Irma to become powerful hurricane as it aims for Lesser Antilles

8:15  AM ET August 31, 2017 – Mark Sudduth

Harvey has been downgraded to a tropical depression and is now a dying low pressure area over northeast Louisiana. It will continue to bring periods of heavy rain to portions of the Southeast as moisture streams in off the Gulf of Mexico. The feeder bands that are still set up well to the east of the gradually filling low pressure center will be capable of dumping several inches of rain where they line up and train over the same area. Everything is slowly moving east and northeast and eventually, the circulation of Harvey will fade away while the people back in Texas and parts of Louisiana continue to clean up and begin the recovery process in its wake.

I am currently in Louisiana as I travel back home to North Carolina after spending a week tracking Harvey from its landfall north of Corpus Christi to the punishing, historic rains that plunged Houston in to disaster this weekend. The data the was collected will be very helpful and the live camera feeds that were set up across Houston provided extraordinary views and even helped to motivate people to evacuate. It was a very successful field mission but I realize that I get to go home to a dry, intact house – thousands of people back in Texas are not able to and will not be able to for some time to come. Help has been arriving and there is more on the way. In time, things will get better even though it may not seem that way right now. It gives me hope, knowing what I do about how impactful hurricanes can be, that so much generosity on so many levels is pouring out to bring aid to those who need it.

The hurricane season does not stop to allow us to pick ourselves up. We saw that in 2004, 2005 and in 2008 when multiple threats and landfalls took place. Unfortunately, we may be seeing a similar pattern set up for this season.

Irma tracking map from the National Hurricane Center showing the distinct dip to the WSW by days 3-5.

Irma tracking map from the National Hurricane Center showing the distinct dip to the WSW by days 3-5.

While Harvey fades from the tracking maps, Irma is beginning to have the look of a very troubling hurricane.

The latest thinking from the NHC indicates that Irma will become a hurricane today and should continue to intensify in to a category three within a day or two from now. I personally think it will be stronger, maybe much stronger. Water temps are above normal across the entire path of Irma and the stage is set for an intense hurricane to bear down on portions of the Lesser Antilles.

Right now, Irma is moving to the west-northwest but strong high pressure to the north and east of the soon-to-be hurricane will cause it to actually lose a little bit of latitude – meaning that it will dip south some as it moves west. This is quite unusual but has happened before – most recently that I can recall was Ike in 2008. This means that the Lesser Antilles may have to deal with Irma passing through within the next week or so. It seems like a long way off and one would think that the model guidance is not that accurate but in this case, over the deep tropics with large-scale weather patterns at play, I do not see any reason to believe this southerly course change won’t happen. As such, interests in the Lesser Antilles need to monitor Irma very closely.

I know that everyone downstream from Irma will be wanting to know where it is likely to end up. Maps from the long-range global models will be posted on social media and message boards. While this is a good thing in terms of getting people to pay attention, don’t let it worry you too much – we will need at least five to seven days before we can really get a handle on whether or not Irma will impact the U.S. Right now, we need to focus on potential impacts to the Lesser Antilles.

I will post a video discussion concerning Irma and the latest on Harvey and its remnant circulation later on this morning.

 

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Karl headed out as we focus on next system

Satellite image showing low pressure area over eastern Atlantic. Most of the global computer models suggest it will gradually develop over the next several days as it moves west.

Satellite image showing low pressure area over eastern Atlantic. Most of the global computer models suggest it will gradually develop over the next several days as it moves west.

Karl passed within about 60 miles of Bermuda in the over night hours bringing tropical storm conditions to the area. The storm is now moving away and will do so with increasing forward speed throughout the weekend. Winds and seas will subside and by sunset this evening, it will be quite gorgeous in Bermuda. There is still a chance that Karl becomes a hurricane over the open Atlantic but it will only be an issue for shipping lanes.

As we say goodbye to Karl, we will need to become more and more vigilant as we monitor a tropical wave and low pressure area moving across the deep tropics. This one has potential for becoming a strong hurricane at some point as all signs point to a change in the conditions that have been preventing the storms this season from reaching their full potential.

The GFS model in particular has been extremely consistent with its run to run depiction of a gradually developing tropical cyclone headed right for the eastern Caribbean Sea. We’re not talking five or seven days out any longer, this looks like it could happen as early as Monday with a possible tropical storm threatening the Windward Islands.

Right now, satellite data indicates  a large area of energy associated with a tropical wave that moved off of Africa a couple of days ago. The moisture content is high, also known as precipitable water. There is increasing vorticity meaning spin in the atmosphere and water temperatures are plenty warm. I see no reason to believe that this system won’t develop as it moves steadily west over the coming days. In fact, the NHC is now indicating a 50% chance of development over the next five days and says that a tropical depression could form as it approaches the Lesser Antilles.

NHC graphical outlook map showing the increasing chance for development of eastern Atlantic tropical wave as it moves west towards the Caribbean Sea.

NHC graphical outlook map showing the increasing chance for development of eastern Atlantic tropical wave as it moves west towards the Caribbean Sea.

For now my concern is for the Lesser Antilles and specifically the Windward Islands. It is impossible to know which area could see the most significant impacts from a system that has not even developed yet. This one looks like the real deal and as such, interests in the Lesser Antilles and eastern Caribbean as a whole need to be paying attention to this feature. Even if it is slower to develop than the GFS is indicating, the threat of heavy rain seems to be almost a certainty at this point. Anything beyond that will be determined by just how quickly it organizes over the next few days.

I will be watching this system very closely. Look for an in-depth video discussion to be posted later this afternoon here, our YouTube channel and to our app.

M. Sudduth 7:30 AM ET Sept 24

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Karl getting stronger, will pass close to Bermuda as we watch low latitude system in tropical Atlantic

Recent satellite image showing strengthening tropical storm Karl closing in on Bermuda. The storm should pass just east and south of the island late tonight or early tomorrow morning.

Recent satellite image showing strengthening tropical storm Karl closing in on Bermuda. The storm should pass just east and south of the island late tonight or early tomorrow morning.

Karl is getting stronger and better organized after sputtering for most of its days on the map. Upper level winds are allowing for development and it won’t be too long until Karl becomes a hurricane.

The official forecast keeps the center of Karl just to the south and east of Bermuda very late tonight or early tomorrow morning. It is likely that tropical storm conditions will be felt in Bermuda with isolated hurricane force wind gusts possible in the higher terrain of the island. Winds and seas will begin to subside quickly once Karl tracks farther away over the weekend.

Eventually there will be some increase in the swell activity along portions of the U.S. East Coast and the north-facing beaches of the Caribbean islands. Surfers can expect at least some beneficial wave action in the coming days so be sure to check your favorite surf report site for specific info.

NHC 5 day tropical weather outlook map indicating an area of interest moving across the deep tropics towards the Lesser Antilles next week.

NHC 5 day tropical weather outlook map indicating an area of interest moving across the deep tropics towards the Lesser Antilles next week.

Once Karl clears the pattern we will need to begin watching a tropical wave in the far eastern Atlantic that has potential to develop as it moves west towards the Windward Islands next week. In general, computer models are supportive of development and it is possible that we could see a tropical storm headed for the eastern Caribbean next week. The low latitude track suggests more favorable conditions and certainly very warm sea surface temperatures. Right now the NHC indicates a low chance of development over the next five days. I suspect we will see that begin to increase with time as the energy gathers and moves steadily west over the tropical Atlantic. There’s plenty of time to monitor the situation and see how things evolve. For now, interests in the Lesser Antilles should keep a close eye on this feature and be ready for possible impacts from it next week.

M. Sudduth 7:55 AM ET Sept 23

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Tropical depression forming from 93L this morning?

Intensity graph showing considerable spread between the regional hurricane models and the larger scale global models

Intensity graph showing considerable spread between the regional hurricane models and the larger scale global models

There is not a lot of it, but deep convection is finally developing around at least part of the circulation of 93L. It is limited to the southern half of the low pressure area and any additional increase, especially on the northern side, would easily bring the system to tropical depression status – maybe even to tropical storm strength as well.

It is remarkable how well the low pressure area has held together amid such dry conditions in the deep tropics. This pattern has been in play for the past few years and, in this case for sure, has kept hurricane activity in this region to a minimum.

Taking a look at the latest intensity guidance, there are mixed signals this morning. Some of the model data suggests that this could become a hurricane while other data maintains a weak system that actually stays weak throughout the coming days. Breaking it down a bit, the regional hurricane models, developed just for predicting the intensity of tropical cyclones, are more bullish on development than the larger scale global models. The GFS, for example, shows the system basically dissipating as it moves across the northern Caribbean Sea. I think that there is a small window of opportunity for 93L to become a tropical storm before more negative conditions hinder additional strengthening. We’ll see – as I have said all along, I am skeptical of deep tropical development right now due to the fact that nothing much has come from this region in quite some time.

The track forecast seems a little more straight forward and indicates a general west to west-northwest movement towards the Lesser Antilles. As such, interests in the area should be watching the progress of 93L closely. While it looks like the impacts would be limited due to the low intensity, it is possible that tropical storm conditions will arrive in the region over the next few days. We’ll see what the NHC has to say about all of this around 11am ET when the first advisory could be issued on what could be tropical depression three or even tropical storm Bertha.

Elsewhere in the Atlantic Basin, all is quiet as we end the month of July.

In the east Pacific, there is plenty of activity to watch but nothing close to land and I see nothing in the computer guidance to suggest a change to that anytime soon.

I’ll have more here later today with additional updates on our Twitter and Facebook feeds.

M. Sudduth 8:07 AM ET July 31

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98L bringing squally weather to the Lesser Antilles but not quite “Rafael” yet

The Hurricane Hunters have been investigating 98L this afternoon and the NHC subsequently issued a lengthy bulletin a little while ago. The info from the NHC tells us that there is not quite a well defined low level center associated with 98L just yet. However, it may be only a matter of hours now until that happens and the system is upgraded directly to tropical storm status (Rafael).

Regardless of the naming, the bottom line is that the region around the Lesser Antilles is experiencing squalls with some winds gusting over tropical storm force. These conditions will persist over the next day or so as the low pressure area moves northwestward.

There really isn’t much change in the overall track or intensity model guidance this evening. I think once we get a true center to form and the computer models can take this information and run with it, that we’ll get a clearer picture of the impacts for the Leeward Islands and possibly Bermuda.

I’ll post another update here around 11pm ET tonight with the latest on 98L.

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