Comment on the 11 PM Gustav forecast discussion

August 30, 2008

11 PM advisory

5 day forecast

11 PM discussion

Nothing terribly surprising out of the latest advisory package.  The estimated wind speed is down to 140 mph due to a degraded appearance on satellite and radar while the forecast track is nudged to the east ever so slightly. As I mentioned in my last post, the next Hurricane Hunter will be in the storm for the 2 AM intermediate advisory.

The discussion mentions the shear analysis, which, if you back it up a couple of times to -6 hr, shows that Gustav didn’t have the most favorable of atmospheric conditions when he strengthened, there was 20 knots or so of shear.  It goes on to comment that the SHIPS output suggests that the shear will go down over the next 12 hours before going up again.  (It doesn’t offer a reason as to why that should be the case, however.  One wonders if the GFS, which is the underlying rationale for SHIPS, has a grasp on the feature that is generating the shear. If it doesn’t have a good grasp of the feature, then SHIPS is going to expect less shear then there actually is).  After noting the hot and cold spots that Gustav is forecast to traverse, the discussion states that the forecast peak is 135 knots (155 mph, just under category five strength), with weakening thereafter due to reduced heat content.  The discussion ended on what to me is an absolute laugher:

DUE TO THE VARIOUS FACTORS...THIS IS A LOW CONFIDENCE INTENSITY FORECAST.

When is there ever a high confidence intensity forecast?  It is always the weak link of the overall forecast!  How many forecast discussions have we seen where the discusison of the recent change in intensity amounts to “Yeah, we didn’t see this coming” or “We Don’t quite understand why this is happening”?  That the forecaster felt compelled to express low confidence makes me wonder if there’s some point of doubt that he didn’t clearly express.

Night owl special tonight as I’ll have a post to cover what the Hurricane Hunter finds as well as anything worth mentioning from the 00Z model runs.

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