NHC indicates high chance of development for invest 90L

NHC two-day tropical weather outlook map showing invest area 90L in the northwest Caribbean Sea along the coast of the Yucatan peninsula.

NHC two-day tropical weather outlook map showing invest area 90L in the northwest Caribbean Sea along the coast of the Yucatan peninsula.

The model guidance trended a little stronger during the overnight hours last night in regards to the eventual strength of invest area 90L. This means there is a pretty solid chance now that we will see either hybrid type storm (subtropical storm) or a purely tropical storm – in either case, a lot of rain and some coastal impacts are likely for portions of the Gulf Coast from Louisiana to the west coast of Florida.

As of this morning, the NHC indicates a 40% chance of 90L becoming at least depression-strength over the next 48 hours. If we look to the next five days, those odds increase to 80%. From the looks of things, we very well may have another out-of-season named storm to deal with.

The timing is not good for obvious reasons as the unofficial start to summer begins this weekend and Memorial Day Monday. Unfortunately, 90L and what ever it evolves in to over the coming days will put a big damper on things for a lot of people.

Right now, it is too soon to pinpoint precisely what locations will receive any impacts from this system. I think we will have to wait until later tomorrow when the model guidance suggests we get a developed low pressure area more consolidated in the southern Gulf of Mexico. At that point, the idea of what impacts and which locations will receive those impacts will become more clear.

What we know right now is that excessive rain is headed for a good portion of the eastern Gulf Coast region from southeast Louisiana over to the Florida panhandle and peninsula. This will also extend inland over parts of the Southeast as the low moves north and eventually inland early next week. I cannot emphasize it enough: the potential for flooding, life-threatening rain is on the table and this needs to be taken extremely seriously. It is impossible to predict which locations will receive the highest rain totals so everyone in the region should be monitoring the progress of this developing situation.

I will produce a video discussion concerning this system later on this afternoon and will go over the various computer models and what the most likely scenarios are. For now, we wait and see as the broad area of low pressure moves slowly along the Yucatan in the northwest Caribbean Sea, spreading showers and thunderstorms along the area.

M. Sudduth 8:10 AM ET May 24

Large low pressure area will bring a lot of rain, some wind and minor coastal impacts this weekend

Invest area 90L, which is tucked away in the northwest Caribbean Sea, just off the coast of Belize, is keeping a lot of people guessing as to what its eventual outcome will be. This is fairly typical of late May or early June tropical systems, especially in the Gulf of Mexico – which is where this system is headed.

So let’s start with what we know as of now:

NHC says development chances are now at 60% over the next five days. This means we could see a subtropical  or purely tropical depression form before all is said and done. What ever it is classified as, it will have some negative impacts on Memorial Day weekend plans, including travel on the busy I-10 corridor and elsewhere.

Right now, the low pressure area is broad, diffuse and void of any solid thunderstorm activity. Dry air in the mid-levels plus strong upper level winds are keeping things in check for the time being.

As we head in to the weekend, the NHC mentions the fact that conditions are forecast to become more conducive for slow development and this is when we may see more organization of the system – perhaps enough so that it is classified as a depression. The subtropical label means it has a mix of mid-latitude storm features, a spread out wind field and a much broader area of overall impacts. On the other hand, a purely tropical depression or storm has a more compact wind and pressure field, tighter overall banding features and a smaller geographic footprint so to speak; in short, it’s more concentrated.

The label won’t matter – I am sure you have heard this a lot about this system already. It’s true – we name weather systems to give us clarity and a way to keep up with everything. The end result is what really matters and for 90L, and/or what ever it ends up being called, that means rain and a lot of it.

WPC's 7 day precipitation map showing a huge area of potentially very heavy rain as the low pressure area takes shape in the Gulf of Mexico.

WPC’s 7 day precipitation map showing a huge area of potentially very heavy rain as the low pressure area takes shape in the Gulf of Mexico.

I have again posted the Weather Prediction Center’s 7 days precip forecast and it shows the potential for widespread heavy rain across a good deal of the Southeast, including all of Florida. Now, this does not mean that this map will verify as depicted, it is a guidance tool to indicate the potential for heavy rain across the region as the low pressure area moves slowly north towards the central Gulf Coast.

If you have plans to travel across the I-10 corridor this weekend, please pay close attention to local weather info and radar updates. Driving at 60-75 mph in torrential downpours can be hazardous to your health – take it from someone who has been in more rain than most people will ever see! Slow down, leave early and take this seriously. Rain is a hazard, even if it’s not causing major flooding like Harvey did last August.

For areas that receive sustained onshore flow, the possibility of large wave action and some minor to perhaps moderate coastal flooding will present challenges as well. We will have to watch this potential problem closely as we get further along in time and the low pressure area develops (or not) more. I suspect that some coastal flood watches will be posted at some point over the coming days.

The wind won’t be too much of an issue overall but consider this: if we get gusts to 45-50 mph in any heavier downpours or thunderstorms, plus the saturated ground, well then, you can imagine the trees with their newly dense leaf system could be toppled in some cases. Obviously, we need to wait and see how strong the low gets but be aware that power outages due to downed trees may be a problem where the wind gusts are high enough to lay some trees over.

So the bottom line is this: we have a real mess on our hands for a very busy weekend ahead. Millions of people will be hitting the road in anticipation of the start of summer. This low pressure system, what ever it ends up being called, will be an issue to contend with. Understanding the totality of the potential impacts is important so I encourage anyone with interests along the Gulf Coast and in to the Southeast to keep up with the latest as we move towards the weekend.

I will post a detailed video discussion later this afternoon and will go over the most updated computer guidance as well as focus on what impacts to expect.

M. Sudduth

8:40 AM ET May 23

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

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

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