Tropical Storm Ana

[Iceberg]

As expected this has now been updated from 99L, given the T2.0 Dvorak numbers.

They take it to a strong 50Kt storm at the end of the range with a 25% chance of a Hurricane, looking GOOD !!

TROPICAL DEPRESSION TWO SPECIAL FORECAST/ADVISORY NUMBER 1

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009

1000 UTC TUE AUG 11 2009

TROPICAL DEPRESSION CENTER LOCATED NEAR 14.4N 28.6W AT 11/1000Z

POSITION ACCURATE WITHIN 25 NM

PRESENT MOVEMENT TOWARD THE WEST OR 270 DEGREES AT 11 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1006 MB

MAX SUSTAINED WINDS 25 KT WITH GUSTS TO 35 KT.

WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL

MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

[Iceberg]

I should caveat in that GFDL, HWRF, the globals and SHIPS do not take TD 2 into a hurricane and probably the best realistic guess at the moment is a max of around a 50-55Kt storm, still it's likely to be first named storm of the season and is likely to stay out over the sea.

Below is also the NHC discussion and the tracks.

FIRST LIGHT VISIBLE SATELLITE IMAGES SHOW THAT THE BROAD LOW

PRESSURE AREA ASSOCIATED WITH A TROPICAL WAVE THAT WE HAVE BEEN

TRACKING OVER THE FAR EASTERN TROPICAL ATLANTIC HAS ACQUIRED

SUFFICENT ORGANIZED DEEP CONVECTION TO BE DESIGNATED AS A TROPICAL

DEPRESSION. THE TROPICAL CYCLONE IS SITUATED OVER MARGINALLY WARM

SEA SURFACE TEMPERATURES AND THE VERTICAL SHEAR IS CURRENTLY RATHER

WEAK. THE OFFICIAL FORECAST SHOWS GRADUAL STRENGHENING OVER THE

NEXT COUPLE OF DAYS AND IS A BLEND OF THE VARIOUS NUMERICAL

GUIDANCE TOOLS. AS USUAL THERE IS CONSIDERABLE UNCERTAINTY AS TO

THE STRENGTH OF THIS SYSTEM LATER IN THE FORECAST PERIOD. IF THE

CYCLONE MOVES FARTHER NORTH THAN ANTICIPATED BELOW IT WILL PROBABLY

ENCOUNTER STRONGER SHEAR AND NOT INTENSIFY AS MUCH AS FORECAST. ON

THE OTHER HAND IF THE SYSTEM MOVES FARTHER SOUTH THAN EXPECTED LATE

IN THE PERIOD...IT WILL PROBABLY BECOME STRONGER THAN ANTICIPATED

HERE.

INITIAL MOTION IS ABOUT 270/11. THIS TRACK IS LIKELY TO MORE OR

LESS CONTINUE FOR THE NEXT 2-3 DAYS DUE TO THE FLOW SOUTH OF A

FAIRLY WELL-ESTABLISHED MID-LEVEL SUBTROPICAL RIDGE. LATER IN THE

PERIOD...A SLIGHT WEAKNESS IN THE RIDGE IS LIKELY TO INDUCE A MORE

WEST-NORTHWESTWARD MOTION. THE OFFICIAL FORECAST IS A LITTLE

SLOWER THAN THE MODEL CONSENSUS AND WELL TO THE SOUTH AND WEST OF

THE BAM TRACKS. THIS IS ALSO SOUTH OF THE LATEST HWRF TRACK.

FORECAST POSITIONS AND MAX WINDS

INITIAL 11/1000Z 14.4N 28.6W 25 KT

12HR VT 11/1800Z 14.6N 30.1W 30 KT

24HR VT 12/0600Z 14.8N 32.3W 35 KT

36HR VT 12/1800Z 15.0N 34.6W 35 KT

48HR VT 13/0600Z 15.2N 36.8W 40 KT

72HR VT 14/0600Z 16.0N 41.2W 45 KT

96HR VT 15/0600Z 17.5N 45.5W 50 KT

120HR VT 16/0600Z 19.5N 49.5W 50 KT

[butler_son]

As expected this has now been updated from 99L, given the T2.0 Dvorak numbers.

They take it to a strong 50Kt storm at the end of the range with a 25% chance of a Hurricane, looking GOOD !!

TROPICAL DEPRESSION TWO SPECIAL FORECAST/ADVISORY NUMBER 1

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009

1000 UTC TUE AUG 11 2009

TROPICAL DEPRESSION CENTER LOCATED NEAR 14.4N 28.6W AT 11/1000Z

POSITION ACCURATE WITHIN 25 NM

PRESENT MOVEMENT TOWARD THE WEST OR 270 DEGREES AT 11 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1006 MB

MAX SUSTAINED WINDS 25 KT WITH GUSTS TO 35 KT.

WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL

MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

:o I'm shocked...hold on, just let me get my jaw back off the floor...does this mean there is actually activity in the Atlantic Basin now? :lol:

[Iceberg]

Yes real activity at last, but we have to wait for TD 3 for the real fireworks !.

[kold weather]

Given its look last night I didn't expect to see tropical depression 2, esp when it looks no better now then it did 2 days ago, but alas there has been some deepening of the convection which has probably been important plus the fact we can confimr the presence of a LLC.

Anyway I have to admit it does look pretty decent, conveciton is slap bang over the center and looks pretty good. Conditions aloft atre good for now even though there is quite a lot of shear dotted around the system below 20N it should remain pretty in decent shear conditons. It should be noted that for now SST's will remain marginal so any strengthening should be slow to occur though SST's do increase around 40W, but however the shear could be an issue by then, we shall have to wait and see.

The models not really seeing much with TD2 however they do suggest a weak system heading WNW generally. The ridge is present however there is a weak trough in the Central Atlantic which is just strong enough to cause Td2 to move WNW. What happens once it gets past the weak trough will be quite interesting to observe. It may briefly bend back west as the upper high closes over the weakness however I still suspect this will be a fish, bar a fluke shot at Bermuda. Still I think its something to watch, may come closer to the US then many are thinking if the weakness isn't as strong. However if this does become a hurricane then it should recurve before that risk ever emerges. The models also aren't too keen on strengthening the system much, with marginal SST's for now I also wouldn't expect much strengthening however the models are probably not really 'seeing' the system very well. The main problem is there is a SAL layer to the north of the system and so as the system heads further WNW t gets closer and the odds of it injesting some is an issue.

Looks like we are going to have TS Ana in the next 24hrs, I'm not so sure about a hurricane mind you but it'll be nice to just finally follow something in the Atlantic!

Edited August 11, 2009 by kold weather

[Iceberg]

Good call from NHC on it's track.

GFDL has now shifted to a more southerly track, even further south than the official NHC forecast. Allowing for a bit more strengthening 55-60Kts.

However atm TD 2 is looking poor, Dvorak numbers have fallen to 1.5 and it's struggling. There is still some good circulation in there but a lack of core covection is really preventing any strenghtening.

[kold weather]

Funnily enough though Iceberg raw Dvorak numbers are actually increasing, even adjusted numbers are now upto 2.6 which equates to about 35kts.

However these numbers aren't the final numbers, though they are slowly increasing at the moment and whilst the longer term average is still 1.5 I suspect in response to the increase in the last few hours we shall see those numbers going up a little bit.

Convection is a bit poor as you say though there is recently a bit of convection developing over the center however it does need to be worked on before we see Ana. Looks like the fairly stable air that is nearby is preventing much in the way of deep convection developing but if it does burst for a good 6-12hrs then we will have Ana in no time at all thanks to the decent circulation.

[Cookie]

Thanks for the updates guys

[toggerob]

NHC going with the system being TS Ana some later today as the SW convective quadrant embeds itself in the system. Looking ahead it seems not much progression to be made by TD02/Ana as it encounters Shear coming towards the Eastern Caribbean region and this will quickly kill off the system.

All is no lost however as TD02/Ana's moisture will help inhibit another TD which has the potential to form into a CAT2 Hurricane in he Antilles region by next week if models are to be believed, though its still a long way off.

[Iceberg]

TD 2 has really got going in the in the last few hours, with deep central convection. Should almost certainly be ANA at 10.00am today.

I hadn't look at the raw Dvoraks KW, only the official, NHC have already upped it to to 30Kt from 25Kt, so now only 5Kt short.

Some evidence of shear, but it's difficult to see the centre until visual pictures allow.

I think the most important factor overnight though has been the forecast change to keep the ridge much stronger, due to this the system is set to stay further south and any turn NW is much more gentle, according to GFS and GFDL this now takes TD 2/ANA over the Bahamas.

Even allowing for this TD2 is not programmed to be a hurricane, so effects should be minimal, if TD2 is still around then.

[Coast]

Updated model tracks:

[Lincs Observation]

Morning all

Im a little concerned we may have a bumpy ride as we head into late summer/Autumn. Ok my reasoning is that the displaced jet we are experiencing may be an express way for any hurricane activity of the coast of America, Now over the past two years this kind of activity has been muted however there is the strong possibility that this year we may see a high level of hurricane activity (in relation to the past two seasons) and as a direct analysis The southern parts of England and Northern France could be susceptible to severe ex tropical depressions riding what has been a very strong jet activity much more south than normal.

So in a nut shell if the jet patterns stay the same and we have a busy hurricane season I would expect a very bad Autumn for the UK this year.

LO

[Iceberg]

So in a nut shell if the jet patterns stay the same and we have a busy hurricane season I would expect a very bad Autumn for the UK this year.

LO

I think that's a sensible conclusion.

Assuming we can get some activity with the El Nino, the the position of the Polar Jet will dictate more of an effect of an TS remnents that maybe in previous years.

TD 2 has been updated and is still a TD.

The centre is not in the centre of the convection, due to shear, T number have increase again overnight though and it probably doesn't make much difference whether it's called TD2 or TS Ana.

There has been a slightly Southward shift in the NHC track, however METO, GFDL and NOGAPS all taking her further south and west still and a further shift south and west in likely IMO.

SATELLITE IMAGES INDICATE THAT A PERSISTENT CLUSTER OF THUNDERSTORMS

REMAINS IN THE WESTERN SEMICIRCLE OF THE DEPRESSION...ALTHOUGH

RECENTLY THIS CLUSTER HAS TAKEN ON A SOMEWHAT ELONGATED APPEARANCE.

MICROWAVE AND SHORTWAVE INFRARED DATA SUGGEST THE CENTER REMAINS ON

THE EASTERN SIDE OF THE CONVECTION AND NOT WELL-EMBEDDED WITHIN THE

MAIN CONVECTIVE CLUSTER. DVORAK ESTIMATES SUGGEST THE MAXIMUM

WINDS ARE NEAR 30 KT...AND THE INITIAL INTENSITY WILL BE HELD AT

THAT VALUE.

[toggerob]

The problem being is that with it being El Nino season all of the explosive formation that we've seen with Katrina/Gustav-like Hurricanes the past few years are limited to the far Western Gulf and Pacific Ocean.

NOAA themselves have concluded that this years season will be a below average for Atlantic based Hurricanes and with only TD2 forming and not making much headway as it progresses into Ana, it seems with it already coming up to the height of the season that NOAA have got it spot on. The other issue is that the jetstream which carries the Hurricanes over the Mid-Atlantic has slipped south in response to the jetstream over the UK which has also done the same this year.

We may get the remants of one ex-Tropical Storm knocking on our doorstep this year, but unless any cold-core storms form (a rarity in itself) then I wont be too optimistic. Our best shot of any 50mph+ winds will be at the end of Autumn as the seasonal winds hit from Barocyclonic Lows.

I hate to be the bearer of bad news, especially as I was wanting to go out to the States myself this year and get inside a Hurricane if any hit the mainland..but theres always next year.

As for now theres TD2 approaching the Bahamas and as mentioned previously, possibly a CAT2 Hurricane on the cards next week in the Caribbean if Models are right.

[Iceberg]

Hopefully this shows TD2's current problem.

The black dot shows where the NHC think the centre is.

TD2 is being very badly sheared with convection strong, but still away from the core. This is certaintly not where I thought the centre was going by Infrared this morning.

The convection should wrap around , particularly if deep convection occurs on the far east of the current blob, but this is certaintly need to have our upgrade to Ana.

The candyfloss outflow from the current convection certainty proves that moisture and SST's are no issue for TD2, but the current lopsided structure, which if I think about it can probably only partly be accounted for by shear, but is also probably made worse by a poor LLCC towards the south and south east needs to improve.

[Lincs Observation]

The problem being is that with it being El Nino season all of the explosive formation that we've seen with Katrina/Gustav-like Hurricanes the past few years are limited to the far Western Gulf and Pacific Ocean.

NOAA themselves have concluded that this years season will be a below average for Atlantic based Hurricanes and with only TD2 forming and not making much headway as it progresses into Ana, it seems with it already coming up to the height of the season that NOAA have got it spot on. The other issue is that the jetstream which carries the Hurricanes over the Mid-Atlantic has slipped south in response to the jetstream over the UK which has also done the same this year.

We may get the remants of one ex-Tropical Storm knocking on our doorstep this year, but unless any cold-core storms form (a rarity in itself) then I wont be too optimistic. Our best shot of any 50mph+ winds will be at the end of Autumn as the seasonal winds hit from Barocyclonic Lows.

I hate to be the bearer of bad news, especially as I was wanting to go out to the States myself this year and get inside a Hurricane if any hit the mainland..but theres always next year.

As for now theres TD2 approaching the Bahamas and as mentioned previously, possibly a CAT2 Hurricane on the cards next week in the Caribbean if Models are right.

I take your points there, however if we do get a seizable deep low pressure remnant the fact that it will most likely be carried toward southern England because of a southern jet pattern maybe more of a concern. the North are normally used to deep low pressure/ex tropical remnants but the south of the Uk is the soft underbelly (re 1980's storms)

It has to be said that any wind over 60mph can have the potential to cause more trouble down south than north.

However if we are mid season for hurricanes then the chances are small at this time, But it would be fair to say as current climate conditions are in relation to the UK all it takes is One ex storm and the south have potential trouble.

Heres hoping not.

LO

Hopefully this shows TD2's current problem.

The black dot shows where the NHC think the centre is.

TD2 is being very badly sheared with convection strong, but still away from the core. This is certaintly not where I thought the centre was going by Infrared this morning.

The convection should wrap around , particularly if deep convection occurs on the far east of the current blob, but this is certaintly need to have our upgrade to Ana.

The candyfloss outflow from the current convection certainty proves that moisture and SST's are no issue for TD2, but the current lopsided structure, which if I think about it can probably only partly be accounted for by shear, but is also probably made worse by a poor LLCC towards the south and south east needs to improve.

I love the structure on this TS, on its west side has straight lines of cloud radiating out like the sun never seen that before, any idea of how thats possible?

LO

[kold weather]

Easterly shear is causing that look, its actually helping the outflow on the western side which is what the fanning is however its also preventing the convection from getting over the center.

These systems that have strong convection tend to only need a 12hrs break in the shear to strengthen into the mid-high end TS range, much like systems such as Barry from 2007, etc. In fact I suspect this probably is a TS already just the NHC are being a little conservative and waiting to see what happens.

Track seems to be getting closer to the NE Caribbean and interestingly the last 12 hours motion has seen a mean of about 265, so its actually lost a little bit of latitude recently.

[Iceberg]

Agree with that KW, She is still going SSW and travelling to the south of the NHC path, so this must be shifted southwards.

A tricky little one is TD 2, presentation still ragged, some convection near the centre but still devoid of any symatry.

Microwave pass shows some strong, convective enhanced wind speeds which I am not convinced of, but might just be enough to warrant an upgrade to 35Kt, personally I wouldn't buy this though.

[Iceberg]

Dvorak increased to 2.5 which equates to a TS 35Kts, So expect our first named system within the hour.

[Iceberg]

Just playing with images really ready for when something interesting happens, here's one that shows the sheared quality of the system and quikscat winds.

Even with a Dvorak of 2.5 it looks bl99dy awful sorry.

[londonsnow]

latest advisory suggests we are teetering towards the first named storm of the season. anyone know how we stand as far as late season starts go?

[Iceberg]

Pretty much what has been said already, Dvorak and quikscat point towards a TS, but it's just not believable given the shear and presentation.

TROPICAL DEPRESSION TWO SHOWS A CLASSICAL SHEAR PATTERN IN SATELLITE

IMAGERY THIS MORNING...WITH UPPER-LEVEL EASTERLY WINDS DISPLACING

THE CONVECTION TO THE WEST OF THE EXPOSED LOW-LEVEL CENTER.

SATELLITE INTENSITY ESTIMATES HAVE INCREASED TO 35 KT FROM TAFB AND

SAB. HOWEVER...A QUIKSCAT OVERPASS AT 0812Z DID NOT SHOW

TROPICAL-STORM-FORCE WIND VECTORS THAT LOOKED RELIABLE. THUS...THE

INITIAL INTENSITY REMAINS 30 KT FOR THIS ADVISORY. AT THIS TIME...

MOST OF THE LOW-LEVEL INFLOW INTO THE DEPRESSION SEEMS TO BE COMING

FROM THE NORTH...REPRESENTING POSSIBLY MORE STABLE AIR PASSING OVER

COOLER WATERS. THE FLOW ON THE SOUTH SIDE OF THE DEPRESSION IS

FEEDING INTO A LARGE DISTURBANCE BETWEEN THE CAPE VERDE ISLANDS AND

AFRICA.

[kold weather]

Shear seems to be if anything increasing over the last 2 hours, convection still hanging on in the western quadrant but its having a hard time holding onto that as the easterly shear increases. Conditions are marginal at the moment and I think the shear is going to have to ease off before we get a tropical storm from this system. Still I'm not sure I totally buying the NHC reasoning for holding it back at the time that advisory was forecasted, dvorak supported 35kts and there was some unflagged Quikscat wind barbs that also supported it. However since then its convection has been forced even further west and I now agree with the idea of 30kts, in truth it was probably wise of the NHC holding back even though IMO it was briefly upto TS strength.

Just need that easterly shear to ease off, as SST's are still high enough and there is clearly good surface convergence allowing the convection to blow up in the first. The next 24hrs are really key though for this system.

Edited August 12, 2009 by kold weather

[Cookie]

At long last we have ANA

[Somerset Squall]

At long last we have ANA

Not yet mate, still a TD in latest update:

TROPICAL DEPRESSION TWO DISCUSSION NUMBER 7

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009

500 PM AST WED AUG 12 2009

THE DEPRESSION APPEARED TO BE ON THE VERGE OF BECOMING A TROPICAL

STORM A FEW HOURS AGO...WITH SATELLITE INTENSITY ESTIMATES OF 35 KT

FROM TAFB AND SAB. HOWEVER...SINCE ABOUT 18Z THE CONVECTION HAS

DECREASED SIGNIFICANTLY AND HAS MOVED FARTHER AWAY FROM THE EXPOSED

LOW-LEVEL CENTER. BASED ON THIS...THE CYCLONE WILL REMAIN A 30 KT

DEPRESSION FOR THIS ADVISORY. THE CURRENT DOWNWARD TREND IN THE

CONVECTION MAY BE DUE TO AN INCREASE IN EASTERLY VERTICAL WIND

SHEAR...AND TO A DRY SLOT WRAPPING AROUND THE CIRCULATION NOTED IN

AMSR-E VAPOR IMAGERY NEAR 1534Z. ALSO...AS SEEN EARLIER...MOST OF

THE LOW-LEVEL INFLOW INTO THE DEPRESSION SEEMS TO BE COMING FROM

THE NORTH...REPRESENTING POSSIBLY MORE STABLE AIR PASSING OVER

COOLER WATERS. THE FLOW ON THE SOUTH SIDE OF THE DEPRESSION IS

FEEDING INTO A LARGE DISTURBANCE BETWEEN THE CAPE VERDE ISLANDS AND

AFRICA.

THE INITIAL MOTION IS 265/12. THE DEPRESSION IS ON THE SOUTH

SIDE OF A LARGE LOW/MID-LEVEL RIDGE...AND THE LARGE-SCALE MODELS

FORECAST THIS TO CONTINUE FOR THE NEXT TWO DAYS OR SO. AFTER THAT

TIME...THE MODELS FORECAST A WEAKNESS IN THE RIDGE THAT WOULD STEER

THE CYCLONE WEST-NORTHWESTWARD. THE TRACK MODEL GUIDANCE GENERALLY

AGREES WITH THIS SCENARIO...AND WHILE THE MODEL CLUSTERS SEEN

EARLIER HAVE MERGED THERE IS STILL A SIGNIFICANT SPREAD BY 120 HR.

THE GFS AND UKMET ARE ON THE SOUTH SIDE OF THE GUIDANCE ENVELOPE

SHOWING A MORE WESTERLY MOTION...WHILE THE HWRF AND BAMD ARE ON THE

NORTH SIDE SHOWING A NORTHWESTWARD MOTION BY 120 HR. OVERALL...THE

GUIDANCE ENVELOPE HAS AGAIN SHIFTED A LITTLE SOUTHWARD...AND SO HAS

THE NEW OFFICIAL FORECAST. THE NEW TRACK IS IN THE CENTER OF THE

GUIDANCE ENVELOPE IN BEST AGREEMENT WITH THE TVCN AND TVCC

CONSENSUS MODELS.

THE DEPRESSION REMAINS OVER SEA SURFACE TEMPERATURES NEAR 27C...WITH

SSTS ALONG THE FORECAST TRACK INCREASING TO 28C AFTER 72 HR. THE

LARGE-SCALE MODELS FORECAST THE DEPRESSION TO ENCOUNTER MODERATE

VERTICAL WIND SHEAR DURING THE FORECAST PERIOD...FIRST FROM THE

EAST AND LATER FROM THE SOUTHWEST. ALSO...WATER VAPOR IMAGERY

SHOWS VERY DRY AIR AT THE MID/UPPER-LEVELS TO THE NORTHWEST OF THE

DEPRESSION. THE LATTER TWO FACTORS SUGGEST THE SYSTEM MAY BE SLOW

TO STRENGTHEN...AND NONE OF THE INTENSITY GUIDANCE CURRENTLY

FORECASTS AN INTENSITY GREATER THAN 55 KT DURING THE FORECAST

PERIOD. BASED ON THIS...THE NEW INTENSITY FORECAST IS AN UPDATE OF

THE PREVIOUS FORECAST IN BEST AGREEMENT WITH THE SHIPS MODEL. IT

IS POSSIBLE THAT THE SYSTEM COULD WEAKEN TO A TROPICAL WAVE DURING

THE FORECAST PERIOD...AS FORECAST BY THE ECMWF...UKMET...AND GFS

MODELS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 12/2100Z 14.3N 35.0W 30 KT

12HR VT 13/0600Z 14.1N 36.7W 35 KT

24HR VT 13/1800Z 14.1N 38.9W 35 KT

36HR VT 14/0600Z 14.2N 41.3W 40 KT

48HR VT 14/1800Z 14.6N 43.7W 45 KT

72HR VT 15/1800Z 16.0N 49.5W 50 KT

96HR VT 16/1800Z 19.0N 56.0W 50 KT

120HR VT 17/1800Z 23.0N 62.0W 45 KT

$$

FORECASTER BEVEN