On Thursday afternoon, Eric Blake, a hurricane specialist at the National Hurricane Center and one of the country's foremost experts on these storms, took to Twitter to offer a few capstone thoughts on the storm bearing down on Florida. "Irma has me sick to my stomach," he wrote. "Need to be very lucky for it to miss Florida now."

Blake lives in Miami, like the rest of the NHC forecasters, and said Irma sends "chills" down the spines of residents there. "This hurricane is as serious as any I have seen. No hype, just the hard facts. Take every life-saving precaution you can. I have little doubt Irma will go down as one of the most infamous in Atlantic hurricane history."

This is a sobering message coming from someone like Blake, who above all preaches calm and preparedness during hurricane season. Here, he is saying that a realistic worst-case scenario hurricane is coming to the state of Florida. As we will discuss below, some questions remain about intensity and track, but parts of the state are going to get hit exceptionally hard.

Intensity

One hopeful sign Thursday night and into Friday was a general weakening of Irma, from 175mph to 150mph (as of 8am ET), bringing the storm to just below Category 5 hurricane status. For the last few days, the storm has remained abnormally strong—typically a hurricane will pulse up in intensity and then fall back down quickly when it reaches Category 5 wind speeds. The critical question now is whether the storm remains this way, weakens further, or pulses back up.

Blake and his colleagues at the National Hurricane Center predict Irma will remain at about this intensity until reaching Florida and come ashore as a 150mph hurricane. But they offer some caveats: If Irma's center dips down over Cuba, that island's mountainous terrain could weaken it some; and secondly, the storm could weaken a bit further as its inner eyewall reforms and then strengthen again before making landfall.

A number of my forecaster colleagues believe the latter is likely, and some of the global models show a "deepening" of the storm as it moves toward the Florida Straits. As noted Thursday on Ars, waters are exceptionally warm between Cuba and The Bahamas. Provided Irma remains offshore of Cuba and it completes its eyewall-replacement cycle, this may very well lead to re-strengthening into a Category 5 hurricane before landfall on Saturday or Sunday.

To be perfectly honest, the physical processes of hurricane intensification are not entirely understood, and therefore they are imperfectly modeled by computer systems. So while it's good that Irma is weakening now, that only goes so far. A Category 4 hurricane is still highly destructive, and Irma may well strengthen significantly during the next 24 to 48 hours.

Track

On Thursday, we also discussed narrowing chances for Irma's track to change, but that doesn't mean there is no chance for it change. Indeed, there was a slight westward shift in the National Hurricane Center's official track during the overnight hours.

This track is essentially a worst-case scenario forecast for southern Florida because it batters the state with extremely dangerous winds, about 10 to 20 inches of rainfall, and a potentially catastrophic storm surge inland across southern Florida from Naples to the Florida Keys and up the coast through Miami.

This track is not set in stone, however. Some of the most important forecast models, including the GFS model and the European model, have shifted a bit westward overnight. They both show a powerful storm moving over the Florida Keys, and into Everglades National Park, before traveling up the spine of the state.

There are some subtle differences in these models, but they are sending a pretty clear signal that Irma is unlikely to miss Florida by turning northward and remaining east of the peninsula. Rather, there appears to be an increasing rainfall and wind threat to Fort Myers, Naples, and southwestern parts of the state.

What remains crystal clear is that an extremely dangerous hurricane is coming to southern Florida this weekend, with rainfall and wind threats extending northward through most of the state and likely into Georgia and the Carolinas. While we cannot precisely say which areas will get hit hard, parts of Florida will certainly see extreme damage.