The Friday Before Hurricane Irma’s US Mainland Landfall: 4 Things That Worry Me

It is Friday morning on Sept. 8. I am sitting in a hotel room in Madison, Wisconsin and could barely sleep at all. Hurricane Irma is approaching the state that I spent many precious years in attaining a BS, MS and Ph.D in meteorology. While at Florida State University, I met some of my lifelong friends, and many of them live in the state.

My dad also lives there. Hurricane Irma is setting up as a potential “worst case” scenario for south Florida and even parts of central Florida will feel the force of the storm.

Here are the four things that worry me at this moment.
NOAA NHC Projected path of Irma as of 8 am on September 8th.
Perception: The world has watched Irma’s record-breaking path across the ocean. The storm has already rendered some Caribbean islands virtually uninhabitable .

This morning the Turks – Caicos and Bahamas are bracing. A sample of the broken records blogged by Dr. Phil Klotzbach of Colorado State University includes:
185 mph max winds for 37 hours – the longest any cyclone around the globe has maintained that intensity on record.

The previous record was Haiyan in the NW Pacific at 24 hours…Strongest storm on record to impact the Leeward Islands defined as 15-19°N, 65-60°W for this calculation, with max winds of 185 mph. Okeechobee Hurricane (1928) and David (1979) were previous strongest at 160 mph…185 mph lifetime max winds – the strongest storm to exist outside of the Caribbean and Gulf of Mexico on record.

What worries me about this sustained run at Category 5 is that the storm is fluctuating in intensity and is now a Category 4 hurricane. This presents a dangerous messaging problem .

With this slight tick down to Category 4 (maximum winds of 155 mph and pressure of 925 mb as of 5 a.m. AST), I fear that people will say, “Oh, it is only Category 4 now, we are safe.

” I fear the media will blast headlines like, “Irma downgraded or weakened to a Category 4.” This would be devastating and potentially deadly. It is a Category 4 storm with a track that will bring it directly into south Florida with the most populated cities of the region on the dangerous right side of the eye.
The National Hurricane Center points out in its 5:00 a.

m. briefing,
Irma is an extremely dangerous Category 4 hurricane and will continue to bring life-threatening wind, storm surge and rainfall hazards to the Turks and Caicos Islands and the Bahamas through Saturday.

Heavy rainfall is still possible across portions of Hispaniola through today. Hurricane conditions will also spread over portions of the north coast of Cuba, especially over the adjacent Cuban Keys through Saturday…Severe hurricane conditions are expected over portions of the Florida peninsula and the Florida Keys beginning Saturday night. Irma is likely to make landfall in southern Florida as a dangerous major hurricane, and bring life-threatening storm surge and wind impacts to much of the state. A Hurricane Warning is in effect for southern Florida, the Florida Keys, Lake Okeechobee, and Florida Bay, while Hurricane Watches have been issued northward into central Florida.

NASA PMM Cat-Scan of Irma using NASA GPM and other satellite assets.
As I have written before, many people often use their experience or historical context with past events to predict outcomes in extraordinary circumstances. Fifty inches of rainfall from Harvey and the particular way Irma is approaching Florida are likely outside of what most people in this region have experienced. However, the “been there, done that” or “ride it out” perspective still exists. My friend and colleague Dr.

Fred Bortz summed up Hurricane Irma very well in social media by saying,
It is worrisome to hear people say they got through x when they are facing x-squared.
Another perception challenge revealed to me while speaking with someone yesterday is the notion that the storm surge is the only problem.

I saw this in Houston with Harvey communication too. This person, who lives in south-central Florida, told me, “I think we will be OK where I am and they have evacuated the coastal areas.” This statement illustrates that there may be too much focus on the storm surge threat, which is indeed significant, and not the wind.

Major hurricane winds will impact much of the peninsula and I am not sure some people understand the dangers associated with that prospect.
The Storm Still May Strengthen: Irma has undergone a series of Eyewall Replacement Cycles or ERCs ( see a prior Forbes piece for an explanation of them ). It appears that a recent ERC possibly took the storm intensity down some, and this is common with such processes. However, NOAA points out in GOES-R training document ,
Tropical cyclone (TC) eyewalls contract as they strengthen to the intense TC threshold.

After the existing eyewall has contracted to its minimum size for that threshold intensity, the TC enters a weakening phase.

All other factors being equal, the TC weakens when an outer eyewall forms; some of the moisture and momentum is taken from the existing eyewall, which dissipates. The outer eyewall contracts gradually and th e TC regains its original strength or becomes stronger .
NOAA NHC Hurricanes Irma, Jose, and Katia.
Irma is also moving into an area of increasingly warm waters. This is the “fuel supply” for the giant hurricane heat engine.

The variability in intensity associated with ERCs and the presence of a significant supply of ocean heat content means that I am not surprised at all that the National Hurricane Center maintains Irma as a major hurricane into Florida. I would also not be surprised at all if it strengthened prior to making landfall. Irrespective of whether it is Category 5 or strong Category 4, it is a major hurricane and the “worst-case scenario” narrative applies . It is worth noting that the wind field will be more expansive with Irma too. It is a larger storm, area-wise, than Andrew was.

For comparison, the satellite image above illustrates how Irma compares in size with Jose and Katia.
NASA Earth Observatory Sea surface temperatures available to Irma as it approaches Florida.
People And Property In The Path: Florida has around 20.7 million people, and many of them live in central and south Florida.

A recent article by Florida Trend points out ,
In 1910, the state had a population of 1 million people.

By 1980 it had grown to 10 million.

Since then, the population has doubled…Florida’s population grew 1.84 percent in the past year, trailing only North Dakota, Colorado and Nevada as the fastest-growing states. Florida trailed only California (39.14 million) and Texas (27.5 million) in overall population.

Florida’s population grew by more than 1,000 people per day
Many of those people live in coastal communities and some have never experienced a hurricane and certainly not one as strong as Irma.
Census Viewer Florida population distribution. Via Census Viewer.
Additionally, there is significantly more “stuff” in the potential path of Irma, and many of those things (condos, businesses, mansions and so forth) are very expensive. As such, many experts have long pondered what an “Andrew or worse” storm might do, in terms of damage, since the development boom. Swiss Re is a giant reinsurer that published a report earlier this summer (quite timely) on damage costs from a “contemporary Andrew.” They point out that a 20-mile shift in Andrew’s path (closer to Miami) would have caused $180 billion in damages instead $26.5 billion.

Irma is possibly Andrew on “steroids” and is why I have seen potential damage estimates that could reach $200 billion or more.
Beyond Florida: As a resident of the state of Georgia, I am keeping close tabs on the post-Florida trajectory of Irma as well. It appears that by late Monday or early Tuesday, ” Tropical Storm Irma ” (or perhaps even a weak Hurricane Irma) could be moving over Atlanta. This could bring significant rainfall, windy conditions, falling trees, and power outages to our region as well.

The southern part of Georgia may indeed experience Irma as a hurricane.
NOAA WPC Potential 4-5 day rainfall totals from Irma..