East Coast May Be Threatened By 'Sandy'

Models are going crazy over the potential for both a snowstorm and a hurricane to hit the northeastern quadrant of the US (Ohio Valley, Northeast, Mid-Atlantic). Let's jump right into this.

First, I will discuss the tropical aspect of this system. Then, I will hone in on the snowfall aspect.

Section 1: TROPICAL

This is the little invest that could cause a very extreme Halloween on the weather spectrum. Invest 99 currently resides in the Caribbean, with a 70% chance of development in the next 48 hours as declared by the National Hurricane Center. The system is expected to stay stationary before moving north. During this time, strengthening into a named tropical system may very well occur, and models are favoring such an idea. Here's a gathering of the models for 48 hours out. If the invest strengthens to a named storm, it will be called 'Sandy'.

All the models are in pretty good agreement that the system will likely strengthen into a tropical storm or something of similar strength. At this point, we can pretty much say that the next 48 hours will not threaten the US mainland.

But there's a different story later on...

The models begin to change forecasts and vary on strengths past the 5 day mark. Let's look at a gathering of the models as far out as they can go. TIP: To see the number of hours this forecast goes out to, look for a 'T = (number of hours) h' on top of each image.

NOTE: Each model's forecast is at a DIFFERENT TIME. See the "T= (number of hours) h" on
the top of the image to see when each model forecast is valid for.

Let's do a model-by-model breakdown of each forecast. Note, confidence levels do not add up to 100% in the end.

NAVY'S Model (NOGAPS):
This model keeps Sandy modest and only moderately strong as it gets dangerously close to Florida. While this seems the most realistic in comparison to stronger forecasts, the NOGAPS does not have a good track record. Confidence level: 15%

European Model (ECMWF):
The ECMWF is an amazing model and commonly claims the best forecasting record when it goes up against other models. It is showing a very strong landfall in the Northeast/Mid-Atlantic, which could seriously hurt the cities closest to the coastline. Despite the ECMWF's great track record, this is the long range forecast, and that must be factored in to my confidence level. Confidence level: 40%

European Ensembles (ECMWF Ensembles):
These are the ensembles of the ECMWF model that combine into an amazing forecast source. Based on the fact that these ensembles originate from the ECMWF model, and that there are so many (I heard 52 members from somewhere) of the individual members in the ensemble set, my confidence level is pretty high on this one. Confidence level: 55%

Canadian Model (CMC/GGEM):
The Canadian model is horrible at long range forecasting, and is absolutely terrible at tropical cyclone forecasting. I'm not even going to think about this model's forecast for the time being. However, the fact that it holds some similarities to the ECMWF and GFS is slightly encouraging. Confidence level: 5%

American Model (GFS):
The GFS claims second place in the best model race right behind the ECMWF. A recent update to the GFS has drastically improved its forecasting abilities, threatening the ECMWF for the title of best model. The ECMWF and GFS are fairly similar, but the ECMWF goes inland while the GFS does a 'drive by' on the East Coast, where it hits the region and goes back out to sea. I'll need some more runs of the GFS to be more confident in this one. Confidence level: 30%

All in all, I believe the East Coast should definitely be prepared. It's always better safe than sorry, and the fact that so many models are even thinking of threatening the East Coast is worrying. Watch for more information coming in the next few days.

Section 2: SNOWFALL

This is the part many of you have been waiting for. So, without any further ado, let's check out the snowfall forecasts.

NOTE: This is material from AccuWeather Pro and should be treated as such;
if you are going to use this image, please reference Accuweather Pro.

This is the ECMWF snowfall forecast for 240 hours, of 10 days away. As you can see, the effect on Sandy going inland is huge- over 20 inches of snow hits Michigan and even more in southern Canada! Several inches of snow are also found in Mid-Atlantic states and parts of the Ohio Valley and Northeast.

This is indeed big, as it is from the ECMWF model. However, one must remember that there are many models out there, each with their own possibilities. So, take the above for what you think it's worth (I don't think it's worth much at the moment), and let's move on to the GFS.

The GFS is much less enthusiastic, and it should be. This forecast of the GFS has the hurricane get dangerously close to the coast before turning back and heading off into the ocean. Again, it's much different than the ECMWF, as the latter goes inland into Canada. Also, both models are in the long range, and all long range forecasts don't have the best chances of verifying, no matter the model.

It will depend on where the system ends up to determine just what (if any) snow falls on the eastern part of the nation. One slight movement in any direction could drastically alter Sandy's course and thus the effects it will have.

Andrew

'Sandy' May Pose Threat To Northeast

There is a disturbance brewing in the Caribbean that may very well become 'Sandy', the next name for a tropical system in the Atlantic.

Satellite imagery indicates a fairly disorganized area of a few clusters of defined thunderstorms and a pretty barren western flank of the system. However, it does appear that convection has been increasing in recent hours in association with this system, indicating that this tropical wave's potential to develop is increasing. Let's look at some of the model forecasts on this system.

The 6z GFS takes the system north, to the point that it is just east of Florida by the time the next full week passes. At that point, low surface pressure tells me that Sandy would have already developed and been named.

If we keep looking at what lies ahead of the tropical system, we see a ridge of high pressure just off the East Coast, with another one in the Western US. This puts the disturbance in a difficult spot. I could see Sandy moving west and actually hitting the Mid-Atlantic, but we'll have to go further into the model's forecast to see what happens.

The Long Range GFS ends bringing an even stronger GFS well into the Northeastern US as what could be a very strong hurricane. At the moment, considering this is the long range, I'm not too worried, but the presence of even the notion of such a strong system hitting the Northeast is concerning in itself. Again, this is in the long range, so take it for what it's worth.

It should be noted that, as the system makes landfall, temperatures as low as 15 degrees (F) may hit much of the central US and Midwest.

The CMC is even stronger with this system, but remember that the CMC vastly exaggerates tropical systems to the point of absolute insanity. That said, I won't show any further forecasts of the CMC, but will leave you with this image and let your own imaginations take over.

I urge the East Coast to closely watch this system as it may have future implications on where Sandy eventually landfalls.

Andrew

Hurricane Season Running Above Normal; Atlantic Not Obeying El Nino

The 2012 Atlantic Hurricane Season is entering its second half, and already we are above normal for total named storms.

The average number of named storms averages out to roughly 11 storms, encompassing tropical storms, hurricanes, and major hurricanes. The number of hurricanes overall stands at 6, while annually, major hurricanes strike about 2 times. This year, statistics show that we have had 15 total storms and 14 named storms (there was one unnamed tropical depression). It is only September, and we have passed the 1966-2009 annual total storm count. The number of hurricanes we have had this year is also above normal, with 8 recorded hurricanes thus far. It has been proven to be an active season. But not many expected this. In a way, this could be the Renegade Hurricane Season of 2012. But what made this season so unexpected?

The hot topic of El Nino (excuse the pun) is to blame. In an El Nino, which is defined as the warming of waters in the Equatorial Pacific Ocean, atmospheric winds in the Atlantic turn unfavorable for tropical cyclone development. The lowest number of named storms in the Atlantic actually result from an El Nino. However, as was explained above, this year is not the case. This could very well be the result of the lack of recognition of the El Nino, as was explained in a previous post.

Because this season has been so odd, the confidence of a long range forecast on the rest of the hurricane season is drastically reduced. However, if I were to take an estimate on what may happen, I have a feeling that this unusual activity will continue. Areas of possible development in the Gulf of Mexico and Caribbean at the time of publishing (uncommon for September tropical development) points to this as well.

Andrew

Tropical Update: Hurricane Leslie and Hurricane Michael (MAJOR)

Analysis of the Atlantic Ocean at this hour shows both hurricanes spinning about in the ocean. We have Hurricane Leslie several hundred miles to the east of Florida, and major hurricane Michael another few hundred miles to the WNW.

There is a fairly strong disturbance to the immediate north of Michael. I believe that this will get Michael up and moving, but the movement will likely end up going west, towards Leslie.

It seems that strong cyclones will try to orbit each other, and this is referred to as the Fujiwhara Rule. In this rule, two strong cyclone vorticies will attempt to orbit each other, and this may very well happen to Michael and Leslie. As a weakening Michael moves towards Leslie, Leslie ought to try and also shift towards Michael. Whether this happens remains to be seen, but will be something to watch for.

Michael is currently a major Category 3 hurricane, with a well defined eye, eyewall and nice structure. Because it is in the northern Atlantic, weakening should begin shortly, with Michael dissipating by the time 10 days from now are up. Nonetheless, Michael is likely to continue to put on a show of its cloud structure over the next several hours before final weakening starts and Michael becomes nothing.

Leslie is also a hurricane, but at a minimum strength Category 1, with winds of 75 MPH. Any weakening would put Leslie back into tropical storm status.

However, I am seeing a depression in what appears to be the center of Leslie. Whether this is the forming of an eye or not, it is something I believe should be eyed closely over the next several hours, as this could indicate strengthening.

Andrew

Hurricane Michael Becomes Major Category 3 Hurricane

Hurricane Michael has strengthened into a Category 3 hurricane, as a well defined eyewall is shown to the visible satellite imagery, and the storm dawdles around the Atlantic.

Michael is currently forecast to meander around its current location for a few days, before taking off northwest. As this meandering takes place, Michael is expected to slowly weaken with time. After Leslie shoots off to the northeast, it looks like Michael will follow in her path and also go north.

It appears the two storms will be intertwined together, trying to keep up with each other as they move off north. While Michael is the stronger storm, it appears the much-larger Leslie will be able to pull Michael into her grasps and carry the both of them off into the northern Atlantic.

Andrew

Atlantic Ocean Analysis: August 31 2012

Isaac
The remnants of Isaac are currently on a northern track, but will be swept east by a frontal boundary also moving to the east. Heavy rains may begin to train over areas as the system takes time to shift directions. Thus, heaviest rains can be expected in Central Illinois.

Kirk
Kirk is in a weakening phase at this time, not moving to the northeast in accordance with a frontal boundary guiding the tropical cyclone along. I am anticipating Kirk dissipating in the next couple of days, before shooting towards Europe.

Leslie (not pictured)
Leslie's track is not well known at the moment, however a general out to sea consensus has been formulated by the models. The frontal boundary guiding Kirk appears to be the instigator, and this out to sea solution appears very valid.

Andrew

Invest 98 Spins in East Atlantic

Invest 98 is currently swirling in the eastern Atlantic, roughly around 41W, 14N. The system has winds of 30 knots and is currently moving west-northwestward.

Latest model tracks indicate that Invest 98 will not pose a threat to land, instead continuing a northwest track and going out to sea. Notice the high level clouds on the western side of the system. The Invest is very close to reaching tropical depression strength, and may do so today.

Andrew

Isaac Ensembles Shifting West; Dangerous Situation Incoming

The global model ensembles are taking a shift west, posing a danger to cities like New Orleans, that were previously not in the path of Isaac. Let's take a look.

This is the NCEP Ensembles, comprised of the GFS Ensembles. In the previous 0z suite, we saw a good consensus on Isaac hitting the Florida Panhandle. However, notice the ensemble members now more spred out. This spread appears to be favoring the west more than the east, and the 12z model suite reflected a westward shift in thinking. I'm not saying that the one member showing a Houston, Texas landfall is correct, but a westward shift is certainly something to take note of, especially on such a large scale of models and ensembles.

This is the CMC Ensemble group. These members are depicting a situation similar to that of the NCEP Ensembles, but more biased towards a MS/AL landfall. This is going along with new model thinking, and is not such a bad idea. However, there remains a considerable amount of spread among the ensembles, which can be mediocre at times, to say the best. However, this time around, the CMC ENS. may have something going for them.

Next, we have the FNMOC Ensembles. The FNMOC Ensembles are based off of the NOGAPS Model, which is from the Navy. The FNMOC ENS. are showing a much more varied, yet arguably well-composed spread, with members stretched from the Florida Panhandle to southern Texas. What I find great about this run of the FNMOC Ensembles is that it is accounting for nearly every reasonable scenario out there. Given, Isaac will likely not hit Mexico/South Texas. However, the FNMOC members are covering ground from Houston to Tallahassee, which is encompassing recent model and ensemble trends. This will be one to watch.

Lastly, the ECMWF Ensembles. Because the institute that runs the ECMWF is so strict about releasing data to the public for free, we are only able to see a mean of the ensembles, this image courtesy of Americanwx. The mean ensembles show a system making landfall in western Florida. This is a nudge to the east of ensemble thinking above, but should very well be counted in, as it was great at indicating that Isaac would be a Gulf threat.

All in all, the latest ensemble runs have been very interesting. Strangely, I am hesitant to count out any of them, for each has its own distinct trait that I find crucial in this forecast. For example, the NCEP has an ensemble group that has shifted with the models, the GEM Ensembles keep the MS/AL landfall as a consensus, and the FNMOC Ensembles account for all reasonable possibilities. This is not a common thing to see, when each group has good things going for them like this.

The question is, will a disturbance moving off the East Coast pick up Isaac?

I have marked the trough moving offshore and Isaac making landfall. The models seem to be having trouble assuming whether the trough influences Isaac and pulls it north, or does not influence Isaac and the hurricane goes west, more towards Louisiana, like the ensembles were beginning to say.

I will make a better calculation on this in the morning, when the ensembles should be a bit more settled than now.

Andrew

Isaac Threatening Florida; Hurricane Warnings Hoisted

Watches and warnings line the northern Caribbean and eastern Gulf Coast this morning, as Isaac leaves Haiti to continue towards the Gulf of Mexico.

Hurricane warnings have been hoisted in the face of Isaac in Florida, as well as tropical storm warnings blanketing Cuba. Isaac has just moved off of Haiti and appears to be heading northwest, towards the Florida Keys and the Gulf of Mexico.
If Isaac makes landfall on Cuba, it appears to be brief, and only a slight change in storm strength would likely be observed. However, if Isaac plows into Cuba, which is unlikely, the tropical storm could have issues with keeping itself together.

The latest Advanced Dvorak Technique (ADT) placement of the center puts Isaac at about 19 N longitude and 74 W latitude. This indicates Isaac has been moving northwest in the past while, but the first NHC graphic appears to show a west-northwest tilt as of the current center.
From this viewpoint, it seems a brief landfall on Cuba is likely, but nothing major as far as going through much of the country.

The forecast from the National Hurricane Center takes Isaac on a northwest path into the Florida Keys before curving north and making landfall on the Florida Panhandle. This does appear to be a fair track, but any wobble in any direction could drastically change the outcome of the track of Isaac. I am looking for hurricane warnings to be spread out across western Florida, the Panhandle, and Mississippi's into Alabama's portions of the Gulf Coast when Isaac nears.

The spread of models appears to be wanting to take Isaac a bit further west, possibly into Alabama or the extreme western Florida Panhandle. Considering the Southern US has been launching special radiosondes at 6z and 18z to aid the models in tracking Isaac, I would expect this to be a good consensus. However, it looks like a few models remain unsure, even 24 hours out, on where Isaac will be.

Intensity forecasts are also very scattered, but seem to have an idea of Category 1 hurricane strength in the next 3-4 days, before making landfall and weakening and possibly degenerating into an extratropical low. After that, some models project Isaac will shoot out to sea.

Storm surge is a big concern. The NHC is projecting that there is anywhere from a 0-30% chance of storm surge levels reaching 5 feet in Florida. The values appear to be so low because of no clear model consensus, but this remains a threat either way. Such a large storm has the potential to produce a very large storm surge area, possibly well inland of western Florida.

Andrew

Isaac Strengthening, Moving Northwest

Tropical Storm Isaac is now strengthening and appears to be in the process of beginning a northwest movement. Let's look at the past track of Isaac.

University of Wisconsin-Milwaukee

The observed track of Isaac shows a recent southern dip, followed by some regulation to the 16N longitude line. Recently, however, a sharp northwest turn was observed, bringing Isaac to about 16.5N. A northward turn is expected as Isaac strengthens. Strengthening of tropical systems commonly leads to the Coriolis effect taking over and turning storms to the north. The Coriolis effect will act as a tugboat, and veer storms to the right (north) in the northern hemisphere, and this could very well be happening now with Isaac.

SSEC CIMSS ADT

The Advanced Dvorak Technique, which helps find the center of tropical systems, has pinpointed Isaac's location at about 16.5 N and 71.35 W in the Caribbean. Looking at the satellite image superimposed with the center of Isaac, we see that the center is dangerously exposed on the west side. When we have a center of circulation (COC) with such an exposed area, it can be very easy for the atmosphere to quickly weaken Isaac. If that should happen, I could see a southward wobble happen, and more model mayhem ensue.

SSEC CIMSS ADT

The ADT also shows the strength of the system, based on satellite estimates and their own Cyclone Intensity scale, which ranges from 1 to 8 on this chart. Looking at recent observations, we see Isaac has endured some weakening in the past 24 hours. However, recent strengthening appears to be rebounding Isaac to a more stable point. This cannot be confirmed, however, until the center of circulation is re-covered.

Now... Model Mayhem Resumes!

Today's 12z European ECMWF model took a 967 millibar hurricane to the central Gulf Coast, keeping the consistency we look for and value so much in model forecasts. While the storm remains a while away, I am pondering this scenario. Isaac has already been shifting west and south and been strengthening and weakening so that a major move north has not been favorable. However, now, with the models recognizing the Gulf Coast threat, and a northwest movement seen above, this could be Isaac's time to shine, as far as moving towards the Gulf.

The GFS is much weaker, taking a 994 millibar tropical system to the Florida Panhandle. I do find this possible, but it is hard to go up against the consistency of the ECMWF. While this solution was shown in the 0z model suite last night, in which data from the Hurricane Hunters in Isaac was used, the ECMWF budged only a small amount east. Should Isaac take any wobble west, or even south, the ECMWF's solution would only become more and more likely.

The SREF is split, but many are projecting a tropical system to hit western Florida and the Panhandle, similar to the GFS. However, notice the major spread along the members. Just because you can make a big spread into a mean forecast does not mean it could be right. The wide variety of forecasts is very concerning to me, and I would like to not count in the SREF until its members can get into a good, solid solution.

Isaac is playing his tricks on us, and all you can do now is prepare. I advise (under my personal discretion, NOT the NHC's) that the Gulf Coast carefully monitor Isaac. The Florida Panhandle area, west to far eastern Louisiana should keep a close eye on Isaac, and consider making preparations for possible impact. We remain a time away, but the models seem to be coming together.

Andrew

All advice and opinions shared on here are those of mine and are not those of the National Hurricane Center. In any case, always disregard my forecasts and advice in favor of the National Hurricane Center's. This is meant as an informative article and should not be used to make major decisions, such as evacuation.

Gulf Coast Preparations Should Begin Now For Isaac

Preword: Do not take the following information as official information. Always disregard other sources in place of government warnings and advice. The following is meant as advice, but is not intended, in any way, to replace NHC forecasts and warnings. Use the following info at your own discretion.

"It's never too early to prepare. Now is the time."

Todays new model forecasts brought in a wide array of solutions, many now hitting the Florida Panhandle rather than affecting the East Coast head-on. What you see above is the European's ECMWF model, recognized as one of the, if not the best, forecasting models out there. Today's forecast off the ECMWF model proved interesting, with a 963 millibar major hurricane slamming into southwest Louisiana/far east Texas. I am not saying it will happen, nor am I saying it will not happen. However, the potential appears to be there.

We are watching a disturbance push its way to the east off the coast of the eastern United States. As you can see, the arrows on the lines show a northeast movement, and this could very well enhance Isaac's track. However, note that the disturbance is largely over the Atlantic and far from Isaac, reducing the potential for a sudden northeast turn that would possibly landfall upon the East Coast.
I want to make it clear that, should the current model consensus hold up, the system would landfall on the Florida Panhandle, move north (and possibly east), and may re-emerge into the Atlantic, where additional landfalling on the East Coast states may occur. However, at that point, Isaac will have dramatically weakened.

 The most recent model guidance as of 18z today shows a general consensus taking Isaac into the Gulf of Mexico and hitting either in the Panhandle of Florida, or more into the central Gulf Coast. Because I don't know these models as well as I do the global ones (GFS, ECMWF), I am not confident giving an assessment on the track. However, if I were to speculate, I would say that the continued westward progression with little north progression is edging the models west, as they should.

As of roughly 20z today, the center of Isaac was observed at roughly 16N longitude and 67W latitude. What I care more about is the longitude. Because Isaac remains in the general 15-17N realm, I cannot see any East Coast forecast models working out. Even a scrape with western Florida is edging out of the question. It is now up to Isaac to either strengthen and get going, or remain weak and disorganized and possibly not make it up to the status the ECMWF is projecting.

Andrew

ECMWF Slams Isaac Into Gulf Coast as Major Hurricane- Why You Shouldn't Count It Out

The 12z ECMWF run today took Tropical Storm Isaac, bombed it out again in the Gulf of Mexico, and slammed Isaac into the Gulf Coast as a major hurricane, with a central pressure of 964 millibars.

Many have been discounting this system as an outlier, and this continues, even as this is not the first time the bombing-out solution has been shown with Isaac. A very similar solution and slightly different track was shown yesterday by the ECMWF.

Now, it's a model war, like the ones we will see in winter: ECMWF vs. GFS for Isaac's track. Let's look at a major component of the track.

In this map, we can see Isaac just about to enter the Caribbean. But notice the large disturbance creating quite a commotion along the East Coast. The models are interpreting this differently. As you can see by the arrows in the dark red off the East Coast, the direction the winds are going is northeast, hence the East Coast-threat tracks being shown by other models.
The question is if the disturbance's influence will be enough to force Isaac north and take an East Coast-threatening track, like the GFS and others say, or will the system be able to pass by the strong northeast winds and pass into the Gulf of Mexico, where a dangerous scenario could unfold, as the ECMWF describes.

I did some deep digging and came upon an observation chart for 12z at 250mb. I also found the 12z GFS' 12z initialization chart at 250mb. I compared the two, and found slightly stronger winds in the GFS' forecast. While it may not seem huge now, the implications could be massive in the long range.

Now, let's check out the 2010 and 2011 model performance statistics for the Atlantic. We will start with 2010.

On the right sidebar is the skill percentage of the models, while the bottom bar has the forecast hour. If we look on the graph and find a light blue line leading the pack in skill, we look to the right and see it is the EMXI model, also known as the ECMWF. This shows that the ECMWF led the model forecasting skill for 2010. While a slight lapse may have occurred towards hour 120, the skill remains at the highest notch.

Moving on to 2011.

In 2011, we see a worse performance by the bottom forecasting models, and a tight race for the best forecasting model for 2011. If we look closely, we see the ECMWF and NHC forecasts tied in the early forecasting hours. But they both dropped off going into hour 120. Here's the thing- the EMXI model (ECMWF) dropped off just a little less than the NHC, showing that the ECMWF emerged victorious for best model track skill.

So, now with two runs of a major Gulf Coast threat under its belt, along with two best model track skill awards, one can not help but wonder if the ECMWF is correct in the assumption that the Gulf Coast is indeed at risk. I, for one, like to keep all options on the table. Frankly, I think the ECMWF is correct, and past analogs with a similar situation as Isaac think so too...

Climatologically, more systems in Isaac's position tend to go into the Gulf of Mexico and make landfall in that area, rather than hitting the East Coast. This is a dramatic shift from a very short time ago, when more analogs were pointing to an East Coast run than the Gulf of Mexico. Time will tell, but this is just another piece to add to the puzzle.

Andrew

Charleston, Myrtle Beach Devastated by Isaac in GFS Individual Ensemble Forecast

A member of the 12z GFS Ensembles is showing a solution that would devastate Myrtle Beach and Charleston. This member shows a very strong hurricane slamming into the Southeast and possibly providing mass flooding and a preceding mass exodus, should this threat become real.

However, realistically, this possibility is very very low. That's why we also have a mean forecast of these individual ensemble forecasts. This is more of a for-show piece, but also demonstrates the potential that Isaac now has, and just what it ends up doing is very uncertain after what the ECMWF put out today, and that is shown below.

At Hour 240, the ECMWF is projecting a 961mb hurricane moving towards the Gulf Coast. Because rapid intensification will have been ongoing to this point, it is very possible that such intensification continues. From then, landfall could likely occur from Louisiana eastward. The ECMWF Ensembles are not as eager, but do show a system entering the Gulf of Mexico, and this could very well get aggressive very, very fast.

More on this will be available tomorrow.

Andrew

BREAKING: Tropical Storm Isaac Forms

Reconnaissance data from aircraft investigating Tropical Depression NINE have sent back information that shows many instances of tropical storm winds being observed, including one wind speed calculated at 44 MPH.

This means that the next National Hurricane Center update will most likely certify this as Tropical Storm Isaac. I will have an evening post up and out later on.

Andrew

BREAKING: ECMWF Bombs TD-NINE Into Major Hurricane in Gulf of Mexico

The fresh-off-the-presses 12z ECMWF has shown a Category 3 major hurricane swirling in the Gulf of Mexico, with a central pressure of 961 millibars- and it's still offshore.
This comes as the models begin to split up on a solution. Now that the ECMWF is sending a major hurricane into the Gulf of Mexico, time will only tell how the next model suite reacts to this news.

Andrew

Tropical Depression NINE Forms in Atlantic

Tropical Depression NINE has formed this morning over the Atlantic out of Invest 94, beginning the process that could land this system anywhere from Texas to Nova Scotia at any strength you can think of. Below is the latest model spread.

The latest 12z model spread is split, but a general consensus keeps the system going on a mainly westward track before curving north and threatening Florida. Which side it threatens remains a question, and that will largely depend on how weak/strong it becomes over the next 24-48 hours. Let's look at the observed track to see recent trends.

The latest trend in Tropical Depression NINE's track is a west-southwest movement, which bodes well for a threat to the Gulf Coast. Now, this threat is not too great to begin with (unless a southwest motion begins), but a Florida threat increases with every motion to the west or west-southwest. Typically, systems above the 10 N line will recurve and go either out to sea or threaten the East Coast. Whether that happens remains to be seen.

Andrew

Past track and forecast tracks from UW-Milwaukee

Invest 94 Poses Serious Threat To Gulf of Mexico

I have looked at a lot of data this evening and have come to the conclusion that the Gulf of Mexico is indeed at risk from Invest 94, soon to be Tropical cyclone Isaac.

Above is the steering flow at 250-850mb. The steering flow is like seeing a current of water in a sink take a small object and move it around within that current's reach. The steering flow shows where storms may go by identifying wind patterns at different levels of the atmosphere.
In the above chart, we recognize Invest 94 at 40W in longitude, and is shown as a blob of yellow and orange. At the moment, this is not the ideal chart, but if/when rapid strengthening occurs, this is the chart that model forecasts indicate should be used.
If we were to use this to give a rough estimate on the possible track of Invest 94, I could easily see it drifting west and following the band of winds that cuts through the Caribbean. However, the system would likely stay north of the full extent of the current, opting to enter the northern Caribbean and continue west, as model guidance is in agreement with at this time.

This map is the 0 hour analysis (not a forecast) of the Atlantic Ocean in the 500mb heights, with added MSLP. We can see Hurricane Gordon to the upper right corner of the image, which is moving towards Europe. But notice the massive high pressure regime in place across the Atlantic. This is a primary reason why I believe the new model trend of westward motion is right and why the Gulf of Mexico is at risk.
As many of you know, high pressure systems spin winds in a clockwise formation, while low pressure systems go counter-clockwise. This clockwise motion of winds would keep Invest 94 in the southern part of the Atlantic and move it towards the Caribbean. Typically, we will see a a few cracks in between high pressure systems, and these cracks will shoot the invest north. However, now that there are multiple high pressure systems, there are next to no cracks for the system to break through and move north.

I am having a feeling that the Gulf of Mexico is indeed at risk on this. I have not had much success with when I use my instinct on weather events like this, but current and forecast atmospheric conditions, combined with the strength and steering flow of the system tells me that a westward motion will continue with this system, and westward enough to put the Gulf of Mexico on alert.

I decided to run the Tropical Cyclone Forecasting (TCF) Model for Invest 94 at this time, only for track and not intensity.
You can find the TCF's Home page by clicking here.

TCF 7:00 PM Run

Andrew