Dorian has to be watched closely as it tracks steadily westward

6Z GFS showing Dorian very well at the 500mb level near the Bahamas

6Z GFS showing Dorian very well at the 500mb level near the Bahamas

I think that Dorian is going to be gaining a lot more attention over the next few days as it moves quickly across the tropical Atlantic. The reason? It has potential to impact land and this includes the United States.

Right now, the storm is fairly strong at 60 mph with a pressure now below 1000 mb. This is not surprising considering the well defined structure easily seen in satellite imagery. Do not be shocked if Dorian becomes a hurricane over the next few days. Remember that intensity prediction is the key area that needs improvement when it comes to tropical cyclone forecasting.

On the other hand, do not be shocked if Dorian suddenly weakens and looks like it will dissipate. I say this to balance out the intensity forecasting issue. It works both ways and with such a small center where most of the convection is, it would not take much dry air and shear to deliver a knock-out punch to Dorian. We’ll see. One thing I do notice is a well defined “tail” extending off to the southwest from Dorian. This is no doubt feeding very moist air in to the storm from hundreds of miles away. Plus, the overall envelope of Dorian is large and once it encounters warmer water temps ahead, it may very well intensify.

The other question is obviously track. Where does Dorian go over the next five to seven days? The answer is quite simple so far: generally westward. The reason is a large high pressure area, like a huge balloon, that will be growing over the central Atlantic. This will not allow Dorian to move north and escape out to sea, not yet anyway. This is not September when we see deep troughs of low pressure plowing in to the western Atlantic, eroding the ridge down and easily turning storms and hurricanes out to sea. In fact, this time of year, we typically see large high pressure areas such as what is building now over the Atlantic. This will keep Dorian chugging along the southern side of that high, moving west day by day.

The GFS global model seems to have a good handle on Dorian so far. It shows the storm getting just a little farther west with each run. The latest run from overnight shows a potential threat to the Bahamas in about a week. It looks like a weak trough tries to build in and knock the ridge down some but then it lifts out and allows the Bermuda High to establish itself again, pushing Dorian west and towards the Bahamas. This is a week away and while the GFS is pretty good, there is plenty of room for error. I just want people to be aware that this does not appear to be an easy “out to sea” type of situation. That can still happen but this time of year, it gets tough to do so with that kind of deep layer ridge sitting over the Atlantic. Keep an eye on Dorian. It could be something that people have to deal with this time next week.

Meanwhile, TS Flossie has formed in the eastern Pacific and is of no concern to land right now. However, beyond the five day forecast period, it could pass close to Hawaii as a dying tropical depression. This would mean an increase in wind and rain chances for the area. Something to monitor as we get in to the weekend ahead.

I will have more on Dorian tonight and will also be posting the daily video discussion to our app, Hurricane Impact. I’ll have the video posted by early afternoon, once the 12z model guidance comes in and I can go over it. We are also about ready to release an Android version of our app. That should be ready sometime next week and I know a lot of people are eagerly awaiting that.

M. Sudduth

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July likely to end without much to talk about

East Atlantic tropical wave with low chance of development

East Atlantic tropical wave with low chance of development

Even though the NHC does have an area outlined in yellow today off the coast of Africa, I think that July will finish up without much to really be concerned about.

There is a formidable tropical wave located just off the African coast today and the GFS model in particular has been suggesting that this would develop. However, conditions in the tropical Atlantic are marginal at best with plenty of mid-level dry air present and a distinct lack of upward motion. As such, I think that this tropical wave will have a tough time developing much in the coming days. It is still July and climatology is a big part of the equation. There is a reason why we do not see much development in the tropical Atlantic this time of year – give it a couple of more weeks and things will change.

In the east Pacific, the NHC is monitoring invest area 98-E for slow development over the next several days. In this case, conditions are fairly favorable but what ever comes of it will move away from Mexico and not pose any threat for folks there.

In other news, our app, Hurricane Impact, is almost ready for Android devices. I am going to be testing it myself later today and will have a good idea of when we can expect it to hit the Google Play store. The app will feature the same features as our iOS version: daily video blog, HurricaneTrack.com blog, live Surge Cam, live weather data feed, field mission video blogs, our own tracking maps along with Twitter and Facebook integrated in to the app. It will also feature content from Mike Watkins of Hurricane Analytics which will be a new addition to our iOS version as well in the coming weeks. We are excited to have both platforms covered and know that the Android users out there will be equally excited. As soon as I know the release date, I’ll post a special blog with the announcement.

Enjoy the quiet pattern while it lasts. August is approaching and a month from now, I would venture to guess that we’ll have a lot to talk about.

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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Wet days ahead for portions of the Southeast as 91L gets better organized

Heavy rains associated with 91L will spread across Florida and parts of the Southeast

Heavy rains associated with 91L will spread across Florida and parts of the Southeast

I hope that umbrellas as not in short supply for portions of the Southeast over the next few days – they are going to be needed. It looks as though a lot of moisture from invest area 91L in the Gulf of Mexico will track northeast across Florida and then in to Georgia and the Carolinas. This means a lot of rain is coming between now and the weekend.

There is currently a fairly substantial burst of deep convection or thunderstorm activity accociated with the weak low pressure area. However, this is due more to interaction with very dry air punching in from the west rather than a sign that true tropical development is now underway. This will continue to result in a lop-sided storm system with almost all of the heavy showers and thunderstorms displaced to the north and east of any low level center.

Most of the reliable computer guidance indicates that the low and its assoicated inclement weather will track northeast out of the Gulf over the next few days and bring a lot of moisture in to the Southeast. Some areas could see as much as five inches of rain. This will impact travel and obviously outdoor activities. There may be some flooding concerns as well for the locally heavier downpours in typical low-lying areas and communities with poor drainage.

Wind will not be a major issue since the energy is spread out over a larger area and not concentrated around a well defined center. However, there will be a steady increase in winds and seas along the west coast of Florida so small craft should be careful when venturing out in to the Gulf.

The rest of the tropics are of no concern right now and this continues to include the east Pacific. I’ll post more here tomorrow morning, sooner if conditions warrant. You may also follow along in our app, Hurricane Impact, which features a daily video blog that is posted each afternoon with analysis of the current goings on in the tropics.

M. Sudduth

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