out here.
Also, find the latest official informarion from the National Hurricane Center here.
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