Matt-hurricanewatcher wrote:At flight level 154 knots=159.39 at the surface...That is closer to Emily was to cat5. I think she was around 158 mph surface winds.
I wouldn't worry about 2 mph differences. The FL*0.9 = sfc wind reduction is a very crude
estimate. For all we know, the actual surface wind may be 130mph, or it may be 160mph. The 10% reduction (or assuming the surface wind is 90% of the flight-level wind) is very much a
"rule of thumb", and some previous studies have shown that, on average, the surface winds in some hurricanes are only 60-75% of the 700mb flight-level wind (which would be 100-105 kts in this case). The vertical wind profile near the eyewall can very drastically from storm to storm. So again, I would round any surface reduction wind to the nearest 5 kts, and probably nearest x0 (100, 110, 120, etc) kts to account for the large uncertainty in the reduction factor. Granted, the use of the SFMR DOES help in estimating a proper reduction factor!
The eye temperature (at flight-level) is 20C, with an out-of-the-eyewall temperature of 12C (per latest VDM). The 8C temperature gradient across the eyewall is pretty good, though not historically great. In addition, the eye temp of 20C is still a good 10C below the measured 30C in the eye of Rita. Perhaps the size of the eye has an impact, but I would imagine that eye temperature can be used as a rough proxy for the intensity of inner-eye compensating subsidence and as a proxy for storm intensity. The more I think about it, the more I would expect the eye temperature to be a partial function of eye diameter too, but the point remains. Anyone happen to know the eye temperature from a Wilma VDM?
930mb seems pretty high for a Cat 5 hurricane. The 2am EDT may set the intensity at 130-135kts, thereby keeping Dean at Cat 4. I'd really like to see the SLP < 920mb to bring Dean up to a Cat 5. I also expect the windfield to continue to expand, and we may see an ERC in the next 18-24 hours. FWIW, my last view of the IR sat imagery shows that cloud tops aren't particularly cold, which also makes me a little hesitant to go to Cat 5 (when combined with the SLP data). It certainly is NOTHING like Wilma, which had a massive, massive area of extremely cold cloud tops from the eye outward to good ways. At any rate, the NHC will likely want more than one datum point to bring Dean to Cat 5. I think this will get folks in a tizzy, but I do think it'll be Cat 5 later today. I can't imagine how strong it'd be if it weren't for the dry air that has plagued the north and northwest sides of Dean for the past couple of days. Symmetry is important for such a hurricane, and dry air on one side of Dean doesn't help in the symmetry arena.
Jamaica is going to get hit hard. Very hard. If it takes a direct hit, we all better hope that Dean is undergoing an ERC at the time.
