Hurricane Bertha (Was category-3)

[Iceberg]

I like the look of the ridge being thrown up by ECM at the 200 range due to the LP over the eastern states. A big long shot and not to be taken too seriously. :lol:

[dallas]

Large amounts of stable airmass to the NW of this system now and also the system has become a little bit lop-sided with convection getting displaced to the NE of the center indicating some shear, SHIPS progs shear levels at 8kts right now. That as well as low SST's (now getting close to the high 24's!) should mean that at least for the next 48hrs the system will have a very hard time doing anything, indeed it wouldn't even be all that unlikely that it weakens down to a bare TS (35kts) but we will see. Once its get clear of the lower SSt's it should hit a better region for development though that will probably only last 24hrs or so.

Iceberg, that sounds shockingly like Bertha 1996 lol!

Kold, am I right in thinking that storms that develop as far east as Bertha, then manage to hold together through colder sst's mormally end up major hurricaines?

[Katherine]

Depends on whether or not the sea temperatures at the time are warm enough to add sufficient strength to the system.....

Bertha's expected to pass over cooler water during the next day or so, so there's little possibility of strengthening in the short term.

[Cookie]

my word what a change in interest between Atlantic systems and none Atlantic systems

Edited July 4, 2008 by cookie

[kold weather]

Well they can do depending on the shear conditions. A system that can hold together well in low SST's must have a good circulation and therefore when it does reach warmer waters they sometimes do go bang as the energy present to use increases. IMO there is a period between 72-96hrs where this could become a hurricane before it starts to reach higher shear levels again.

Shear still coming up from the south over Bertha right now which is limiting any development depsite constant bursting convection to the north of the center. SST's still lowering at the moment but should bottom out tomorrow and then start to rise again on Sunday...I think this disproves the fact that 26.5C is always a magic number, many other factors need to be counted...

Models still shifting southwards, Carolinas northwards might be brought into the mix if this carries on.

Edited July 4, 2008 by kold weather

[Cookie]

thanks for the updates Kold.

[Iceberg]

Morning all,

Bertha is continuing to keep us guessing.

Firstly strength. This remains a solid 40-45Kt according to a recent scatt pass about 1.5hrs ago.Shear is taking a toll but structure is still half decent( A bit like a half full glass so this could be taken either way ! ). Future strength is still very variable. The tropical storm specific models all develop her as Kold says once she moves into more favourable waters. The Globals though tend to destroy her and quickly. So some big differences there. Personally I think Bertha will survive and continue to make a CAT 1 status. Shear is the biggest factor though for this and my head says that the GM's will have a better handle on the shear.

As to path, the break in the ridge is a very quickly disappearing option, HWRF plays with something but without much heart, GFDL looks a pretty decent estimate and takes Bertha around the high with a chance at an east coast hit.

Again the Globals which indicate a wave feature by then take her even more westwards, Meto indicates a leewards hit.

Whilst GFS indicates a Bahamas hit.

The globals are probably too far west but cannot be discounted. At the moment GFDL seems the best estimate but the possible envelope is huge.

[kold weather]

Agreed Iceberg globals may well too far west esp given this will likely hit a much more favorable upper patter around 65W comvined with SST's that are in the 27's we could well see decent development there which would allow the system to lift to the NW/NNW more. However if this happens it does make it a very close call for the USA, one thats a little to tight to call right now!

As for current strength not really much to add to what Iceberg said. the fact its still bursting convection quite often under sheared conditions and also under what are now very low sea surface temperatures (below 25C, I think SHIPS estimated about 24.8C or something) is impressive and eventually when it does get out of the sheared set-up probably in about 18hrs time breifly we could see some strengthering occuring as SST's also re-increase steadily.

At least we are going to get recon however which will be interesting.

[Iceberg]

Track is still very uncertain and as Kold indicated the near term shear and SST's and current condition of Bertha are vital as she needs to survive.

I've attached the latest shear and the 24hr forecast which shows a more favourable environment.

The SST's are also given the NHC track/sat picture and indicate nicely the warmer waters ahead. IMO 27C are needed to sustain a CAT 1.

Current conditions according to recent SCAT indicate that 40+KT winds are still evident however there are certainly less and I wouldn't be surprised if NHC lower the forecast to 40Kt.

Other than that Shear is still evident to the south, but Bertha is also still managing to keep up the convection needed, the LLCC is still in very good shape and things look promising for re-intensification later.

Edited July 5, 2008 by Iceberg

[tinybill]

http://www.nhc.noaa.gov/graphics_at2.shtml...?large#contents

looks like it could be Florida at the moment some were near Orlando to Jacksonville by my eye of the storm 3000 program

Edited July 5, 2008 by tinybill

[Katherine]

If it does hit land, I'm guessing that Bertha might make landfall just north of Florida.....

[Iceberg]

Bertha still has some very good shape and with some increase convection which is predicted over the warmer SST's in the next 24 hrs or so a Hurricane might quickly be in the making.

To try and forecast further strength you also have to forecast it's path, see the NHC discussion below.

The models are generally persisting with there own tracks.

The globals with more of a westerly and the tropicals with more northerly.

"BERTHA CONTINUES TO MOVE RAPIDLY WESTWARD WITH AN INITIAL MOTION OF

280/18. THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT

36-48 HOURS COURTESY OF A STRONG RIDGE TO THE NORTH. THEREAFTER...

THE CYCLONE BEGINS TO ENCOUNTER A WEAKNESS IN THE SUBTROPICAL RIDGE

AND TRACK MODELS DIVERGE SIGNIFICANTLY. IN FACT...THE SPREAD IN

THE TRACK MODELS SPAN NEARLY 1300 MILES AT DAY 5 WITH THE UKMET

MODEL KEEPING BERTHA HEADED WESTWARD AND THE HWRF TURNING THE

CYCLONE NORTHWARD. GIVEN THE UNCERTAINTY...THE OFFICIAL FORECAST

IS SIMILAR TO THE PREVIOUS FORECAST AND LIES IN THE MIDDLE OF THE

TRACK MODEL ENVELOPE.

IT SHOULD BE NOTED THAT THERE IS LARGER THAN NORMAL UNCERTAINTY IN

BOTH THE TRACK AND INTENSITY FORECASTS OF BERTHA. ACCORDINGLY...IT

IS MUCH TOO EARLY TO DETERMINE IF BERTHA WILL OR WILL NOT POSE A

THREAT TO ANY LAND AREAS.

"

She has just past the 26C isotherm and will pass the 27C some time late afternoon.

An interesting path has been thrown up by ECM. Still 10 days but we have a major hurricane baring down on the eastern seaboard some where around NY.

I am not sure that anywhere south of the carolinas will be hit, but the possibility still exists.

[Cookie]

its going to be an interesting watch

[Iceberg]

Bertha is looking quite good , she has a solid CDO forming and is sustaining it nicely.

Should be some intensification underway soon, Winds have yet to respond, with Scat charts still showing 40-45Kt max.

Temps will be getting up to 28C

[kold weather]

Bertha does look good shear seems to have finally started to ease, there are hints that the center has tucked a little further into the convective mass over the last couple of hours which a very interesting development. SST's are now increasing and I think its now in a position where a hurricane is a real possibilty. As you say Iceberg got a solid CDO now and now shear is not present the mass should stay nicely right over the center.

The SHIPS do prog higher shear in about 72hrs which may limit development after that but we shall have to wait and see, right now it does look like a steadily developing storm. Track to the W/WNW looks the most likely option out to 4-5 days then things become more complicated as another upper trough tries to dig down the east coast of the USA. I'm not sure quite how well the trough will dig down, the models do sometimes over estimate the ability of these to dig down (as us winter watchers should know with the northerlies that downgrade.) but we shall have to wait and see.

Oh and finally, we have our first recon date fixed for late Tuesday, 18z.

[mezzacyclone]

Is advisory No. 15 due out at 9pm our time tonight?

(Below: end of no.14 Bertha advisory:)

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT

500 PM AST.

[tinybill]

http://www.nhc.noaa.gov/graphics_at2.shtml...?large#contents

looks like south/north caroline is in line for this one

[kold weather]

Update needed quite urgently, recent microwave imagery shows an eyewall and eye has formed and this has become evident on Vis.imagery as well just recently. Center made a sizeable WNW/NW wobble and is now at 18.2 looking at current estimates of mine. The last 3hrs however has seen a mean movement back towards due west again. Therefore its possible Bertha is stair-stepping, which means its meaning a WNW but wobbling from a westerly track to a NW track over the space of 12-24hrs.

Should see a hurricane in the next 6-12hrs from bertha if this current rate of organisation continues to occur.

[Somerset Squall]

Agreed KW, Bertha really seems to be responding well to the increase in sea temperatures. The only thing in Bertha's way is the possible shear later in the forecast period, but until then the only way is up for Bertha.

Satellite image showing the developing eye:

[summer blizzard]

000

WTNT42 KNHC 062057

TCDAT2

TROPICAL STORM BERTHA DISCUSSION NUMBER 15

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008

500 PM EDT SUN JUL 06 2008

A COUPLE OF MICROWAVE IMAGES JUST RECEIVED SUGGEST THAT BERTHA'S

VORTEX IS TILTED A LITTLE. THE IMAGES INDICATE THAT THE

LOW-LEVEL CENTER IS LOCATED JUST SOUTHWEST OF THE MID-LEVEL CENTER.

HOWEVER...THESE IMAGES ALSO SUGGEST THAT THE OVERALL STRUCTURE HAS

IMPROVED WITH THE APPEARANCE OF AN EYE FEATURE...SUGGESTING THAT

BERTHA IS STRENGTHENING. DVORAK INTENSITY ESTIMATES WERE 45 KT AT

18Z...BUT WITH THE IMPROVING STRUCTURE THE INITIAL INTENSITY IS

INCREASED TO 50 KT. CONDITIONS APPEAR CONDUCIVE FOR STRENGTHENING

DURING THE NEXT COUPLE OF DAYS AND BERTHA COULD BECOME A HURRICANE.

HOWEVER...INDICATIONS ARE THAT BEYOND 48 HOURS...WESTERLY SHEAR

COULD HALT ANY ADDITIONAL STRENGTHENING AS SUGGESTED BY THE SHIPS

MODELS.

BERTHA IS MOVING WEST-NORTHWESTWARD OR 285/17 KT. ALL OF THE

AVAILABLE GUIDANCE SHOWS A NORTHWEST TURN AS THE RIDGE OVER THE

WESTERN ATLANTIC WEAKENS IN A FEW DAYS. HOWEVER...THERE REMAINS

SOME SPREAD IN THE GUIDANCE AS TO WHEN THE TURN OCCURS. THE HWRF

AND GFDL...WHICH DEPICT A STRONG TROPICAL CYCLONE REMAINS ALONG

THE EASTERN EDGE OF THE MODEL ENVELOPE. THE UKMET WHICH KEEPS

BERTHA WEAKER IS ALONG THE WESTERN EDGE. THE NEW TRACK

FORECAST IS ADJUSTED SLIGHTLY EASTWARD...BUT STILL REMAINS

WEST OF THE MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 06/2100Z 18.1N 47.0W 50 KT

12HR VT 07/0600Z 18.7N 49.6W 55 KT

24HR VT 07/1800Z 19.5N 52.3W 60 KT

36HR VT 08/0600Z 20.2N 54.6W 65 KT

48HR VT 08/1800Z 20.9N 56.7W 70 KT

72HR VT 09/1800Z 23.0N 60.5W 70 KT

96HR VT 10/1800Z 26.0N 64.0W 70 KT

120HR VT 11/1800Z 29.0N 65.5W 70 KT

$$

FORECASTER BROWN

Seems they have already noted the eye feature, however the low level centre is slightly detached.

[Cookie]

wounderground reckon could be cat 1 hurricane by Tuesday morning

[Katherine]

I've got a hunch that, looking at the predictions and maps of said prediction, Bertha won't hit the USA.

[kold weather]

Maybe Katherine, the models are still split with some of the models re-building the high to the north of the system again and that sends it back west closer to the USA in about 144hrs, meanwhile other models curve this into the Atlantic. mind you some of the models are very close to bermuda so its a situation that needs to be watched. I will give a breif summery tomorrow as I'm signing off soon to sleep!

Still Bertha is getting strong, probably close to 55kts right now, probably got another 9-12hrs of sustained development before it may reach hurricane strength IMO.

[mezzacyclone]

Will see how Accuweather`s forecast turns out?

highly probable of a Cat 1 before the early hours of wednesday surely?

[Iceberg]

I am not convinced of any further intenstification overnight since the microwave pass (see the attached where the forming eye wall with the strong winds can clearly be seen.)

She might well be getting tighter but it's difficult to tell, scatt passes are inconclusive.

Saying all this the Dvorak is currently upped to 4.0 which translates to...

4 65 KTS 75 MPH 987 mb CAT 1 (64-83 KTS)

Without recon, bouy or ship data it's very diffcult to judge on the pressure. If NHC go by this she could be Hurricane Bertha in 2.5hrs time when the next discussion is sent out. Personally I don't think she looks as good as early but what do I know.

Outlflow remains impressive and banding features are still present.

Track is now alot more certain with even the Meto now indicating a close pass by with Bermuda. A US hit now seems unlikely.