TC Bertha

[brunota2003]

MHX's discussion:

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY NIGHT/...
-- Changed Discussion --
UPR TROF WILL BE LIFTING ACROSS AREA BY LATE TUE WITH MODELS
INDICATING A WEAK SHFT WV ROTATING IN BEHIND IT. UPR FLOW BECOMES
MORE ZONAL WED-THU WITH ADDITIONAL DISTURBANCES MOVING THROUGH BUT
HARD TO TIME AND NOT ENOUGH CONFIDENCE TO GO WITH POPS ABOVE 40
PERCENT. MOS BLEND FOR TEMPS.
-- End Changed Discussion --


&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
-- Changed Discussion --
MODELS AND HPC GDNC SUPPORT FRONT MOVING IN FRI..STALLING OVER AREA
SAT-SUN...AND DISSIPATING MON. APPREARS THERE WILL BE ENOUGH UPR
TROFFING OFFSHORE TO RECURVE BERTHA. IF FRONT PUSHES WELL S OF AREA
COULD SEE DRY WEEKEND BUT STUCK WITH CLIMO 20-30 POPS FOR NOW.
-- End Changed Discussion --

Definitely will be interesting to watch and see if it holds true!

[wxman57]

very interesting wxman57, how far west it gets in that time period will probably determine how much of a threat this is to Bermuda. FWIW the GFDL doesn't even show that WNW and just has it going more and omre to the NW/NNW over time.

It's possible that being as strong as it is, Bertha makes the NW-N turn up the TUTT rather than taking a jog around the high to its WNW. In that case, then the track would have to be adjusted east like the GFDL. But the way Bertha is slowing down, it may not make it through the first weakness.

[KWT]

Amazing presentation as well Hurakan, a most impressive eyewall as well has to be said cold cloud tops around the center thats for sure, even though they aren't quite as exceptional as some we've seen in the past, this is pretty damn impressive for early July.

[fci]

Yes, it looks like Bertha has reached the TUTT weakness. And with a stronger storm it's taking more of a turn for now. But by tomorrow, that high off the southeast U.S. Coast builds eastward and weakens. This should keep Bertha on a WNW track for another 36-48 hours followed by a turn to the north. Bertha may even track westerly for a bit, maybe 275-280 degrees. Right now I'm measuring about 301 degrees at 10 kts.

And when it takes the temporary jog to the West, my brethern here in FL will start with "the sky is falling" posts!

One of the fun things about S2K, it happens every year and is the one predictable thing about Hurricane Season!!

[arkestra]

Simple question: why some days (hours) ago the models and most of us thought Bertha would have been a cat1 at its peak, and why do we have a cat3?

[Matt-hurricanewatcher]

I say 110 knots from this.

It is sad that we don't have recon.

[cheezyWXguy]

Dont be so sure its absolutely needs to have the reds on IR to keep strengthening, though it likely does in this case. An example of a cat 5 without reds is, well, isabel. Take a look at this:

[KWT]

Yeah I don't think the reds matter as much with higher latitude storms because obviously heat content isn't as high. Saying that with Isabel being Annular that may not be a fair comprasion to use!

[deltadog03]

Here is an updated take on how I think things will go down....Now, just remember, if that ridge over bermuda dosn't break down as much......well.......

[wxman57]

Simple question: why some days (hours) ago the models and most of us thought Bertha would have been a cat1 at its peak, and why do we have a cat3?

I have a good answer for that. You have to understand how the current models predict intensity. Let's take a look at how the SHIPS model predicts/accounts for shear (very simplified explanation). The model looks at quite a large area latitude-wise to compute the shear. Based on the projected shear value (among other things), an intensity forecast is made. This method may break down for a smaller storm like Bertha, as the wind shear in the southern part of the SHIPS calculation box is much less than the average shear it assumes. It's seeing the TUTT trof and higher shear well north of Bertha and assuming that shear is impacting Bertha, but it isn't. There was talk at the last AMS tropical meeting about reducing the size of the box where shear is calculated to improve intensity forecasts, or for the forecasters to at least be aware of this limitation.

[Cryomaniac]

With a major forming this early in an area where tropical storms are rare at best does not bode well for this season. Those waters are awefully fertile.

I've got to agree with that, unfortunately. I think this season could be pretty hyperactive.

it's only the second storm of the season. how can you say it'll be a hyperactive season? There may not be another storm for (let's just pull a number out) for another 8 weeks.

That could be true, but we can't see into the future. I never count anything out until it's over. I'm not saying it will happen like that, but it certainly looks like it could.

I really hope we don't get a season like '05, but I personally would like a season with 21+ fish storms.

[Normandy]

Dont be so sure its absolutely needs to have the reds on IR to keep strengthening, though it likely does in this case. An example of a cat 5 without reds is, well, isabel. Take a look at this:

Not that this has anything to do with Bertha now, but damn look at the size of Isabel. I mean picture that thing over Florida....not good. But yes good example of how deep reds =/= major hurricane.

[brunota2003]

Simple question: why some days (hours) ago the models and most of us thought Bertha would have been a cat1 at its peak, and why do we have a cat3?

I have a good answer for that. You have to understand how the current models predict intensity. Let's take a look at how the SHIPS model predicts/accounts for shear (very simplified explanation). The model looks at quite a large area latitude-wise to compute the shear. Based on the projected shear value (among other things), an intensity forecast is made. This method may break down for a smaller storm like Bertha, as the wind shear in the southern part of the SHIPS calculation box is much less than the average shear it assumes. It's seeing the TUTT trof and higher shear well north of Bertha and assuming that shear is impacting Bertha, but it isn't. There was talk at the last AMS tropical meeting about reducing the size of the box where shear is calculated to improve intensity forecasts, or for the forecasters to at least be aware of this limitation.

Perhaps break the box down into two separate boxes? Have the SHIPS run the shear for the North side of the track and the south side separately, thus showing two different intensity forecasts? Is that possible?

[deltadog03]

NHC said it best today imo....Something like, this should prove how hard it is to forecast RI...

[soonertwister]

Simple question: why some days (hours) ago the models and most of us thought Bertha would have been a cat1 at its peak, and why do we have a cat3?

I have a good answer for that. You have to understand how the current models predict intensity. Let's take a look at how the SHIPS model predicts/accounts for shear (very simplified explanation). The model looks at quite a large area latitude-wise to compute the shear. Based on the projected shear value (among other things), an intensity forecast is made. This method may break down for a smaller storm like Bertha, as the wind shear in the southern part of the SHIPS calculation box is much less than the average shear it assumes. It's seeing the TUTT trof and higher shear well north of Bertha and assuming that shear is impacting Bertha, but it isn't. There was talk at the last AMS tropical meeting about reducing the size of the box where shear is calculated to improve intensity forecasts, or for the forecasters to at least be aware of this limitation.

Thanks, wxman. Sometimes I think there's a bit too much reliance on the tools being used rather than common sense. For a well-defined major huricane to completely lack hurricane winds in the southern half intuitively makes no sense to me.

[storms in NC]

Okay with it being a bigger Hurricane now it seem it will go more to the west like you said Wxman57. if it does that then there is a small chance that it will feel the weakness more to the west? I have heard that they really can go where they want after they get so big?

[x-y-no]

Perhaps break the box down into two separate boxes? Have the SHIPS run the shear for the North side of the track and the south side separately, thus showing two different intensity forecasts? Is that possible?

Funny, I was just thinking the same thing ...

[Normandy]

Simple question: why some days (hours) ago the models and most of us thought Bertha would have been a cat1 at its peak, and why do we have a cat3?

I have a good answer for that. You have to understand how the current models predict intensity. Let's take a look at how the SHIPS model predicts/accounts for shear (very simplified explanation). The model looks at quite a large area latitude-wise to compute the shear. Based on the projected shear value (among other things), an intensity forecast is made. This method may break down for a smaller storm like Bertha, as the wind shear in the southern part of the SHIPS calculation box is much less than the average shear it assumes. It's seeing the TUTT trof and higher shear well north of Bertha and assuming that shear is impacting Bertha, but it isn't. There was talk at the last AMS tropical meeting about reducing the size of the box where shear is calculated to improve intensity forecasts, or for the forecasters to at least be aware of this limitation.

Thanks, wxman. Sometimes I think there's a bit too much reliance on the tools being used rather than common sense. For a well-defined major huricane to completely lack hurricane winds in the southern half intuitively makes no sense to me.

Oh its very possible. One good case study would be Andrew....140kt winds in the northern quadrant, 100kt winds in the southern quadrant. If we dumbed Andrew down to a 100 kt storm, the southern quadrant would register 60 kt winds, which is TS force. Of course comparing Andrew to this is stupid, because the latter is moving much much slower. Andrew was racing westward at 22 mph at landfall.

[HURAKAN]

[arkestra]

Simple question: why some days (hours) ago the models and most of us thought Bertha would have been a cat1 at its peak, and why do we have a cat3?

I have a good answer for that. You have to understand how the current models predict intensity. Let's take a look at how the SHIPS model predicts/accounts for shear (very simplified explanation). The model looks at quite a large area latitude-wise to compute the shear. Based on the projected shear value (among other things), an intensity forecast is made. This method may break down for a smaller storm like Bertha, as the wind shear in the southern part of the SHIPS calculation box is much less than the average shear it assumes. It's seeing the TUTT trof and higher shear well north of Bertha and assuming that shear is impacting Bertha, but it isn't. There was talk at the last AMS tropical meeting about reducing the size of the box where shear is calculated to improve intensity forecasts, or for the forecasters to at least be aware of this limitation.

Perhaps break the box down into two separate boxes? Have the SHIPS run the shear for the North side of the track and the south side separately, thus showing two different intensity forecasts? Is that possible?

Thank you, I understand better how the models work... But even people didn't expect that (I like to understand why we didn't understand , and I'm quite new in "pure" hurricane science), so Bertha gives new food for thought. And that's why I like tracking hurricanes.