Hurricane Bertha (Was category-3)

[Iceberg]

Tropical Depression TWO Forecast Discussion

--------------------------------------------------------------------------------

Home Public Adv Fcst/Adv Discussion Wind Probs Maps/Charts Archive

--------------------------------------------------------------------------------

000

WTNT42 KNHC 030859

TCDAT2

TROPICAL DEPRESSION TWO DISCUSSION NUMBER 1

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008

500 AM EDT THU JUL 03 2008

THE STRONG TROPICAL WAVE AND SURFACE LOW OVER THE EASTERN ATLANTIC

OCEAN HAS ACQUIRED ENOUGH ORGANIZED CONVECTION TO NOW BE CONSIDERED

A TROPICAL DEPRESSION. SATELLITE IMAGES INDICATE THAT A STRONG

BURST OF CONVECTION HAS PERSISTED FOR OVER 12 HOURS NEAR OR JUST

WEST OF THE APPARENT CENTER OF THE SYSTEM. BANDING FEATURES ARE

ALSO BECOMING MORE PRONOUNCED IN THE NORTHWESTERN PART OF THE

CIRCULATION. THE INITIAL INTENSITY OF 30 KT IS BASED ON A QUIKSCAT

PASS FROM LATE YESTERDAY THAT SHOWED SOME RELIABLE 25-30 KT WINDS.

IT SHOULD BE NOTED THAT MOST GLOBAL MODELS...ESPECIALLY THE

GFS...SUGGESTED THE POSSIBILITY OF GENESIS IN THIS AREA OVER A WEEK

AGO...A REMARKABLE ACHIEVEMENT.

MIDDLE-LEVEL RIDGING IS STEERING THE STORM TOWARD THE WEST-

NORTHWEST...ABOUT 285/8. THIS RIDGING GETS STRONGER DURING THE NEXT

COUPLE OF DAYS...WHICH SHOULD CAUSE A FASTER FORWARD MOTION BY LATE

TOMORROW. GLOBAL MODELS ARE IN GOOD AGREEMENT WITH THE TRACK UNTIL

THE SYSTEM POTENTIALLY REACHES A BREAK IN THE SUBTROPICAL RIDGE

ALONG ABOUT 50W-55W AT THE END OF THE FORECAST PERIOD. THE MODELS

THAT SHOW THE STRONGEST REFLECTION OF THE CYCLONE...SUCH AS THE

GFS/HWRF/GFDL...TURN THE DEPRESSION MORE TOWARD THE NORTHWEST...

WHILE THE UKMET/ECMWF MODELS KEEP A WEAKER TROPICAL CYCLONE ON A

WEST-NORTHWESTWARD TRACK. THE OFFICIAL FORECAST IS CLOSE TO A BLEND

OF THE FIVE MODELS ABOVE BUT JUST A SHADE TO THE LEFT OF THAT

CONSENSUS.

VERTICAL WIND SHEAR IS FORECAST TO REMAIN LIGHT FOR THE NEXT FEW

DAYS NEAR THIS SYSTEM...SO THE BIGGEST LIMITING FACTOR ON THE

FUTURE STRENGTH OF THE DEPRESSION IS THE COOLER WATERS AND MORE

STABLE AIR IN ITS PATH. AFTER ABOUT 24 HR ON THE NHC TRACK...SSTS

DROP BELOW 26C AND STAY BELOW THAT THRESHOLD FOR A COUPLE DAYS.

THEREAFTER SSTS WARM SLIGHTLY AND MOST GLOBAL MODELS FORECAST AN

ENVIRONMENT THAT WOULD FAVOR SOME INTENSIFICATION. THE OFFICIAL

INTENSITY FORECAST REFLECTS THIS SCENARIO...SHOWING STRENGTHENING

AT THE START AND END OF THE FORECAST PERIOD AND NO SIGNIFICANT

CHANGE IN BETWEEN WHILE THE SYSTEM IS OVER THE COOLEST SSTS. THE

SHIPS/GFDL MODELS ARE A LITTLE MORE BULLISH WITH THIS

SYSTEM...MAKING IT A HURRICANE WITHIN 5 DAYS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 03/0900Z 12.6N 22.7W 30 KT

12HR VT 03/1800Z 13.0N 24.5W 35 KT

24HR VT 04/0600Z 13.8N 27.2W 45 KT

36HR VT 04/1800Z 14.7N 30.0W 45 KT

48HR VT 05/0600Z 15.8N 33.3W 45 KT

72HR VT 06/0600Z 17.5N 40.0W 45 KT

96HR VT 07/0600Z 20.0N 46.5W 50 KT

120HR VT 08/0600Z 23.0N 51.0W 55 KT

[Iceberg]

Bertha(very nearly) has some potential IMO.

There are clearly a couple of camps here.

Meto and ECM are not keen on intensification, they hold the ridge in place and keep it on a more western motion.

GFS and it's various outputs which include HWRF and GFDL both weaken the ridge and allow more strengthening.

The GFS solution has to be the favourite currently and the System will stay out to see. Should be interesting to watch though.

Latest pictures show that a CDO is forming quite readily now, however it's position is not good for Sat coverage.Arrrgggg

[kold weather]

Well firstly some hot news, models are now starting this as Tropical Storm Bertha at 35kts so should be upgraded.

Anyway prospects about the same as before, over warm water for the next 12hrs then temps fall away pretty rapidly as it moves WNW. I suspect when the system starts to go over the cooler waters and therefore lower heat content much of the deeper convection will reduce and so it may struggle to keep up its strength unless it really develops over the next 12-24hrs. Eventually track should take the system WNW/NW back towards the warmer water around 20N/40W however by that time it heads towards a upper low which could begin to shear the system. Therefore it may have a hard time getting much beyond a weak system but if the shear is lower then we do have a shot at something stronger further west.

[Iceberg]

Yep it's been upgraded on Dvorak as well.

2.5 35 KTS 40 MPH 1005 mb 997 mb

Which would indicate Bertha.

What do you think about the chances of an ECM/Meto Track Kold ?

[kold weather]

Its hard to know really Iceberg, right now its track is 285 which is close to WNW and its moving faster as well now. I suspect a middle ground between the GFS/GFDL very hard right turn and the slower WNW movement of the ECM and UKMO, indeed the current NHC thinking is probably close to what I think.

Should be noted SHIPS hit this system with 37kts of shear by 120kts as it heads towards the upper low, if its even close to being right the system should weaken quite a lot by that time, of course shear forecasts are never all that good to be honest that far out.

[Cookie]

at long last we get a second system

[kold weather]

Yep and its also the most easterly system to form in July EVER, beating...hurricane Bertha in 1996 which formed on the 5th of July close to Cape Verde...uncanny comprasion. Track however for Bertha 2008 should be a good bit different then that of Bertha 96.

I think this is not the last we have seen from the Cape Verde region this hurricane season, temps will only rise in the east atlantic, esp above 15N over the next 2 months till they peak in early September and seasons in the past with similar atmospheric conditions across the globe have often featured strong cape verde seasons and sometimes they make it all the way across the Atlantic, though a good deal of the time the storms recurve and I think Bertha will likely fall into that group.

[Cookie]

thanks Kold

The hurricane season of 2008 sets a new record

Today's formation of Bertha at 25° West longitude is the farthest east a tropical storm has ever formed in the Atlantic so early in the season. It is also the farthest east a tropical storm has formed in the month of July. Reliable records of Eastern Atlantic storms go back to 1967, the beginning of the geostationary satellite era.

http://www.wunderground.com/blog/JeffMaste...p;tstamp=200807

[James M]

Another one! it's going to be interesting this season. I must say thanks everyone for the updates on these threads it makes for fascinating reading.

[tinybill]

http://www.nhc.noaa.gov/graphics_at2.shtml?5day#contents

looking at that its heading for Cuba at the moment

http://www.nhc.noaa.gov/aboutcone.shtml

but on this one could easily head for Florida

[Iceberg]

I think this one will keep people guessing, very different tracks from HWRF and GFDL and very different intensities. The weaknesses in the ridge might or might not let Bertha through.

Some outstanding rotation on the system and very good banding as well.

Meto take it below TS strength tomorrow. Many others take it to boardline Hurricane.

[tinybill]

http://www.nhc.noaa.gov/graphics_at2.shtml?5day#contents

looking at that its heading for Cuba at the moment

[Cookie]

its going to be an interesting watch

[kold weather]

Do you mean Bermuda tinybill?

Iceberg, indeed the problem is sometimes the models over-estimate these weaknesses in the high pressure cells and thus allow a poleward movement too quickly. Also the longer it takes to develop the less latitude it should gain, in theory anyway becuase of the Beta effect, which in basic terms is the stronger the storm the greater tedency to get pulled poleward. Models have shifted a little further to the west over the last 12hrs and I think this may well continue to occur. The key is these little shifts in the track to the west have big ramifications upstream, esp for Bermuda because the further west it can get the more chance of bringing this island into the frame. Its one to watch.

Also I agree its got cracking banding features. Convection isn't all that deep IMO but given its under 25C SST's thats to be expected. I suspect development will be slow at least for the next 48hrs but its excellent shape should keep it from weakening I think depsite being over waters that would typically induce slow weakening.

Finally future strength is totally dependant on exact track. SST's rise back upto 26-27C again by 72hrs and this is probably the most likely time for strengthening to really occur, wouldn't surprise me if it comes into the region in good shape that it will strengthen quite smartly into a strong TS. Beyond that a lot of uncertainty with the shear levels that will be present in about 5 days. Models do raise the shear alot (SHIPS is upto 35kts by 120hrs!) but whether or not this will happen its just too early to know to be honest!

[Somerset Squall]

Bertha has managed to sustain some deeper convection over the centre this morning, and banding features remain good. NHC have upped the intensity to 40kts based on dvorak intnesity estimates. Bertha is expected to remain in a low shear environment for now but waters will remain near 25C which should mean development will be slow for Bertha until it reaches warmer waters in a couple days. The intensity forecast brings Bertha to 60kts in 72hrs, just shy of hurricane strength, and then maintains intensity for the rest of the forecast period as shear is still expected to increase at this point.

[Iceberg]

Bertha does look good on the sat at the moment and finally she is poking her nose on GOES East so we can have 30 min updates and more info available, track will also be easier to view.

GFDL takes it to CAT 3 and a CAT 1 later today!(maybe a little soon)

HWRF hardly develops it still.

[dallas]

Bertha does look good on the sat at the moment and finally she is poking her nose on GOES East so we can have 30 min updates and more info available, track will also be easier to view.

GFDL takes it to CAT 3 and a CAT 1 later today!(maybe a little soon)

HWRF hardly develops it still.

That would be some rapid intensification, I agree cat 1 would be to soon today

[kold weather]

Convection is indeed still fairly deep with Bertha though slightly on the NE side of the center with the other quadrants somewhat bare thanks to the close presence of the SAL to the NW. SST's are now getting very marginal but are just about enough to support convective development and the fact it has a good circulation that has been rotating now for a good several days is probably helping to provide a certain amount of energy to keep the system ticking over.

I think the future strength will probably hold close to 40-45kts for the nxt 36hrs providing no dry air intrusion occurs (which is possible.) after that then there may well be a window as it starts to get back towards the higher heat content. Its then that we have IMO a good chance of seering more pronouced development occur, esp with the good looking structure it has right now, whilst too early to say there is probably a 24-48hr window where this could become a hurricane. After that then things get much more complicated as it starts to ghet closer to a major upper low in the Atlantic that is responsible for breaking the Bermuda high down very slowly and thus allowing Bertha to eventually head northwards according to the GFS. I don't really want to comment on shear that far out as it can be hard to know exactly what role and how strong it will be.

Also should be noted models are still shifting westwards, looks like they have overdone the weakness to the north. GFS now gets to 60W before curving NW/NNW and takes it very close indeed to Bermuda by 180hrs. The UKMO and the ECM however take it even further west then that and the ECM indeed has it very close t othe USA by 240hrs, granted both models do have a much weaker system then the GFS which probably is why they are further south as they are being driven by lower level steering currents which favor a more westerly track.

[mezzacyclone]

esp with the good looking structure it has right now,

Touching further on this Kold/IceB/SS et al, has one ever been so apparently well organised at this latitude coming off the west africa area/this time of year etc.?

Bertha 14.2N 28.3W

[Iceberg]

A bit out of date now but the Goes pictures and scats which indicate a 40-50Kt storm travelling slightly north of the projected track.

[Iceberg]

I believe floater 1 is now over Bertha.

[Iceberg]

Latest advisory from NHC indicates yet another westward shift.

I have a gut outside possibility of a NY hit as a CAT 2, don't know why..........

[dallas]

Latest advisory from NHC indicates yet another westward shift.

I have a gut outside possibility of a NY hit as a CAT 2, don't know why..........

The five day track is suggesting a turn east at the end

[tinybill]

on my eye of the storm 3000 program at the moment its heading for oak island to Norfolk or Richmond be able to know better by Sunday did any one watch that film about a hurricane heading for new York!!!!!!!

and this one has it heading to new york!!!

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

[kold weather]

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!