TC Bertha

[Normandy]

At this point, it would take heavy (heavier than now) amounts of shear to completely dissipate Bertha. Bertha has a pretty potent circulation, which is why it has made it this far despite less than ideal conditions over the past two days.

[KWT]

Yep the main core of the jet streak is heading eastwards as the TUTT moves out of the way, there will still probably some higher shear that it will have to move through and this may be a sign of it but right now the center is still under the convection which is still deep.

[Andrew92]

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I kinda think I'm seeing where the UKMET and now NCEP global models are getting the idea for Bertha to weaken to a wave, but I still think it doesn't happen. Yes, seeing that satellite image, Bertha is getting sheared.

This is Bertha's test, if you know what I mean. How well can she handle adversity? Kinda like sports teams that are doing well and then all of a sudden one player gets injured - thus defining what the rest of the team is truly made of. Even if the shear only lasts 12-18 hours or so, we're going to find out what indeed Bertha is made of. If she holds her own, she will still likely go on to become a hurricane in about 2-3 days. If she can't show any signs of trying to re-organize, she's done.

Personally, I still think she will hang on and become a hurricane eventually. Yes, she looks sheared, but I've seen storms look worse than this and survive like this before.

-Andrew92

[KWT]

Bertha should hang on quite fine, lets consider that this TS stayed at 45kts over 24-25C SST's and probably 15kts of SW shear between Friday-Saturday, whilst there is some more severe shear nearby right now its not over this region. SHIPS currently show 9kts of shear, it probably will increase but we will see, I'd guess its probably a touch higher now then 9kts.

[Recurve]

Anybody have any insight on why the GFS ensembles are so far south?

[KWT]

Personally I suspect Recurve that they don't have as high resolution as the op runs and thus are not digging the trough down as far. As it happens I wouldn't discount the truth being closer to the ensembles given the op runs do seem prone to overdoing those upper troughs, esp the GFS runs.

[cheezyWXguy]

Anybody have any insight on why the GFS ensembles are so far south?

They likely show Bertha missing the trough coming down...even the operational GFS(I think the latest) showed Bertha stalling out of the SE coast, bringing it very close to the carolinas.

[vacanechaser]

Anybody have any insight on why the GFS ensembles are so far south?

They likely show Bertha missing the trough coming down...even the operational GFS(I think the latest) showed Bertha stalling out of the SE coast, bringing it very close to the carolinas.

true, but what i have herd from mets in the pst, they believe the ensambles a lot over the operational gfs due to it taking into consideration all veriables and scenarios and them comes up with a solution to those questions as it were... the ensambles seem to do better... jmo...


Jesse V. Bass III
http://www.vastormphoto.com
Hurricane Intercept Research Team

[Innotech]

I think this will end up far more southerly and westerly than the models are suggesting. This storm is being sheared and remains weaker, so I dont really see a large recurve until it is potentially impacting the CONUS in some way or very close to it. Its embedded in a fast moving easterly flow and doesnt really seem strong enough to head out to sea on its own. I really think that if it continues to be weak like this, a land hit is very possible. The storm will likely not be very powerful at that point though.

[Recurve]

Thanks. I should have seen that.
There's an interesting situation here now with a weak ULL, weak wave and a lot of moisture around Sfla. We finally got some good soakings.

Another question -- if a storm misses a trof or weakness, will it gain any latitude from poleward tendency alone or does the Bermida high block that?

[Andrew92]

I think Derek did mention the NCEP global is showing Bertha becoming an open wave too, and I'm wondering if the GFS is following suit now. I'm not sure I agree with that, but Bertha does look sheared and it is an option, especially if she has a tougher time with the shear than previously thought.

-Andrew92

[gatorcane]

It looks like Bertha may a little wobble WNW but is now back to a nearly due west heading. She maybe starting to "stair-step" though. We shall see.

[KWT]

Yeah its hard to say about the track because there is some light shear from the SW, a microwave loop would probably show what is really happening.

I'd just be careful assuming this will stay weak, there is a much better set-up off to the west around 36-48hrs where its likely to pick up some good strengthening.

[MiamiensisWx]

It is interesting to note that Bertha has only gained ~1-2 degrees of latitude over the past few days since it briefly turned WNW near the Cape Verde islands. Most of the movement over the past ~24 hours has been nearly due west with essentially no gains in latitude as well. In regards to the current upper level shear, it is induced by the TUTT which is "lifting out" to the NE as Bertha moves west and experiences the influence of it. As Bertha continues to move west, passes the TUTT, and coincides with the rebuilding upper level ridge and exiting TUTT, it will likely enter reduced upper level shear and a conducive upper level regime. At that point, the divergence from the departing TUTT may actually aid further gradual intensification of the TC. I believe Andrew 1992 is an example when it passed the upper low, which weakened and developed to a broad TUTT as it departed to the NE. I'm not expecting an outcome remotely similar to Andrew, but I'm highlighting the fact that tropical cyclones often intensify as they pass a departing TUTT/upper low. Bertha's intensification also depends on the possible evolution of a second TUTT at the upper levels over the next few days.

http://www.nhc.noaa.gov/1992andrew.html

Significant changes in the large-scale environment near and downstream from Andrew began by 21 August. Satellite imagery in the water vapor channel indicated that the low aloft to the east-southeast of Bermuda weakened and split. The bulk of the low opened into a trough which retreated northward. That evolution decreased the vertical wind shear over Andrew. The remainder of the low dropped southward to a position just southwest of Andrew where its circulation enhanced the upper-level outflow over the tropical storm. At the same time, a strong and deep high pressure cell formed near the U.S. southeast coast. A ridge built eastward from the high into the southwestern Atlantic with its axis lying just north of Andrew. The associated steering flow over the tropical storm became easterly. Andrew turned toward the west, accelerated to near 16 kt, and quickly intensified.

http://www.ssd.noaa.gov/goes/east/tatl/loop-vis.html

[Derek Ortt]

GFS is the NCEP global model

[gatorcane]

It is interesting to note that Bertha has only gained ~1-2 degrees of latitude over the past few days since it briefly turned WNW near the Cape Verde islands. Most of the movement over the past ~24 hours has been nearly due west with essentially no gains in latitude as well. In regards to the current upper level shear, it is induced by the TUTT which is "lifting out" to the NE as Bertha moves west and experiences the influence of it. As Bertha continues to move west, passes the TUTT, and coincides with the rebuilding upper level ridge and exiting TUTT, it will likely enter reduced upper level shear and a conducive upper level regime. At that point, the divergence from the departing TUTT may actually aid further gradual intensification of the TC. I believe Andrew 1992 is an example when it passed the upper low, which weakened and developed to a broad TUTT as it departed to the NE. I'm not expecting an outcome remotely similar to Andrew, but I'm highlighting the fact that tropical cyclones often intensify as they pass a departing TUTT/upper low. Bertha's intensification also depends on the possible evolution of a second TUTT at the upper levels over the next few days.

http://www.nhc.noaa.gov/1992andrew.html

Significant changes in the large-scale environment near and downstream from Andrew began by 21 August. Satellite imagery in the water vapor channel indicated that the low aloft to the east-southeast of Bermuda weakened and split. The bulk of the low opened into a trough which retreated northward. That evolution decreased the vertical wind shear over Andrew. The remainder of the low dropped southward to a position just southwest of Andrew where its circulation enhanced the upper-level outflow over the tropical storm. At the same time, a strong and deep high pressure cell formed near the U.S. southeast coast. A ridge built eastward from the high into the southwestern Atlantic with its axis lying just north of Andrew. The associated steering flow over the tropical storm became easterly. Andrew turned toward the west, accelerated to near 16 kt, and quickly intensified.

http://www.ssd.noaa.gov/goes/east/tatl/loop-vis.html

Andrew track from

[Nimbus]

The last 8 advisories or so have kept Bertha at 45 knots but she is moving into a better environment obviously.

Andrew was a good example of just how hard forecasting can be even within a 36 hour window. It is very rare to have such an unforecastable upper air environment as they did with Andrew.

[MiamiensisWx]

Andrew track from

This is not going to be an Andrew redux in terms of track and intensity. I was merely utilizing Andrew as one example of an intensifying TC after it bypasses a TUTT/upper low and experiences favorable upper level divergence and gradually decreasing shear.

[Innotech]

she sure does look impressive on visible. The chances of her becoming another andrew though are probably impossibly small though. hitting the Carolinas is another story.

[KWT]

Yeah a more comparable system may be Bertha 96 rather then Andrew, not really the same kettle of fish in terms of both eventual track as well as strength. IF it does make it far enough west I do wonder what may happen over the gulf waters but thats still another 6-7 days away yet.

I agree once it gets to the west of the TUTT axis then things may become a little more favorable slowly, though I think there will probably be some shear on this for a little while yet.