More going on in the tropics than we’ve seen in quite some time

It’s the end of August and the tropics are busy. We have a pair of hurricanes that are headed towards Hawaii, one in the Atlantic that poses no threat to land, two disorganized depressions and one significant tropical wave that has just emerged off of Africa. Did I miss anything? I think that’s it. So let’s look at each area beginning in the central Pacific…

Hurricane Madeline

Hurricane Madeline track forecast from the Central Pacific Hurricane Center

Hurricane Madeline track forecast from the Central Pacific Hurricane Center. Click for full size.

Just a couple of days ago the forecast for Madeline did not indicate it would even reach hurricane strength. My how that changed – it is now a category four with winds of 130 mph. It is currently moving west but is expected to track a little south of west over the next day or so and this just might keep the core of the worst weather south of Hawaii where a hurricane watch is currently in effect for the Big Island.

The official forecast brings the center fairly close and the Big Island would be within the right-front quadrant of the hurricane as it passes by. This is usually the stronger side of a hurricane relative to its forward movement and as such, it is possible that hurricane conditions could be experienced throughout portions the region. In addition, dangerously high waves along with very heavy rain could cause localized damage. Hawaii is a unique geographic location for hurricanes to impact and so pinpointing the effects is hard to do; so much depends on the eventual track and intensity. Needless to say, residents and visitors on the Big Island need to be preparing for a hurricane today and tomorrow in anticipation of Madeline’s arrival or close passage sometime on Thursday.

Hurricane Lester

Meanwhile, off to the east of Madeline is hurricane Lester with winds of 125 mph, down from a peak of 140 yesterday.

The good news here is that Lester is currently forecast to track to the north of the islands over the next few days and should also weaken considerably while doing so. As such, I am not nearly as concerned about impacts from Lester as I am about Madeline for Hawaii.

There will be another increase in the swells and local high surf due to the intensity of Lester in recent days. While the surfers in Hawaii can take advantage of this, novice swimmers should avoid tangling with the big waves headed to the area.

Satellite photo showing hurricane Gaston, TD8 and TD9

Satellite photo showing hurricane Gaston, TD8 and TD9

Hurricane Gaston

Moving along in to the Atlantic where hurricane Gaston has weakened some overnight. Top winds here are 100 mph but there is a large eye apparent on satellite imagery. It is possible that the hurricane could strengthen again over the fairly warm waters of the subtropical Atlantic. Gaston is only an issue for shipping lanes as it will likely turn northeast out over the open water with an increase in forward speed.

TD8

Tropical depression 8, just off the North Carolina coast, is trying to wrap deep thunderstorms around its well defined center of circulation this morning. It won’t take much for it to strengthen over the very warm water and become a tropical storm. If it does so before TD9 does, it would be named Hermine.

The effects overall will be minimal with a few passing rain bands and locally gusty winds at times for the Outer Banks of North Carolina. Even the waves will not be too much of an issue since the wind is not very strong right now but locally higher surf is possible within any squalls that happen to make it to the coast.

The forecast is for the depression to possibly become a tropical storm and then turn north and eventually northeast and away from land.

TD9

The forecast for TD9 remains very complex which seems to have been the case ever since it was just an area of interest or tropical wave several days ago.

During the overnight hours, deep thunderstorms have managed to expand and possibly cover the low level center. If this is the case, it might be that we finally have a tropical storm out of this system. The Hurricane Hunters will be investigating the depression off and on today and we’ll know more later if it’s not obvious based on satellite that it has in fact strengthened.

Overall the idea of a Florida Big Bend area landfall on Thursday seems intact. The question is really more about how strong it manages to get before that time. Upper level winds are not particularly favorable but could be just enough so that the depression makes it to tropical storm intensity plus perhaps a little more strengthening after that.

I see two main impacts from this system that concern me. First, storm surge flooding along the immediate coast. The area of Florida that the system is forecast to move in to is very vulnerable to storm surge from tropical storms and hurricanes. The onshore flow, combined with the fact that the would-be storm will be pushing water in the direction that it is moving means several feet of inundation is possible. We won’t know how much is being predicted until later on and especially so when and if it becomes a tropical storm. Areas in the Big Bend region down to the Nature Coast should be prepared for some coastal storm surge issues on Thursday – this includes an increase in wave action as well along what is normally a very placid Gulf of Mexico.

Rainfall forecast over the next few days highlighting the chance for excessive rain totals in parts of Florida.

Rainfall forecast over the next few days highlighting the chance for excessive rain totals in parts of Florida.

The other significant impact will be the heavy rain. Several inches is likely to fall across portions of Florida and this will lead to areas of localized flooding. It’s impossible to pinpoint which areas will receive the most rain and when but it’s a good bet that north-central Florida will see rainfall totals exceeding 5 inches with isolated higher amounts.

I am not as concerned about the wind since the model guidance does not suggest a very high chance of this becoming a hurricane. However, the official forecast calls for 65 mph near landfall which is enough to knock down some trees and cause minor damage to property. Scattered power outages will also occur but it all depends on the final intensity near the time of landfall.

Once inland, the threat of heavy rain will spread in to southeast Georgia and northern Florida as the storm system moves towards the Atlantic. From there, things get very interesting. It is possible that we will see quite a ramping up of intensity once it gets out over the very warm water and begins moving off to the north and east. It is possible at that point that it could become a hurricane.

We will have to watch closely how the pattern evolves over the coming days as there is some hint in the models that the system could track fairly close to the coast as high pressure tries to build in across the western Atlantic again. If it gets blocked enough, it is not out of the question that another landfall or very close approach to the coast could take place farther north. This is something we can worry about later on but it is beginning to show up in some of the models so keep that in mind along the Mid-Atlantic states and points north. I’m not too concerned just yet but the trend has my attention.

I am planning to head down to Florida tomorrow to set up a couple of our unmanned cameras along the immediate coast. I will also have the ability to provide live wind and pressure data from the on-board weather station atop my Chevy Tahoe. I will not set out any additional weather stations for this event but will have a live stream coming from the vehicle so that I can relay instant wind readings as I record them on the anemometer.

I will outline not only the goings on in the tropics but also my plans for setting up the cameras along the Gulf Coast of Florida in anticipation of the landfall on Thursday during my video discussion which I will post early this afternoon. This will be followed by another blog post early this evening.

M. Sudduth 8:30 AM ET Aug 30

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Mixed signals mean low confidence forecast for TD9

I am going to address TD9 in this blog post and will cover the other activity around the Atlantic and what is going on in the Pacific in my video discussion to be posted early this afternoon. With all of the interest in what happens with TD9 and its potential impact to Florida, I figure I would tackle that first.

Some deep convection has developed with TD9 in the region around wetern Cuba and just south of the island. Whether or not this is the start of a strengthening trend remains to be seen. Click for full size image.

Some deep convection has developed with TD9 in the region around wetern Cuba and just south of the island. Whether or not this is the start of a strengthening trend remains to be seen. Click for full size image.

During the overnight hours, deep thunderstorms began to develop in association with the depression in the vicinity of western Cuba and even to the south of the island. It is not clear just yet if this convection is near the low level circulation center or if perhaps that center has reformed closer to the thunderstorm activity. We will know more as morning visible satellite images come in and recon flies in to the system later today.

For now, the NHC is classifying it as a tropical depression with winds of 35 mph. The forecast is very uncertain due to a variety of mixed signals in the overall pattern for the days ahead.

Normally, a tropical depression over the Gulf of Mexico this time of year would be concerning. While it is somewhat concerning this time around, the limiting factors are fairly substantial.

First of all, strong winds blowing across the top of the depression from north to south are likely keeping the convection removed from the low level center. This is extremely important to the health of the depression and until the shear relaxes, assuming it ever does, we won’t see much strengthening.

Most of the models that do develop the depression in to a tropical storm or a hurricane do so in a couple of days – not in the immediate future. So we have some time to watch and see how the upper level pattern evolves over the eastern Gulf of Mexico. With water temps in the upper 80s in most areas of the Gulf, it won’t take much to allow the system to ramp up quickly.

The other issue is dry mid level air that would need to be mixed out in order for more efficient convection to take place. Dry air is a stable environment and tends to limit the amount of thunderstorms a tropical cyclone can produce. It is not clear whether or not the dry air will remain a limiting factor. Here too, if it abates and the low can generate deep thunderstorms, it’s only a matter of time before it starts intensifying.

Track forecast model plots showing a fairly tight clustering of the models in the Big Bend area of Florida. This could change over the next few days.

Track forecast model plots showing a fairly tight clustering of the models in the Big Bend area of Florida. This could change over the next few days. Click for full size image.

The track forecast is also tricky since we are talking about several days out for one and secondly, Florida’s western coastline is shaped that changes in the course of the would-be storm will have potentially huge impacts on who feels what effects.

For now, the official forecast calls for the center to pass in to the Big Bend area of Florida, in the northeast Gulf of Mexico. This is concerning to me because the region is very prone to storm surge, even from “weak storms”. Obviously a hurricane would be worse but even moderate tropical storm winds can push several feet of water onshore within portions of the Big Bend region.

The next area of concern is Tampa Bay. While most of the model guidance suggests a track farther north, we need to watch this closely since this area is also very susceptible to storm surge from even minor tropical storms.

It appears that it will all come down to the mid level trough that is forecast to come in and erode the strong high pressure area that steered the depression in to the Gulf in the first place. At some point, it will round the western edge of the high and begin turning more north then northeast. When and where this happens will determine what part of Florida receives the most substantial impacts. Obviously the intensity will come in to play at that point as well. It’s still just too soon to know with any degree of confidence – something we have grown accustom to dealing with concerning this system.

For now, I think that the biggest impact will be heavy rain and the possibility of storm surge flooding along the coast. It goes without saying that if the depression becomes a hurricane, those impacts are elevated quite a bit. We’re going to have to wait it out and see what happens with the upper environment over the next few days. The NHC makes it very clear in their forecast that the intensity portion especially is of low confidence. Sometimes that’s just the way it goes.

As I said, I will have a full video discussion posted here by early this afternoon. I will go over the very latest on TD9 plus what to expect as we watch TD8 off the North Carolina coast. Meanwhile, Hawaii is watching TS Madeline and hurricane Lester very closely as both could bring impacts to the region later this week. I will also discuss the coming week to 10 days and what to look for as we head in to September.

M. Sudduth 8:20 AM ET Aug 29

 

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Update: 10:50 AM ET – 91L becomes TD8

TD #8 track map from the NHC.

TD #8 track map from the NHC.

Well, that escalated quickly. The NHC has upgraded invest area 91L to TD #8 well off the NC coast this morning. The forecast calls for it to become a tropical storm and turn north just shy of Cape Hatteras. No watches or warnings are in effect but the increase in wind and agitated sea state off shore will lead to the threat of rip currents along parts of the coastline over the next few days.

I will have more on this and the rest of the tropics later today.

M. Sudduth 11AM ET Aug 28

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