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

Tropical storm likely to form in Gulf of Mexico

Invest 91L seen in red as well as TS Florence way out in the eastern Atlantic

Invest 91L seen in red as well as TS Florence way out in the eastern Atlantic

We now have invest area 91L which is situated in the Atlantic Ocean, not far off the coast of Cuba and well to the southeast of Miami. The NHC currently indicates a high chance of further development and it’s likely that we will see the system become a tropical depression and then a tropical storm before making landfall along the central Gulf Coast around mid-week.

The main impacts will be squally weather and gusty winds for portions of Cuba, the central and northwest Bahamas and eventually south Florida, including the Keys.

Water temps are plenty warm and there is abundant moisture available for the system to tap in to. The main inhibiting factor right now is shear – strong upper level winds keeping the tropical wave from organizing quickly. There are indications that this shearing pattern will relax enough for it to become a tropical storm at some point. Precisely how strong it can get remains to be seen. I do worry about these smaller systems since they don’t have to bundle as much energy and can ramp up quickly.

As for the Gulf Coast, the main impact will be periods of very heavy rain and possible severe weather and the circulation closes in Tuesday and Wednesday. Along the immediate coast, the usual storm surge prone areas could see several feet of inundation, something we will have to wait and see about as time progresses.

If you have travel plans across I-10 from Alabama through Louisiana this coming week, pay close attention to the forecasts and be prepared for delays. The potential exists for 5-10 inches of rain or more in some locations and this will make travel difficult at times.

I will be heading down to the region beginning tomorrow for local coverage and data collection. I’ll take several of my live cams plus our two weather stations. If anything, this will be an opportunity to continue to test the equipment and if 91L becomes stronger than anticipated, I will be well positioned to know exactly how strong should that happen.

You may follow along via our iPhone app, Hurricane Impact, just search for those exact words on the App Store. We had an Android version but it kept having issues and the cost to keep it going was too much.

I will also embed the live vehicle YouTube feed on this page, in our app and on Patreon for anyone to follow as well.

As for TS Florence, it’s not bothering any land areas for the time being but it’s worth tracking closely over the coming days as models are beginning to suggest it may not curve out to sea as originally thought. We have plenty of time to monitor the situation so no need to worry about Florence just yet.

I’ll post an updated blog later tonight.

M. Sudduth 12:20 PM ET Sept 2