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

East Pacific getting busy – will western Caribbean/Gulf follow?

East Pacific tropical storm Aletta tracking map from the NHC

East Pacific tropical storm Aletta tracking map from the NHC

The east Pacific has its first named storm – Aletta – which is forecast to become a hurricane at it moves away from the Mexican coastline over the coming days. The formation is right in line with what we would expect to see this time of year in the eastern Pacific, so nothing unusual happening here.

We will likely also see another storm develop further to the south and east towards the weekend but with strong deep layer high pressure to the north, it too is probably going to remain offshore of Central America and Mexico. This is fairly common to see this time of the year when upper level troughs are few and far between in this region. Later on during the season, usually in latter August and in to September, we see the pattern shift and tracks tend to bend back towards the north and east, threatening the Pacific coast of Mexico and even the southwest United States.

6z GFS showing the beginnings of a new tropical system developing out of the Caribbean Sea in about a week. Something to watch for now as none of the other reliable guidance seems to suggest such an event.

6z GFS showing the beginnings of a new tropical system developing out of the Caribbean Sea in about a week. Something to watch for now as none of the other reliable guidance seems to suggest such an event.

On the other side of the land mass, the Atlantic Basin remains quiet for now. We do need to monitor an old frontal boundary that is draped across the northern Gulf of Mexico. There are some signs within the global models that a small but potent area of vorticity or spin may try to develop and hug the coast, eventually moving in to the Atlantic off the coast of Jacksonville. Plenty of additional rain is likely while the stalled front hangs around – and any development of a low pressure area would only enhance this; something we will need to monitor over the next day or two.

And finally, the GFS is alone again in forecasting the development of a tropical cyclone originating out of the western Caribbean in about a week. It’s hard to say if the model is simply having issues handling energy being pulled in off of South America, generating the kick so to speak to get things started, or if we may in fact need to watch the region closer in the coming days. I suppose it never hurts to at least be aware and wait and see what happens.

I will have a full rundown on all of these topics and more during today’s video discussion to be posted later this afternoon.

M. Sudduth

9:00 am ET June 6

No major track changes with Maria from the overnight model runs

8:50 AM ET Friday, September 22

So far, no major changes in the overall track and future progress of the hurricane as it moves past the Turks and Caicos today – eventually turning more north with time.

In general there is a subtle shift more to the north with the track guidance rather than west although the ECMWF is perhaps a little more west than we saw 24 hours ago. The outcome seems to be the same, however, and that is the fact that Maria should turn away from the East Coast of the U.S. with time.

After Maria clears the pattern, we will begin to shift our focus to the western Caribbean where most of the long range guidance suggests a lowering of pressures and the potential for development over the coming weeks. October is notorious for powerful hurricanes originating from the western Caribbean and it will not surprise me at all to see this happen this season.

Here is the first of two video posts coming for today:

M. Sudduth

 

Maria likely to turn out before directly impacting USA…but….

9 AM ET Thu Sept 21

Satellite photo of the western Atlantic with Jose to the north and Maria to the south

Satellite photo of the western Atlantic with Jose to the north and Maria to the south

After a devastating, crushing landfall across Puerto Rico this time yesterday, Maria is now out over the warm waters of the southwest Atlantic. The eye has become quite large with hurricane force winds now extending out from the center some 60 miles. Maria has regained category three intensity and I think it will get stronger still once it moves farther away from the island of Hispaniola.

As the people of Dominica, St. Croix and Puerto Rico labor to begin the process of rebuilding their lives and their communities, there remains one more chapter to the Maria story still unwritten. I say unwritten, though the outline sure seems to be solid at this point: Maria never makes it to the USA coastline.

All of the available track guidance suggests, at least at first glance, that Maria will turn a graceful curving path away from the Southeast coast over the next five to seven days. The closest it is likely to get to land again will be today and tomorrow as it approaches the Turks and Caicos islands – but remaining just east in terms of the dangerous core of the hurricane.

After this time period, it seems almost certain that the lack of strong high pressure over the western Atlantic, due mainly to the presence of Jose, will allow Maria to eventually lose its western progress and begin turning back towards the east and eventually on out in to the open waters of the Atlantic.

Sounds like all is well for the East Coast…except for one thing: it hasn’t happened yet.

Now I know this sounds obvious but a forecastĀ is subject to error; whether by humans who lay out projections on a map for the center position of a tropical cyclone or by computers which use numerical prediction to guide the humans. If it hasn’t happened yet then it is only a forecast and remains under the limitations of modern weather prediction – even if it looks like a lock.

Let’s look at it from a different perspective. Instead of “why is Maria turning out to sea?”, let’s approach it from “what would it take for Maria to turn back towards the coast?”

Here is my answer: If we see more ridge (high pressure) developing north and east of Maria then it will not fade east and has a chance to continue to gain longitude (westward progress). Right now, something very important is occupying the space that would normally be filled with a dome of air and that is a tropical storm named Jose.

As a hurricane, Jose literally moved up in to and split the ridge, causing an alley-way or weakness for Maria to follow. As long as this alley stays open, Maria will turn out. This is quite likely what will happen. However, if Jose turns back west and comes inland over the Northeast or Mid-Atlantic states then what does that tell us? Why would Jose turn back to the west? Blocking high pressure. That’s why. The atmosphere is forecast to build what we call “heights” over the coming days in a fashion that would normally steer something like Maria in to the Southeast coast. But, with Jose having cut the ridge out enough, Maria is probably going to gain more northward progress with a turn out to the east with time.

Probably. Not certainly.

What we need to look for is how far west Maria tracks over the next 48-72 hours. We also need to watch what Jose does. I believe from what I have read and seen in the model guidance, that if Jose turns west and even south of west, and is driven in to the coast of say, New Jersey (however weak Jose may be it is still something to watch for), then Maria could pinwheel in as well as the models seemed to suggest yesterday. It’s a long shot but there are several members of the 51 runs of the ECMWF model that show this scenario. I cannot display that model output here as it is licensed for use by commercial weather companies. This is the advantage of having an ensemble prediction system – it allows the “what if” cards to be played. In the case of Maria, we are not yet seeing all 51 members of the ECMWF model depict an “out to sea” path.

To be fair, the 21 members of the GFS ensemble group do show 100% “out to sea” as far as USA impacts go. Which model will be correct? Wish I knew.

So the bottom line here is that while the odds favor the East Coast of the USA having to never deal with Maria directly, those odds are not 100% just yet. We’re getting close but close is not the same as there.

I’ll post a video discussion this afternoon after the 12z GFS and ECMWF models complete their runs and we’ll see if the odds have changed any.

M. Sudduth

Speed of movement is apparently an important key for future track of Jose

11:25 pm ET Friday, September 15

I have posted a new video discussion outlining some interesting clues that the latest NHC forecast discussion yielded in tonight’s 11pm ET advisory package.

As you’ll see, the forward speed of Jose is apparently critical in terms of how soon it is able to approach the East Coast of the USA before a small but significant piece of energy dips down to sweep it eastward and away from the coast. Check out the latest video – it’s neat how it all makes sense and is shown within the 18z GFS model:

M. Sudduth