Watch 96L closely this weekend

Current radar from San Juan, Puerto Rico

Current radar from San Juan, Puerto Rico

As of this writing, the convection associated with 96L is beginning to burst and is likely bringing heavy rain and gusty winds to portions of the northeast Caribbean Sea. Areas such as Puerto Rico and the Dominican Republic could see quite a bit of rain as the tropical wave and its weak low pressure area move through today.

So far, 96L has not become all that better organized but this has been expected per most of the reliable intensity models. Even the NHC makes mention of this in their outlook and we shouldn’t expect to see much strengthening until later in the weekend.

Once the system passes Hispaniola and vicinity today and tonight, it will begin affecting the southeast Bahamas with periods of heavy rain and general squally weather. It’s this point in time that we could see it begin to organize more and eventually become a tropical depression followed by a tropical storm. In fact, the NHC says this scenario is “likely” over the weekend.

Beyond the next couple of days, the forecast is very complicated for both track and intensity.

Right now, 96L is still a loosely organized, weak tropical low. Some of the intensity forecasts do increase the winds to hurricane force over the next few days. Other models do not see it that way. Water temps are plenty warm and vertical instability should become more favorable in the coming days. This means that we should see a steady increase in strength over time. Also, going by what we’ve seen so far this season, I would expect an increase in strength once the system gets north of about 24 degrees of latitude. It seems that we’re seeing tropical cyclones in the Atlantic (both of them this season anyway) reaching their peak intensity once clear of the dry, sinking air of the deep tropics. Do not be surprised if 96L eventually becomes the 3rd hurricane of the Atlantic season.

The track forecast is about as muddled as I’ve seen in quite some time. There’s been a lot of talk about this system reaching the Gulf of Mexico – at least earlier this week. Now, we have a lot of chatter about it simply turning out to sea, possibly impacting Bermuda. What people fail to realize is that the pattern is always changing and computer models are not as reliable as we would like to think. And in this situation, it’s even more complex due to the pattern that we happen to be in.

Basically it’s like trying to catch a bus. Let’s say for the sake of this discussion that 96L becomes a named storm which it is likely to do – the name will be Cristobal. It wants to catch the bus by virtue of finding a weakness in the Bermuda High or western Atlantic ridge, which ever term you like to use. That escape route is there now but seems likely to close and block the exit, forcing Cristobal to wait for another bus. This is becoming more and more plausible with each passing model cycle. Case in point – the ECMWF, highly regarded as the top global model on the planet, now gets the would-be storm much closer to the North Carolina coast than any other run of that model. And just this morning, the GFDL, for what it’s worth, looks eerily similar to the track of Sandy in 2012, bending what ever 96L does in fact strengthen in to back towards the Mid-Atlantic coast.

Yes, there are plenty of other model solutions that send the system off to the northeast, passing by or close to Bermuda and out to sea. My point is that we are starting to see more and more evidence that a possible threat to the Carolinas and points north from this system is not out of the question as we get in to next week.

It’s all a matter of timing – seems like it’s always that way, doesn’t it? Sometimes the forecast is fairly cut and dry and it’s a matter of who gets the impacts instead of if they get the impacts. In this case, we know that the Caribbean islands and eventually the Bahamas will feel some effects as the low moves through. After that – no one knows for sure but I’m here to tell you, I’ve seen it enough in the past to know not to write off something that is only a few days away from the U.S. coastline. School is starting back for many kids along the East Coast and families will be very busy with that (I know I will starting Monday morning). It is important, in my professional opinion, that people along the Southeast coast up to the Mid-Atlantic watch this system very closely. As I have said before, we can hope it heads out to sea but rest assured, hope is not a planning tool.

I’ll post more here tonight.

M. Sudduth 9:36 AM ET Aug 22

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Chantal bringing rain to Hispaniola and that will be biggest issue today

Forecast track and model plots for TS Chantal

Forecast track and model plots for TS Chantal

Chantal is barely hanging on as a true tropical cyclone this morning. The cloud presentation is rather amorphous and does not resemble as well defined circulation at all. There are, however, these bursts of deep convection or thunderstorm activity that wax and wane. These bursts are capable of dropping heavy rain and producing gusty winds but are not enough, it appears, to sustain the heat engine of Chantal.

The official forecast track has changed significantly over night. Instead of tracking over Hispaniola and in to the southeast Bahamas, Chantal is now forecast to move over Cuba and in to south Florida before turning northward. I think there is still more westward adjustment to be made and it is possible that the storm, or what ever is left of it, will move to the west of the Florida peninsula this weekend. The reason being is that a less organized storm moves more with the low level flow than one that is deep in the atmosphere such as a well developed hurricane would be. Remember the atmosphere has layers and tropical cyclones are steered based on how many layers of the atmosphere it reaches in to. It looks now like Chantal or its remnants will move more with the trade winds and surface flow than the deeper steering currents that will be present over the western Atlantic.

It will be interesting to see how far west Chantal makes it before turning north. If it gets in to the eastern Gulf of Mexico, there is a chance it could survive long enough to strengthen again at some point. It’s tough to say as it may completely shear out and dissipate in to scattered showers and no surface circulation at all. This is why July tropical storms and hurricanes are rare. Conditions are just not ideal, which is a good thing because Chantal had a vigorous circulation at one point and looked very impressive while east of the Lesser Antilles. As I mentioned earlier in the week, I feel that this is a sign of things to come later in the season and I hope that people realize that and will make an extra effort to be ready. Chantal might not be a major issue for any single area but its very existence should serve to motivate coastal residents to be prepared this season – it’s only July, we have a lot of season to go.

I’ll post an update this evening and will have the daily video discussion posted to our app near 2pm ET.

M. Sudduth

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Chantal not very well organized this morning as its future track and intensity remain questionable

TS Chantal track and forecast models

TS Chantal track and forecast models

Looking at a satellite shot of Chantal right now, one would have a tough time believing that there is even a tropical storm out there. As noted by the NHC’s 5am discussion, the storm lacks any solid evidence of decent structure. The fast movement, some dry air around and modest wind shear is likely keeping the storm from intensifying right now. In fact, the pressure reported of 1010 millibars is very high for a tropical storm, especially in the deep tropics.

Assuming Chantal does not fall apart today and transition in to a tropical wave again, which is possible, there is a chance it could strengthen as it moves in to the eastern Caribbean Sea. As such, interests in the region from the northern Leeward Islands to Puerto Rico and eventually Hispaniola need to be ready for the impacts from the storm.

I am most concerned about the heavy rain threat for Hispaniola where mountainous terrain lies in the path of the storm. We’ve seen the results many times before when too much rain falls in this region. Chantal is expected to slow down at some point as the ridge of high pressure over the Atlantic weakens some thus exerting less influence on the storm’s motion. This could keep Hispaniola under the threat of heavy rain for 24 hours or more, a situation we will need to monitor closely.

Beyond that time frame, assuming there is a tropical storm or depression left after passage over Hispaniola, Chantal could do something quite interesting and fairly surprising to most. Instead of turning north up the coast or east out to sea, the storm could slow down or stall off the Florida coast. This is becoming more and more likely as the global computer models are indicating that the trough of low pressure swinging past will do so and then allow the Bermuda High to build back in, blocking an escape for Chantal out to sea. This means the storm would be turning back towards Florida at some point beyond the five day forecast period. This also means a more suitable environment for strengthening for Chantal after the trough goes by which increases the threat to Florida for tropical storm conditions early next week.

It is a complex situation and fairly unusual for July to say the least. Right now, the impacts will be felt in the Lesser Antilles through Puerto Rico and Hispaniola. We have plenty of time to see how things shape up with the compute model guidance which is constantly changing, even if only in subtle ways from run to run. These changes can have enormous implications in the longer range and as such, people from the Bahamas to Florida and perhaps the eastern Gulf of Mexico need to watch Chantal. There is a chance it fades away completely but until it does so, the next several days are going to prove to be quite interesting for a lot of people. Stay tuned.

I will have another update on Chantal early this evening. I will also be posting my daily video blog to our iPhone app later this morning with a thorough explanation of Chantal’s possible track and intensity using graphics and computer model maps. If you don’t have our app yet, now’s a great time to pick it up at the App Store. It features the video blog I mentioned plus exclusive tracking maps that we generate as well as landfall data, web cam images and video reports from the field during our missions. We’ll have an Android edition soon as well.

M. Sudduth

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Tropical depression and eventually a hurricane could form from 99L in the Caribbean

A look at invest 99L in the Caribbean Sea

A look at invest 99L in the Caribbean Sea

The MJO and climatology are working together to bring about what I have been alluding to for the past couple of weeks. It seemed almost inevitable that at least one more named storm would develop in the Caribbean Sea and the way things look now, it’s only a matter of time.

We have 99L moving through the central Caribbean this afternoon. The NHC gives it a high chance of becoming a tropical depression within the next couple of days. Water temps and ocean heat content in the region are high while upper level winds continue to become more favorable. Most of the reliable intensity models indicate that 99L will become a tropical storm and eventually a hurricane. Before any of that happens, it will be a persistent rain maker for the region. This will have its own set of problems as areas like Jamaica, Hispaniola, eastern Cuba and eventually the southeast Bahamas could see a lot of rain over the next several days.

The problem is that steering currents are relatively week. This is not a system that will develop and scoot out rapidly to the northeast. It’s going to take some time, perhaps nearly a week, for it to clear the Caribbean entirely. This will lead to excessive rain fall totals for some of the islands in the area and this needs to be taken very seriously. Tropical cyclones and even those in the genesis stage can dump 10 to 20 inches of rain in short order. The longevity of this event for the Caribbean is going to be serious.

For now, the track of the low pressure area will be west and south of west for a couple of days. This will place the low in the western Caribbean first as it awaits a pattern change that should spring it loose and eject it out to the northeast. Exactly when this happens remains to be seen but none of the guidance shows it impacting Florida. However, the impacts to Jamaica, Cuba and Hispaniola could be significant, especially with the aforementioned rain event.

In the longer term, the models suggest that what is almost certain to become “Sandy” will strengthen in to a hurricane. When it does so is tough to say, it could be after it tracks out of the Caribbean which would be good news. My only concern is all of the warm water available and the inability of the models to do well with intensity forecasting historically. Interests in the entire area need to monitor 99L’s future progress very closely.

I’ll have another post here tomorrow. If you have our iPhone app, be sure to check the video section for today’s video blog as it has been posted recently.

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Complex weather pattern shaping up for the end of October as MJO arrives

GFS shows chance of heavy rain for portions of the Caribbean islands next week

GFS shows chance of heavy rain for portions of the Caribbean islands next week

The next two weeks or so will likely be characterized by quite a bit of unsettled weather across a good deal of the Caribbean Sea and southwest Atlantic Ocean. The reason? The arrival of the wet phase of the MJO or Madden-Julian Oscillation and the resulting increase in convection across the Caribbean.

As I have been alluding to for some time now, the MJO was forecast to arrive in the western portions of the Atlantic Basin by mid to late October. Well, that seems to be happening now as we are beginning to see an increase in convection from the southeast Pacific to the Caribbean Sea. Over the next several days, a broad area of low pressure at the surface, also known as the monsoon trough, will set up across the southwest Caribbean, extending back to the west in to the east Pacific.

This pattern is very complex and often results in a lot of rain fall for the tropical areas. The result is usually a series of low pressure areas or depressions that form from this “grape vine” that is literally snaking its way across hundreds of miles of the tropics. As such, development is likely to be fairly slow but it is possible that we could have an east Pacific system followed by one in the Atlantic Basin, probably in the western or central Caribbean Sea.

My concern right now is for the heavy rain that seems almost a certainty of taking place. Reading the various NWS forecast discussions gives the notion that several days of heavy rain are possible for areas such as Hispaniola and possibly Cuba and as far east as Puerto Rico. Interests in the region should closely monitor the weather over the next five to ten days as this pattern begins to take shape.

It is also interesting to see how the various global models handle the upcoming pattern with regards to potential impacts to Florida. The GFS shows next to nothing really while the ECMWF forecasts a broad low pressure area to affect much of the peninsula with wind and rain by day ten. Obviously, this is quite far out in time and a lot can change between now and then. I think the bottom line here is that we are about to enter a two week period where a marked increase in convection and associated rain will take place for a wide swath of the Caribbean and southeast Pacific. Beyond that, we’ll just have to wait and see how the monsoon trough plays out and if any single low pressure center can take over and bundle all of the energy that is building across the region.

I’ll have regular updates each day here followed by the daily video blog posted to our iPhone app.

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