SIO: INVEST 91S


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Extratropical94
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SIO: INVEST 91S

#1 Postby Extratropical94 » Thu Sep 07, 2017 3:45 pm

91S INVEST 170907 1800 4.0S 88.0E SHEM 15 NA

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Re: SIO: INVEST 91S

#2 Postby BYG Jacob » Fri Sep 08, 2017 6:12 pm

For the life of me, I cannot find a windshear map for the Indian Ocean, so I'll just assume its minimal, SSTs are warm, and there doesn't appear to be any real dry air. This has a decent chance of developing.
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Re: SIO: INVEST 91S

#3 Postby Extratropical94 » Fri Sep 08, 2017 6:22 pm

The Meteo France meteorologists aren't too confident about this invest developing into anything big. This is from their 12Z tropical weather discussion:

"Deep convection has evolved over the last 24 hours to concentrate near 7°S between 80 and 90°E
on the southern edge of the TPE. An elongated clockwise circulation can be estimated within this
trough and centered approximately at 5.4S / 83.5E. The buoy located at 7.6°S / 83.3E at 0700UTC
allows to estimate a minimum pressure of 1008 hPa.
In the next hours, the low-level circulation could intensify but rapidly due to a persistent strong
vertical windshear
and mid-level conditions less and less humid, the numerical models available do
not deepen this circulation during the next few days."

http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_201709081000.pdf

The Australian wind shear map barely covers the area, but it's probably enough to see the unfavorable conditions.

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Re: SIO: INVEST 91S

#4 Postby BYG Jacob » Fri Sep 08, 2017 9:25 pm

Extratropical94 wrote:The Meteo France meteorologists aren't too confident about this invest developing into anything big. This is from their 12Z tropical weather discussion:

"Deep convection has evolved over the last 24 hours to concentrate near 7°S between 80 and 90°E
on the southern edge of the TPE. An elongated clockwise circulation can be estimated within this
trough and centered approximately at 5.4S / 83.5E. The buoy located at 7.6°S / 83.3E at 0700UTC
allows to estimate a minimum pressure of 1008 hPa.
In the next hours, the low-level circulation could intensify but rapidly due to a persistent strong
vertical windshear
and mid-level conditions less and less humid, the numerical models available do
not deepen this circulation during the next few days."

http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_201709081000.pdf

The Australian wind shear map barely covers the area, but it's probably enough to see the unfavorable conditions.

Image

Yeah, in that case it probably doesn't develop unless it gets north quickly.
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Re: SIO: INVEST 91S

#5 Postby BYG Jacob » Sun Sep 10, 2017 7:09 pm

Extratropical94 wrote:91S INVEST 170907 1800 4.0S 88.0E SHEM 15 NA

Image

Any updates on this? I tried looking, but couldn't find anything. I looked at water vapor earlier and it looks like its getting better organized.
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Re: SIO: INVEST 91S

#6 Postby Extratropical94 » Mon Sep 11, 2017 2:07 am

This is from yesterday:

Since a few days, a weak clockwise circulation is developing within a Near Equatorial Trough branch East of 70E. At 0854Z, a SSMI swath reveals a low level circulation center (LLCC) near 9.3S/84.4E, consistently with the visible sat. animations. This Micro-Wave image shows several clear but scattered curved bandings, suggesting that the circulation is well established within the low troposhere. This morning ASCAT swaths show winds of 15kt around the LLCC, reaching 20 to 25kt in the Southern semi-circle because of the pressure gradient. The SLP is estimated at 1005hPa at the center.
Over the next days, the equatorward low level convergence should remain weak, which will really impede the development of the low. The upper shear should weaken from tomorrow, as the system drifts Southward under the axis of the Near Equatorial Ridge. But a mid-level shear should take over and the underlying waters are still relatively cool South of 15S at this time of the year (no more than 23°C). Within this rather unconducive environment, the low is forecast to maintain until Tuesday and then begin to slowly weaken, as the poleward convergence also disappears with the Eastward shift of the high pressure cell. The available guidance is in good agreement with this scenario.
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Re: SIO: INVEST 91S

#7 Postby BYG Jacob » Mon Sep 11, 2017 6:44 am

Extratropical94 wrote:This is from yesterday:

Since a few days, a weak clockwise circulation is developing within a Near Equatorial Trough branch East of 70E. At 0854Z, a SSMI swath reveals a low level circulation center (LLCC) near 9.3S/84.4E, consistently with the visible sat. animations. This Micro-Wave image shows several clear but scattered curved bandings, suggesting that the circulation is well established within the low troposhere. This morning ASCAT swaths show winds of 15kt around the LLCC, reaching 20 to 25kt in the Southern semi-circle because of the pressure gradient. The SLP is estimated at 1005hPa at the center.
Over the next days, the equatorward low level convergence should remain weak, which will really impede the development of the low. The upper shear should weaken from tomorrow, as the system drifts Southward under the axis of the Near Equatorial Ridge. But a mid-level shear should take over and the underlying waters are still relatively cool South of 15S at this time of the year (no more than 23°C). Within this rather unconducive environment, the low is forecast to maintain until Tuesday and then begin to slowly weaken, as the poleward convergence also disappears with the Eastward shift of the high pressure cell. The available guidance is in good agreement with this scenario.

Alright, looks like we can stick a fork in this one.
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