I think there is an expression that goes something like this, "The devil lives in the air between my words and your ears." It s more poetic than that.somewhere out there.

The difference between a storm surge and a tsunami is the source of the energy causing the height of the ocean waters.

A tsunami is caused by land displacement and storm surge is caused by the wind PUSHING water in front of the edge of the wind.

Waves are what is caused by the size of the body of water. A lake has a wave motion far more contained than the Pacific Ocean. Waves are caused by the sloshing around of water in the WATER BASIN. It is more complicated than that because there are waves caused by the rotation of Earth. 

TIDES are gravitational caused by the moon.

So there are many impacts of water caused by Irma. There are the 'normal waves,' the tides and the storm surge AND IF there is land displacement all that can be complicated by a tsunami.

...Newton’s law of universal gravitation states (click here) that the gravitational attraction between two bodies is directly proportional to the product of their masses, and inversely proportional to the square of the distance between the bodies (Sumich, J.L., 1996; Thurman, H.V., 1994). Therefore, the greater the mass of the objects and the closer they are to each other, the greater the gravitational attraction between them (Ross, D.A. 1995)....

When the National Hurricane Center (NHC) looks at the potential storm surge it is with the knowledge of the entire movement of water on Earth. They are not trying to create confusion. The experts at the NHC actually have simplified, even as it looks confusing, the actual storm surge as they know it. They don't say a lot of the numbers involved. They apply the physics and math and settle on the storm surge.

Also, they are looking at EVIDENCE where Irma has already passed over. WHERE AND WHEN IT IS POSSIBLE.

Part of what occurs in the reporting of the experts of these storms is ASSESSMENT. Today, assessment is called, "Continuous Quality Improvement." The knowns of the storm before actual measurements are available (hurricane planes) are calculated and then that calculation is measured against REAL TIME DATA.

The 'ideas' of modern society with internet connections that are supposed to be innovative are actually old paradigms. That is not bragging, that is fact. So the calculations and it's assessment of facts as they become available is long lived and long before digital computers were available.

HURRICANE IRMA FORECAST/ADVISORY NUMBER 39

NWS NATIONAL HURRICANE CENTER MIAMI FL AL112017

2100 UTC FRI SEP 08 2017...

...A STORM SURGE WARNING IS IN EFFECT FOR...

* SEBASTIAN INLET SOUTHWARD AROUND THE FLORIDA PENINSULA TO VENICE

* FLORIDA KEYS

A STORM SURGE WATCH IS IN EFFECT FOR...

.* NORTH OF SEBASTIAN INLET TO THE FLAGLER/VOLUSIA COUNTY LINE

* NORTH OF VENICE TO ANCLOTE RIVER

* TAMPA BAY

There is nothing unclear about that warning. Where it becomes unclear is when society rejects the warning for it's own interpretation. That is not a scientific problem, that is a social problem.

The real question about why people die unnecessarily due to storms has to be assessed and rarely is it because there was not sufficient warning. Not in the year 2017. I suggest an examination of the lies made to the American people, existing corruption, cheating by those that can and ordinary suffering of the people might bring them to conclusions about the agencies of it's government are not to be believed or trusted. In the case of their scientific organizations that is not an issue. All the scientists I know, which are many (inside and outside the government of the USA), there is not one interested in falsehoods.