Hurricane Irma no-hype 10am Update: Forecast, modeling and comics included

Author: || Published: 9/9/2017 at 10:51am

Hurricane Irma continues to straddle Cuba. Maximum sustained winds are near 125 mph with higher gusts, making Irma a Category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. The storm is forecast to restrengthen once it moves away from Cuba, and expected to remain a powerful hurricane as it approaches Florida.

9/9/17 10am Advisory from the National Hurricane Center

Here is a look at Hurricane Irma this morning from space…

Another view of Irma…

As a quick note, I know a lot of folks are on Facebook, and that’s awesome. but for following the weather in situations like this Twitter is – by far – a better social media platform to use. It is constantly updated with the newest information. And, unlike facebook, doesn’t put stuff from three days ago at the top of your newsfeed. If you download the twitter app or sign up online and ONLY use it during severe weather, I guarantee it would be worth it.

Irma continues moving near Cuba and toward the United States. But before you get too concerned, here is an objective look – in plain English – at the storm and what you need to know about it. Between the images from the Leeward Islands, the stories from Harvey, and everyone’s memories of Katrina, the last thing we need is hyperbole. So here is a #nofilter look at everything Irma. Still borrowing a line from former United States Secretary of Defense Donald Rumsfeld, we are going to look at the known knowns. The known unknowns. And the unknown unknowns.

Known knowns

Irma is weaker. But it is still a Major Hurricane.

Hurricane Irma is now a Category 3 storm with winds near 125mph. It is moving west at 9mph. New Hurricane Watches and Tropical Storm Watches are up for points a bit further west than late last night. This is for areas in the Florida panhandle.

A Tropical Storm Watch is in effect for…
* North of Edisto Beach to South Santee River
* West of Indian Pass to the Okaloosa/Walton County Line

A Hurricane Watch is in effect for…
* North of Fernandina Beach to Edisto Beach
* West of the Aucilla River to Indian Pass

Latest stats:

ESTIMATED MINIMUM CENTRAL PRESSURE 941 MB
EYE DIAMETER 10 NM
MAX SUSTAINED WINDS 110 KT WITH GUSTS TO 135 KT.
64 KT……. 60NE 60SE 30SW 60NW.
50 KT…….100NE 90SE 50SW 80NW.
34 KT…….160NE 160SE 120SW 170NW.
12 FT SEAS..420NE 30SE 30SW 120NW.

Irma continues to be weakest on the southwest side. This isn’t good news, though, as the southwest side is the side most likely to stay out to sea as it makes its trek northward up the west coast of the Florida peninsula. Hurricane-force wind extends nearly 60 miles from teh center on the other sides. Tropical Storm-force wind extends nearly 100 miles from the center on the northeast side.

From the National Hurricane Center:

KEY MESSAGES:

1. Irma will continue to bring life-threatening wind, storm surge, and rainfall hazards to portions of the Bahamas and the north coast of Cuba, especially over the adjacent Cuban Keys, through tonight.

2. Irma is expected to make landfall in Florida as an extremely dangerous major hurricane, bringing life-threatening wind impacts to much of the state regardless of the exact track of the center. Wind hazards from Irma are also expected to spread northward along the coast of Georgia and South Carolina where a Hurricane Watch has been issued.

3. There is an imminent danger of life-threatening storm surge flooding in portions of central and southern Florida, including the Florida Keys, where a Storm Surge Warning is in effect. The threat of catastrophic storm surge flooding is highest along the southwest coast of Florida, where 10 to 15 feet of inundation above ground level is expected. This is a life-threatening situation and everyone in these areas should immediately follow any evacuation instructions from local officials.

4. Irma is expected to produce very heavy rain and inland flooding. Total rain accumulations of 10 to 20 inches, with isolated amounts of between 20 and 25 inches, are expected over the Florida Keys, the Florida peninsula, and southeast Georgia from Saturday through Monday. Significant river flooding is possible in these areas. Early next week Irma will also bring periods of heavy rain to much of the southeast United States where an average of 2 to 6 inches is forecast, with isolated higher amounts, from North and South
Carolina to Tennessee and eastern Alabama. This includes some mountainous areas which are more prone to flash flooding. Residents throughout the southeast states should remain aware of the flood threat and stay tuned to forecasts and warnings.

More from the National Hurricane Center on Twitter:


Take home points from the National Hurricane Center:

HAZARDS AFFECTING LAND
———————-
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 is expected to reach the following HEIGHTS ABOVE GROUND if the peak surge occurs at the time of high tide…

Cape Sable to Captiva…10 to 15 ft
Captiva to Ana Maria Island…6 to 10 ft
Card Sound Bridge through Cape Sable, including the Florida Keys…5 to 10 ft
Ana Maria Island to Clearwater Beach, including Tampa Bay…5 to 8 ft
North Miami Beach to Card Sound Bridge, including Biscayne Bay…4 to 6 ft
Isle of Palms, South Carolina to Fernandina Beach…4 to 6 ft
Clearwater Beach to Ochlockonee River…4 to 6 ft
Fernandina Beach to North Miami Beach…2 to 4 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

The combination of a life-threatening storm surge and large breaking waves will raise water levels ABOVE NORMAL TIDE LEVELS by the following amounts within the hurricane warning area near and to the north of the center of Irma. Near the coast, the surge will be accompanied by large and destructive waves.

Ragged Island in the Bahamas…15 to 20 ft
Central and Northwestern Bahamas…3 to 6 ft
Northern coast of Cuba in the warning area…5 to 10 ft

WIND: Hurricane conditions are expected to continue within the hurricane warning area along the north coast of Cuba through today. Hurricane conditions are expected in portions of the northwestern Bahamas today, and in portions of the Florida peninsula and the Florida Keys tonight and Sunday.

Hurricane and tropical storm conditions are possible within the watch area on Sunday.

RAINFALL: Irma is expected to produce the following rain accumulations through Wednesday:
Northern Cuba…10 to 15 inches, isolated 20 inches.
Southern Cuba…5 to 10 inches, isolated 15 inches.
Western Bahamas…3 to 6 inches, isolated 10 inches.
The Florida Keys…10 to 20 inches, isolated 25 inches.
The Florida peninsula and southeast Georgia…8 to 15 inches, isolated 20 inches.
The eastern Florida Panhandle…3 to 6 inches, isolated 8 inches.
Rest of eastern Georgia, western South Carolina, and western North Carolina…4 to 8 inches.
Western Georgia, eastern and northern Alabama, and southern Tennessee…2 to 5 inches.
In all areas this rainfall may cause life-threatening flash floods and, in some areas, mudslides.

TORNADOES: A few tornadoes are possible today and tonight over southern Florida.

SURF: Swells generated by Irma are affecting the southeastern Bahamas, the Turks and Caicos Islands and the southeast coast of the United States today. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

As Irma moves north, here are some estimates for wind speeds and the overall area that will deal with wind from Irma

From the NWS:

The sea surface temperatures are warm in the area near Cuba, the Bahamas and Florida. Currently temperatures across the Atlantic are sitting in the Top 3 warmest during last 20 years trailing only 1998 and 2005. The atmospheric environment ahead of the storm – during the next 24 to 48 hours – is sufficient for sustaining or the continued strengthening of Irma.

Known unknowns

It is pretty much the same list as eight hours ago. And the big question is the same, too: When – exactly – it will turn north. And I know, this is something that we’ve been saying will happen “during the next six to 12 hours,” every time this is updated. The delay in a northward turn is still due to a handful of factors. We are still watching the same group of atmospheric parameters as before to figure out the eventual path:

Atmospheric Interaction around Irma on Sunday

1. Placement of ridge of High Pressure in the Atlantic
– We have a pretty good handle on the center of it, but the little elbow of it that extends across Florida continues to be just strong enough. It is difficult to pinpoint exactly where it is and where the weakness in it is, too.

2. Strength of ridge of High Pressure in the Atlantic
– So far, as noted by the National Hurricane Center, the ridge has been more stubborn than predicted, allowing Irma to make it further West than anticipated.

3. Just how much that shortwave trough / mid-level low in the southeast will matter
– There are a few pieces of atmospheric energy diving to the southeast from the Rockies during the next few days. The exact placement of these is unknown, we have a pretty good idea about where they are headed, but pinpointing it isn’t possible. And the placement will have a big impact on how far west Irma will stay as it moves north. Or if it will drift back to the east as it move north. The stronger it is, the more bending back to the east that Irma will do as it moves north. The weaker it is the more Irma will move a bit west of north.

5. What influence – in the long-term – the interaction with Cuba has on Irma
– Land-Sea-Air interactions in tropical systems are tricky. I’m not even going to act like I understand them. At all. This is almost an unknown unknown to me. But generally Land-Sea-Air interactions slow down a hurricane, weaken it, and cause the forecast track to become a bit more uncertain in the short-term.

And, truly, until Irma turns north, a lot of these known unknowns will remain unknown. That is what is making this forecast so difficult. It is also the reason that spaghetti plots continue to shift west and why the official forecast does, too.

Unknown unknowns

Because it is the atmosphere, there are going to be things that are going to happen that we cannot foresee at this time. That is why it is important to be prepared for all possible outcomes. Live along the East Coast? Or along the Gulf Coast? Check your Hurricane Preparedness Kit. Don’t have one? Buy one! Here is a great link for that. There is no need to do much else yet. Check your plan, make sure your kit is ready to go and wait for the meteorological world to figure out what will happen with Irma.

Being prepared today means when it is time to act, you’ll be ready to go!

Bottom Line

Irma will turn north during the next six to 12 hours. Once it gets through the entire turn, we will have . amuch better idea of who – specifically – will see the worst of this storm. Until then, we can speak generally about the impacts.

Florida: Get ready for – AT LEAST – Category 1 wind, heavy rain, storm surge, flooding, and in some areas, catastrophic damage at some point between now and Monday morning
Georgia: Get ready for a fair amount of rain and some Tropical Storm-force wind as well as the threat for isolated tornadoes starting Monday afternoon
Alabama: On the western size, you’ll have some wind and some rain, by Monday evening but specifics are still unclear
Mississippi: Depending on the final track, some rain with breezy conditions possible by mid-week next week
Tennessee: Rain and some wind, flooding may be possible starting Tuesday and into Wednesday, but specifics are unclear


Author of the article:


Nick Lilja

Nick is former television meteorologist with stints in Amarillo and Hattiesburg. During his time in Hattiesburg, he was also an adjunct professor at the University of Southern Mississippi. He is a graduate of both Oregon State and Syracuse University that now calls Houston home. Now that he is retired from TV, he maintains this blog in his spare time.