Hurricane Helene

[biggerbyte]

The folks in the north and northeast gulf coast will be ground zero with this one. There could even be another system follow this exact path a few days out. This pattern is great for Texas. We don't need another Beryl around here. One is one too many. God help those that are not so fortunate.

There will be a little shear and dry air in the mix, but upwelling could very well negate such negative effects. Some say a major is coming. I'm not sure that extreme is a certainty. These folks should be preparing for a cat 1 or 2.. Hopefully the GFS is off its rocker.

[tireman4]

Blake Mathews
@BlakeMathews08
Those living from Pensacola to Sarasota should be in full Hurricane plan/prep mode for a potential powerful hurricane.

THIS is when SST’s matter: when you have good atmospheric conditions. Unfortunately, there is tremendous TCHP laying in its path which will aid in rapid strengthening.

We should have our first cone soon along with Hurricane watches. If told to evacuate, do so without delay.

[tireman4]

The Eyewall
@TheEyewallWx
We will have an updated post by 10:30 CT or so. We are waiting to see if the NHC pushes a cone for a potential tropical cyclone. Models continue to hone in on the Florida Panhandle for a hit from something close to or into major hurricane intensity.

[Cromagnum]

Cone definitely has it going to Florida.

[Pas_Bon]

The notion that its COC could completely avoid any land en route to the Gulf is disheartening and worrisome. I vividly remember Hurricane Lili (2002) jogging around (literally going out of her way to avoid) Jamaica (and the Isle of Youth, if I'm not mistaken) as it traversed just south of Cuba
Lili rapidly intensified over the next 36-48hrs to reach Cat. 4 status before losing steam as it approached coastal Vermilion Parish, La.

[biggerbyte]

This is a very sad day for the weather community. Major potential has increased today. My prayers go out in advance to anyone in the path of this system. If any of you have family in the panhandle of Florida, or even anywhere in the realm of uncertainty. ..

[tireman4]

Read on blog or Reader
Site logo image The Eyewall
Potential Tropical Cyclone 9 likely to become significant Hurricane Helene with widespread Florida & Southeast impacts
By Matt Lanza on September 23, 2024

Headlines
Potential Tropical Cyclone 9 is likely to become a depression and/or tropical storm by tonight or tomorrow morning.
It will accelerate north toward the coast of Florida, with a landfall likely on Thursday somewhere between Pensacola and Tampa. Hurricane impacts will spread across Florida's west coast and Panhandle.
PTC 9 or Helene is expected to be a significant storm and potentially a major hurricane (cat 3+).
Because of fast forward motion, PTC 9 or Helene will spread damaging wind far inland from th coast, across South Georgia, possibly into the Atlanta area (depending on track) and into the Carolinas.
PTC 9/Helene will be a significant, disruptive storm for the Southeast Thursday, Friday, and possibly beyond.
Give our site a bookmark and check back in later today and/or tonight for some additional updates to this post.

Potential Tropical Cyclone 9

The forecast track for PTC 9 suggests a storm tonight or tomorrow morning, and a hurricane by Wednesday, with impacts beginning in Florida by Thursday.
We have our potential tropical cyclone now, and it will be known as PTC 9. Expect this to formally become a depression later today and a tropical storm tonight or tomorrow morning. This should take on the name Helene.

The first forecast track from the NHC is very much in line with strong model consensus right now, which takes Helene somewhere between about Pensacola and Tampa, with the majority of guidance favoring the Panama City to Cedar Key corridor, close to the Big Bend of Florida. One thing to be very, very clear about: There is still a fair bit of spread among individual ensemble and tropical model members. You can use the slider here to compare the 6z runs of the European and GFS ensemble member forecasts for Thursday around midnight.


The 6z European ensemble (white background) and GFS ensemble show clustering of tracks in the Panama City-Cedar Key corridor with some tracks as far southeast as Sarasota or Fort Myers and some back closer to Pensacola. (Weathernerds.org)
The latest tropical models are very clustered on the west side of Apalachee Bay, with a track very near Tallahassee once inland. So you can see that the model guidance is in great agreement right now on the broad picture of things. I would still watch this very closely in Tampa and Sarasota, as well as Pensacola, as those locations are in the "margin of error" as you might say.

There is also a fair bit of cross-track spread in timing, with some models showing landfall as early as Thursday afternoon and others more into Thursday night. Assume you have until Thursday morning to finalize your preparations on the coast. Anything beyond that is just proverbial icing on the cake.

PTC 9's intensity outlook
One thing we are unfortunately continuing to be confident in is that this storm has a high ceiling in terms of intensity. There remains a significant spread within tropical model guidance with intensity, as some models suggest tropical storm intensity, while others are at the top end of major hurricane intensity, perhaps a higher end cat 3 or cat 4.


Model guidance shows a substantial spread in intensity forecasts with a handful just at tropical storm intensity, while some more hurricane-focused models show high end Cat 3 or Cat 4 potential.
The NHC projecting a peak intensity of around 110 mph, just on the cusp of major hurricane strength is a good place to be right now, but do realize that the risk for a stronger storm is very much on the table. As we've been noting, this track is about the worst possible one a storm could take from a "fuel" standpoint in the Gulf of Mexico. PTC 9 is likely to travel over significant ocean heat content the majority of its life cycle, and water temperatures never really cool off much on approach to landfall. Given the anticipated forward speed of PTC 9, we are likely to see this storm come ashore at or near peak intensity.


The forecast track from the NHC underlaid by ocean heat content and water temperatures shows a storm that is likely to spend most of its time over some of the warmest water in the Gulf or Atlantic.
Folks in Florida should be preparing for a major hurricane impact in the Big Bend or Apalachee Bay with all the threats you'd expect: Surge, wind, waves, flooding, etc. This has the potential to be as bad or worse than Idalia and much worse than Debby in the Big Bend.

Inland risks
The threats from PTC 9 are going to extend much farther inland than usual. The storm will be hauling as it moves inland. Even if it comes ashore weaker than forecast right now, it is likely to carry tropical storm and hurricane force winds well inland from the coast. Those impacts should begin Thursday night and continue much of Friday. This includes much of South Georgia, as well as possibly South Carolina, north Georgia, and portions of North Carolina or Tennessee. The map below shows wind gusts as forecast by the GFS model earlier today. Keep in mind that the final track will determine exactly where those winds occur. A track closer to Tallahassee will shift this farther west. A track closer to Cedar Key will shift this a little to the east.


Tropical storm force winds are likely to extend far inland from PTC 9, with widespread wind damage possible across Georgia and into South Carolina.
This is important because this type of scenario could mean widespread, significant power outages and wind damage across Georgia and South Carolina. Metro areas, including Tallahassee, Atlantic, Macon, Savannah, Columbia, Charleston, Greenville-Spartanburg, and Charlotte should be prepared for this scenario and prepare with at least a few days of food and water should this come to fruition.

In addition, heavy rainfall will occur with PTC 9, and flash flooding will be possible, especially in mountainous areas well inland from landfall.


Significant rainfall is likely well inland from landfall with PTC 9, and flash flooding is likely. Thankfully, the forward speed may help mitigate total rainfall a bit. (Pivotal Weather)
This is going to be a significant, disruptive storm for portions of Florida and the Southeast U.S., in addition to perhaps western Cuba and the Cayman Islands where 10 to 12 inches of rain may fall. Impacts will be widespread and damage could be significant. Folks should begin preparing immediately and follow forecast changes closely in the days ahead.

[jasons2k]

The notion that its COC could completely avoid any land en route to the Gulf is disheartening and worrisome. I vividly remember Hurricane Lili (2002) jogging around (literally going out of her way to avoid) Jamaica (and the Isle of Youth, if I'm not mistaken) as it traversed just south of Cuba
Lili rapidly intensified over the next 36-48hrs to reach Cat. 4 status before losing steam as it approached coastal Vermilion Parish, La.

My wife and I were on our honeymoon cruise during Lili. It was an interesting cruise. The Norwegian Captain kept referring to her as “The Lili” in his nordic accent haha. When we departed Galveston I told my new bride there was a possibility our car would be flooded when we got back. Fortunately, that didn’t happen.

This storm has me concerned about my relatives and property in the Bay Area. I hope the track doesn’t shift east again but unfortunately that’s usually the trend with these.

[DoctorMu]

Given the way UF's season has gone, Helene will probably blast through Ben Hill Griffin Stadium and Lagway can thro the ball out of the stadium with some serious tailwind.

[Pas_Bon]

The notion that its COC could completely avoid any land en route to the Gulf is disheartening and worrisome. I vividly remember Hurricane Lili (2002) jogging around (literally going out of her way to avoid) Jamaica (and the Isle of Youth, if I'm not mistaken) as it traversed just south of Cuba
Lili rapidly intensified over the next 36-48hrs to reach Cat. 4 status before losing steam as it approached coastal Vermilion Parish, La.

My wife and I were on our honeymoon cruise during Lili. It was an interesting cruise. The Norwegian Captain kept referring to her as “The Lili” in his nordic accent haha. When we departed Galveston I told my new bride there was a possibility our car would be flooded when we got back. Fortunately, that didn’t happen.

This storm has me concerned about my relatives and property in the Bay Area. I hope the track doesn’t shift east again but unfortunately that’s usually the trend with these.

Crazy stuff. I went back to my parents’ house (from Baton Rouge) in Abbeville, La for Lili to help them and rode it out there.

I was petrified when she rapidly intensified the day prior to landfall. Thank God she ramped way down

[Ptarmigan]

HAFS-A infrared simulation. Looks like a full blown Category 5 hurricane.

[biggerbyte]

I have this horrible sinking feeling. God bless all involved.

[Pas_Bon]

I have this horrible sinking feeling. God bless all involved.

Same. Godspeed

Huge potential wind field, also
She may be a monster.

[tireman4]

Read on blog or Reader
Site logo image The Eyewall
PTC 9 continues to get itself in order as we focus on the risks to Florida and beyond
By Matt Lanza on September 24, 2024

Headlines
PTC 9 continues to fight off a little shear which is slowing its initial organization.
As that relaxes, rapid intensification and organization should ensue, with PTC 9 expected to become Major Hurricane Helene by Thursday.
Landfall is a little later on Thursday now, likely somewhere between Panama City and Tampa with a focus on Apalachicola through Cedar Key. There is still some uncertainty on this.
Storm surge from the Big Bend and Nature Coast through Tampa Bay is expected to be as bad or worse than what occurred during Hurricane Idalia in 2023.
Impacts from wind and rain will extend far beyond the landfall point with Georgia and the Carolinas likely to see strong winds and flash flooding.
PTC 9 this morning
PTC 9 continues to lack the ingredients necessary to be a depression just yet, but we continue to edge closer to that point.


PTC 9 continues to slowly organize in the northwest Caribbean.
What's holding it back so far? There's a bit of wind shear mixed in with all this from an upper low over the Yucatan. Tropical systems don't like wind shear, and as long as that continues, the pace of development will be sluggish. That is not expected to be the case, however, as modeling weakens the shear in the next day or so, allowing PTC 9 to have a less hostile environment over some of the warmest water in the Atlantic basin. That should lead to strengthening and potentially rapid strengthening at that.

PTC 9's forecast: Angles matter
The overall forecast for PTC 9 has not changed a whole lot since yesterday.


The forecast for PTC 9 continues mostly in line with what was predicted yesterday.
The cone has narrowed a hair to between Panama City and Tampa. Hurricane Watches are now in effect for the Florida coast, as well as inland in the Panhandle. Tropical Storm Watches including Orlando are now posted as well. Expect some of these watches to expand later today.

On the surface, this looks like a pretty easy forecast: Tropical models are in generally good agreement on a track to the northwest, then north, then north-northeast. The clustering is pretty solid in the modeling in Apalachee Bay or near the Big Bend of Florida. So, simple right? For my college football fans: Not so fast, my friends.

The fundamental problem in predicting storms that turn is the angle at which it all happens. Generally, models handle the concept of this well, and indeed we have very good agreement right now in the models.


Tropical models for PTC 9 are in good agreement on the general track. Florida's geography poses a unique challenge.
Because of Florida's unique geography with a peninsula jutting out to the south, the exact landfall point gets harder and harder to pin down when a storm comes in from the south or southwest. A shift of 10 to 15 miles out over the Gulf can lead to a shift of 20 to 40 miles with respect to landfall location in Florida. We often talk about not focusing on the exact track, and indeed there's a reason for that as impacts extend far from the center. But for things like storm surge, that exact landfall point is crucial in determining how things will turn out. It also makes the difference for places even well inland to be on the "dirty" eastern side of the storm or the slightly less menacing western side.

As long as the tropical models are correct, we're likely to see this chug north-northeast into Apalachee Bay or the Big Bend. However, if the models are not quite grasping the interaction with an upper low over Arkansas properly, well, that could change things a bit. There's a path to get a storm much closer to Tampa, as we discussed last night and as the ICON model continues to show this morning with a track coming ashore near Cedar Key rather than Apalachee Bay. For now, the most likely window for landfall appears to be Apalachicola to Cedar Key, with lesser bands around that to Panama City on the west and Tampa on the south/east.

The takeaway here is that this is a storm where focusing on the entire cone makes a lot of sense.

In terms of intensity, not much has changed since yesterday. We still struggle with intensity forecasts. One needs to only look at Hurricane John yesterday, which came ashore after 9 PM as a 120 mph category 3 storm in Mexico while initially forecast to be a 70 mph tropical storm at 3 AM. (Credit to the NHC however for constantly stating in their discussions that there were higher risks, and even substantially higher risks than the explicit forecast showed).

But we still expect that PTC will become Hurricane Helene and a major hurricane at that. The National Hurricane Center has this as a category 3 storm at landfall. And model support is generally for a strong storm.


Model forecast intensities for PTC 9 still show a very wide spread in options, but most seem to agree on this becoming at least a category 2 or 3 storm.
The takeaway: A powerful hurricane is likely to strike Florida's coast late Thursday, likely somewhere between Apalachicola and Cedar Key but with risks extending just beyond those goal posts.

Impacts from Helene/PTC 9
We have our first look at storm surge today from the NHC advisory, and it's not great news.


Storm surge as high as 10 to 15 feet above ground level is possible near and east of where PTC 9/Helene comes ashore in Florida. About 5 to 8 feet of surge is possible in Tampa Bay. (NOAA NHC)
Values of 10 to 15 feet in the Big Bend would be in line with or worse than what occurred in Idalia last summer. A 5 to 8 foot surge in Tampa Bay would also be in line with or worse than Idalia. So for planning purposes, those areas should consider Idalia as a benchmark for minimum impacts, with risk for something worse. The wind field and size of this storm is expected to be somewhat broader than in Idalia, which also is concerning from a potentially worse impact standpoint.

PTC 9's forward speed is likely to aid in carrying tropical storm and hurricane force winds well inland. The map below shows roughly where, given the current track, tropical storm and hurricane force winds could extend. And that's a huge area. Things get complicated on Florida's east coast, including Jacksonville, as well as up toward Savannah where stronger winds are possible than in other inland areas near there.


A rough outline of where tropical storm and hurricane force winds could occur with Helene/PTC 9 as it comes inland.
The extension of hurricane force winds inland will depend on the intensity of the storm at landfall and its exact forward speed from there. But suffice to say this has the potential to be a destructive inland wind event too, extending from North Florida into much of Georgia and South Carolina and even parts of North Carolina.

In addition to the wind will be heavy rainfall, and that's expected to cover a massive area of the Southeast.


While these aren't the most extreme rain totals we've seen in recent years, the coverage and intensity of this rain is likely to contribute to widespread flash flooding in the Southeast. (NOAA WPC)
We've seen worse rain events, but spatially, this is going to put a lot of places at risk of flash flooding.

Obviously, isolated tornadoes are a possibility along and to the right/east of where this storm goes.

The takeaway: Significant impacts from PTC 9/Helene are expected to extend well inland from the coast.

We will update this post today as we can if anything changes. We'll aim to have another post out early this evening with the latest.

[tireman4]

062
WTNT34 KNHC 241458
TCPAT4

BULLETIN
Tropical Storm Helene Advisory Number 5
NWS National Hurricane Center Miami FL AL092024
1100 AM EDT Tue Sep 24 2024

...TROPICAL STORM HELENE FORMS OVER THE NORTHWESTERN CARIBBEAN
SEA...
...HURRICANE AND STORM SURGE WATCHES REMAIN IN EFFECT FOR PORTIONS
OF THE FLORIDA GULF COAST...


SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.5N 84.3W
ABOUT 180 MI...295 KM ESE OF COZUMEL MEXICO
ABOUT 170 MI...275 KM SSE OF THE WESTERN TIP OF CUBA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

A Tropical Storm Warning has been issued for the Lower Florida Keys
west of the Seven Mile Bridge and for the Dry Tortugas.

A Tropical Storm Watch has been issued for the Middle Florida Keys
from the Seven Mile Bridge to the Channel 5 Bridge.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Watch is in effect for...
* Indian Pass southward to Flamingo
* Tampa Bay
* Charlotte Harbor

A Hurricane Watch is in effect for...
* Cabo Catoche to Tulum, Mexico
* Cuban province of Pinar del Rio
* Englewood to Indian Pass
* Tampa Bay

A Tropical Storm Warning is in effect for...
* Dry Tortugas
* Lower Florida Keys west of the Seven Mile Bridge
* Grand Cayman
* Rio Lagartos to Tulum, Mexico
* Cuban provinces of Artemisa, Pinar del Rio, and the Isle of Youth

A Tropical Storm Watch is in effect for...
* Middle Florida Keys from the Seven Mile Bridge to the Channel 5
Bridge
* Flamingo to south of Englewood
* West of Indian Pass to Walton Bay County line

A Storm Surge Watch means there is a possibility of life-
threatening inundation, from rising water moving inland from the
coastline, in the indicated locations during the next 48 hours.
For a depiction of areas at risk, please see the National Weather
Service Storm Surge Watch/Warning Graphic, available at
hurricanes.gov.

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within the next 36 hours.

A Hurricane Watch means that hurricane conditions are possible
within the watch area. A watch is typically issued 48 hours
before the anticipated first occurrence of tropical-storm-force
winds, conditions that make outside preparations difficult or
dangerous.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

Wind and storm surge warnings will likely be required for the
U.S. later today.

For storm information specific to your area in the United
States, including possible inland watches and warnings, please
monitor products issued by your local National Weather Service
forecast office. For storm information specific to your area
outside of the United States, please monitor products issued by
your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM EDT (1500 UTC), the center of Tropical Storm Helene was
located near latitude 19.5 North, longitude 84.3 West. Helene is
moving toward the northwest near 12 mph (19 km/h), and this
general motion is expected to continue through early Wednesday. A
northward to north-northeastward motion at a faster forward speed
is expected on Wednesday and Thursday. On the forecast track, the
center of Helene will move across the far northwestern Caribbean
Sea through tonight, and then move across the eastern Gulf of
Mexico Wednesday and Thursday, potentially reaching the Gulf coast
of Florida late Thursday.

Data from an Air Force Reserve Hurricane Hunter aircraft indicate
that the system has acquired a well-defined center of circulation,
and maximum sustained winds have increased to near 45 mph (75 km/h)
with higher gusts. Additional strengthening is forecast, and
Helene is expected to become a hurricane on Wednesday. Continued
strengthening is anticipated after that time, and Helene could
become a major hurricane on Thursday.

Tropical-storm-force winds extend outward up to 140 miles (220 km)
to the east of the center.

Data from the Hurricane Hunter aircraft indicate that the minimum
central pressure is 1000 mb (29.53 inches).


HAZARDS AFFECTING LAND
----------------------
Key Messages for Helene can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC
and on the web at hurricanes.gov/text/MIATCDAT4.shtml

RAINFALL: Helene is expected to produce total rain accumulations of
4 to 8 inches over western Cuba and the Cayman Islands with isolated
totals around 12 inches. Over the eastern Yucatan Peninsula, 4 to 6
inches of rain are expected with isolated totals over 8 inches. This
rainfall brings a risk of considerable flooding.

Over the Southeastern U.S., Helene is expected to produce total rain
accumulations of 4 to 8 inches with isolated totals around 12
inches. This rainfall will likely result in areas of considerable
flash and urban flooding, with minor to moderate river flooding
likely, and isolated major river flooding possible.

For a complete depiction of forecast rainfall associated with
Helene, please see the National Weather Service Storm Total Rainfall
Graphic, available at hurricanes.gov/graphics_at4.shtml?rainqpf and
the Flash Flood Risk graphic at
hurricanes.gov/graphics_at4.shtml?ero.

STORM SURGE: The combination of a dangerous storm surge and the
tide will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline. The water could
reach the following heights above ground somewhere in the indicated
areas if the peak surge occurs at the time of high tide...

Ochlockonee River, FL to Chassahowitzka, FL...10-15 ft
Chassahowitzka, FL to Anclote River, FL...6-10 ft
Indian Pass, FL to Ochlockonee River, FL...5-10 ft
Anclote River, FL to Middle of Longboat Key, FL...5-8 ft
Tampa Bay...5-8 ft
Middle of Longboat Key, FL to Englewood, FL...4-7 ft
Englewood, FL to Bonita Beach, FL...3-5 ft
Charlotte Harbor...3-5 ft

For a complete depiction of areas at risk of storm surge inundation,
please see the National Weather Service Peak Storm Surge Graphic,
available at hurricanes.gov/graphics_at4.shtml?peakSurge.

Storm surge could raise water levels by as much as 2 to 4 feet above
normal tide levels in areas of onshore winds along the southern
coast of Pinar del Rio, Cuba, including the Isle of Youth.

Storm surge could raise water levels by as much as 2 to 4 feet above
ground level in areas of onshore winds within the warning area along
the east coast of the Yucatan Peninsula.

WIND: Hurricane conditions are possible within the watch areas in
Cuba and Mexico by early Wednesday. Hurricane conditions are
possible within the U.S. watch areas Wednesday night and early
Thursday. Tropical storm conditions are expected in the warning
areas in the Cayman Islands, Cuba, and Mexico today. Tropical
storm conditions are expected in the warning area in the Lower
Florida Keys beginning on Wednesday, and are possible in the watch
area in the Middle Florida Keys beginning late Wednesday.

SURF: Swells generated by Helene will affect the southern coast
of Cuba and the Yucatan Peninsula of Mexico during the next couple
of days. Swells will spread northward toward the west coast of
Florida and the northeastern Gulf Coast on Wednesday and Thursday.
These swells are likely to cause life-threatening surf and rip
current conditions. Please consult products from your local weather
office.


NEXT ADVISORY
-------------
Next intermediate advisory at 200 PM EDT.
Next complete advisory at 500 PM EDT.

$$
Forecaster Berg

[biggerbyte]

Forever changing forecasts. Today things looks a little better than yesterday. There seems to be a little drop in the intensity forecast, and this systems landfall location keeps shifting eastward. Even a Cat. 2 is no picnic, but compared to a 4 or 5..

[Stratton20]

Its still unfortunately likely going to become a major hurricane as the environment in the gulf is primes for explosive intensification , cat 2 is being pretty conservative at this point by the NHCZ

[tireman4]

000
WTNT34 KNHC 241751
TCPAT4

BULLETIN
Tropical Storm Helene Intermediate Advisory Number 5A
NWS National Hurricane Center Miami FL AL092024
200 PM EDT Tue Sep 24 2024

...HELENE ORGANIZING OVER THE NORTHWESTERN CARIBBEAN SEA...
...HURRICANE AND STORM SURGE WATCHES REMAIN IN EFFECT FOR PORTIONS
OF THE FLORIDA GULF COAST...


SUMMARY OF 200 PM EDT...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...19.4N 84.5W
ABOUT 175 MI...280 KM ESE OF COZUMEL MEXICO
ABOUT 175 MI...280 KM S OF THE WESTERN TIP OF CUBA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...999 MB...29.50 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The government of the Cayman Islands has discontinued the Tropical
Storm Warning for Grand Cayman.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Watch is in effect for...
* Indian Pass southward to Flamingo
* Tampa Bay
* Charlotte Harbor

A Hurricane Watch is in effect for...
* Cabo Catoche to Tulum, Mexico
* Cuban province of Pinar del Rio
* Englewood to Indian Pass
* Tampa Bay

A Tropical Storm Warning is in effect for...
* Dry Tortugas
* Lower Florida Keys west of the Seven Mile Bridge
* Rio Lagartos to Tulum, Mexico
* Cuban provinces of Artemisa, Pinar del Rio, and the Isle of Youth

A Tropical Storm Watch is in effect for...
* Middle Florida Keys from the Seven Mile Bridge to the Channel 5
Bridge
* Flamingo to south of Englewood
* West of Indian Pass to Walton Bay County line

A Storm Surge Watch means there is a possibility of life-
threatening inundation, from rising water moving inland from the
coastline, in the indicated locations during the next 48 hours.
For a depiction of areas at risk, please see the National Weather
Service Storm Surge Watch/Warning Graphic, available at
hurricanes.gov.

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within the next 36 hours.

A Hurricane Watch means that hurricane conditions are possible
within the watch area. A watch is typically issued 48 hours
before the anticipated first occurrence of tropical-storm-force
winds, conditions that make outside preparations difficult or
dangerous.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

Wind and storm surge warnings will likely be required for the
U.S. later today.

For storm information specific to your area in the United
States, including possible inland watches and warnings, please
monitor products issued by your local National Weather Service
forecast office. For storm information specific to your area
outside of the United States, please monitor products issued by
your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 200 PM EDT (1800 UTC), the center of Tropical Storm Helene was
located near latitude 19.4 North, longitude 84.5 West. Helene has
been wobbling a bit now that a well-defined has just recently
formed, but the longer-term motion is toward the west-northwest
near 12 mph (19 km/h). A turn toward the northwest is expected
later today. A northward to north-northeastward motion at a faster
forward speed is expected on Wednesday and Thursday. On the
forecast track, the center of Helene will move across the far
northwestern Caribbean Sea to near the northeastern coast of the
Yucatan Peninsula of Mexico through tonight, and then move across
the eastern Gulf of Mexico Wednesday and Thursday, potentially
reaching the Gulf coast of Florida late Thursday.

Maximum sustained winds are near 45 mph (75 km/h) with higher gusts.
Strengthening is forecast, and Helene is expected to become a
hurricane on Wednesday. Continued strengthening is anticipated
after that time, and Helene could become a major hurricane on
Thursday.

Tropical-storm-force winds extend outward up to 140 miles (220 km)
to the east of the center.

Data from NOAA buoy 42056 indicate that the minimum central pressure
is 999 mb (29.50 inches).


HAZARDS AFFECTING LAND
----------------------
Key Messages for Helene can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC
and on the web at hurricanes.gov/text/MIATCDAT4.shtml

RAINFALL: Helene is expected to produce total rain accumulations of
4 to 8 inches over western Cuba and the Cayman Islands with isolated
totals around 12 inches. Over the eastern Yucatan Peninsula, 4 to 6
inches of rain are expected with isolated totals over 8 inches. This
rainfall brings a risk of considerable flooding.

Over the Southeastern U.S., Helene is expected to produce total rain
accumulations of 4 to 8 inches with isolated totals around 12
inches. This rainfall will likely result in areas of considerable
flash and urban flooding, with minor to moderate river flooding
likely, and isolated major river flooding possible.

For a complete depiction of forecast rainfall associated with
Helene, please see the National Weather Service Storm Total Rainfall
Graphic, available at hurricanes.gov/graphics_at4.shtml?rainqpf and
the Flash Flood Risk graphic at
hurricanes.gov/graphics_at4.shtml?ero.

STORM SURGE: The combination of a dangerous storm surge and the
tide will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline. The water could
reach the following heights above ground somewhere in the indicated
areas if the peak surge occurs at the time of high tide...

Ochlockonee River, FL to Chassahowitzka, FL...10-15 ft
Chassahowitzka, FL to Anclote River, FL...6-10 ft
Indian Pass, FL to Ochlockonee River, FL...5-10 ft
Anclote River, FL to Middle of Longboat Key, FL...5-8 ft
Tampa Bay...5-8 ft
Middle of Longboat Key, FL to Englewood, FL...4-7 ft
Englewood, FL to Bonita Beach, FL...3-5 ft
Charlotte Harbor...3-5 ft

For a complete depiction of areas at risk of storm surge inundation,
please see the National Weather Service Peak Storm Surge Graphic,
available at hurricanes.gov/graphics_at4.shtml?peakSurge.

Storm surge could raise water levels by as much as 2 to 4 feet above
normal tide levels in areas of onshore winds along the southern
coast of Pinar del Rio, Cuba, including the Isle of Youth.

Storm surge could raise water levels by as much as 2 to 4 feet above
ground level in areas of onshore winds within the warning area along
the east coast of the Yucatan Peninsula.

WIND: Hurricane conditions are possible within the watch areas in
Cuba and Mexico by early Wednesday. Hurricane conditions are
possible within the U.S. watch areas Wednesday night and early
Thursday. Tropical storm conditions are expected in the warning
areas in the Cuba and Mexico today. Tropical storm conditions are
expected in the warning area in the Lower Florida Keys beginning on
Wednesday, and are possible in the watch area in the Middle Florida
Keys beginning late Wednesday.

SURF: Swells generated by Helene will affect the southern coast
of Cuba and the Yucatan Peninsula of Mexico during the next couple
of days. Swells will spread northward toward the west coast of
Florida and the northeastern Gulf Coast on Wednesday and Thursday.
These swells are likely to cause life-threatening surf and rip
current conditions. Please consult products from your local weather
office.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM EDT.

$$
Forecaster Berg

[Pas_Bon]

Based on recent history, I will - by default - expect any hurricane in the Gulf to rapidly intensify. I will believe otherwise only in the face of direct observation.

[biggerbyte]

Helene is getting a beating from shear for the time being, and she could get in on a little land interaction. Things continue to look better as far as intensity at landfall goes. However, that is subject to change. I'd bet the NHC updated report does not show a major.