Hurricane Helene

[kold weather]

A little update required because things are moving faster then i first thought. Helene is now showing signs of being very close to hurricane status with some impressive banding features, esp in the southern quadrant. Outflow has also yet improved and Helene will probably be a hurricane by tommorow morning if it keeps on organising like it is presently.

As with hurricane Gordon i don't see any reason why Helene can't get upto major status give nthe warm waters its under right now and the favorable heat content plus the shear levels being very low, plus the dry air that was about 24hrs ago seems to have mixed quite well with the outer sections of the convection and isn't being a hinderance right now at all.

The new models have Helene at 60kts now, which is just 5kts below hurricane status, or in other words at 70mph.

Track hasn't changed, still looking quite likely that a re-curve will occur sometime after 72hrs though quite when it starts depends on the exact strength of the weakness but there is nearly total model agreement and thats something you just don't go against unless there is a very good reason. As the center of Helen is pretty obvious now the models should get a better grip on the track. Still despite this i think there is prehaps a shot that if the models have over-done the weakness that Helene could well be a minor threat to Bermuda. It's a long shot but its possible. most likely track is to get to 50W then a track somewhere in the northerly region, give or take prehaps upto 45 degrees angle!!!!

Nothing is ever certain, but Helene is starting to impress me now with its shape, its fairly large and also has some deep convection so could end up being a pretty powerful hurricane in a couple of days.

[Gray-Wolf]

Does it look as though Helene has cast off a sizable chunk of her easrtern block of convection and is this forming another circulation there in the way that Florence did with Gordon? There is also a very big disturbance crossing over the last bit of Africa before the Atlantic (and another one alrerady into the coastal strip!) All in all I think Helene may turn out to be a complex storm to predict if so many other 'possibles' are already waiting to join her out in the Atlantic!.

[kold weather]

Well despite me thinking i'd wake up to a hurricane but alas it seems like there was siome dry air intrusion after i went to bed and while it still has got a cracking structure that probably has delayed it a touch. despite that I still fully expect a hurricane in the next 24hrs and I still think its got every chance at getting upto at least cat-2 status and quite possibly higher as well.

The track has become more complicated sinc elast night though as Helene has turned back to the west. Coupled to this the models, esp GFS is delaying any recurveature. Helene should still be no threat to the USA mainland but if the west shift continues then it does bring possibly bring Bermuda into play which has already had a close shave with Florence. So I'm still favouring re-curve, but possibly further west then I had first expected.

[crimsone]

Wish granted NHC are now calling it Hurricane Helene.

[kold weather]

Indeed I thought it was looking too good fr it not to be upgraded today. Since this morning Helene seems to have injested some dry air around it and the system does seem to be a little lop-sided with most of the decent deep convection on its western side. However despite the dry air intrusion Helene has continued to get better organised with a very ragged eye forming. There is also a ragged eyewall forming on its western side which also adds evidence to the probable strengthening trend. If it can get some more deep convection on its eastern side then we may see a fairly pretty hurricane within the next 24hrs and also a strengthening on as well.

Track ideas is still very uncertain, with the ECM and GFS both taking Helene on the further west option that I mentioned this morning, while other models such as GFDL and UKMO take the first northerly turn that the models so uniformally agrred on a few days ago. This also means that Bermuda will have to pay very close attention to this system late next week.

[kold weather]

Overnight it seems like Helene has strengthened a little and the shallow ragged eye I noted last night sdeems to have developed a little more anfd the convection has become better organised on the eastern quadrant. I'd take a guess and say that we now have a 75kt hurricane.

However a MAJOR change is occuring now in the model tracks. We have got quite a mammoth split in the models. Quite a few are still going for re-curveature. However an increasing numbver are now progging Helene to turn back westward and to move towards the USA. Indeed the 18z GFS even has it making landfall in NE USA. I'd be suprised if it gets that far west but there is a trend for Helene to move further west then was expecte dat first. Indeed this quote from NHC is also very intresting:

...THE MODELS DIVERGE QUITE

SIGNIFICANTLY WITH THE GFDL...UKMET...CANADIAN...AND NOGAPS MODEL

TAKING HELENE NORTHWARD...WHEREAS THE GFS...GFS ENSEMBLE...THE

BAMS...AND THE STATISTICAL-DYNAMICAL MODELS KEEP THE HURRICANE ON A

MORE WESTWARD COURSE AS A MID-LEVEL RIDGE BUILDS TO THE NORTH AND

NORTHWEST OF HELENE OFF THE U.S. MID-ATLANTIC COAST BY DAY 5. WATER

VAPOR IMAGERY AND 00Z UPPER-AIR DATA INDICATE THE UPPER-LOW THAT

HAS RECENTLY MOVED OFF THE U.S. MID-ATLANTIC COAST HAS BEEN MOVING

EASTWARD SIMILAR TO THE GFS SOLUTION...RATHER THAN DIGGING

SOUTHEASTWARD TOWARD BERMUDA AS FORECAST BY THE OTHER MODELS. WITH

THE STRONGEST WINDS NOW INDICATED BY WATER VAPOR IMAGERY AND

UPPER-AIR DATA TO BE ON THE SOUTH AND EAST SIDE OF THE UPPER-LOW...

THE 18Z GFS RUN MAY BE INDICATING A SIGNIFICANT CHANGE IN THE MODEL

FORECAST TRACKS COULD BE FORTHCOMING. HOWEVER...UNTIL THE OTHER

MODELS MAKE A CHANGE SIMILAR TO THE GFS...

In other words they are saying that the upper air set-up is being hndled better by the GFS model then the others and that the upper lows aren't digging in the right way to pick Helene up and so the Ridge to its north and carry Helene further west then expected...which could well mean that the idea of a large westward shift and a massive increase in threat to Bermuda and maybe even the east coast. Looks like Helene will have to be watched very closely and its going to be with us for a long time as well, probably at least 7-10 days!

[summer blizzard]

Okay, this map is slighly out of date however a split in the models has developed, several, including the GDFL want to take Hurricane Helene into the weakness created by Hurricane Gordan, which is a logical progression given the relative position and anologues of storms forming in the vicinity of Hurricane Helene however some of the models do not want to induce recurviture due to the ridge being stronger than forecast and instead forecast a westward or even south westward movement of Hurricane Helene, while i would normally back the anologues and still will for the next 48 hours at least, Hurricane Helene has already started a more westward motion than forecast resulting in the NHC ajusting there forecast to the west...

Given that the system is south of the forecast position and turning ever more westward, i think that the westward motion is entirely plausable and if the system is not north of 22N by midnight tonight, i will back the westward motion with a possible Florida landfall.

I have annotated the possible track if recurviture is avoided...

The next 24 to 48 hours will be crutial in terms of the track of this system.

[summer blizzard]

000

WTNT43 KNHC 171436

TCDAT3

HURRICANE HELENE DISCUSSION NUMBER 21

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006

1100 AM EDT SUN SEP 17 2006

VISIBLE SATELLITE IMAGES SHOW THAT HELENE HAS DEVELOPED A LARGE

RAGGED EYE SURROUNDED BY A RING OF DEEP CONVECTION. SATELLITE

INTENSITY ESTIMATES FROM ALL AGENCIES HAVE INCREASED TO 5.0 ON THE

DVORAK SCALE. THE 3-HOUR AVERAGE ADVANCED OBJECTIVE TECHNIQUE FROM

THE UNIVERSITY OF WISCONSIN IS 5.6. ON THIS BASIS...THE INITIAL

INTENSITY HAS BEEN INCREASED TO 90 KNOTS. THERE IS A CHANCE FOR AN

ADDITIONAL STRENGTHENING DURING THE NEXT DAY OR TWO BEFORE THE

SHEAR INCREASES AS SUGGESTED BY SHIPS MODEL. THE OCEAN IS EXPECTED

TO REMAIN WARM ALONG THE FORECAST TRACK.

HELENE IS MOVING TOWARD THE NORTHWEST OR 305 DEGREES AT 9 KNOTS. THE

FORECAST SCENARIO COULD BE DESCRIBED AS SUCH...HELENE CURRENTLY

LOCATED ON THE SOUTHWESTERN EDGE A SUBTROPICAL RIDGE AND MOVING

TOWARD A WEAKNESS CAUSED BY A SHARP MID-LEVEL SHORT WAVE JUST EAST

OF THE UNITED STATES CAST. THEN...AS THE SHORT WAVE MOVES OUT THE

AREA...THE RIDGE WILL LIKELY BUILD WESTWARD FORCING HELENE TO

TEMPORARILY TURN MORE TO THE WEST-NORTHWEST. AFTER 3 DAYS...A

LARGER TROUGH IS EXPECTED TO MOVE EASTWARD AND FINALLY PICK UP

HELENE. THE DILEMMA IS HOW FAR WEST WILL HELENE GO SINCE TWO GOOD

MODELS DIVERGE...PUTTING ME BETWEEN A ROCK AND HARD PLACE. THE GOOD

GFS AND THE GFS ENSEMBLE MEAN HAVE THE WESTERNMOST SOLUTIONS WHILE

THE OUTSTANDING AND HARD TO BEAT GFDL HAS HELENE TURNING NORTHWARD

FARTHER EAST. SINCE THE REST OF THE GUIDANCE IS IN BETWEEN THESE

TWO EXTREME OPTIONS...THE OFFICIAL FORECAST DOES IT AS WELL.

FORECAST POSITIONS AND MAX WINDS

INITIAL 17/1500Z 20.5N 49.0W 90 KT

12HR VT 18/0000Z 21.3N 50.1W 95 KT

24HR VT 18/1200Z 22.5N 51.5W 100 KT

36HR VT 19/0000Z 23.0N 53.0W 100 KT

48HR VT 19/1200Z 23.5N 54.5W 95 KT

72HR VT 20/1200Z 24.5N 57.0W 90 KT

96HR VT 21/1200Z 27.0N 59.0W 85 KT

120HR VT 22/1200Z 30.0N 59.5W 80 KT

$$

FORECASTER AVILA

[kold weather]

Helene has strengthened today very nicely and is now a category-2 hurricane. Structure does look more impressive then this morning and the eye has cleared out very nicely and the convection is pretty deep across the entire system. Given the heat content under it, it wouldn't be that suprising to see Helene get upto category-3. Indeed some of the Satelite data is suggesting that Helene is already a category-3 and this may not be far wrong, i'd take a guess that Helen will be upped to 95kts, or 110mph next advisory. The models are forecasting some shear to impact Helene and possibly weaken the hurricane a little in the next 48hrs however I'm not actually that sure about this simply because the model have been known to be very poor with forecasting shear which nereds to be considered.

As for track, certainly SB has layed it out as it is. I'd personally still favor the re-curve track but the models are shifting westwards which may prick the ears of those in the east coast region sof the states, but even more so thoswe in Bermuda, esp as they had a very close shave with Florence as well. Coupled to this Helene should be stronger then Florence as well at its peak and it does leave for the possiblty of a powerful hurricane coming close to land. Despite the small threat to the east coast, I think people there will still be keeping one eye on this hurricane because it could turn out to be quite potent and given the model uncertainty it could be anther few days before we get a better idea. Still if more models shift westwards on the 12z run, expect the NHC to slowly keep adjusting westwards as well.

[AtlanticFlamethrower]

Helene the best so far?

Has a good shape, size and seems like it will be the strongest.

Let's hope she both avoids the sheer and recurves away from Islands and the US.

[crimsone]

Models are continuing to diverge...

[summer blizzard]

This is getting seriously interesting, not only do the A98E model and the UKMO want to turn Hurricane Helene to the west but the GFS wants to put Hurricane Helene 1000 miles east of Florida south of a deep layer upper ridge, if that were to happen, there would be damage on the scale of Hurricane Andrew, not only because of the strength of the storm, but the sheer size.

[crimsone]

We now have Major Hurricane Helene!

Pressure is now 962mb - it's dropped like a stone overnight. Forecast models are more divergent than ever - it all depends on whether a trough will sufficiently weaken the forming ridge to allow for Helene to be caught in the weakness. I don't really need to say much though - it's all here in this forecast advisory...

HURRICANE HELENE DISCUSSION NUMBER 23

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006

1100 PM EDT SUN SEP 17 2006

THE HURRICANE IS LOOKING STRONGER THIS EVENING WITH THE RING OF

EYEWALL CONVECTION COOLING AROUND THE WARM EYE. IN ADDITION... THE

INNER CORE IS MORE SYMMETRIC THAN A FEW HOURS AGO WITH CIRRUS

OUTFLOW EXPANDING IN ALL DIRECTIONS... ESPECIALLY TO THE EAST.

SUBJECTIVE AND OBJECTIVE DVORAK ESTIMATES SUGGEST THAT HELENE IS A

MAJOR HURRICANE AND THE INITIAL INTENSITY HAS BEEN CONSERVATIVELY

INCREASED TO 100 KT... MAKING HELENE THE SECOND MAJOR HURRICANE OF

THE SEASON. THERE ARE NO OBVIOUS HINDRANCES TO FUTURE

INTENSIFICATION OVER THE NEXT COUPLE OF DAYS AS HELENE MOVES OVER

PROGRESSIVELY WARMER WATERS AND STAYS IN A RELATIVELY LIGHT SHEAR

ENVIRONMENT. CURIOUSLY... THE SHIPS/GFDL DO NOT SHOW MUCH FURTHER

STRENGTHENING IN AN ENVIRONMENT THAT IS SEEMINGLY FAVORABLE FOR

MORE INTENSIFICATION. THE OFFICIAL WIND SPEED FORECAST IS A LITTLE

HIGHER THAN SHIPS/GFDL AND CLOSE TO THE FSU SUPERENSEMBLE. A SLOW

WEAKENING COULD COMMENCE IN A COUPLE OF DAYS AS SOME MODELS HINT AT

AN INCREASE IN SHEAR. HOWEVER THE LARGE SPREAD OF THE TRACK MODELS

IN THE EXTENDED PERIOD MAKES FOR A MORE UNCERTAIN INTENSITY

FORECAST THAN USUAL AT 3-5 DAYS.

THE INITIAL MOTION IS A LITTLE SLOWER THAN PREVIOUSLY ESTIMATED...

ABOUT 315/7. GLOBAL MODELS ARE IN GOOD AGREEMENT ON THIS GENERAL

MOTION CONTINUING FOR ABOUT 24 HOURS FOLLOWED BY A TURN TOWARD THE

WEST OR WEST-NORTHWEST AS RIDGING REBUILDS IN BETWEEN GORDON AND

HELENE. THEREAFTER... THE BIG PROBLEM IS IF A TROUGH... NOW

CURRENTLY JUST OFFSHORE OF THE UNITED STATES... WEAKENS THE RIDGE

ENOUGH TO ALLOW THE HURRICANE TO BE PICKED UP BY A SECOND TROUGH IN

A FEW DAYS. MODEL GUIDANCE IS GENERALLY SPLIT INTO TWO CLUSTERS.

THE GFS/UKMET/NOGAPS SUGGEST THAT THE TROUGH WILL LEAVE THE

HURRICANE BEHIND WHILE THE ECMWF/GFDL BELIEVE THE TROUGH WILL

ACCELERATE THE HURRICANE OUT TO SEA. MODEL GUIDANCE HAS BEEN

TRENDING WESTWARD WITH TIME... AND THE OFFICIAL FORECAST LEANS

TOWARD THE WESTWARD CLUSTER OF GFS/UKMET/NOGAPS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 18/0300Z 21.6N 49.4W 100 KT

12HR VT 18/1200Z 22.3N 50.2W 105 KT

24HR VT 19/0000Z 23.0N 51.5W 110 KT

36HR VT 19/1200Z 23.3N 53.1W 110 KT

48HR VT 20/0000Z 23.6N 54.8W 110 KT

72HR VT 21/0000Z 25.0N 58.0W 100 KT

96HR VT 22/0000Z 27.5N 59.5W 95 KT

120HR VT 23/0000Z 29.5N 61.5W 90 KT

$$

FORECASTER BLAKE/PASCH

[kold weather]

Helene does look good right now though the eyewall still looks a little open on its NW side which is probably preventing any more major strengthening in the short term. Once thats patched up further strengthening is possibly but I'm not sure that the heat content is impressive enough in this patch of water to get much above 105-110kts. Despite this Helene is a good looking hurricane and certainly deserves to be our second major of the season.

[summer blizzard]

Hurricane Helene has taken a sharp turn to the north over the past 24 hours and the models unanimously agree on recurviture, so once again it looks like the GDFL is the form horse.

[Thundersquall]

This is getting seriously interesting, not only do the A98E model and the UKMO want to turn Hurricane Helene to the west but the GFS wants to put Hurricane Helene 1000 miles east of Florida south of a deep layer upper ridge, if that were to happen, there would be damage on the scale of Hurricane Andrew, not only because of the strength of the storm, but the sheer size.

Ermm - what's that monster of a storm to the east of Patagonia, on the lower part of the image?

That looks quite serious to me. I've never seen what looks like a hurricane that far south before!

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Do we in the UK need to keep a close eye on Helene's movements over the next week or so?

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

[summer blizzard]

I have opened a thread about Hurricane Helene in the Autumn section, and yes we do need to keep an eye on the system (no pun).

The storm in the southern hemisphere is a regular low fueled by a large thermal gradiant.

[BrickFielder]

Helene

INITIAL 19/0900Z 24.4N 52.1W 100 KT

12HR VT 19/1800Z 24.6N 53.4W 105 KT

24HR VT 20/0600Z 25.1N 55.0W 110 KT

36HR VT 20/1800Z 26.4N 56.3W 110 KT

48HR VT 21/0600Z 28.3N 57.1W 110 KT

72HR VT 22/0600Z 33.6N 56.1W 100 KT

96HR VT 23/0600Z 38.0N 52.0W 90 KT

120HR VT 24/0600Z 42.0N 45.0W 80 KT

This is a fairly large and strong hurricane which looks to be taking a path slightly north of Gordon. It could even make it to the UK as a substantial storm although models disagree at the moment.

[kold weather]

Very quick post on Helene. Helene looks very good right now however it does appear that Helene is ready to under-go some sort of eyewall replacement cycle given the dry outside the eyewall that has occured recently, classic sign of a EWRC about to take place. Despite this pressure is still down at 956mbs.

[kold weather]

As noted in yesterdays post, looks like Helene is undergoing a complicated EWRC or at least is trying too, with three disticnt eyewalls noted on the microwave imagery, despite this intensity is still held at 110mph, or 95kts with recon noting pressure at 960mbs.

[Thundersquall]

I understand eyewall replacement ocurred with Hurricane Andrew so is Helene similar?

It's a bit worrying it's curving to the NE and potentially threatening the UK with storm-force winds.

[Mondy]

Helene

INITIAL 19/0900Z 24.4N 52.1W 100 KT

12HR VT 19/1800Z 24.6N 53.4W 105 KT

24HR VT 20/0600Z 25.1N 55.0W 110 KT

36HR VT 20/1800Z 26.4N 56.3W 110 KT

48HR VT 21/0600Z 28.3N 57.1W 110 KT

72HR VT 22/0600Z 33.6N 56.1W 100 KT

96HR VT 23/0600Z 38.0N 52.0W 90 KT

120HR VT 24/0600Z 42.0N 45.0W 80 KT

This is a fairly large and strong hurricane which looks to be taking a path slightly north of Gordon. It could even make it to the UK as a substantial storm although models disagree at the moment.

http://www.nhc.noaa.gov/refresh/graphics_a...html?5day?large

[Rustynailer]

HISS BOOOOOO Just when the fax charts look cool

[Mondy]

The NOGAPS model has a UK hit, the other models are playing safe...too far away yet for certain

[Soaring Hawk]

I rather like the NOGAPS model. I'm in Scotland on my own from Saturday for a week walking & R&R. The only problem is I won't have access to a computer to be able to track Helene. How frustrating; the one time I get out of the non-weather event capital of the UK.