Hurricane Bertha (Was category-3)

[liquidjp]

The latest image this morning shows the eyewall seems to have closed up, certainly not as clear at it was yesterday, is this a sign of weakening, ERC, or just one of those things... EDIT: The first then... thanks Iceberg

Edited July 8, 2008 by liquidjp

[opplevelse]

The latest image this morning shows the eyewall seems to have closed up, certainly not as clear at it was yesterday, is this a sign of weakening, ERC, or just one of those things... EDIT: The first then... thanks Iceberg

Could be an ERC, but people tend to automatically jump on that bandwagon whenever they cannot see a well defined eye. More likely some high clouds obscuring the eye, the IR still shows a reasonably good eye. Unfortunately there have not been any good satellite passes for a while so we cant see any of the other products (eg 85GHz) to tell ... oh well, we will find out in the next few hours.

Oh and this is the same sat shot as yours liquidjp, but zoomed and slightly higher resolution

[Iceberg]

The eye is intact but there is no outer wall for an ERC to take place. The inflow has virtually stopped and Bertha is starving to death.

The WV image shows this nicely.

The size of the cane on the western side is wafer thin. Dry air could so so easily break through providing a mortal blow.

[opplevelse]

The eye is intact but there is no outer wall for an ERC to take place. The inflow has virtually stopped and Bertha is starving to death.

The WV image shows this nicely.

The size of the cane on the western side is wafer thin. Dry air could so so easily break through providing a mortal blow.

Yep, and the air on that western side is bone dry. But shear will be her death. No cyclone can withstand 40kts.

[Iceberg]

The eye has now collapsed I would suggest that intensity has dropped to somewhere between 75-80Kt so a CAT 1 more than likely.

Moisture is continuing to be an issue and shear is also evident.

[Iceberg]

A rather generours 90Kt from NHC, particularly given the 77KT given by Dvorak on there latest upgrade.

Dry air, Shear and the collapse of the western wall are all rather severe.

CONVENTIONAL AND MICROWAVE IMAGERY SHOW A RAPID DEGRADATION OF

BERTHA'S STRUCTURE DURING THE LAST 6 HOURS. THE EYE HAS

DISAPPEARED AND CLOUD TOPS HAVE WARMED CONSIDERABLY. THERE IS ALSO

EVIDENCE IN MICROWAVE IMAGERY THAT THE WESTERN PORTION OF THE

EYEWALL HAS ERODED. A BLEND OF THE FINAL T AND CI NUMBERS FROM THE

DVORAK TECHNIQUE SUPPORTS AN INITIAL INTENSITY OF 90 KT AND LATEST

OBJECTIVE T NUMBERS SUGGEST AN EVEN LOWER INTENSITY. THE INITIAL

INTENSITY IS CONSERVATIVELY SET AT 90 KT. IT WOULD APPEAR THAT

BERTHA HAS FINALLY ENCOUNTERED THE HIGHER SHEAR ENVIRONMENT WE'VE

BEEN FORECASTING. ADDITIONALLY...THE CYCLONE IS MOVING OVER

SLIGHTLY COOLER WATERS AND THERE ARE SOME INDICATIONS IN SATELLITE

IMAGERY THAT IT COULD BE ENTRAINING DRY AIR. BOTTOM LINE...THE

ENVIRONMENT LOOKS RATHER HOSTILE AND BERTHA SHOULD CONTINUE TO

WEAKEN IN THE SHORT-TERM. TOWARDS THE END OF THE FORECAST

PERIOD...THE SHEAR COULD RELAX AND SSTS INCREASE SO THERE IS SOME

POTENTIAL FOR A LITTLE RE-INTENSIFICATION. HOWEVER...GIVEN THE

UNCERTAINTY IN INTENSITY FORECASTING...THE OFFICIAL FORECAST MERELY

SHOWS SLOW WEAKENING THROUGH THE FORECAST PERIOD AND IS IN GOOD

AGREEMENT WITH A CONSENSUS OF THE VARIOUS INTENSITY MODELS.

[BrickFielder]

Theres a jetstreak to the north east of the hurricane which is creating a nice area of upper level divergence. This is creating a new area of thunderstorm development while dry air is getting entrained in the hurricane. I would not be surprised for it to all merge and for a new hurricane to form.

[Iceberg]

Bertha is nolonger a hurricane IMO. Dvorak stands at 3.5 or only 55 KTS, it's possible it might be kept as a CAT 1 but that would be very generous, more so than the 90Kt early which IMO was way to high.

The LLCC is exposed and will start to break up soon.

It's a possibility BrickFielder but it will likely have lost it's tropical charecterisitics, the Jet streak will produce a system that would be baroclinic in nature and might well not have time or conditions to gain the tropical traits. Worth keeping an eye on.

[kold weather]

Hmmm I think your being way too hasty Iceberg, deep convection has recently re-developed over the center and though there is still clearly some SW shear on Bertha but at the very least its held steady over the last few hours. On top of that its yet to cross over the highest heat content region to the NW which will add yet more juice to the system. Shear is starting to decrease over the system according to the shear maps and ther eis a zone between 26-30N where we could see some steady strengthening IMO.

As of now I think 70kts is probably a good reflection, it may have breifly weakened below hurricane status but the re-burst of convection near the center makes me convinced its probably still a hurricane.

One othjer interesting to note is the track appears to have swang back WNW, this is because as the system has rapidly weakened it has been steered by a slightly lower level where the weakness is not quite as strong and this may mean the track has to be re-adjusted a little bit back to the west but this all depends on whether the system strengthens again or not, if it does strengthen then it will shift back onto a NW/NNW track.

[adamavfc]

Someone from where i work is going on holiday to Florida next week for two weeks, is their any chance of this hurricane heading that way if it regains strength?

[opplevelse]

...

The LLCC is exposed and will start to break up soon....

LLCC - low Level Cloud Center? Sorry haven't heard that abbreviation before.

BTW There is a Terra MODIS shot due for 14:05 today, which should be smack bang over Bertha, will provide a good view. will put it up when it is uploaded.

I was wrong, the Terra shot was a little too south ... damn ...

http://rapidfire.sci.gsfc.nasa.gov/realtim....php?T081901405

[Cookie]

come on people been a few questions asked in this thread that have been ignored!

[Iceberg]

No chance of this Hitting Florida thankfully, it also looks pretty quite down there from anything else at present.

LLCC sorry also called LLC. Dvorak estimates are still 55Kt, without an eye but with some outflow and a CDO still. This equals TS IMO but I fully understand that the NHC are keen to keep it a hurricane not sure what the evidence is though.

[opplevelse]

Ahhh LLC I should have guessed, so that means LLCC stands for Low Level Circulation Center or something?

[Iceberg]

Well it has gone down to 65KT so just by a hair a hurricane. They acknowledge this is to the higher of there scale.

Still an improvement is the look of Bertha is evident this morning and with all canes anything can happen.

[*Stormforce~beka*]

NOAA Expecting big bertha to get a bit bigger in the next 2 days. They are expecting her to stay a cane for til Sat/Sun.

000

WTNT32 KNHC 090830

TCPAT2

BULLETIN

HURRICANE BERTHA ADVISORY NUMBER 25

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008

500 AM AST WED JUL 09 2008

...CATEGORY ONE HURRICANE BERTHA CONTINUES NORTHWESTWARD...

AT 500 AM AST...0900Z...THE CENTER OF HURRICANE BERTHA WAS LOCATED

NEAR LATITUDE 23.5 NORTH...LONGITUDE 56.5 WEST OR ABOUT 560 MILES...

905 KM...NORTHEAST OF THE NORTHERN LEEWARD ISLANDS AND ABOUT 790

MILES...1275 KM...SOUTHEAST OF BERMUDA.

BERTHA IS MOVING TOWARD THE NORTHWEST NEAR 10 MPH...17 KM/HR...AND

THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 48 HOURS

WITH SOME DECREASE IN FORWARD SPEED.

MAXIMUM SUSTAINED WINDS ARE NEAR 75 MPH...120 KM/HR...WITH HIGHER

GUSTS. A SLIGHT INCREASE IN STRENGTH IS POSSIBLE OVER THE NEXT 48

HOURS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 30 MILES...45 KM...FROM

THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140

MILES...220 KM...MAINLY TO THE NORTH AND EAST.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB...29.15 INCHES.

REPEATING THE 500 AM AST POSITION...23.5 N...56.5 W. MOVEMENT

TOWARD...NORTHWEST NEAR 10 MPH. MAXIMUM SUSTAINED WINDS...75 MPH.

MINIMUM CENTRAL PRESSURE...987 MB.

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

1100 AM AST.

$$

FORECASTER PASCH

[kold weather]

Bertha has re-organised quite a lot in the last 6-9hrs with convection really increasing over the center again and the inner core has tightened up somewhat. Indeed recent vis.imagery shows a small cloud filled eye may have emerged. With this being the case strengthening is looking quite possible over the next 12hrs and with the small eye once again there may be quick fluctuations in the intensity, we will have to wait and see. Shear still looks present with hints of the eye being a little tilted again thanks to shear, though the shear has eased down so I don't think it will strengthen nearly as much nor as rapidly as the first time round but presentation looks much better now, I'd guess 70kts is reasonable estimate though NHC may hold 65kts for a little while yet.

Edited July 9, 2008 by kold weather

[Somerset Squall]

Bertha is really going for it again, looks pretty impressive at the moment, I would put it back up at about 90 kts as a guess?

[kold weather]

I'd go even higher then that SS, I'd go 95-100kts which is what raw Dvorak numbers would suggest, though adjusted numbers aren't nearly as high yet, they are none the less increasing pretty rapidly which is suggesting that like before rapid intensification is occuring, which is always possible given Bertha has small compact inner core.

[opplevelse]

Yep! the shearing environment has eased somewhat but it is still 20-30kts, which is still way to high to sustain a cyclone. I still cant see it lasting too much longer.

Lovely 250m res MODIS Shot today here

http://rapidfire.sci.gsfc.nasa.gov/realtim....php?T081911445 I\ll do a bit of image manip to it to bring out the details.

Vapor has improved,

and looking at the 85Ghz image *bottom left of the multi spectrum image below), convection around the core has re grouped. Still a bit patchy though.

[opplevelse]

Ok Here is a BW version of the original Terra pic from 2:45pm UTC today(stretched and adjusted by the good people at NASA to make sure it doesnt look odd)

And here is a version i like to do every so often to highlight cloud top structure ... If you click on the image, a much larger version will come up ... but even this is at about half full resolution. IMHO it looks much better and gives far more information.

Enjoy!

James

[Somerset Squall]

Great images Oppelvelse, thanks for sharing!

Here is the latest from the NHC:

HURRICANE BERTHA DISCUSSION NUMBER 27

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008

500 PM EDT WED JUL 09 2008

BERTHA'S SATELLITE PRESENTATION HAS DRAMATICALLY IMPROVED DURING THE

LAST 6 HOURS. THE CYCLONE NOW HAS A DISTINCTIVE EYE AND IS

SURROUNDED BY A SYMMETRIC RING OF COLD CLOUD TOPS. THE INITIAL

INTENSITY IS RAISED TO 90 KT BASED ON A BLEND OF THE SATELLITE

CLASSIFICATIONS FROM SAB AND TAFB. BERTHA IS FORECAST TO BE IN A

SEEMINGLY FAVORABLE ENVIRONMENT FOR THE NEXT DAY OR SO AND

CONTINUED STRENGTHENING IS EXPECTED IN THE SHORT-TERM. BEYOND 36

HOURS...VERTICAL SHEAR IS STILL EXPECTED TO GRADUALLY INCREASE AND

SSTS SLOWLY FALL. THIS ENVIRONMENT IS EXPECTED TO RESULT IN A SLOW

WEAKENING TREND THROUGH THE END OF THE FORECAST PERIOD. IT SHOULD

BE NOTED THAT BERTHA COULD BECOME A LITTLE STRONGER THAN CURRENTLY

FORECAST IN THE FIRST 24 HOURS.

BERTHA HAS RECENTLY WOBBLED A LITTLE RIGHT OF THE PREVIOUS MOTION

ESTIMATE BUT THE 12 HOUR AVERAGE MOTION IS ESSENTIALLY

UNCHANGED...305/10. THE TRACK FORECAST PHILOSOPHY IS THE SAME AS

IN THE PREVIOUS ADVISORY. A MID-TROPOSPHERIC ANTICYCLONE

CURRENTLY OVER THE WESTERN ATLANTIC IS FORECAST TO MOVE

NORTHEASTWARD WHILE A SHORTWAVE TROUGH MOVES OFF OF THE U.S. EAST

COAST. THIS SHOULD RESULT IN BERTHA MAKING A GRADUAL TURN TOWARD

THE NORTH DURING THE NEXT 2-3 DAYS. HOWEVER...THIS TROUGH IS

FORECAST TO BYPASS BERTHA TO THE NORTH AND LEAVE IT BEHIND IN

RELATIVELY WEAK STEERING CURRENTS. ACCORDINGLY...THE OFFICIAL

FORECAST SHOWS A SLOW NORTHWARD MOTION AT DAYS 3 AND 4. A SECOND

TROUGH MOVING OFF THE UNITED STATES EAST COAST ON DAY 5 COULD

RESULT IN SOME NORTHWARD ACCELERATION LATE IN THE FORECAST PERIOD.

IN GENERAL...TRACK MODELS HAVE CHANGED LITTLE SINCE THE LAST

ADVISORY...AND THE NEW OFFICIAL TRACK FORECAST IS ESSENTIALLY AN

UPDATE OF THE PREVIOUS ONE.

IT IS STILL TOO EARLY TO KNOW WHETHER BERTHA WILL HAVE AN IMPACT ON

BERMUDA. INTERESTS ON THAT ISLAND SHOULD CONTINUE TO MONITOR THE

PROGRESS OF THIS HURRICANE OVER THE NEXT COUPLE OF DAYS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 09/2100Z 24.8N 58.1W 90 KT

12HR VT 10/0600Z 25.6N 59.2W 100 KT

24HR VT 10/1800Z 26.8N 60.2W 100 KT

36HR VT 11/0600Z 28.0N 61.0W 100 KT

48HR VT 11/1800Z 29.1N 61.3W 95 KT

72HR VT 12/1800Z 31.0N 61.5W 85 KT

96HR VT 13/1800Z 32.5N 61.0W 80 KT

120HR VT 14/1800Z 35.5N 60.0W 75 KT

$$

FORECASTER RHOME

[Somerset Squall]

Bertha has developed a small and very well defined eye now, wouldn't be surprised Bertha has regained major hurricane status, it looks perhaps as strong as it was before (110kts).

[kold weather]

Sat.estimates suggests this is just about a major hurricane (T numbers around 5.4, which is 99kts...) and therefore its quite likely that we will see Bertha upgraded again to a category-3. shear seems to have all but gone bar maybe the far northern segment of the system which has allowed a very good structure to once again develop. heat content in the area suggests an MPI probably around 110kts so Bertha probably isn't all that far away from reaching that though there are no signs yet of any EWRC which probably means there is still some small scope for movement which is probably helped by the tight inner core, even though the CDO of the system has increased in size compared with when it was first a major hurricane.

Edited July 9, 2008 by kold weather

[Cookie]

brilliant images guys and thanks for the updates

Edited July 9, 2008 by cookie