Hurricane Irma's Destructive Path

Ed Temperley

by on

Updated 43d ago

Hurricane Irma is an extremely dangerous Category 5 hurricane. You can keep an eye on the live track of the storm here.

UPDATE: Tuesday, September 12
The toll Hurricane Irma has had on its destructive path is being measured up. The storm has been significantly downgraded with sustained winds of 50 mph, as it pushes further north.

UPDATE: Monday, September 11
Irma has now been downgraded to a Tropical Storm but is still lashing Georgia and Florida. Winds are up to 70mph and the storm is set to weaken as it continues on its path.

UPDATE: Monday, September 11
Hurricane Irma has been downgraded from a Category 3 to a Category 1 hurricane as it makes its way up the west coast of Florida. It is currently around the Tampa area. More then 4 million people have been left without power and three people have been killed as a result of the storm. The impact of Irma is currently being assessed.

UPDATE: Sunday, September 10
Hurricane Irma is now a Category 4 hurricane has reached the Florida Keys. Evacuation orders have been issued for 6 million people and more than 400,000 people have been left without power.

UPDATE: Friday, September 8
Current intensity: 135 KT 155 MPH

Aircraft observations indicate that Irma is currently undergoing an eyewall replacement cycle and has been downgraded slightly. However Irma is forecast to remain over favourable warm water and light shear for the next 36 to 48 hours. The intensity guidance shows a slow weakening during this time, but the NHC expect Irma is to remain at least a Category 4 hurricane until landfall in Florida with devastating winds and storm surges for Southern Florida. Keep up to date here.

In terms of landfall in Florida we are forecasting currently forecasting 47ft @ 14 secs with winds gusting in excess to 133mph for Miami's South Beach, which draws unfavourable historical comparisons with the 1926 Miami hurricane, commonly called the "Great Miami" hurricane. More on this soon.

To pile on the pain for the Leeward Islands, hot oh the heels of Irma we have another major Hurricane Jose forecast to pass very near the northern Leeward Islands late Friday and into Saturday. Please follow NHC guidelines.

UPDATE: Thurs, September 7
Current intensity: 155 KT / 180 MPH

After carving a destructive swathe through Barbuda and St Martin, Irma now looks set to inflict similar heartbreaking levels of damage to the Bahamas and Turks and Cacos before kinking north and heading up the coast of Florida, Georgia and South Carolina.

This Irma track graphic which shows the expected turn to the north just south of Florida also represents the extensive coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow).

This Irma track graphic which shows the expected turn to the north just south of Florida also represents the extensive coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow).

Irma should remain in warm-water, and a low shear environment for about the next three days, and thus is expected to remain a strong hurricane, most likely Category 5 or 4 right up until landfall in Florida as a probable Cat 4 and hurricane watches are expected to be issued for Southern Florida shortly.

Irma is heading towards an area with high water temperatures, which will help the hurricane to fuel its intensity / limit any drop in intensity due to land interaction.

Irma is heading towards an area with high water temperatures, which will help the hurricane to fuel its intensity / limit any drop in intensity due to land interaction.

Hurricane Irma Approaches Puerto Rico. The GOES-16 satellite captured this geocolor image of Hurricane Irma - a category 5 storm with winds as high as 185 miles per hour on September 6, 2017.

Hurricane Irma Approaches Puerto Rico. The GOES-16 satellite captured this geocolor image of Hurricane Irma - a category 5 storm with winds as high as 185 miles per hour on September 6, 2017.

Showing both wind and swell, we can see the destructive swathe Irma is expected to carve through the Bahamas.

See HERE for more companion charts of Hurricane Irma.

Showing both wind and swell, we can see the destructive swathe Irma is expected to carve through the Bahamas.

See HERE for more companion charts of Hurricane Irma.

KEY MESSAGES FROM NHC:

1. Irma is a potentially catastrophic Category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to the northern coast of Hispaniola today, and the Turks and Caicos and southeastern and central Bahamas tonight and Friday.

2. Hurricane watches are in effect for the northwestern Bahamas and much of Cuba. Irma is likely to bring dangerous wind, storm surge, and rainfall to portions of these areas on Friday and Saturday.

3. The threat of direct hurricane impacts in Florida over the weekend and early next week continues to increase. Hurricane watches will likely be issued for portions of the Florida Keys and the Florida peninsula later this morning.

Current forecast for Miami's South Beach on Sunday, Sep 10, has downgraded slightly - but it is still highly dangerous with a Cat 4 wind driven storm surge combined with 30ft+ seas.

Current forecast for Miami's South Beach on Sunday, Sep 10, has downgraded slightly - but it is still highly dangerous with a Cat 4 wind driven storm surge combined with 30ft+ seas.

UPDATE: Tues, September 5

Drawing a line across the top of the Caribbean, Irma is expected to affect the northeastern Leeward Islands, accompanied by life-threatening wind, storm surge, and rainfall. She is also expected to affect the British and U.S. Virgin Islands, Puerto Rico, the Turks and Caicos, the Bahamas and Cuba.

There is a reasonable chance of seeing severe impacts from Irma in the Florida Peninsula and the Florida Keys later this week with Miami currently forecast to receive a direct hit.

Miami's South Beach forecast for Sunday, September 10.

Miami's South Beach forecast for Sunday, September 10.

See below for the current forecast track from Hurricane Irma.

Why has Hurricane Irma intensified over warmer waters?
The engine of a hurricane is powered by water vapour condensing into liquid and releasing latent heat. We hear this a lot, but what exactly does that mean?

Imagine water vapour bubbling out of the ocean surface which has to be around 26.6 degrees C (80 degrees F) – think of it as a bubbling cauldron expelling rising columns of hot air which are lighter than the surrounding air. Half a mile up, as the air cools, the water vapour condenses back into minuscule liquid water droplets which form vast clouds.

At this point the water vapour releases the latent heat (which the sun imparted into it earlier) back into the atmosphere and we have a storm. If you were an observer floating above this developing system you would suddenly be able to to see vast towering thunderclouds being created, some rising to 10 miles high as the hurricane's engine kicks into gear.

UPDATE: Monday, September 4

Irma has taken a turn for the worse, tracking to the south along a strong mid-level ridge over the central Atlantic. She is expected to hit the Leeward islands as a major hurricane, before bumping along the Northern Caribbean on a destructive path through to Florida and beyond. See below for the full official warnings from this exremely dangerous storm.

Additional intensification appears likely with development to Category 4 expected within the next 24 hours.

KEY MESSAGES FROM NHC:

1. Irma is expected to affect the northeastern Leeward Islands as a dangerous major hurricane, accompanied by life-threatening wind, storm surge, and rainfall impacts, along with rough surf and rip currents. Hurricane warnings have been issued for portions of the Leeward Islands. Preparations should be rushed to completion, as tropical-storm force winds are expected to first arrive in the hurricane warning area by late Tuesday.

2. Irma could directly affect the British and U.S. Virgin Islands and Puerto Rico as a dangerous major hurricane later this week. Hurricane watches have been issued for these areas, and tropical storm-force winds could arrive in these areas by early Wednesday.

3. Irma could directly affect Hispaniola, the Turks and Caicos, the Bahamas, and Cuba as a dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

4. There is an increasing chance of seeing some impacts from Irma in the Florida Peninsula and the Florida Keys later this week and this weekend. In addition, rough surf and dangerous marine conditions will begin to affect the southeastern U.S. coast by later this week.
Otherwise, it is still too early to determine what direct impacts Irma might have on the continental United States. However, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

Irma's predicted location for Thursday, September 7.

Irma's predicted location for Thursday, September 7.

UPDATE: Saturday, September 2

As expected, Irma has downgraded overnight and the forecast is far from certain during the next few days as the system moves over lukewarm SSTs and encounters dry air. In three to five days the water is set to warm and the atmosphere will contain more moisture which should fuel intensification, however Irma will also encounter increased wind shear which will limit development. The National Hurricane Centre have altered their forecast guidance accordingly to between Category 2 and 4 by the middle of the week.

Things are more certain in terms of storm's track with good model agreement (see image above) of a turn to the west-northwest on Tuesday and skimming the Lesser Antilles. Beyond that there is the possibility of Irma making some kind of landfall between the Outer Banks and New York, if it misses the Bahamas and Florida. The official advice is that too early to determine what direct impacts Irma will have on the Bahamas and the continental United States but for everyone to be prepared.

Right now September 10 doesn't look like a good day for Long Beach, but a lot can, and will, change.

Right now September 10 doesn't look like a good day for Long Beach, but a lot can, and will, change.

In terms of surf? Look for locations west of Irma which will get the swell without the consequences. We hear that Kelly Slater is bemoaning his inability to freqent a favoured locale.

UPDATE: Friday, September 1

Irma intensified to a Category 3 system on Thursday and is forecast to hit Category 4 status (sustained winds of 130-156 mph or 209-251 km/h) somewhere east of the Leeward Islands early next week. Following a period of rapid intensification, the system is currently moving through a cooler area of ocean, which will limit further development and promote some weakening. Thereafter, Irma is expected to move into a more favourable thermodynamic environment while remaining in low wind shear conditions, which should allow the hurricane to intensify further.

Hurricanes need water above 26°C to gain strength – think of them as an engine driven by heat, one which is potentially incredibly destructive but also fragile. Too much wind shear, not enough moist air, or too much interaction with land and the storm will weaken. And it is this opposite combination of warm water and low wind shear which could fuel further intensification early next week.

So far so good in terms of what we know, however long range hurricane tracks and intensity are notoriously difficult to predict, and the current scenarios for Irma range from a pass into the Caribbean, through to a king-hit of the Outer Banks or New York. There are two clusters of model agreement in terms of long term direction for this system with the ECMWF and HWRF models calling for southerly track at about 5 days out, whilst the UKMET, GFS, CTC and HMON favouring movement to the north.

We'll keep an eye on this doubled-edged system which could potentially impact the Caribbean, or provide perfect surf to parts of islands like Barbados before skirting north of the Leeward Islands and hitting mainland USA. For surfers a best case scenario for Irma would be to emulate Hurricane Bill as a surf producer – if she peels north and hits a high level westerly flow. Unfortunately this latter scenario, whilst ideal for East Coast surfers and fans of hurricane swells, is currently an edge case.

*Any images or vids you have from Hurricane Irma please upload to the site here or email in to press@magicseaweed.com


Ed Temperley

MSW editor. Instagram @edtemperley