Florida to Feel the Brunt of TS Debby

As of 4PM, TS Debby had maximum sustained winds of 45 mph and was located about 30 miles off the coast of Apalachicola, Florida, and was moving NE at 5 mph. Debby has been a very slow moving system and as a result, has dumped copious amounts of rain on the Florida panhandle as well as the northern half of the peninsula. Here are rain totals just since Friday morning around 8AM...some areas south of Tallahassee are approaching 20 inches:

More rain is expected as Debby continues to track NE, closer to Florida. Current satellite and radar shows one batch of torrential rain just to the north of the center of circulation, drenching parts of the panhandle:

Not only is flooding a big concern, rain bands pinwheeling around Debby have been responsible for numerous reports of tornadoes. A tornado watch remains in effect for most of the peninsula through 11PM tonight, but I would not be surprised to see additional watches issued:

As far as Debby's track is concerned, the models are still coming into better agreement that Debby will come ashore on the coast of the Florida peninsula. Here is the 18Z guidance from a few of the models:

Additionally, the most recent forecast cone from the NHC has shifted well to the east, showing Debby coming ashore as either a weak tropical storm, or a strong depression- either way, the flooding potential and tornado potential are threats that need to be taken very seriously-:

Despite being in the Gulf for several days now, Debby has yet to really organize into a 'classic' tropical system. The main convection still remains on the eastern side of the storm, and never was able to wrap around to the western side. Significant strengthening is still not expected, and most of the models keep Debby as a tropical storm over the next 132 hours:

Several different 'steering' mechanisms are playing into Debby's evolution. Note over the central US, a very strong heat ridge is holding tough, acting to block Debby from moving in a more westerly direction. The trough digging down over the eastern US is acting as a lure or 'path of least resistance' for Debby to follow and be picked up by, as well as another area of High pressure located east of the Greater Antilles helping to steer Debby. Below is the 500-850hPa mean steering wind, valid at 21Z:

Has Debby Decided Florida?

As of 10PM , Tropical Storm Debby was stationary just over 100 miles off the coast of Apalachicola, Florida with maximum sustained winds of 60mph. Note that a majority of the rain and squalls are still located east of the main center of circulation, pummeling Florida with flooding rains and even tornadoes:

The intense squalls rolling through Florida have been responsible for numerous reports of tornadoes, structural damage, injuries, and even 1 fatality so far. Here is an image from Jupiter, Florida, taken by Steve Weagler:

Currently a very intense rain band is passing through the panhandle, moving closer to Orlando with numerous severe t-storm warnings out. Here is current radar:

For several days now, Debby has presented the weather models with a very challenging situation. Up until today, there had been a decided split between major, reliable global models as well as the tropical models- Texas or Florida? With every recent run, it seems as though the models are becoming better in-line with Debby coming ashore along the Florida Gulf Coast somewhere near Apalachicola. 

First, we'll visit a few of the major models and you'll note very good agreement. Each image is the forecast valid for Monday morning at 7AM:

European

GFS

NAM

GFDL

Canadian

Even the GFS ensembles are coming into better agreement:

18Z Run:

The obvious shift in the models has prompted the National Hurricane Center to re-draw their forecast path to now show Debby coming ashore on the Florida Panhandle:

Notice NHC is not expecting Debby to achieve hurricane status, however, do not let that be misleading as this system is still causing life-threatening conditions, especially in the form of high surf and dangerous rip currents in areas where huge swells are not very common.

Aside from that, remember that a little over 2 weeks ago, parts of the Florida panhandle received more than 20 inches of rain and Debby is expected to dump up to a foot more in some areas. Below is the NAM's forecast of how much rain will fall over the next 84 hours (keep in mind some areas have already seen close to 10 inches:

In addition to the rain, TS force winds will be felt over a large area around Debby. Below is what the Hurricane Center is forecasting over the next 5 days:

Also note Tropical Storm Watches and Warnings, Coastal Flood Warnings, Flash Flood Watches, and even Tornado Watches are out for parts of Florida:

CONCLUSIONS: Uncertainty still remains on the exact track Debby will take and additional changes to the forecast path could certainly happen. Because Debby is stationary right now, in theory, she could literally start moving in any direction and until some semi-consistent motion becomes present, we cannot be totally sure of her exact destination, although the recent (better) agreement among the models does look promising. 

Major Shift in Debby Track

Per the NHC 4AM EDT update, Tropical Storm Debby had inched a little closer towards the US Coast; the center of circulation is about 165 miles southeast of the mouth of the Mississippi River. Debby still contains maximum sustained winds of 50mph and was moving north at 3mph.

NEW OVERNIGHT: Some of the reliable tropical models and global models have made some dramatic shifts in their tracks for Debby. For example, the Canadian and European model which have consistently tracked Debby to Texas by the middle of next week have now drastically shifted Debby's track. The Euro, which had been showing a Debby landfall on the central Texas coast is now bringing Debby ashore on the Louisiana coastline early next week:

Above is the Euro solution valid for Wednesday evening at 7pm.

Even more dramatic is the change that the Canadian is showing. The Canadian is now showing Debby tracking into the central Florida panhandle into early next week:

The image above is the Canadian's forecast valid for Monday at 7pm.

The NAM had also been showing a Texas landfall for Debby but is now suggesting Debby may actually be quite stationary over the open Gulf for the next several days. Below is the NAM forecast valid for Wednesday at 1pm:

What has remained unchanged is the fact that most tropical models keep Debby BELOW Hurricane status, regardless of where she comes ashore:

Notice again overall, there has been a pretty dramatic shift towards the right as far as the models are concerned:

Coastal flooding will be a major problem, especially if Debby keeps moving at such a slow pace. Below is the HPC's expected rainfall totals over the next 5 days:

What to take away from this post: The track of Debby, while still somewhat of a toss-up, seems to be evolving into more of a central Gulf Coast storm. Until the storm actually makes a turn toward the west or east, we won't know exactly where she'll go, but if Debby continues north, she will come ashore on the Louisiana coastline. The central Gulf Coast states need to prepare and no one can rule this storm out just yet- not even Texas.

The latest forecast from path from the NHC:

I would not be surprised to see this change dramatically once the 8AM EDT  update comes out...

Stay tuned for more updates here as well as new advisories from the National Hurricane Center.

TS Debby Forms in the Gulf

As of the official 5PM EDT NHC update, Tropical Storm Debby was named. The system had maximum sustained winds of 50mph. Debby was slowly drifting towards the north, but then is expected to make a curve towards the west.

The deep convection is only located on the eastern side of the center of circulation, which is located about 220 miles SSE of the mouth of the MS River. In fact, nasty squalls have been pummeling south Florida for the past few days, even a few tornado warnings have been issued this afternoon.

For several days now, the Canadian and Euro models, and recently the NAM, have been consistently showing Debby ultimately tracking towards Texas. 12z data from the Canadian has this system continuing a northward jog and brings into south Louisiana, but I do not agree with this solution and it is definitely and outlier. 

The GFS and GFDL have consistently showed Debby tracking east towards Florida and eventually up the east coast, assuming the current trough over the Northeast would act to lure Debby eastward. However, the building ridge of High pressure over the central US is becoming more influential, and the clockwise flow around the High will help steer Debby westward towards Texas. 

Notice, however, the amount of uncertainty among the models as to the evolution of Debby:

The National Hurricane Center began issuing advisories on Debby per the 5PM EDT  update. The NHC has obviously sided more with the Euro, CMC, NAM, HRWF solution, tracking Debby toward Texas into next week. Here is the latest forecast path:

As we know, forecasts can and do change (sometimes drastically), so it is very important to stay up-to-date  of the latest information. That information can be found at www.nhc.noaa.gov.

Interesting side note, Debby is the earliest 4th storm in historical records, surpassing Dennis which formed on July 5, 2005.

At this time, most of the tropical models keep Debby as a Tropical Storm, however, some of the global models, such as the Canadian and Euro, suggest Debby may strengthen into a hurricane once we get into next week:

Right now, it appears that the only adverse affects that will be felt along the Louisiana, Mississippi, and Alabama Gulf coasts will be higher surf, dangerous rip currents, and occasional t-storms each afternoon.

Model Madness: Turmoil in the Tropics

There is almost no doubt that our next tropical system to form will be in the Gulf of Mexico. If so, the storm would take on the name Debby. The real question is where will this storm go once it becomes organized? The latest satellite imagery shows a broad, disorganized area of thunderstorms near the tip of the Yucatan Peninsula:

Hurricane hunters will be investigating this area of low pressure in the coming days, but for now, we'll refer to this as Invest 96L. Current max winds are only at 30mph. 

The real question on everyones mind is where will this system go? Keep in mind there will continue to be a lot of uncertainty over the next day or so, and we will not become more certain of track or intensity until "Debby" becomes better organized.

Much of the uncertainty comes from the fact that there is a decided split in how the forecast models are handling this system. For example, the European and Canadian develop this system and track towards the Texas coast. In fact, the Canadian seems to be the most aggressive, developing this storm into a strong hurricane and bringing into the central Texas coast- the European tracks it more towards south Texas.

Below are some images that show exactly what the Canadian and European are calling for:

Above is the operational European's 120-hour forecast. Note the area of low pressure off the south Texas Coast. Below is the European ensemble, indicating decent agreement with the operational, tracking the system towards the S Texas coast.

Below, is the Canadian model's much more aggressive 120-hr solution of a strong hurricane tracking toward the central Texas Gulf coast...

Note the Canadian ensemble is not in great agreement with the operational, some members (red numbers) show the system's location off the Texas coast, but a few track the system more towards Florida:

Check out each member of the Candian ensemble's solution:

Interestingly, the GFS along with a majority of its ensembles develop this system and track closer to Florida, and eventually up the East Coast. The GFS solution shows the weakest intensity.

The 'tropical' models seem to be in agreement with the GFS' solution of a more northeastward track:

Right now, it looks as though meaningful development of this system will be slow as wind shear is still a bit of a limiting factor over the southern Gulf, but it looks by at least Sunday or Monday, we should have a better organized system on our hands and will have a much better idea of where "Debby" will go.

Tropical Development Lurking in the Gulf

Despite having the first hurricane of the 2012 Atlantic Hurricane season churning in the north Atlantic, a majority of the attention is now turning towards the Gulf for possible development early next week. For several days now, a trough has been responsible for a deluge of showers and thunderstorms over parts of Cuba, south Florida, the Bahamas, and the eastern Yucatan Peninsula. It looks as though upper-level winds will relax somewhat allowing for better organization of this system into more a tropical system. Here is the latest information from the Hurricane Center:

Many of the trusted numerical weather models are picking up on this system as well. The Canadian and European seem to be the most aggressive, however, they also have the most spread or difference in track. The Canadian develops a tropical cyclone and tracks it west across the Gulf into south Texas by the middle of next week. The map below is the forecast valid for Tuesday at 7pm:

The European develops this system but tracks it more northeast, towards Florida, and eventually up the east coast. The following is the European's forecast valid for Tuesday at 7pm:

The latest run of the GFS shows a much weaker system developing, but the track is still very similar to the European's. Here is last night's run of the GFS valid for Monday morning at 7am:

A few other factors will play a key role in the track of this system, most notably the strong heat ridge over the central US. We will certainly have to monitor the Gulf closely as tropical development is becoming more and more likely.

Severe T-Storm Watch until 10PM

An long-lived MCS continues to drop south out of north Mississippi this afternoon. This complex of severe storms has brought extensive wind damage across the Memphis Metro area, as well as parts of NE Arkansas and extreme N Mississippi. This complex is feeding off a very unstable airmass as it continues to chug south towards central Mississippi. Wind gusts have been recorded and/or estimated well over 60mph across west Tennessee, and some gusts have even been as high as 80mph. Roof and tree damage has been reported as well. As these storms continue to build south, the main threat will be damaging straight-lined winds that could easily bring down trees and power lines and cause roof damage. Below is an updated watch graphic: