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Atlantic Invest Thread 2009


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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

With the Atlantic hurricane season starting in June, discuss any invests (tagged disturbed areas suspect for TC development) that form here.

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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

It's too far south, unless it can gain lattitude then its not going to develop, however conditions north of the wave are not faviourable.

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  • 1 month later...
Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Well, we have the first invest of the year for the Atlantic now, 90L.

From NHC:

SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT AN AREA OF

DISTURBED WEATHER HAS FORMED OVER EASTERN CUBA...THE SOUTHEASTERN

BAHAMAS...AND THE ADJACENT WATERS. SLOW DEVELOPMENT OF THIS SYSTEM

IS POSSIBLE DURING THE NEXT DAY OR TWO AS IT MOVES GENERALLY

NORTHWARD AT 10 TO 15 MPH. AN AIR FORCE RESERVE HURRICANE HUNTER

AIRCRAFT WILL INVESTIGATE THE SYSTEM ON TUESDAY...IF NECESSARY.

THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM

BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

Waters are just about warm enough to support development, however, 90L has a big battle against shear (around 30kts of it). If this system does develop, I don't think it would have much potential for much strengthening. It's a big IF really this disturbance developing at all, conditions are less than favourable, but the models have been keen on developing this system. It could just end up being extratropical but a subtropical cyclone is not out of the question and maybe a minimal tropical system IF the shear eases.

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

90L is currently being absorbed by a larger, non-tropical low near Florida. Therefore, what small chance of development that 90L had of developing has diminished. The NHC do not expect the larger low to gain tropical or subtropical characteristics either.

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset
its officially gone :)early days

Absolutely, the season hasn't even officially started yet, an invest this early is fairly good going!

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

As Cookie has pointed out in the wave/disturbance thread, the low in the GOM has been re-classified as invest 90L. 90L has developed a warm core, however the LLC remains exposed due to moderate shear and dry air impinging on the system. 90L is moving north towards the gulf coast, so is running out of time for significant development. At risk of sounding like a stuck record, there is a small chance that a tropical depression may form before landfall but more than likely convection won't build over the LLC in time. Most of the convection is still displaced east of the centre indicating the system is sheared.

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Posted
  • Location: High Wycombe, Bucks
  • Location: High Wycombe, Bucks
As Cookie has pointed out in the wave/disturbance thread, the low in the GOM has been re-classified as invest 90L. 90L has developed a warm core, however the LLC remains exposed due to moderate shear and dry air impinging on the system. 90L is moving north towards the gulf coast, so is running out of time for significant development. At risk of sounding like a stuck record, there is a small chance that a tropical depression may form before landfall but more than likely convection won't build over the LLC in time. Most of the convection is still displaced east of the centre indicating the system is sheared.

Ello ello ello, what do we have here? Well, judging by the NHC Special Tropical Weather Outlook, it's in an unfavourable location conditions wise, and even if it did intensify, it's too close to land and will "landfall" before acquiring TD status. Well, that's about the Layman's of it all, I should probs have a look at the imagery and the nitty gritty of the system (at least it's got a warm core this time), but I've just got in from the pub after a long day so CBA. I don't reckon we'll get a fully fledged tropical system for quite a while yet, that's mainly a hunch, but I'm not sure Atlantic temps are warm enough for one thing (without having looked at them, I probs oughta). Still, we'll see.

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Posted
  • Location: Liphook
  • Location: Liphook

90L has really improved in presentation over night, big convective blowup just to the NE of the center plus there is an obvious circulation at lower levels. In the end its going to be upto the NHC as to whether they decide to upgrade it, but they upgraded Arthur when it was overland last year so its not impossible for 90L to organise right upto landfall and for the NHC to make the call then. It really is 50-50 as to whether they go for it or not, personally I'd upgrade it based on its imporved structure and the overnight tightening of a central LLC.

Sea surface temps look marginal but it needs to be remembered that this systems origins is from a pretty cold cored upper low and therefore upper air temps are likely still lower then normal, which means whilst SST's aren't amazing with a lower base to start with, they are good enough to keep the lapse rate up and allow convective development.

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Well, NHC didn't upgrade 90L, and the system is now movind inland. The LLC is still pretty well defined but should lose definition over land over the next day or so until dissipation.

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Posted
  • Location: Dorset
  • Location: Dorset

Invest 91L has was named a little while ago.

Tbh it looks pretty slim to amount to anything else, SST's are 25C or below and as it moves up the eastcoast it's likely to turn more and more extratropical.

Still an outside chance (less than 10%) that it might get something together which can take advantage of a passover of the Gulf Stream.

post-6326-1243430036_thumb.png

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Posted
  • Location: Dorset
  • Location: Dorset

I have to admit I think this one is a bit of a barmy decision, they openly admit that it's not tropical, it's over SST's of around 22C and has a cold upper centre with 500's of -20 or so.

This one would stuggle to become sub tropical.

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Latest outlook in 92L:

SATELLITE AND MICROWAVE OBSERVATIONS INDICATE THAT THE AREA OF LOW

PRESSURE LOCATED ABOUT 400 MILES NORTH-NORTHEAST OF THE AZORES

ISLANDS HAS ACQUIRED SOME TROPICAL CHARACTERISTICS. HOWEVER...THIS

SYSTEM IS MOVING TO THE NORTH-NORTHWEST AT ABOUT 10 MPH OVER

INCREASINGLY COOLER WATERS AND FURTHER DEVELOPMENT...IF

ANY...SHOULD BE SLOW TO OCCUR. THERE IS A LOW CHANCE...LESS THAN

30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL OR SUBTROPICAL

CYCLONE DURING THE NEXT 48 HOURS.

Convection is certainly increasing over the centre, giving the system a more tropical appearance. It may still be upgraded yet!

If it were to be upgraded surely it would be some kind of recorde for the area of formation for June?

post-1820-1243964300_thumb.jpg

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

92L is rapidly deepening, and now has sustained winds of 45kts. However, the system still does not meet the requirements of a subtropical or tropical storm classification. Models are forecast the deep low to move southeastwards towards Portugal. Waters get marginally warmer on the southeast track but still far below what is normally required to create a tropical cyclone. However, 92L is maintaining some thunderstorms near the centre, and there is a low risk of some hybrid development.

The image below shows just how far northeast this system is. It's not far from Spain and ourselves! Which is why, logically, TC development appears unlikely.

92L is located around 45N, 25W:

xxirnm7.GIF

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Posted
  • Location: Dorset
  • Location: Dorset

This looks like one of thoe lows to me that we discuss occasionally in the winter where lows develop, look a bit sub tropical in nature, but you examine why and think there is no way in the world, as you say Somerset this is really close to Ireland (as you can see from the SST diagram) and is further north than Spain.

SST are between 14-17C which isn't just marginal, its bizarre.

Looking at the latest sat loops from the floater there seems to be frontal convection associated with it.

Finally as to why it formed, my guess would be on the cold uppers brought down by NW flow as shown by this previous ECM.

That part of the Atlantic has been very cold, coming over the slightly warmer atlantic, with a warmer lower flow, add in a bit of Jet, with a marginal 40C temp difference and you get come activity. Almost a little cut off low with more convection near the centre due to it's size.

Maybe the NHC just wanted a little practise. But for the life of me I can't see the normal tropical drivers for this, nor sub-tropical really.

post-6326-1244009702_thumb.png

post-6326-1244009711_thumb.png

post-6326-1244009722_thumb.jpg

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Thanks for the explanation Iceberg, really explains the situation well.

Nice image there Kaja. Still shows a well organised system. It just isn't tropical despite it's appearance. Certainly an interesting little invest.

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