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Posted
  • Location: Liphook
  • Location: Liphook

    Our first tropical system of the season in the Atlantic has formed out of invest 91L. Deep convection blew up over it during the last 12hrs and whilst that has weakened a little since then it still has maintained the deep convection. Adjusted dvorak numbers are suggestive that Td1 is't far away from becoming tropical storm Ana. It is ridging the Gulf stream though temps are very marginal indeed shear is very relaxed above it with signs of outflow present backing this idea out. Whether it becomes Ana or not is uncertain but regardless of what it does Td1 should continue to race NE/ENE out into the Atlantic slowly losing its warm core properties it has developed over the last few days and weaken into an extra tropical system, being no threat to land.

    The big uncertainty is does this become the first named system of the season?

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    Posted
  • Location: Dorset
  • Location: Dorset

    I never thought it would develop either tbh. SST's are very very marginal, it's also only just topical IMO but a think a good call by NHC. I still don't think it will develop any further but a surprise TD.

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    Posted
  • Location: High Wycombe, Bucks
  • Location: High Wycombe, Bucks
    I never thought it would develop either tbh. SST's are very very marginal, it's also only just topical IMO but a think a good call by NHC. I still don't think it will develop any further but a surprise TD.

    I'd echo that exactly - how are the SSTs (or so I thought) warm enough to sustain TD development? Maybe just naivity, but what are the conditions, such as SSTs and shear, that have aided the formation in this case?

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset
    I'd echo that exactly - how are the SSTs (or so I thought) warm enough to sustain TD development? Maybe just naivity, but what are the conditions, such as SSTs and shear, that have aided the formation in this case?

    Waters are around 26C at the moment, which is just about warm enough to support a shallow system. TD 1 is moving over the narrow area of warmer waters associated with the Gulf Stream, but the system doesn't have much more time over these waters. Shear is currently low, and there are signs of improving outflow too. Basically the upper level environment is very favourable and this has allowed this small depression to form over marginally warm waters.

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    Posted
  • Location: High Wycombe, Bucks
  • Location: High Wycombe, Bucks
    Waters are around 26C at the moment, which is just about warm enough to support a shallow system. TD 1 is moving over the narrow area of warmer waters associated with the Gulf Stream, but the system doesn't have much more time over these waters. Shear is currently low, and there are signs of improving outflow too. Basically the upper level environment is very favourable and this has allowed this small depression to form over marginally warm waters.

    Sounds about right. I was assuming, given its location, that low SSTs would hamper this, but wasn't banking on the low shear...but like you said, not much legs once out of the Gulf Stream...

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset
    Sounds about right. I was assuming, given its location, that low SSTs would hamper this, but wasn't banking on the low shear...but like you said, not much legs once out of the Gulf Stream...

    Yes, this system is lucky to have moved over the Gulf Stream, waters elsewhere at this lattitude are still too cold for development, just watch over the next day or so this system falling apart or rapidly becoming extratropical as soon at it leaves the luxury of the Gulf Stream. Yes, shear seems to be very low in the area, a little surprising for me too, especially when the NHC was giving the system a "low" chance of development this morning. I think it caught them out a bit too!

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    Posted
  • Location: Dorset
  • Location: Dorset

    It's stayed further south than expected keeping it just in the Gulf Stream, this seems to have allowed some reasonable development in the last few hours. I think it will be extra tropical within maybe 12 hrs of leaving the GS.

    It does look good atm though with a slight chance of being Ana at the next update.

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset
    I've tryed to be positive as always but I don't think we're going to get a named system of out this.

    I agree Cookie. The depression is very close to the northern edge of the Gulf Stream now and will likely move over much colder waters today which will induce extratropical transition as Iceberg says. Convection has waned a little over the last few hours, and at the moment winds around the circulation are below tropical storm force. NHC no longer include strengthening to a TS in their latest forecast. Still, we could be proved wrong!

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset

    Latest satellite imagery clearly shows TD1 is now a very sheared system, with strong westerly shear now overwhelming the depression. Most of the remaining convection is lumped to the east of the entirely exposed LLC. NHC forecast ET to occur within the next 12 hours before the remnants are absorbed.

    post-1820-1243610846_thumb.jpg

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