Florence is going to be a problem – one way or another

GFS ensembles which show most of the members turning well off the East Coast of the U.S.

GFS ensembles from the overnight run which show most of the members turning well off the East Coast of the U.S.

Florence has weakened considerably from where it was just a couple of days ago when it had reached category four intensity. Strong upper level winds and cooler sea surface temps have taken a toll on the structure of the storm and this has allowed it to do something very important and critical to the final outcome of its track. Move west.

Since Florence does not fill up as much of the atmosphere due to the collapse of deep thunderstorms or convection, it is being steered more by the lower to mid-level flow which is more east to west. This means that the storm will gain much more longitude (move more west) than latitude (north). At this point, the longer Florence remains in this weakened, sheared state, the higher the stakes in terms of where it ends up in about a week.

Unfortunately, it looks as though Florence will again become a strong hurricane over the very warm water of the western Atlantic and by the time it does so, it would have tracked far enough south of any weakness in the high pressure (trough) to make the connection and turn north. The irony is glaring: a weaker Florence now means an increased threat for a major hurricane landfall along the Southeast or Mid-Atlantic later. This is not unheard of, however. In 1992, hurricane Andrew underwent a very similar evolution and ended up as the 3rd category five to ever strike the United States. I am not suggesting that Florence will become a cat-5 or make landfall in south Florida, but the overall plot line seems eerily familiar.

The models

I generally look at 3 camps of global models: GFS, UKMET and ECMWF. I like to see what the operational or deterministic runs show and then take a peak at the “what if” scenarios outlined in what we call the ensembles or multiple runs of the same models using different variables to show different outcomes. It’s fairly easy to understand what to look for. The more spread in the overall model guidance, the more uncertainty there is and vice versa.

So far, the GFS remains the good news messenger with a track that would spare the U.S. coast a direct hit. Even its ensembles are mostly well offshore.

On the other hand, the UKMET and ECMWF operational models both paint an ugly picture for the Southeast coast, essentially bringing Florence ashore as a strong hurricane. Right now, the “exactly where” part is irrelevant since we’re talking six to seven days away. The point is, those two global models and most of their ensembles strongly suggest a landfall somewhere. As such, the official NHC track forecast has Florence positioned at 30N and 70W in 120 hours. From there, it either turns more north and we all breathe a sigh of relief or the intensity of preparing for a major hurricane landfall begins to ramp up in to overdrive for a stretch of coastline.

I simply do not know how this will play out but the trends are not positive right now, especially considering how warm the water is off the East Coast and the strong, solid high pressure area that is keeping summer very much alive from the Northeast down to Florida.

The bottom line is that Florence poses a threat of some level of impact to the U.S. coast (Bermuda too) and we will notice this over the weekend as swells begin to roll in; delighting surfers I am sure. This will be the first signs of a possible major hurricane heading our way. I think we will know definitively about whether Florence turns north in time or not within the next 24 hours. After that, we can begin to focus more on exactly where it could end up.

92L and 93L

There is also growing concern that we see development from invest areas 92L and 93L as they track across the now warm waters of the Main Development Region. We have several days to monitor the progress but I think it goes without saying that we need to keep a close eye on 92L as models suggest it could impact the Lesser Antilles directly.

Olivia and Hawaii

As if all the activity in the Atlantic weren’t enough to keep up with, we also have what is currently hurricane Olivia churning in the east-central Pacific. Here too we may have the threat of direct impacts for Hawaii but this time, coming in from the north and east. The official forecast from the CPHC indicates that Olivia will weaken below hurricane strength with time. Here too, we have a few days to watch and see how the steering and intensity patterns evolve with Olivia. Obviously, any major rain threat for Hawaii is concerning, much less a tropical cyclone heading their way. I will keep up with the latest on this situation as well.

I will address all of these topics more and more in subsequent updates to the blog and within my video discussions which I will also post here at least once per day.

M. Sudduth 6:20 AM ET September 7

Harvey moving through the Windward Islands today bound for western Caribbean

TS Harvey track map from the NHC

TS Harvey track map from the NHC

Tropical storm Harvey is moving quickly through the Windward Islands where it has dumped heavy rain, resulting in some flooding in portions of Barbados this morning. The quick motion off to the west will mean that conditions begin to improve by this afternoon across the region as the storm enters the eastern Caribbean Sea.

Once Harvey clears the Windwards today, the next two or three days will be spent watching the evolution of not only its intensity but also its track. Some of the computer guidance suggests that Harvey will become a hurricane and a lot will depend on how close to Central America the storm gets. Obviously the more land interaction there is, the less Harvey will strengthen. Water temps in the western Caribbean are very warm with plenty of fuel for development.

The track forecast is fairly straight-forward essentially taking Harvey generally westward across the Caribbean through the weekend. Towards the end of the five day track the storm is expected to slow down some and gain a little more latitude. How much farther north remains to be seen but it is entirely possible that Harvey will end up over Honduras and move inland from there – never coming back out over water again. We will just have to wait a couple of days to see how the steering pattern plays out over the United States and what changes to the track result.

In the mean time, invest area 92L is holding on for now, probably as a tropical depression but since it is not near land, it really doesn’t matter in my opinion. Strong upper level winds are beginning to impact the system which means it will not have much time to strengthen further and it may just dissipate on its way west-northwest to the north of the Lesser Antilles. There is an outside chance that 92L survives the strong upper winds in a few days and thus could be an issue for the Bahamas or Florida but right now, that seems to be a long shot. We never say never this time of year but as of today, I am not too concerned with the future of 92L.

NHC begins new era of forecast advisories today

Newly designated "potential tropical cyclone two" and the 5-day track map. What does this mean? Watch the video discussion to learn more.

Newly designated “potential tropical cyclone two” and the 5-day track map. What does this mean? Watch the video discussion to learn more.

It looks as though invest area 92L will go on to become a tropical storm at some point. The shower and thunderstorm activity associated with it has become better organized as today has progressed and as a result, the NHC has begun issuing advisories on it….even though it is not yet a tropical depression or a storm.

This new initiative by the NHC was slated for starting this season though I am sure not many people thought it would be implemented so soon, especially for a tropical wave out in the tropical Atlantic. This is certainly highly unusual to say the least.

I have prepared a special video discussion covering this developing situation which you may view below. I’ll have more coverage here tomorrow, including the latest concerning 93L in the NW Caribbean Sea – which is also forecast to strengthen further and likely become a tropical storm.

M. Sudduth 5:20 PM ET June 18

92L in the tropical Atlantic bears watching as we wait and see about potential Gulf system

The hurricane season is getting off to a somewhat busy start. While we have not had a new named storm since the beginning of the season, that may be about to change.

Currently, the NHC is monitoring two areas for possible development. One is way out in the deep tropics and has been designated as invest area 92L. The other is a slowly organizing system in the western Caribbean that has potential for further development once it reaches the southern Gulf of Mexico.

I am most interested right now in 92L out in the deep tropics. It has the potential to become a tropical depression and maybe a tropical storm as it approaches the Windward Islands in about 5 days.

The Gulf system is less of a concern at the moment since it is unclear whether or not a low pressure area will ever actually take shape. Could be a large lop-sided area of showers and storms with some tropical storm force winds on the east side, but we’ll just have to wait and see.

I go over all of this and more in my video discussion for today which is posted below.

M. Sudduth 2:30 PM ET June 16

Weak low pressure moving across Florida worth watching, Edouard stays well out to sea

Invest area 92L moving over southern Florida this afternoon

Invest area 92L moving over southern Florida this afternoon

A weak low pressure area, easy to spot on visible satellite imagery, is crossing south Florida this afternoon. Strong upper level winds have kept it from becoming any better organized by pushing the deep convection away from the low level center.

The low has brought periods of heavy rain to portions of south Florida but so far, nothing widespread has occurred and it looks to remain that way.

Forecasts from various computer models indicate the low will move westward and in to the Gulf of Mexico by tonight. Normally this would be cause for concern since Gulf water temps are in the mid to upper 80s. However, the strong upper level wind pattern is not likely to abate anytime soon. This should keep the low from strengthening too much as it gets pushed across the Gulf towards Texas.

It is obviously worth watching since we’re in the peak of the hurricane season and water temps are so warm. However, without any significant strengthening indicated by the models, I am not too concerned just yet. The low could bring heavy rain to any land areas that it eventually interacts with but beyond that, I see little to be concerned with.

Meanwhile, TS Edouard formed yesterday in the open Atlantic well to the east of the Lesser Antilles. The NHC is forecasting Edouard to turn out in to the Atlantic with a path that takes it northward between 55 and 60 degrees west longitude. This will keep it away from Bermuda. Edouard is forecast to become the season’s fourth hurricane which will help to add to the ACE score which is a numeric method of measuring how active a hurricane season has been. Right now the ACE score is around 20, well below the long term normal of about 100 or so. Edouard should add a few points to the total but it looks like we are going to end up well below the average unless a particularly intense hurricane forms before the end of November.

In the east Pacific, TS Odile continues to move to the west-northwest. It is expected to turn more northwest with time, parallel to the Baja peninsula but well offshore. Higher surf will be felt once again up and down a good deal of the Pacific coast from the Baja up in to southern California – especially once Odile becomes a hurricane. In fact, it is forecast to become a strong hurricane peaking out at 105 mph.

The rest of the east Pacific remains active with disturbances and another depression but none of them pose any threat to land at the moment.

I’ll keep an eye on the low over Florida and will post any updates to Twitter with a full blog post here tomorrow.

M. Sudduth 1:34 PM ET Sept 12