On 19 Aug, 16:30, sutartsorric wrote:

I'd say it's because there's a very large, resolvable, forecastable
high pressure around which Bill is moving. Given the relative size of
the hurricane and the guiding high pressure, it's almost like Bill is
a passive tracer in the grand scheme of things.

Richard

I would say it is because of the improved model resolution. Grid
points 150km apart could hardly resolve a hurricane properly however
large the anticyclone.

I personally you don't need to resolve the hurricane to be able to
forecast its track. The changes in the global models (from, say 200km
to about 50km) in the last 10 years are well below the scale of the
anticyclone.

Richard

On Aug 19, 6:40*pm, Richard Dixon wrote:
On 19 Aug, 16:30, sutartsorric wrote:

I'd say it's because there's a very large, resolvable, forecastable
high pressure around which Bill is moving. Given the relative size of
the hurricane and the guiding high pressure, it's almost like Bill is
a passive tracer in the grand scheme of things.

Richard

I would say it is because of the improved model resolution. Grid
points 150km apart could hardly resolve a hurricane properly however
large the anticyclone.

I personally you don't need to resolve the hurricane to be able to
forecast its track. The changes in the global models (from, say 200km
to about 50km) in the last 10 years are well below the scale of the
anticyclone.

Richard

Well I think you do have to resolve it,

So shall we agree to differ?

The way I see it, if you cant resolve a hurricane in a 150km x 150km
grid square, how can you move it around the globe?

Stuart

On 19 Aug, 19:03, sutartsorric wrote:

So shall we agree to differ?

Indeed.

The way I see it, if you cant resolve a hurricane in a 150km x 150km
grid square, how can you move it around the globe?

They're not resolved in full detail but the pressure min / vorticity
max are there enough to be trackable at low resolution - however if
anyone's using global model output to try and work out the intensity,
they're on a hiding to nothing !!

I recall seeing a talk a few years ago about ways of diagnosing
tropical systems in coarse climate model output.

Richard

"Richard Dixon" wrote in message
...
On 19 Aug, 19:03, sutartsorric wrote:

The way I see it, if you cant resolve a hurricane in a 150km x 150km
grid square, how can you move it around the globe?

They're not resolved in full detail but the pressure min / vorticity
max are there enough to be trackable at low resolution

however if
anyone's using global model output to try and work out the intensity,
they're on a hiding to nothing !!

Hence the process of bogusing the existing storm data into the global models
http://ams.allenpress.com/perlserv/?...a1cfe593954c6c

Jon