Complicated forecast for 99L, easy one for 90L

Convection or thunderstorm activity has increased substantially over night with 99L. You can also see here that invest area 90L is well on its way to becoming a tropical depression.

Convection or thunderstorm activity has increased substantially over night with 99L. You can also see here that invest area 90L is well on its way to becoming a tropical depression.

As I mentioned yesterday in my blog post, it looks as though invest area 99L will continue to struggle and not be much of an issue for land areas anytime soon. However, the recent development of convection or deep thunderstorms suggests that perhaps things are changing, even if only a little bit right now.

The very latest info from the NHC indicates that development chances are going up slightly – now up to 50% in the five day time frame. It appears the warmer sea surface temperatures and a better overall environment are slowly playing in to favor of this system developing.

One aspect that I cannot get over is the large size of the overall envelope of energy with 99L. It is not a small, weak and fragile tropical wave. It’s quite the opposite in fact with a large area of circulation and deep precipitable water profile. What this means is that this feature is not just going away despite the marginal conditions in the atmosphere. As we have seen in the over night hours, convection actually began to increase and persist with 99L and this morning, the satellite shot indicates continued slow organization. If this continues, we may have something to deal with in the coming days as it moves generally WNW towards the Caribbean Sea. Interests in the northern Leeward Islands, Puerto Rico and Hispaniola need to monitor 99L closely. At the very least, it could bring periods of heavy rain and gusty winds as the week progresses.

5 day tropical weather outlook grpahic showing the likely development areas and tracks for 99L (orange) and 90L (red)

5 day tropical weather outlook grpahic showing the likely development areas and tracks for 99L (orange) and 90L (red)

The longer term outlook for 99L is tough to call right now. So much is based on whether or not it goes on to fully develop in to a tropical depression or a storm. Generally speaking, the weaker and shallower in the atmosphere a system is, the farther west it tracks under the low level flow pattern. For now, the NHC is showing a potential track area extending up in to the Bahamas by later this week. There are some indications that the track could be farther south but we will have to wait and see about that. Very warm water temps await this system and if conditions improve aloft, it could be an interesting week ahead with not much time to prepare should this threaten land areas from Florida northward to the Carolinas. While this is not indicated by any particular solid forecast right now, it goes without saying that the closer this gets to the U.S. the shorter the time frame for reacting will be.

As for the short term, I want to emphasize again that this large wave energy should bring heavy rain and squalls to portions of the Caribbean Sea over the next few days. Do not count 99L out just yet. It’s late August, water temps are very warm and we have a large system heading westward. Let’s not get caught off guard.

Meanwhile, what should become the season’s next hurricane, and a strong one at that, is developing in to a tropical depression right now far out in the eastern Atlantic.

The NHC should begin advisories on TD7 later today. The model guidance is in excellent agreement that it will strengthen quickly in to TS Gaston and eventually become a hurricane. I see nothing to suggest that this will ever affect land but it will add to the seasonal ACE score, something that is tracked to help size up the quality of the storms/hurricanes that form.

In the eastern Pacific, a pair of disturbances well off the coast of Mexico both have a shot to develop as they move west to west-northwest out in to the open Pacific. No other areas of concern are seen over the next several days for Pacific Mexico or the Baja peninsula.

I’ll have more here in my daily video discussion. Also, you can follow all of my updates using our app, Hurricane Impact, available in the App Store. This blog, social media posts, video updates and field mission reports/data all goes in to the app. We’ve had it since 2012 as a great way to keep up with HurricaneTrack.com info while on the go. Search “Hurricane Impact” on the App Store.

M. Sudduth 8:15 AM ET Aug 22

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False alarm looking likely for 99L but tropical wave off Africa, 90L, is on its way to developing

99L and its proximity to the Saharan Air Layer compared to 90L to the east.

99L and its proximity to the Saharan Air Layer compared to 90L to the east.

It has been an interesting few days to say the least. A lot of attention was placed on invest area 99L in the eastern Atlantic. By all accounts, it looked like it had a good chance of becoming a tropical storm and possibly even a hurricane. Long range models suggested a possible landfall somewhere in the United States, others did not. It was back and forth but the bottom line appeared to be that “Gaston” was destined to form from this large, sprawling tropical wave.

I guess that’s what probabilities are all about. Unless it’s 100%, it’s not a guarantee – ever. The highest probability that I saw from the NHC regarding 99L developing in to a tropical depression or stronger was only 60%. That’s notable but not very high compared to say, 90%. In this case, for the next few days anyway, it looks like the 40% portion will win out and 99L will not develop much further.

I think the reason can be attributed to the large size of the tropical wave. It needs a lot of energy to keep going and to thrive. Right now, despite warm water temps, the atmosphere just isn’t providing. The ever-present Saharan Air Layer might be playing a role as well. But how can that be? Invest area 90L, which is just off the coast of Africa, is almost a shoe-in to become a tropical storm early next week. Isn’t its proximity to Africa enough to keep it from developing? One would think, after all, looking at the SAL analysis map I have posted here, you can see there is much more dry air and dust to the north of 90L than is surrounding 99L to the west. I just don’t know sometimes but the end result is that while we certainly won’t ignore 99L, it doesn’t look like much of an issue for now. It should bring some showers and thunderstorms, along with gusty winds at times, to portions of the Lesser Antilles early next week but beyond that, no development seems like the most likely outcome right now. We will see what happens when the energy makes its way in to the southwest Atlantic later next week. Until then, 99L will not become Gaston.

That leads me to discussing 90L which, as I mentioned, is situated just off the African coast, not far off from Senegal. The NHC and indeed most of the computer guidance, is telling us that 90L will go on to develop over the coming days. And true to what I posted yesterday about how soon systems develop and how that relates to their eventual impact to land, it looks as though the track will be out over the open Atlantic. Indeed, the sooner they develop, the less likely they are to ever reach the United States or other land masses in the western Atlantic. We can’t say for sure that this will have zero impact but odds are it will be a big ACE producer (that is the measure of energy output from tropical storms and hurricanes during a single season) and little more.

The negative phase of the MJO, outlined in red, dominates the Atlantic Basin right now. Unless this changes, hurricane development will be tough to come by.

The negative phase of the MJO, outlined in red, dominates the Atlantic Basin right now. Unless this changes, hurricane development will be tough to come by.

One other note. The lack of uplift or what we call upward motion is probably also partly aiding in the anemic look to the Atlantic Basin as of late. The favorable phase of the Madden-Julian Oscillation, which is a fancy way of saying that widespread favorable conditions exist, is no where near the Atlantic right now. In fact, it seems semi-stuck over in the west Pacific where a couple of storms spin off the coast of Japan. Tropical storms and hurricane can form without the MJO being favorable but its enhancing effects really seem to help when it is present. So far, none of the long range models show it reaching the Atlantic Basin anytime soon. This could make it tough to see much in the way of hurricane activity except in certain spots where favorable conditions exist – but those will be few and far between.

M. Sudduth 9:40 AM ET Aug 21

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Low pressure off the Carolina coast bringing rain, breezy conditions and some rough surf

Recent satellite picture of 90L off the Carolina coast

Recent satellite picture of 90L off the Carolina coast

The area of low pressure, also known as 90L, continues to try and get better organized this morning. If it were say, August, then we would likely already have a tropical storm. As it is, we are still a few weeks away from the official start to the hurricane season and as such, the conditions just aren’t very conducive right now for significant development.

According the latest statement from the National Hurricane Center, there is a 70% chance that 90L becomes a subtropical storm before all is said and done.  I suppose it is still possible that it could be classified as purely tropical but that will be up to the Hurricane Hunters to determine once they investigate the low later today.

As I have mentioned in previous posts, the effects will be minimal overall. Seas will be higher, surf rougher and steady rain from time to time. That is about the extent of it. However, some of the rain could be heavy at times, especially if the low develops any deep convection or thunderstorm activity. Should this happen, then it is possible, though not very likely, that some isolated locations along the coast could experience tropical storm conditions with winds exceeding 39 mph, especially in any heavy rain bands or thunderstorms. It is impossible to predict when and where those might occur so it’s best to just monitor your favorite radar site or app and you’ll be in the know.

The track forecast from most of the computer models suggests a landfall over the South Carolina coast followed by a slow turn to the north and northeast with time. This means that the coastal Carolinas are likely to be unsettled, wet and breezy over the next several days. Not the best golf weather but we all know it could be much, much worse.

That’s about all there is to say on the system right now. Once the NHC issues more info later today, I’ll post an update then. And perhaps, if conditions are interesting enough, I will head out to the beach with a special camera system we have developed – sometime tomorrow – for some live reporting from a very unique perspective. Stay tuned….

M. Sudduth 9:35 AM ET May 7

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Chances for storm to form off Southeast coast going up

Satellite photo of invest area 90L off the coast of Florida

Satellite photo of invest area 90L off the coast of Florida

It looks like we may have a preseason named storm before too long. The NHC has increased the chances of development for what is now invest area 90L, just off the east coast of Florida. As of this morning, the odds were placed at 60% for either a subtropical or purely tropical storm to form over the next 48 hours or so.

As you can see from the satellite picture, the low pressure area is beginning to organize but it still has that spread out, subtropical look to it. This is common when seeing systems develop from non-tropical origins, especially this early in the (almost) season.

It is interesting to note that some of the computer models do suggest a quick transition in to a purely warm-core, tropical storm before it impacts the coast Friday or Saturday. Water temps are only just warm enough to support such a scenario but we have seen instances when storms have ramped up despite having less-than-ideal conditions to work with.

All that being said, it’s not the heart of the hurricane season and as such, we do not need to be concerned with a high-impact event. However, that is not saying that we need to downplay the impacts and ignore what ever forms off the coast.

At the beach, an increase in surf and associated rip-currents will be an issue from parts of Florida up through the mid-Atlantic. Check your local NWS site for more information specific to your area.

Breezy conditions are likely (winds are already picking up now here in Wilmington, NC where my office is) as the low takes shape and moves slowly northward. I suppose that there is at least a chance for tropical storm conditions in parts of the Carolinas along the immediate coast as we end the week. A lot will depend, obviously, on how well organized the storm becomes while over the warm water of the Gulf Stream.

The other impact will be rain, sometimes heavy as bands move onshore. This is likely to be more of a nuisance than a true flood threat. Any outdoor plans Friday and Saturday should take this in to consideration. We’re looking at a few inches of rain at the most since the system is likely to be rather shallow in terms of deep thunderstorm activity. This should help to keep the rain from being too heavy over a wide area.

The Hurricane Hunters will eventually investigate the area and we will know more about its structure and intensity at that point. This probably won’t be until tomorrow. Kind of ironic that they are touring in Myrtle Beach right now as part of the NHC’s East Coast Hurricane Awareness Tour. Timing could not be better, eh?

I’ll have more here tonight with a brief update. I’ll also post a video blog to our app, Hurricane Impact. If you haven’t opened it in a while, now is a good time. Check the video section later today, I will have the discussion posted by 1pm ET.

M. Sudduth 11:35 AM ET May 6

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