Senior meteorologist at The Weather Channel. Proud to be a weather-obsessed weather geek. Would be a DJ if not a meteorologist.
By: Stu Ostro , 1:28 AM GMT on September 10, 2012
Jeff Masters, Bryan Norcross and I were among the meteorologists asked by TWC to participate in a Q&A (a blog roundtable of sorts) about forecasting and communication challenges with Hurricane Isaac.
The article is at this link.
In it my answers were interspersed amidst the others, and not all of my quotes were used. They are together and in full here:
1. What aspects of Isaac and its environment proved most challenging to the forecast models?
The subtle difference between just enough of a weakness in a ridge of high pressure to its north to allow it to move north into Florida, or that ridge being just strong enough to force Isaac farther west to the central Gulf Coast, as is what happened.
2. Why didn’t Isaac intensify as much as it could have?
It seemed to be fighting relatively dry, stable air throughout its whole life. There was a bit of wind shear at times, though generally Isaac had enough upper-level outflow (the storm’s “exhaust”) that is conducive to strengthening. Also, it can be easier for tiny tropical systems to be able to spin up in a shorter period of time than massive ones like Isaac, but such large size does not preclude rapid intensification of the core if conditions are right.
3. What turned out most surprising to you about the direction and development of Isaac?
There wasn’t much that was very surprising. Although the track had some wiggles, it was generally pretty straightforward from the Leewards to Haiti & Cuba and the Gulf of Mexico. As noted above, the meteorological difference between its ultimate destination being the central Gulf Coast vs. Florida was subtle but clear in why that was the case, and did not represent a huge geographical difference in those model track forecasts at the time frames involved. And Isaac’s pace of formation and strengthening was understandable given its size and the things in the atmosphere it was fighting.
4. What does Isaac teach us about the state of the science in predicting both path and intensity of tropical cyclones right now?
We already knew what the advancements and challenges are, and Isaac didn’t change that. Debby, earlier this season, was a much more interesting case forecast-wise, when two of our main models predicted it to go in completely opposite directions, and what is generally thought of as being the more reliable and accurate model had the storm going west to Texas, which was an epic FAIL.
One thing Isaac did was to reinforce that advancements have been made in models’ predictive ability in the long range – that they can sometimes be able to correctly identify two or more weeks in advance that a potent tropical cyclone is likely to develop – while also highlighting the limitations in track forecast accuracy and precision that can exist more than a couple days in advance, and expectations in that regard need to be realistic.
5. Is there a need for a scale that takes into account more of a storm’s variables than the Saffir-Smpson Hurricane Wind Scale?
Yes. We have the Saffir-Simpson scale for wind intensity. We have the “cone of uncertainty” for the track. There needs to be a way to better address the *size* of the storm. Size matters for geographical extent, duration, and in some cases magnitude of impacts. Compared to if Isaac had been a tiny hurricane of the same intensity, its power outages were far more widespread, and its storm surge affected more locations along the coast and in some places was much higher.
What is known as “IKE” – Integrated Kinetic Energy – is a measure that incorporates both intensity and size, and from which is computed a “destructive potential rating” on a scale of 0 to 6 for wind and surge, but it has its own share of technical limitations and communication complexities. The trick is to find a way to best make, for example, the message of "Isaac is immense and it shouldn’t be thought of as 'only' a Category 1" really resonate and stick.
6. Where is the breakdown between forecasters and the message they attempt to pass along regarding the impending threat of a hurricane and the public's uneven response to those warnings?
If there was one, it was the answer to #5 above.
Image credit: NASA Earth Observatory
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