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

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

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

GFS Smashes Hurricane into Texas in Late August

The latest 12z GFS is projecting a landfall of a hurricane right into downtown Houston, Texas at the very end of August.

Yesterday, the 12z GFS also showed a major landfall of a hurricane on the East Coast. Now, the wide variability of the track is not reassuring, but I am seeing a trend of a system threatening the US. As of now, there is nowhere near a track, but when you get a few scenarios within several runs where a major event happens within a certain range, it usually means something.

Because Invest 94 (the system that would be responsible for this) has begun a westward trend rather than a northwest trend, this track would seem like an OK solution. However, the GFS is known for being deliberately too strong and too fast with tropical systems, so take this for what it's worth.

Andrew

"Go Ahead, Make My Day."- Invest 94 To Rapidly Strengthen

Graphics from the RAMMB CIRA agency indicate a very high potential of tropical cyclone formation in between the 35W- 50W longitude lines in the Atlantic.

Tropical cyclone formation potential over the waters where Invest 94 is about to move into is at a very good level at this time, with the RAMMB CIRA folks outlining a large area of 'good' potential in red where Invest 94 is only miles away from.

A look at satellite imagery shows a very well defined circulation in the invest, but an exposed eastern side of the system. However, a strong cluster of showers and storms is currently in place over the western and northern sides of the system. Should we see more development over the western portion of the system, the invest would quickly become a tropical cyclone, and this may be only hours away.

Andrew

GFS Landfalls Hurricane on East Coast In Late August

Screenshotted from Americanwx Models

The latest 12z GFS model has produced a scary scenario in extremely late August/Early September, where a hurricane with pressure as low as 980mb landfalls on the East Coast. The worry comes as the GFS is unusually skilled in forecasting tropical cyclones.

From CIMSS

The GFS is projecting Invest 94, shown above currently stationed offshore Africa, to move west and quickly develop into a deep tropical system. As you can see, right now Invest 94 is not too organized. Despite the lack of major convection, I am seeing some startling signs of circulation, with a very defined banding pattern evident across the invest's cloud extent. This is very worrying to me, and only a few sustained bursts of convection would be needed to get the invest into a serious player.

From RAMMB CIRA

The current tropical cyclone formation probability suggests a pretty elevated chance of a tropical system to form in the presence of Invest 94, which is roughly near the 30 W and 15 N lines. If we look back to the satellite imagery, one can also see where it may go in the future.  The 10 N line can be used as a reference point to help determine tropical cyclone tracks. For example, systems to the north of 10 N typically have a better chance of recurving north and out to sea, while systems below the 10 N line typically have a better chance to move west and impact the Caribbean.

However, the past track of Invest 94 displays the clear west-northwest motion of Invest 94. If the system is to pose a threat to the East Coast, a nearly perfect westward path would need to be established, and development would have to be delayed. As we saw with Ernesto, a lack of strength with the system can have the system keep at a westward path, with motions to the south possibly tainted in there as well.

Because the GFS is so long range with it, I question the validity, as I do with all long range forecasts. However, a strangely well-defined circulation and fair west-northwest movement tells me that the East Coast is indeed in a possible path of this system.

Andrew

Tropical Storm Helene Suddenly Forms In 'Last Words' Before Landfall

Tropical Storm Helene suddenly formed today, only miles from the coast of Mexico, in a way displaying its 'last words' before landfall.

Helene is composed of the remnants of Tropical Depression SEVEN, which had formed days ago but dissipated shortly after.

Helene is expected to move northeast and hit Mexico, before quickly dissipating into a post-tropical low after encountering land. This track has some feel of Tropical Storm Ernesto, which also hit the Yucatan Peninsula before making a second landfall in Mexico. Ernesto, however, proceeded southwest.

Andrew

East Atlantic About to Get Much More Active

The Eastern Atlantic is about to get much more active over the next several days.

Satellite imagery shows a couple clusters of intense convection in western Africa at this time. As these disturbances move west, they will certainly pose a tropical development risk as they move offshore. I have not seen clusters this strong this season in the time I have been monitoring the East Atlantic / West Africa.

The steering layer for the East Atlantic shows that these systems will likely start out their journey in the ocean by moving west. A big player in the track of each of these disturbances will be how far south they start when they move offshore. For instance, some disturbances will be too far north and end up swinging north into the middle of the ocean, whereas others will be far enough south to keep a westward track and possibly eye the Caribbean.

If I were to take a guess on the track of each of the two disturbances shown on the satellite image shown, I would say that the first cluster closest to the ocean will probably end up going out to sea, whether immediately after leaving Africa or just before entering the Caribbean.
I do believe that the second disturbance shown has a better threat to aim for the Caribbean, due to its dislocation to the south of the first disturbance.

Andrew

Ernesto Dissipates; Redevelopment in East Pacific Likely

Tropical Storm Ernesto dissipated today as it encountered landfall in Mexico, but as it emerges into the open waters of the East Pacific, redevelopment appears likely.

The NHC has outlined this system with a 60% chance of redevelopment into a tropical cyclone. There will be some obstacles in the way, however, with shearing already above 30 knots in Ernesto's path and upper level divergence at a pretty high value. Despite this, the system is maintaining a good form by satellite standards, and it would only take additional convection and strengthening to get the system where it needs to go.

The SHIPS forecasting model has it reaching above 100 knots of wind speed, as seen below.

                TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 20 17 16 16 19 30 43 56 67 78 90 100 106

Note: 'No Land' refers to the strength it can reach with no land interaction.

Andrew

Caribbean May Be At Risk Over Invest 92

I believe that model guidance may be incorrect in assumptions that Invest 92 will be a threat to the East Coast and skirt the Virgin Islands to the north, as the steering layer chart above differs from the model guidance.

Steering charts are used for storms within a certain boundary of strength. This one is used for systems with central pressures at or above 1000mb, so we will use this chart to determine where Invest 92 will go. While it is not clearly defined, one can find it in the warm colors below the massive ridge in the Atlantic Ocean.

Looking at this steering chart, the models have good reason to be confused on the track- it is just below the ridge of high pressure. If it were to be influenced by this ridge, as many models are saying, the system would keep straight west and fire off towards the East Coast.
However, as a few models are starting to trend to, there is a tight belt of winds just below the ridge that would take the system southwest, through the Caribbean and possibly towards the USA. I find this to be more possible, as the warmest colors are in the belt of higher winds, and thus would have more influence on where the storm goes. Additionally, this is where the NHC indicates the system is, as shown below on the most recent NHC chart. Invest 92 is the one circled in red.

Andrew

June 1- Low Potential for Tropical Cyclone Formation (Evening Discussion)

This morning, we reported to you a system that could have potential for brief tropical cyclone formation. We are here to report that the development did not occur, and there is now a much lower chance of tropical cyclone formation.
Below is satellite imagery of the Atlantic.

The system to the west of Florida is the system that had been catching our eye earlier today. The system moved over Florida as a low pressure system only. It now has a 10% chance for tropical cyclone formation over the next 48 hours.
We are watching another system down by Central America. That area also has a 10% chance of tropical cyclone formation over the next 48 hours. However, the NHC has indicated that more favorable conditions for development are possible beyond the 48 hour period.
We will be closely watching that system.
However, let's get back to the first system near Florida.

(Image use not allowed)

The latest ensemble suite for this system is more southerly, with the general consensus to take the system across the Gulf of Mexico and potentially into Mexico itself. While you may be thinking that the Gulf of Mexico is perfect for tropical cyclone formation, it just isn't for this system. That's the plain and simple of it.
There is also the intensity ensemble forecast for this system below.

(Image use not allowed)

While the earlier ensembles had been showing a minimum tropical storm strength, the ensembles are more cautious at this point, but still thinking that a partial consensus will be for a tropical storm to form. One aggressive model takes the system into a Category 1 hurricane. However, I do not believe that will happen.

It looks like this system will be more of a simple low pressure system, although I will not rule out the potential for a tropical depression to come out of the system.
We will be closely watching the second system mentioned in this post closely, as the system will be stationary and could become a tropical cyclone going into this weekend.