Gabrielle strengthens fast

[numerobis]

The NHC had forecast a peak strength for Hurricane Gabrielle at 90 kt for days, and yesterday's 0900 UTC forecast had it looking to only get to 85 kt. Six hours later, the next forecast came out and suddenly there was a risk of rapid intensification with a slight chance of becoming a major hurricane at the peak, 36 hours from then. At 0900 UTC today, it forecast strengthening to a major hurricane in a bit over 12 hours, peaking at 105 kt in 24 hours. Four hours later, at 9am, NHC announced that Gabrielle was already a major storm at 105 kt and now forecast to peak at 115 kt. So in 26 hours we went from predicting category 2 to category 4. That's not a lot of warning!

Thankfully there's no land anywhere nearby to be affected by this, unlike when Hurricane Maria hit PR, and ships would avoid even category 2.

It seems we've gotten very good at modelling where the storm is going to go, and about when it's going to hit its peak strength. Gabrielle was expected to peak tonight as early as a 5-day forecast possibly could forecast this peak; five days ago it was forecast strengthening until now. Basically the forecast absolutely nailed it on where and when.

But we aren't yet great at forecasting peak intensity. What's the key thing we aren't capturing that would allow better predicting the top speed of the storm, say, three days out rather than mere hours?

 

[infernal666]

The NHC had forecast a peak strength for Hurricane Gabrielle at 90 kt for days, and yesterday's 0900 UTC forecast had it looking to only get to 85 kt. Six hours later, the next forecast came out and suddenly there was a risk of rapid intensification with a slight chance of becoming a major hurricane at the peak, 36 hours from then. At 0900 UTC today, it forecast strengthening to a major hurricane in a bit over 12 hours, peaking at 105 kt in 24 hours. Four hours later, at 9am, NHC announced that Gabrielle was already a major storm at 105 kt and now forecast to peak at 115 kt. So in 26 hours we went from predicting category 2 to category 4. That's not a lot of warning!

Thankfully there's no land anywhere nearby to be affected by this, unlike when Hurricane Maria hit PR, and ships would avoid even category 2.

It seems we've gotten very good at modelling where the storm is going to go, and about when it's going to hit its peak strength. Gabrielle was expected to peak tonight as early as a 5-day forecast possibly could forecast this peak; five days ago it was forecast strengthening until now. Basically the forecast absolutely nailed it on where and when.

But we aren't yet great at forecasting peak intensity. What's the key thing we aren't capturing that would allow better predicting the top speed of the storm, say, three days out rather than mere hours?

Minimum? Probably square kilometer resolution of ocean temps down to the sea floor itself, knowing exactly how much energy it can draw/lose from the water it's passing over would be excellent.

 

[numerobis]

Minimum? Probably square kilometer resolution of ocean temps down to the sea floor itself, knowing exactly how much energy it can draw/lose from the water it's passing over would be excellent.

A better understanding of the amount of energy available near the surface, not just at the surface, I could see. I don't expect that higher resolution would help all that much -- the storm is large enough it's hitting multiple grid squares anyway even at multi-km^2 resolution.