When 80% is not enough

Wednesday, August 17 at 2pm ET the National Hurricane Center issued the first outlook on what would become probably the most talked about area of interest (invest) in the history of mankind. That outlook began a process that kept scores of weather geeks, emergency managers, TV meteorologists, weather forecasting firms and the general public glued to their Internet-connected devices. From the get go it looked like this could be “the one”. It had potential to make it all the way across the Atlantic and possibly affect the United States after roaring through the Caribbean. And so here we are at the other side of that long journey and what became known as “99L” to millions of people will long be remembered for what it didn’t do: failed to develop.

As the process of tracking the tropical wave got underway, computer models were generally in agreement that the system would move westward at a fairly low latitude. However, it was clear early on that mid-level dry air, somewhat associated with the Saharan Air Layer (SAL), would be an inhibiting factor for development. Never the less, by early Saturday morning the 20th, it looked as though a tropical depression would form. Chances went from virtually nothing to 50% in just three days.

By Monday evening the 22nd, the probability increased to 60% and it looked as though a hurricane was possible for the southwest Atlantic Basin, maybe even close enough to Florida or the Carolinas to warrant concern. The social media hurricane machine was in full throttle mode with every expert (and non-expert) opinion you could imagine being thrown in to the mix. It was “invest 99L” overload and it would only get worse.

Leading the charge for development at first was the dynamic duo of the GFS and the ECMWF. Both seemed to latch on to 99L and make something of it. At first, it looked like a track towards Florida and then a turn north was likely. At times, the GFS had an enormous hurricane sitting not too far off the North Carolina coast, moving harmlessly out to sea in the longer term. It looked like this would be a close call but no guarantees yet for a landfall.

As the days went by, seemingly very slow considering we can watch the computer models come and go virtually 24 hours a day, things began to change. The GFS dropped the development almost completely while the ECMWF put memories of Katrina, Andrew and Betsy in our collective minds. It wasn’t just the Euro, the new and improved HWRF model, which is specifically designed to forecast tropical cyclones, showed similar forecasts of a hurricane headed towards south Florida and then turning west as it tracked south of a strong high pressure area over the mid-Atlantic. The hurricane world went in to full meltdown mode. It had been since before Twitter, Facebook as we know it, the iPhone and even the birth of One Direction that Florida had been hit by a hurricane. It was Tuesday, August 23 and 99L had a 70% chance of developing in to at least a tropical depression. The “H” word was bound for Florida.

To make matters worse, the ECMWF ramped up 99L to beast mode and sent it towards Louisiana, the LAST PLACE that needs a hurricane this season. Meanwhile, the GFS showed almost nothing at all. Just weak energy coming across and never really doing much. People were scoffing that if the Euro was right, congressional hearings needed to take place immediately to “fix the GFS!”. It was pure madness because, you know, the ECMWF nailed Sandy’s forecast from 8 days out. People were hung up on a hurricane from four years ago, forgetting the failures of even recent events like Erika last season and Fiona in 2010. Oh yeah, let me tell you about that one.

In 2010, we had Earl, headed for a possible landfall up the East Coast. Meanwhile, the ECMWF was advertising Fiona to be “the next Katrina”. A few in the weather business bit off on this and ran with it like the end times were coming. Earl was going to be a dud while Fiona would be a disaster of epic proportions. All the while, the GFS showed Earl doing exactly what it ended up doing: coming close to the NC Outer Banks then turning out to sea as a strong hurricane. As for Fiona, the GFS showed it as nothing more than a nuisance and that’s how it all turned out. GFS right, Euro wrong. Funny how few people remember that. I remember, trust me, I was on the Outer Banks where Earl brought 85 mph wind gusts to our anemometer that was set up next to Oregon Inlet.

By Wednesday morning, just 48 hours ago, the chance for 99L to develop made it to 80%. It looked like a sure thing now. I mean 80% is pretty good, right? In basketball an 80% free throw shooter is considered to be almost lethal from the line. You foul that player and you might as well put two points on the board. Eight times out of ten the shots go down.

But what happens when that player is in the title game and his team is down 1 with .90 seconds on the clock and he is fouled driving to the hoop? Everyone holds their breath as he lofts the first shot to tie the game. He misses. It’s stunning. The announcers balk about his percentage and how they can’t believe he missed. Must be the immense pressure. Time for try number two. He misses. No one gets the rebound and the clock expires. His team loses the National Championship for one simple reason: 80% is not enough. It’s not 100%. There was a 20% chance he missed either of those two shots. Now this is purely hypothetical but it makes my point. Sometimes high probability is mistaken for certainty.

In the case of 99L, it looks dead and gone now. The GFS, in its past few days of runs, turned out to be correct, for the most part. No hurricane coming for south Florida this weekend like the Euro showed. To be fair, the HWRF did as well and it busted big time. Instead, the Euro now has weak energy bringing possible heavy rain to portions of Florida. No hurricane in to Louisiana or elsewhere, just a strung out mess.

Odds of development over the next five days are down to 60%. Strong wind has all but beat the system in to oblivion. There is virtually no convection or thunderstorm activity with it and the USAF Hurricane Hunter crew has been grounded since there’s nothing there to investigate.

Sixty percent. Hmmmm. That’s not too high nor is it very low either. What is the reason behind this number? It’s because there is still a chance, apparently a 60% chance as of this writing, that 99L will develop some in the Gulf of Mexico. How could this be? The Euro “dropped it”. Well, the ever-excited HWRF sure didn’t and the GFS now shows limited development in a few days with some rather wacky tracks thrown in for good measure. To be honest, it’s giving me a headache to watch this day in and day out and all we have is an area of interest, even if fading to an area of blue skies.

I caution that while the gist of my post is aimed at pointing out the obvious, that anything short of 100% probability has a chance of falling short, it is also true that unless it’s zero, there’s still a chance. Even the 60% free throw shooter is sometimes the hero.

There is still some energy down in the region near the southeast Bahamas that might be able to survive long enough to warrant keeping an eye on. None of the computer models that show any development potential do so until later in the weekend – so let’s see what happens. Perhaps 80% was too high early on but 60% will be just enough for now.

We want to be able to trust the computer guidance to give us time to prepare if in fact something is going to develop. However, the public should understand probability and know the limitations of forecasts even in the relative short term. Most people don’t have time or interest to fully invest their energy in to making sense out of it all. I do my best and could not for the life of me understand why the GFS gave up on this system while the Euro did not. Sometimes you need to look out the window, so to speak, and view the actual weather and not just the predictions. The satellite presentation of 99L never really looked promising for development. It came close a couple of days ago but the reality was it didn’t have that “look”. So logic should have dictated that if it looks poor and one of the major global models insists on non-development, then maybe that’s why: because it won’t. It’s a simple concept and for now, it turned out to be right. Shear and lack of convection and overall organization has kept 99L from developing but it’s not necessarily over.

I think the next 48 hours will be all we need to know how this ends. If nothing happens by then and the wave of energy basically spreads out or dissipates completely, then we’re golden. Until that happens, it’s obviously prudent to keep an eye on things – just in case 60% is just enough to do what 80% could not.

I’ll have more in my daily video discussion posted here, to our app and on YouTube later this afternoon.

M. Sudduth 9AM ET Aug 26

Slower development means more of a chance for impact later

Recent satellite shot showing invest 99L and the limited convection associateed with it currently. This will allow the tropical wave to move farther to west since it will not be influenced by any weakness in the subtropical ridge, allowing it to turn out to sea.

Recent satellite shot showing invest 99L and the limited convection associated with it currently. This will allow the tropical wave to move farther to the west since it will not be influenced by any weakness in the subtropical ridge.

It looks as though the Main Development Region or MDR is still struggling in terms of the ability for tropical cyclones to take shape. The area between Africa and the Lesser Antilles is usually fertile grounds for development this time of year but it seems that for the past several years, dry air has been the rule. The result is we see vigorous tropical waves move off of Africa, various computer models over-develop them and then nothing much happens. It’s like the models (some, not all) are simply not “aware” of the dry, more stable environment that has become a semi-permanent feature of the deep tropics.

However, this is not necessarily a good thing in the end. I’ll explain why…

It is actually quite simple. The longer a tropical wave takes to develop, the farther west it will track. The low level easterly flow which is dominant in the tropics this time of year pushes the tropical waves generally westward. If they don’t develop at all, they often end up in the southeast Pacific and try to develop there. It’s when they don’t develop until they get past about 60 degrees west longitude that is problematic for land areas.

Think about it, a larger storm or hurricane in the atmosphere will more than likely feel the effects of the mid-ocean trough that is usually waiting to allow systems to turn north and eventually northeast and away from land. Sometimes, like 2008, the subtropical ridge of high pressure is so well established that even hurricanes such as Ike can make it from Africa to Texas. Obviously this is rare – otherwise no one would want to live on the coast of Texas or anywhere else for that matter – the hurricanes would be too numerous year after year.

On the other hand, a shallow tropical wave, void of deep convection or thunderstorms, can sail along with the easterly trades and gain longitude day after day. Eventually, conditions improve and a tropical depression forms. By now, the system is nearing the eastern Caribbean and it will most certainly bring squalls, heavy rain and brief high seas to the region.

Hurricane Earl is an example of this scenario. The parent tropical wave struggled as it raced westward across the tropical Atlantic and in to the Caribbean Sea. It was not until it reached the western Caribbean that it developed and became a hurricane. It made landfall in Belize instead of developing early, way out in the MDR, and turning out to sea.

So what does this have to do with anything currently going on in the tropics? Perhaps it has huge relevance. This is because as we watch the recent trends with 99L, we have seen some of the models delaying development until it is only a day or so away from the Caribbean Sea. This ends up sending a slowly strengthening tropical system in to the region, bringing heavy rain and other hazards to the region. Beyond that time frame, anything seems possible, including threats to the United States.

Even though we expect development out in the open Atlantic, just because it doesn’t happen there doesn’t mean it won’t happen at all. The farther west these tropical waves track, the warmer the sea surface temps get. It’s only a matter of time, I believe, until we see something strengthen quickly and close to home. I just don’t know whose home yet.

Bottom line – over the coming days we will see a lot of variations of the “end result” for 99L and perhaps even Fiona and soon-to-be 90L coming off Africa now. The down side to delayed development is that more people take notice when a hurricane is coming from seven to ten days out. It makes sense, the hurricane is there longer and it gets more attention and more people know about it. If it blossoms later, like Katrina did in 2005 (5 days from tropical storm to landfall) then it gives us all less time to react.

The next few weeks will likely be very busy with one named storm after another forming in the Atlantic Basin. Some will be possible impact threats, others will not. It will be important to keep up with what’s going on at least daily if not more. The advantage of seeing a hurricane coming from a week out might not be there and as such, being ready in case one pops up with only 72 hours to prepare will be more important than ever.

I will go over this topic in greater detail on today’s video discussion which I will post here. You can also follow along in our app, Hurricane Impact, available on the App Store. All of our blog posts and video discussions are posted to the app for easy access on the go. Plus, the app has incredible landfall features which I will talk about more when and if the time comes.

M. Sudduth 12:20 PM ET Aug 20

Plenty to monitor over the next several days but beware of “scary maps”

NHC map showing potential for development in the eastern Atlantic, spreading towards the Caribbean, as the days progress

NHC map showing potential for development in the eastern Atlantic, spreading towards the Caribbean, as the days progress

We have several areas to monitor in the Atlantic Basin and one area in the east Pacific. Fortunately, none pose a direct threat to land for the time being but one area, in particular, warrants close scrutiny in the days ahead.

First up, tropical storm Kay in the eastern Pacific. Not much to say here except that it will weaken as it tracks well off of the Baja peninsula and eventually turns westward over cooler water. I do not see any appreciable impacts from this storm for the southern Baja except some added moisture. Once Kay dissipates early next week, that should do it for the time being in the eastern Pacific with no additional areas of development seen.

Next we have tropical storm Fiona in the open central Atlantic. Top winds are only 45 mph with limited deep convection noted on satellite imagery. Overall the dry mid-level air, partly due to the incessant Saharan Air Layer (SAL), is keeping Fiona from strengthening and this will likely remain the case over the next five days. In fact, the NHC is forecasting the storm to weaken as it moves farther to the north and west, well to the southeast of Bermuda. While I do not anticipate any issues arising from this storm, we never just ignore them until they dissipate or are headed away from land areas.

Of greater concern, especially for the eastern Caribbean islands, is invest area 99L deep in the eastern tropical Atlantic. The NHC gives it a 50% chance of becoming a tropical depression or stronger within the next five days.

The overall envelope of energy with the tropical wave is impressive. The large sprawling size makes me believe that development will be gradual at best. The SAL is far enough to the north to allow for slow but steady organization and it should go on to become the next named storm. If so, it will be “Gaston”.

Computer models are very aggressive with strengthening, perhaps a little too much so. Most of the intensity guidance suggests 99L will become a hurricane but I think its large size and overall state of the deep tropics will limit intensification until later in the period.

Interests in the Lesser Antilles should be watching 99L closely. Almost all of the track models indicate a general westward movement in to the eastern Caribbean early next week. As we have seen time and time again, it does not take a strong tropical storm or a hurricane to cause life-threatening flooding. The people in parts of Louisiana know this all too well and we need only to look back at Erika last season as a reminder for the Caribbean. There’s not much you can do to prepare for heavy rain, just being aware and making sure there is safe haven is at least something as opposed to nothing.

There is no doubt going to be a lot of speculation about where 99L and its eventual transition in to a tropical storm (or hurricane) will end up. In today’s world, computer model forecast maps can be shared with literally millions of people at a moment’s notice. Under the wrong context, this can be harmful. Not everyone has the weather geek know-how to realize that a 5, 7 or 10 day map has extreme limitations. On top of that, graphs showing intensity will only lead to more anxiety when it is probably unwarranted.

My point is, we are likely going to have to deal with a tropical storm and possibly a hurricane some time next week. The first area of concern is for the eastern Caribbean Sea. Beyond that, it’s wait and see just like it has been since I began this site back in 1999. Sure, the Internet has made things a lot faster, more weather models are available and so forth but with great access comes great responsibility (sorry Spiderman, had to borrow your uncle’s catch-phrase). Staring at a map that shows a giant hurricane on it 10 days out is not helpful to most people. If you see such things in social media, say to yourself, “Hmmm, guess I better keep an eye on that one”. Worrying about it this soon is futile – instead, maybe do a little more to prepare in case this, or any future storm/hurricane, comes your way. I’ve said my piece on this issue but just know, it’s coming (the scary weather maps) and you’ve been warned. Be smart and don’t spread the fire by sharing such images.

Last in my list of things to cover, the NHC has highlighted the area just off the African coast, out in to the eastern Atlantic by a few hundred miles for possible development next week. This too is just something to monitor but hey, if you live in the Cape Verde Islands, you could be impacted by squally weather as this tropical wave moves by.

It’s getting towards late August and we were told this hurricane season could be the busiest in four years. So far, it has generally lived up to that expectation. We are headed in to a busy period with a lot to keep up with. Considering the world around us and the inherent, constant distractions, it will be more important than ever to stay aware and be ready….just in case.

I’ll have more in my video discussion later this afternoon followed by another blog post in the morning.

M. Sudduth 2:30 PM ET Aug 19


Tropics about to get quite busy as we head deeper in to August

Satellite image of the eastern Atlantic where TS Fiona is moving out over open water. We are also watching for more tropical wave energy just off the coast of Africa for possible development.

Satellite image of the eastern Atlantic where TS Fiona is moving out over open water. We are also watching for more tropical wave energy just off the coast of Africa for possible development.

There are indications that things are going to be busier and busier over the coming days and weeks as far as the Atlantic Basin goes. You may recall that the east Pacific was producing storm after storm, with a few hurricanes thrown in too, back in July? While I do not see that much activity coming, I do think there is potential for several more development areas over the next two weeks.

First up is tropical storm Fiona. Obviously this system poses no threat to land and probably won’t as it moves generally northwestward over the open Atlantic.

The combination of dry mid-level air being ingested from time to time and some stronger upper level winds will likely keep Fiona from becoming too strong. Water temps gradually increase out ahead of the storm and if the background environment changes enough, the chance for it to become a hurricane is there. However, this would only affecting shipping lanes and add to the ACE score for the season. I just don’t see any reason right now to be concerned with Fiona directly impacting land.

As we watch Fiona, we also need to monitor activity just off the African coast for possible development down the road. Computer models are suggesting the possibility of additional development from one or two more tropical waves over the next five to seven days. This would be the most active the MDR or Main Development Region has been for quite some time. It also fits in perfectly with the time of year we are in as the latter part of August tends to see an increase in potential for development across much of the tropical Atlantic.

Meanwhile, the east Pacific will likely have a new named storm before too long. The NHC is tracking invest area 97-E well off the coast of Mexico. Conditions appear favorable for this to continue to develop and become a tropical storm as it moves northwest but off shore of Mexico and the Baja peninsula.

I will have more in my video discussion which will be posted here and to our app, Hurricane Impact, later this afternoon – followed by more blog coverage here tomorrow morning.

M. Sudduth 10:20 AM ET Aug 18

Tropics becoming more active with TS Fiona named – additional system to watch off Africa

Atlantic tracking map showing TS Fiona out over the open water

Atlantic tracking map showing TS Fiona out over the open water

You know it’s getting later in to August when the tropics begin to pick up and make news headlines. Even though we have nothing near or threatening to land, any named storm this time of year is a hot topic.

The latest is tropical storm Fiona. All of the Shrek jokes aside, it does make the 6th named storm of the year. More importantly to me, it formed in the MDR or the Main Development Region between Africa and the Lesser Antilles. This is where we are supposed to see development this time of year and it could mean the busy season we’ve heard so much about it coming to fruition.

Before worrying too much about what might be, let’s look at the current set up.

Right now, top winds are 40 mph and are forecast to increase only modestly. The main inhibitor is mid-level dry air that keeps getting ingested by the convective process of the storm. To put it in simpler terms, each time a large cluster of thunderstorms (convection) develops, the inflow sucks in more dry air from the surrounding environment. This acts to quickly “deflate” the convection and slowing the process of intensification. Unless Fiona is able to escape this fairly stable air mass, it will continue to struggle and shouldn’t reach hurricane intensity. We’ll have to wait and see how this works out but the overall models are not very aggressive with strengthening.

The track forecast is interesting. Right now, the NHC shows an angle that would suggest the storm remains out over the open Atlantic. However, it has been trending more west and south with time due to the structure of the storm. A larger, deeper storm in the atmosphere would feel the effects of any weakness in the subtropical ridge (Bermuda-Azores high) and find a way out. On the other hand, a smaller, thinner storm, with less deep convection reaching high in to the atmosphere, tends to be steered more by the lower level flow which is more westerly than north. It is likely that Fiona will eventually turn away from the United States and elsewhere but it is not a guarantee just yet. Again, this is something we will just have to monitor in the coming days. The longer Fiona stays weak, the farther west it is likely to travel.

In the western Atlantic, Caribbean and Gulf of Mexico, we have nothing to worry about right now.

Off the coast of Africa, we will have to watch as a new, strong tropical wave emerges in the coming days. Computer models are generally in favor of development. Obviously, we would have ample time to watch and see how things progress but it is a sign that the season is getting more active.

In the east Pacific, nothing of note seems to be poised to develop anytime soon and certainly nothing that would threaten land areas.

I’ll have more here tomorrow morning.

M. Sudduth 5:30 PM ET Aug 17