Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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Posts: 2565
Loc: Melbourne, FL
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Something is out of kilter with regard to the current intensity forecast (and therefore its influence on the track forecast) of Tropical Storm Bertha. The current projection places Bertha near 22.5N 60.5W at 09/12Z with sustained winds at that time of 70 knots. Upper level wind shear is projected to be 20-25 knots at that time for that location. While it is true that SSTs will be increasing to at least 27C in that area, the upgrade in sustained wind is difficult to envision in light of the wind shear. Two normally reliable models, the UKMET and the (at least rather reliable with stronger systems), decrease the intensity of Bertha and ultimately lose the system - the UKMET in three days and the in four) - and they have been indicating this decline for a couple of days.
The upcoming shear zone is rather narrow, so any disruption of Bertha could be short-lived - if it survives it. Both the track and the intensity beyond the next couple of days are very much uncertain at this time. Its way too early to postulate on mainland impacts since a week from now Bertha may not even exist. By late Monday (or even Tuesday) the longer range evolution of Bertha should become a little easier to forecast with a better degree of reliability.
ED
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cieldumort
Moderator
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Posts: 2825
Loc: Austin, Tx
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At this time, I suspect that the coordinates and intensity being used may be wrong.
Based on the most recent visible loops and a healthy 1620 UTC TRMM pass, my money is on Bertha being located a little north and left of where the has her.. ATTM closer to 18N, and more or less now nuzzled closer to or just within the deeper convection to the LLC's west, and a long, arcing band that wraps around from the south to east to north and back around from the west.
Given this position, I suspect that Bertha has already started to intensify, has a Current Intensity much closer to 3.5, and is now in a better state to respond to any weaknesses in the ridge. How long this lasts, I think, will largely be based on how much shear Bertha encounters up ahead, as the significantly warming SSTs in her path should be countering the negative impact of the increasing wind shear, but maybe only by a little bit.
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