96L Not a Tropical Storm Yet – Model Trend Shifting Westward

We’ve been watching Invest 96L, currently north of Hispaniola, for several days now and there hasn’t been much change in overall organization since Thursday.  However, now that the wave axis is moving away from the high terrain of the Dominican Republic and Haiti, the center of the system is expected to consolidate and we could have a tropical storm within the next 12-18 hours.

There is still considerable uncertainty for the FL peninsula and the southeast US coast however.  96L is expected to start slowing down as steering currents collapse north of the Bahamas, which will give the system some time to organize over very warm waters.  After that, the forecast models are split into two distinct camps.

Latest models as /of 8AM EDT on Saturday, 8/23/2014

Latest models as /of 8AM EDT on Saturday, 8/23/2014

Scenario 1 has the system feeling a weakness in the subtropical ridge and moving north, impacting the southeast Bahamas before turning out to sea.  This scenario had been favored by both the GFS and Euro, but many other global and dynamic models have been advertising…

Scenario 2 leaves a more west-northwest moving system either over or very close to FL by the middle of next week – as a result of a slightly stronger ridge of high pressure blocking 96L and a track further south.

The graphic shows the older models from this morning, but the new guidance is coming in.  The GFS is close to the east coast of FL before recurving, the Euro has also shifted south and west but not as far west as FL.  The UKMET is showing a westward shift over FL and into the Gulf of Mexico (as does the NAVGEM) – and the GFS Ensembles are basically split between the above two ideas.

Of course, no one knows which is correct – however – environmental sampling and recon will be picking up starting tonight which will help feed the models better data.  And – once the center does develop it will give the models a better starting place to use to project possible track and intensity.  So – stay tuned throughout the weekend if you are any place in the southeast US or the Bahamas.

MWatkins – 8/23/2014 2:45PM EDT

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Watch 96L closely this weekend

Current radar from San Juan, Puerto Rico

Current radar from San Juan, Puerto Rico

As of this writing, the convection associated with 96L is beginning to burst and is likely bringing heavy rain and gusty winds to portions of the northeast Caribbean Sea. Areas such as Puerto Rico and the Dominican Republic could see quite a bit of rain as the tropical wave and its weak low pressure area move through today.

So far, 96L has not become all that better organized but this has been expected per most of the reliable intensity models. Even the NHC makes mention of this in their outlook and we shouldn’t expect to see much strengthening until later in the weekend.

Once the system passes Hispaniola and vicinity today and tonight, it will begin affecting the southeast Bahamas with periods of heavy rain and general squally weather. It’s this point in time that we could see it begin to organize more and eventually become a tropical depression followed by a tropical storm. In fact, the NHC says this scenario is “likely” over the weekend.

Beyond the next couple of days, the forecast is very complicated for both track and intensity.

Right now, 96L is still a loosely organized, weak tropical low. Some of the intensity forecasts do increase the winds to hurricane force over the next few days. Other models do not see it that way. Water temps are plenty warm and vertical instability should become more favorable in the coming days. This means that we should see a steady increase in strength over time. Also, going by what we’ve seen so far this season, I would expect an increase in strength once the system gets north of about 24 degrees of latitude. It seems that we’re seeing tropical cyclones in the Atlantic (both of them this season anyway) reaching their peak intensity once clear of the dry, sinking air of the deep tropics. Do not be surprised if 96L eventually becomes the 3rd hurricane of the Atlantic season.

The track forecast is about as muddled as I’ve seen in quite some time. There’s been a lot of talk about this system reaching the Gulf of Mexico – at least earlier this week. Now, we have a lot of chatter about it simply turning out to sea, possibly impacting Bermuda. What people fail to realize is that the pattern is always changing and computer models are not as reliable as we would like to think. And in this situation, it’s even more complex due to the pattern that we happen to be in.

Basically it’s like trying to catch a bus. Let’s say for the sake of this discussion that 96L becomes a named storm which it is likely to do – the name will be Cristobal. It wants to catch the bus by virtue of finding a weakness in the Bermuda High or western Atlantic ridge, which ever term you like to use. That escape route is there now but seems likely to close and block the exit, forcing Cristobal to wait for another bus. This is becoming more and more plausible with each passing model cycle. Case in point – the ECMWF, highly regarded as the top global model on the planet, now gets the would-be storm much closer to the North Carolina coast than any other run of that model. And just this morning, the GFDL, for what it’s worth, looks eerily similar to the track of Sandy in 2012, bending what ever 96L does in fact strengthen in to back towards the Mid-Atlantic coast.

Yes, there are plenty of other model solutions that send the system off to the northeast, passing by or close to Bermuda and out to sea. My point is that we are starting to see more and more evidence that a possible threat to the Carolinas and points north from this system is not out of the question as we get in to next week.

It’s all a matter of timing – seems like it’s always that way, doesn’t it? Sometimes the forecast is fairly cut and dry and it’s a matter of who gets the impacts instead of if they get the impacts. In this case, we know that the Caribbean islands and eventually the Bahamas will feel some effects as the low moves through. After that – no one knows for sure but I’m here to tell you, I’ve seen it enough in the past to know not to write off something that is only a few days away from the U.S. coastline. School is starting back for many kids along the East Coast and families will be very busy with that (I know I will starting Monday morning). It is important, in my professional opinion, that people along the Southeast coast up to the Mid-Atlantic watch this system very closely. As I have said before, we can hope it heads out to sea but rest assured, hope is not a planning tool.

I’ll post more here tonight.

M. Sudduth 9:36 AM ET Aug 22

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Fork in the road developing?

Recent plot of various computer model guidance for the track of invest area 96L

Recent plot of various computer model guidance for the track of invest area 96L

Wanted to post a quick update tonight on 96L. Not much new really with the structure and current intensity but there is some new info regarding its future track.

As we saw a couple of days ago when people were posting day 8-9 images of a hurricane in the Gulf of Mexico, today we’ve seen quite a bit of “it will turn out to sea” posts and blogs in social media. This may very well turn out to be the eventual fate of the system, no matter how strong it ever gets, but what if it’s not? Nothing is ever concrete with weather.

Take a look at the latest computer model plots for 96L. Note the obvious group of models that do in fact bend it out to the northeast with time.

Now look at the ones that take it more north and even some that bring it back westward towards the end of the five days. Look really close. One of them is the TVCA or consensus model (yellow track). This is significant in my opinion since it is often cited within NHC discussions as being a model of reference to build a forecast on. You’ll often times read “the forecast is X of the TVCA or consensus model” which means that the official forecast is usually not too far off that model’s track. It may be nothing and one model cycle does not mean a trend is beginning. Let’s see what happens over the next 24 to 36 hours. I think by this weekend, we’ll know whether or not 96L or Cristobal (the name it would get when/if it becomes a TS) is going to be something we need to be concerned with here along the Southeast U.S. coast.

For now, the low pressure area is bringing squally weather to portions of the northeast Caribbean Sea and this will spread westward tonight and throughout tomorrow. Heavy rain and occasional gusty winds will accompany the rain bands as they move through so interests in the region need to be aware and not get caught on a boat or otherwise unprepared.

I’ll have more here tomorrow morning.

M. Sudduth 10:21 PM ET Aug 21

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Pattern probably not set up for U.S. hurricane hit right now

The same amount of caution must be used when discussing the possibility of a non-hurricane hit as when we talk about one that could hit a particular location, no matter how general. This is one of those cases and my aim here is to point out the reasons why I believe that 96L or what ever it becomes will turn away from the United States. Of course, this is how things look now, obviously the weather is subject to change but sometimes you get clues that are pretty large and cannot be ignored.

First, the here and now.

96L is a large, sprawling low pressure area without a well defined center of circulation. Such large envelopes of energy in the tropics often take time to consolidate and close off a low level center.

96L is not in an ideal location for upward motion which helps to aid in organized deep thunderstorm development

96L is not in an ideal location for upward motion which helps to aid in organized deep thunderstorm development

Dry air continues to impede development to some extent but the overall lack of upward motion or, to put it another way, sinking air, seems to be a big issue, perhaps more so than dry air. As you can see in the graphic I have posted, 96L is located in an area that is only marginal for rising motion. Sure, there are worse conditions elsewhere around the globe but it is not located in a prime area for divergence aloft which would allow for more efficient upward motion and thus convection.

The motion is currently WNW and this should continue for the next day or so. At this track and heading, showers and squally weather will spread over portions of the Lesser Antilles today and tomorrow. Eventually, Puerto Rico and parts of Hispaniola could feel the effects with heavy rain and gusty winds possible. For now, it’s the eastern most islands of the Caribbean Sea that are having to deal with this slowly developing system.

So what about the future? Some of it is complicated but overall, I think the pattern is showing us what should ultimately happen.

Right now, 96L is being driven west by a ridge of high pressure to its north. It acts like a ceiling keeping a helium balloon from escaping in to the sky while a fan blows it laterally along the plane of the ceiling. If you were to open a hole in that ceiling, up, up and away the balloon would go. The same is generally true for tropical cyclones. High pressure at the steering layers keeps them moving more or less westward. As the pressure eases off, the cyclones literally gain latitude or move poleward (north). If the Atlantic were dominated by one large area of high pressure, like we saw in 2008 with Ike, then tropical waves that develop could travel from Africa to Texas without any chance of turning north and out to sea. This does happen but has not been the case for quite some time. The reason? Troughs of low pressure that erode the Atlantic ridge down and create the hole needed for a hurricane to escape through.

500 millibar forecast from the GFS model showing the position of various large (and small) scale weather features

500 millibar forecast from the GFS model showing the position of various large (and small) scale weather features

Check out the second graphic I have posted. It is the 500 millibar forecast from the most recent GFS model run (valid 5 days out). Notice where 96L (or what ever it may be at the time). Also note the two well defined areas of high pressure on the map. One is over the eastern portions of the USA. The other is located over the central Atlantic. These massive domes of air will not allow a tropical cyclone to penetrate them. Instead, they have to go around like a blob of jello navigating around more dense blobs of jello. They each react to one another in subtle ways but the end result is that the smaller blobs (hurricanes) cannot go through the larger, more dense blobs (high pressure areas).

Now notice the trough over the Atlantic between the two ridges – this is the opening between the continental ridge and the Atlantic ridge. If the two were connected, then we’d be talking about a system cruising through the Caribbean Sea right now. Instead, a through of low pressure has carved out enough of an opening in in the Atlantic ridge to allow a possible escape for what ever 96L evolves in to – be it a tropical storm or a hurricane. It will “feel” that weakness or hole and likely turn away from the Southeast U.S.

The GFS global model and the ECMWF global model both show this scenario right now. Can it change? Yes it can but the overall pattern is not likely to change enough to affect the outcome and that is to send 96L packing and out to sea.

There is one glaring issue that needs to be considered. We are talking about computer model data that is days away from becoming reality. These are computer projections of the weather almost a week out in time. I am wanting to explain the situation as it appears today. This also strongly emphasizes the issue of posting graphics that show a hurricane knocking on the door of some coastal location in seven to 10 days. It’s nonsense. Especially without any explanation beyond “this is just one model run and it could be wrong”. Anyone can say that – I wanted to point out the actual players, so to speak, and explain the process in a way that I hope you can understand.

For today, we know that there is a slowly organizing tropical wave and low pressure area which is affecting parts of the eastern Caribbean Sea. Recon is currently investigating the system now and we’ll know more about its structure, etc. soon enough. From there, we will see what happens as each model cycle gives us more clues as to the eventual outcome.

In the eastern Pacific, busy is not strong enough of a word to describe the activity there. We have TS Karina along with hurricane Lowell. In addition, another large low pressure area is about to become the next depression well off the coast of Mexico. It too should strengthen in to a hurricane but is forecast to track parallel to the coast and not bring any significant impacts to the region.

I’ll have another update here late tonight.

M. Sudduth 2:25 PM ET Aug 21

 

 

 

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Beware the hurricane trolls

The official NHC 5-day graphical Tropical Weather Outlook

The official NHC 5-day graphical Tropical Weather Outlook

As we get in to August, especially late August, the tropics begin to spring to life as conditions become more favorable across the Atlantic Basin.

This time of year also sees a marked increase in what I like to refer to as Hurricane Trolls. These are the people who like to post images, paths, swaths, cones of death – what ever – showing a snap shot of some distant model time period that conveniently has a strong hurricane parked off of some poor, unsuspecting city.

The result? Lots and lots of “shares” and “likes” of said graphic and a few moments of glory for the person who posted it.

What good did it do? How many people have any clue as to what they are looking at? Does it raise awareness or just make people nervous? These are all issues that we have to deal with in the age of instant information and global model output readily – and freely – available to the masses.

The National Hurricane Center now has an experimental five day graphical Tropical Weather Outlook that highlights any areas of concern out to five days. It never, ever shows a single frame from any particular model run to try and drum up interest or increase Facebook likes. Instead, a well thought-out discussion of what players there are on the field is written up and illustrated to outline any potential formation areas in the tropics. Beyond five days is just too uncertain and has little merit to even discuss with any degree of accuracy.

The same hype machine is fired up during winter when a similar group of Snow Trolls comes out of the wood work to post snap shots of day 10 ECMWF snow accumulation graphics which depict some region of the I-95 corridor buried in “The Day After Tomorrow” type snow. Funny, I never see this done when that much snow is forecast for a swath of real estate extending from Montana to Kansas. Wonder why? Again – the more people who could be impacted, the more likes and shares the trolls accumulate.

There is no question that people are interested in the weather, especially when it turns ugly. It’s inherently exciting to think about the possibility of a cat-3 hurricane bearing down on you. It doesn’t mean it’s a good thing but it is exciting by definition. What the Hurricane Trolls fail to consider is how this excitement can lead to anxiety and fear. Posting an image of something that may not happen has more negatives associated with it than positives. It does not help the cause and that is to spread awareness and useful information. While there is a chance that a tropical cyclone could be somewhere in the Gulf of Mexico within the next seven to ten days, there is no way to know how strong it might be. It’s getting towards late August – there’s a chance within any 10 day window that something could pop up. The global models are good but putting faith in a seven, eight or ten day forecast to point of sharing it with fans of your website or Facebook page is doing them a disservice. There’s no education behind the image, only some ill-fated attempt to become the hurricane go-to guy, if only for a brief time.

Now, as far as what is really going on out in the tropics today? Nothing to be alarmed about, just something to keep an eye on as we would any suspect area brewing this time of year. It’s not like hurricanes are something new that we are still adjusting to. They’ve been around ever since the oceans could support them. What we need to get used to is the idea that information put in the wrong hands can be detrimental – always check the source. When ever in doubt, use the ole reliable: hurricanes.gov. No traffic-driven agenda to worry about there, just hard working, dedicated government employees giving you the facts and a wealth of educational info to go with it. Be smart and remember: don’t feed the trolls…they may bite and are known to be aggressive.

I’ll have more here tomorrow.

M. Sudduth 11:10 AM ET Aug 20

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