Hurricane Helene

[kold weather]

Right well its offical everyone, we have the tropical depression 8 just a couple of hundred miles off Africa.

anyway structure is extremely impressive, as is its size considering its presently just a tropical wave as well. latest IR imagery shows some immensely cold cloud tops with this wave, something that isn't that common when they come off from land. shear looks low however just one thing to note is that ther eis some dry air to its west presently but as the wave is quite sizeable and has got a lot of moisture in all probablity it'll mix that dry air out as it isn't super dry.

Judging by its favorable postion this one has every chance of being a pretty powerful big hurricane and also quite possibly 7 days down the line have a good shot at becoming a cat-3 providing it doesn't get hit by a ULL like several other storms have this year. Still I don't really see many things that will prevent this onre from being a big powerful system and indeed the SHIPS take Td8 upto 103kts which is category-3 status.

Track is also extremely intresting, though not that tough at least in the short-mid term. A strong HP is to the north of Td8 which will keep TD8 on a west/WNW type direction until at least 120hras. Then we start to have a larger problem in track and one that probably can't be forecasted with any real accuracy. it's all to do with the exact track and speed that Gordon moves and how much latitude Td8 gains in the next few days. I'd personally suspect a re-curve in a pretty similar place as Gordon is right now but ther eis a very real chance that the Azores high will build strong enough that will keep it quite far south and that the weakness left by Gordon will close keeping TD8 stil lon a WNW which then leaves a chance open for a landfall in either the Cairbbean or the USA/Bermuda. Still thats a monsterous length away and for now a westward track looks most likely.

[Calrissian]

Well hello there Helene-to-be !

Now this indeed looks far far better for some entertainment. I think the storm freaks can get a little big excited about what this one might do.

Forget about Gordon... Helene is the one to watch

Calrissian: eyes on ISS

[Thunder Snow]

Hopfully she will be a good storm lol

[Mondy]

It's a monster wave!

[Calrissian]

Helene-to-be looks mighty impressive at this early stage, way better than Florence or Flash did. Even though there would be around 12-14 days until a potencial usa landfall, it does look very well defined.

Look at it, its almost got an evil eye about it. There is something of the night about it. You see it too, right?

Calrissian: time for lunch

[Blackie]

That's West Africa it has just left not Mordor, my precious.

Edit: oops, wrong side of the continent

[Kain]

The great eye is ever watchfull..

Anyway WOW, she looks a beast, and shes only a wave! TS helen by Wednesday evning I guess!

Very impressive.

Kain

[crimsone]

No. She's not only a wave - she's officially TD8 - as per the NHC advisory...

000

WTNT43 KNHC 121431

TCDAT3

TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 1

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006

1100 AM EDT TUE SEP 12 2006

THE CLOUD PATTERN ASSOCIATED WITH THE TROPICAL WAVE THAT EMERGED

FROM AFRICA YESTERDAY HAS BECOME SIGNIFICANTLY BETTER ORGANIZED

THIS MORNING. A FAIRLY WELL-DEFINED CURVED CONVECTIVE BAND HAS

FORMED OVER THE WESTERN SEMICIRCLE OF THE SYSTEM AND DVORAK

CLASSIFICATIONS ARE AT T1.5 FROM TAFB AND SAB. TWO REPORTS OF

NORTHERLY 19 KT AND SOUTHERLY 10 KT WINDS...FROM SHIPS WITH CALL

SIGNS PBCJ AND UCAB RESPECTIVELY...CONFIRM THE PRESENCE OF A CLOSED

SURFACE CIRCULATION. BASED ON THE ABOVE DATA...ADVISORIES ARE

BEING INITIATED ON TROPICAL DEPRESSION EIGHT. PRESENTLY THE SYSTEM

APPEARS TO BE IN AN ENVIRONMENT OF WEAK EASTERLY SHEAR AND IT

SHOULD BE TRAVERSING SEA SURFACE TEMPERATURES OF AROUND 28C.

HOWEVER...WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL TROUGH NEAR

40W-45W NORTH OF 15N AND THE GLOBAL MODELS INDICATE THAT THIS

FEATURE WILL PERSIST FOR THE NEXT COUPLE OF DAYS. IF THIS SCENARIO

VERIFIES...THE ENVIRONMENT COULD BECOME LESS CONDUCIVE FOR

STRENGTHENING. THE OFFICIAL FORECAST SHOWS ONLY SLOW STRENGTHENING

OVER THE NEXT COUPLE OF DAYS BUT PRESUMES THAT THE CYCLONE WILL BE

ABLE TO EVENTUALLY STRENGTHEN INTO A HURRICANE. THIS OFFICIAL

FORECAST IS SOMEWHAT LOWER THAN THE CURRENTLY AVAILABLE INTENSITY

GUIDANCE.

INITIAL MOTION IS ESTIMATED TO BE 270/16. OVER THE NEXT SEVERAL

DAYS...THE CYCLONE IS LIKELY TO BE STEERED BY EASTERLY FLOW TO THE

SOUTH OF A MID-LEVEL SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC.

LATER IN THE FORECAST PERIOD....THERE ARE DIFFERENCES OF OPINION

AMONGST THE DYNAMICAL TRACK PREDICTION MODELS. THE U.K. MET OFFICE

AND ECMWF GLOBAL MODELS TURN THE SYSTEM NORTHWARD TO THE EAST OF

50W...WHEREAS THE GFS FORECASTS LESS OF A WEAKNESS IN THE RIDGE

NEAR 50W AND TAKES THE SYSTEM FARTHER SOUTH AND WEST. THE OFFICIAL

TRACK FORECAST IS BETWEEN THESE POSSIBILITIES AND FAIRLY CLOSE TO

THE TRACK DEPICTED IN THE 0600 UTC GFDL RUN.

THIS MORNING...DROPSONDES ARE BEING LAUNCHED FROM A DC-8 AIRCRAFT IN

THE VICINITY OF THE SYSTEM AS PART OF THE AFRICAN MONSOON

MULTIDISCIPLINARY ANALYSIS PROJECT...AMMA. THESE SOUNDING DATA ARE

BEING INCORPORATED INTO THE GLOBAL TELECOMMUNICATIONS SYSTEM

AND...HOPEFULLY...INTO THE GLOBAL MODELS TO IMPROVE THE

INITIALIZATION OF THIS TROPICAL CYCLONE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 12/1500Z 12.5N 23.0W 25 KT

12HR VT 13/0000Z 12.7N 25.3W 30 KT

24HR VT 13/1200Z 13.0N 28.4W 35 KT

36HR VT 14/0000Z 13.5N 31.5W 40 KT

48HR VT 14/1200Z 14.0N 34.8W 50 KT

72HR VT 15/1200Z 15.5N 41.5W 65 KT

96HR VT 16/1200Z 17.0N 47.0W 75 KT

120HR VT 17/1200Z 19.0N 51.0W 85 KT

$$

FORECASTER PASCH

[kold weather]

Models still favoring a re-curve and so am I. Given there seems to be a long term weakness around 60W so far this month thats quite probably where TD8 will probably re-curve at roughly the same point as Florence. What this does mean is that I think the Bermuda islands may have to just keep a close eye on this system WAY down the line. In all fairness though its far too early to make any accurate forecast path more then 72-96hrs.

Should see a TS from this probably tommorow sometime I'd guess, the 8th of the season and while the ACe ( ACE link) is some way behind these storms will go some way to whacking that back towards average.

[Calrissian]

The great eye is ever watchfull..

Anyway WOW, she looks a beast, and shes only a wave! TS helen by Wednesday evning I guess!

Kain

Please remember, the Americans are incompetent.....at spelling. It'll be Helene, not Helen.

Calrissian: Eyes on the Growing Beast

[Brrr]

KW... recurve... sigh..... (obviously not great if you're in Bermuda though)

Wonder if we'll get any majors in the GOM this year at all..... looks a bit unlikely at this stage.....

[Taras Incognito]

Does something as big as this affect later waves comming off of the continent?

[Calrissian]

Does something as big as this affect later waves comming off of the continent?

Hmm, well everything is linked. Of course, the most basic issue is that any storm - in its wake, the waters will be churned up, with lower sea temps, and thus less chance of the next wave becoming a storm.

So, as Helene-to-be increases in strength, its using up more of the energy in that area, and thus everything in the infamous 'African wave train' has less to work with.

Calrissian: Waving at the tropical beasts

[summer blizzard]

I agree with the recurviture idea.

Tropical Depression EIGHT Public Advisory

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000

WTNT33 KNHC 122032

TCPAT3

BULLETIN

TROPICAL DEPRESSION EIGHT ADVISORY NUMBER 2

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006

500 PM EDT TUE SEP 12 2006

...DEPRESSION NEARING STORM STRENGTH...

SATELLITE IMAGES AND SHIP REPORTS INDICATE THAT THE TROPICAL

DEPRESSION OVER THE FAR EASTERN ATLANTIC IS GRADUALLY INTENSIFYING.

AT 500 PM EDT...2100Z...THE CENTER OF TROPICAL DEPRESSION EIGHT WAS

LOCATED NEAR LATITUDE 12.0 NORTH...LONGITUDE 23.9 WEST OR ABOUT 195

MILES...315 KM...SOUTH OF THE SOUTHERNMOST CAPE VERDE ISLANDS.

THE DEPRESSION IS MOVING TOWARD THE WEST NEAR 15 MPH AND THIS

GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS.

MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 35 MPH...55

KM/HR...WITH HIGHER GUSTS. STRENGTHENING IS FORECAST DURING THE

NEXT 24 HOURS...AND THE DEPRESSION COULD BECOME A TROPICAL STORM

TONIGHT OR EARLY WEDNESDAY.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB...29.74 INCHES.

REPEATING THE 500 PM EDT POSITION...12.0 N...23.9 W. MOVEMENT

TOWARD...WEST NEAR 15 MPH. MAXIMUM SUSTAINED WINDS...35 MPH.

MINIMUM CENTRAL PRESSURE...1007 MB.

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

1100 PM EDT.

$$

FORECASTER PASCH

[Gray-Wolf]

This storm looks more like it means business! I think I'll watch this one and Florences remnants over the next couple of days. :unsure:

Talking of things off Africa I think that flowing off N. Africa towards S. Italy looks ominous too! It's a shame the Med. isn't wider!!!

EDIT: I take it that with Florence, Gordon and the ULL to the NE of Gordon, churning away over the west side of the pond that the disturbances may help TD8 recurve over the mid atlantic and maybe treat us to a bit of what Newfoundland is currently having?

[summer blizzard]

000

WTNT43 KNHC 132036

TCDAT3

TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 6

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006

500 PM AST WED SEP 13 2006

SATELLITE IMAGERY THIS AFTERNOON INDICATES THAT TROPICAL DEPRESSION

EIGHT IS SLOWLY BECOMING BETTER ORGANIZED. A CONVECTIVE BAND HAS

FORMED IN THE NORTHWESTERN QUADRANT...ALTHOUGH THE BAND IS MORE

THAN 100 N MI FROM THE CENTER IN MOST AREAS. THE OVERALL

CIRCULATION IS MORE CIRCULAR AND BETTER DEFINED THAN 6 HR AGO.

SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB...AND 30 KT FROM

SAB AND AFWA. THE INITIAL INTENSITY REMAINS 30 KT. IT SHOULD BE

NOTED THAT THE INITIAL POSITION IS SOUTH OF THE SATELLITE FIXES...

AND THE CENTER MAY BE TRYING TO RE-FORM FARTHER NORTH CLOSER TO THE

CONVECTION.

THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 275/16...WITH A POSSIBLE

FASTER MOTION OVER THE PAST FEW HOURS. THE DEPRESSION REMAINS

SOUTH OF A DEEP-LAYER RIDGE OVER THE EASTERN ATLANTIC...WHICH

SHOULD KEEP THE SYSTEM MOVING QUICKLY WESTWARD FOR 24 HR OR SO.

AFTER THAT...THE LARGE-SCALE MODELS FORECAST THE CYCLONE TO

GRADUALLY TURN WEST-NORTHWESTWARD AND THEN NORTHWESTWARD TOWARD A

WEAKNESS IN THE RIDGE NORTHEAST OF THE LESSER ANTILLES. THE UKMET

AND THE NOGAPS FORECAST MORE RIDGING NORTH OF THE DEPRESSION THAN

THEIR PREVIOUS RUNS...AND THEY TURN THE CYCLONE TO SOMEWHAT TO THE

LEFT AFTER 96 HR. THIS IS REFLECTED IN THE NEW FORECAST TRACK.

THE CANADIAN REMAINS A LEFT OUTLIER....ALTHOUGH IT HAS SHIFTED TO

THE RIGHT OF ITS PREVIOUS TRACK. THE GFS...GFDL...AND ECMWF ARE

SIMILAR TO THEIR PREVIOUS RUNS...WITH THE GFDL FASTER THAN THE

OTHER MODELS AFTER 72 HR. THE NEW FORECAST TRACK IS FASTER THAN

THE PREVIOUS TRACK DURING THE FIRST 24 HR...THEN IS SLOWER THAN THE

PREVIOUS TRACK AFTER 72 HR. IT LIES NEAR THE SOUTH EDGE OF THE

MAIN CLUSTER OF GUIDANCE.

THE BROAD STRUCTURE SUGGESTS THAT SHORT-TERM INTENSIFICATION SHOULD

BE SLOW. THIS IS REFLECTED IN THE FIRST 24 HR OF THE INTENSITY

FORECAST. THE SYSTEM SHOULD THEN STRENGTHEN AT A FASTER RATE IN A

LIGHT VERTICAL SHEAR ENVIRONMENT...AND IT IS FORECAST TO BECOME A

HURRICANE IN ABOUT 72 HR. THE INTENSITY FORECAST IS IN BEST

AGREEMENT WITH THE GFDL. THERE REMAIN TWO COMPLICATING FACTORS IN

THE INTENSITY FORECAST. THE FIRST IS DRY AIR PRESENT NORTH AND

WEST OF THE CYCLONE. HOW MUCH OF THIS AIR WILL BE ENTRAINED INTO

THE SYSTEM IS UNCLEAR. THE SECOND IS AN UPPER-LEVEL TROUGH

FORECAST BY THE LARGE-SCALE MODELS TO THE NORTH OR NORTHEAST OF THE

LESSER ANTILLES BY 96-120 HR. WHILE THE MODELS AGREE THE TROUGH

WILL EXIST...THEY DO NOT AGREE ON THE LOCATION OR ON THE POSSIBLE

IMPACT TO THE CYCLONE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 13/2100Z 12.7N 30.7W 30 KT

12HR VT 14/0600Z 12.9N 33.3W 35 KT

24HR VT 14/1800Z 13.6N 36.4W 40 KT

36HR VT 15/0600Z 14.7N 39.0W 50 KT

48HR VT 15/1800Z 16.1N 41.1W 60 KT

72HR VT 16/1800Z 18.5N 44.0W 70 KT

96HR VT 17/1800Z 20.5N 46.5W 80 KT

120HR VT 18/1800Z 22.0N 49.5W 85 KT

$$

FORECASTER BEVEN

Given that the models unanomously agree on a trough in the vicinity of the lesser Antiles, i doubt that the ridge will rebuild.

[crimsone]

000

WTNT43 KNHC 140253

TCDAT3

TROPICAL STORM HELENE DISCUSSION NUMBER 7

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006

1100 PM AST WED SEP 13 2006

INFRARED SATELLITE IMAGERY THIS EVENING INDICATES CONTINUED GRADUAL

DEVELOPMENT WITH A DISTINCT CURVED BAND ON THE NORTHWESTERN

SEMI-CIRCLE. BASED UPON UNANIMOUS DVORAK T-NUMBERS OF 2.5 AND

EARLIER AMSU INTENSITY ESTIMATES...THE INTENSITY IS ANALYZED AT 35

KT AND IS GIVEN THE NAME HELENE.

THE TROPICAL STORM APPEARS TO HAVE SPED UP WITH AN INITIAL MOTION OF

285/19...THOUGH THIS IS SOMEWHAT UNCERTAIN GIVEN THE SPREAD IN

POSITIONS. HELENE SHOULD CONTINUE WEST-NORTHWESTWARD FOR THE NEXT

DAY UNDER THE INFLUENCE OF A DEEP-LAYER RIDGE. BETWEEN 36 AND 72

HOURS...A MID TO UPPER TROUGH INDUCES A WEAKNESS IN THE RIDGE AND

THIS MAY ACT TO STEER THE SYSTEM TOWARD THE NORTHWEST. AFTER THIS

TROUGH BY-PASSES HELENE...A WEST-NORTHWESTWARD TRACK SHOULD RESUME

AT DAYS 4 AND 5. ALL RELIABLE GUIDANCE SHOWS THIS STAIR-STEP

SCENARIO...WITH NOGAPS BEING A MODEST OUTLIER TO THE SOUTHWEST OF

THE PACK. THE FORECAST TRACK IS NEAR THE MODEL CONSENSUS AND IS TO

THE RIGHT OF THE PREVIOUS FORECAST.

WHILE THERE IS A LARGE SAHARAN AIR LAYER TO THE NORTH AND WEST OF

HELENE...TOTAL PRECIPITABLE WATER ANALYSES FROM CIRA SUGGEST THAT

THIS VERY DRY AIR IS NOT REACHING HELENE'S INNER CORE. THE

SYSTEM'S PROJECTED TRACK SHOULD TAKE IT OVER WARM WATER...THROUGH

ABUNDANT MOISTURE AND INTO LIGHT VERTICAL SHEAR FOR THE NEXT THREE

DAYS. SHIPS AND THE FSU SUPER-ENSEMBLE THUS BRING HELENE UP TO

ABOUT 100 KT IN THREE DAYS. THE GFDL...ON THE OTHER HAND...IS

SUBSTANTIALLY WEAKER...LIKELY BECAUSE IT DEPICTS MORE SHEAR BEING

IMPARTED ON HELENE DUE TO THE AFOREMENTIONED MID TO UPPER TROUGH.

AT DAYS 4 AND 5...ALL GUIDANCE SUGGESTS THE SHEAR WILL PICK UP AND

LIMIT FURTHER INTENSIFICATION. THE INTENSITY FORECAST IS CLOSE

TO...BUT JUST BELOW...BOTH SHIPS AND THE FSU SUPER-ENSEMBLE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 14/0300Z 13.3N 32.7W 35 KT

12HR VT 14/1200Z 13.7N 35.0W 45 KT

24HR VT 15/0000Z 14.7N 37.4W 55 KT

36HR VT 15/1200Z 15.9N 39.5W 65 KT

48HR VT 16/0000Z 17.4N 41.0W 75 KT

72HR VT 17/0000Z 20.0N 43.5W 90 KT

96HR VT 18/0000Z 21.5N 45.5W 95 KT

120HR VT 19/0000Z 22.5N 49.0W 85 KT

$$

FORECASTER AVILA/LANDSEA

[Kain]

So I missed an e, hardly worth being told off about it eh?

Anyway...

Kold, how does the dust hamper development?

Kain

[Martin N]

Well, I have noticed the almost Florence-like struggle with organisation that this large system has. It will become a hurricane but I'm afraid it will recurve eventually. Frontal activity out of the North American continent will prevent mid-Atlantic storms form making westward progress in the immediate future.

If you want hurricanes/tropical storms to make landfall...you need to be thinking about homegrown storms in the very warm Carribean and GoM. However models are not hinting at any sign of development there either...atm...

[Paranoid]

So far all these recurving storms have been good news to the people in the GOM, we've only seen one storm form in the GOM which was Alberto in June. I'm surprised we havent seen other storms form there or even an invest. Is there something hampering development there?

[crimsone]

Is there something hampering development there?

One of the oil rigs probably sprang a deliberate leak spewing a film of long chain hydrocarbons over the surface. Good for oil production, and particularly good for the investigation of the new oilfield they think they've found in the GoM (apparently large enough to rival the alaskan one.)

Or at least... it wouldn't suprise me. lol

[Martin N]

SST's in Caribbean and GoM are very high but the models are not even hinting at developing anything in the Western Atlantic atm. If there isn't anything in the area (a wave) to take advantage of the energy inherent...then there is no chance of anything.

There's time yet...but as I say...anything growing in the Eastern Atlantic basin is not going to see land (ex Bermuda and Islands et al).

[Gray-Wolf]

On looking at the N. Atlantic Vis Loop I could see a point (soon) when the southerly feed of the remnants of Florence will sit above the southerly feed of Gordon which, in turn, will sit above the southerly feed of Helene.

What a warm, moist air conveyor that will be for a while.

I wonder if we'll all 'benefit' from that happenstance (I'm thinking storms )?

[Brrr]

So far all these recurving storms have been good news to the people in the GOM, we've only seen one storm form in the GOM which was Alberto in June. I'm surprised we havent seen other storms form there or even an invest. Is there something hampering development there?

I posted a 'why' in the Florence thread...

- basically El Nino and a few other things...

Hostile Conditions are hindering hurricanes

A developing El Nino event -- abnormal warming of the eastern tropical Pacific Ocean -- may be partially to blame (or thank) for the relatively quiet season so far.

Here's the full article.....

http://www.al.com/news/mobileregister/inde....xml&coll=3

Belinda

[kold weather]

Actually the thing people don't understand is that on average only one storm actually forms in the Gulf of Mexico itslef...and we've already have had one, which was Alberto. The thing is we've just beena little spoiled in terms of powerful systems in there.

Anyway Helene seems to have finally sorted out some of its inner core problems. The probkem for Helene has been the same as florence in that its quite a sizeable system which takes a while to sort out its core.

Still its done that now and the convection has become quite deep around the center which now, at least appears, to be under the main blow-up of convection. I don't think Helen is under-going rapid strengthening but it is certainly strengthening steadily today and the organsiation has vastly improved since yesterday with some much better defined banding features.

With this in mind the winds will probably be upped to about 50-55kts come the next advisory shortly. Track is still slightly uncertain but general trend seems pretty solid to me, with the system getting to about 50-55 west then re-curving northwards and eventually NE as a second trough picks it up and shots it into the jet stream. This mis given more creadit when there has been a constant weakness in the Azores/Bermuda high chain, though that has shifted from 60W now to about 55-50W which is where Gordon is slipping through presently.