ATL: ISAAC - Post-Tropical - Discussion

[Shuriken]

Interesting stuff at noon today: a couple of shallow outflow boundaries have formed on the east side, and, contrary to what you might expect, will actually assist an intensification trend later this afternoon. How, you ask: answer, by lifting easterly inflow above the surface boundary layer, it can really rocket into the 700mb circulation friction-free.

[Aric Dunn]

well appears there is still a large area of light winds. which means there are still multiple vorts

[cycloneye]

...CENTER OF ISAAC NOW MOVING WEST-NORTHWESTWARD SOUTH OF PUERTO
RICO...


SUMMARY OF 200 PM AST...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...16.0N 66.4W
ABOUT 165 MI...255 KM S OF SAN JUAN PUERTO RICO
ABOUT 275 MI...445 KM SE OF SANTO DOMINGO DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES

[bucman1]

All indications are that Isaac center (dominent) is at 15.4 N 67 W moving WNW at 13 mph. This will also in all likelihood keep it offshore of Hispaniola and enter Cba near the South Central coast west of the Sierra Maestras. If this is the case than we are looking at a whole different picture for the Florida straits, Key and Southern Fla and SE Gulf.

What would that possibly do to the track?

[HurrMark]

I don't see this at 16N...this is much closer to 15N at this point, moving almost due west. Looking for the VDM...

[dizzyfish]

...CENTER OF ISAAC NOW MOVING WEST-NORTHWESTWARD SOUTH OF PUERTO
RICO...

Wasn't it moving WEST at the last update? So now the turn starts?

[TwisterFanatic]

Still not looking super hot today. Dry air still being sucked in.

[Zeno8]

I don't see this at 16N...this is much closer to 15N at this point, moving almost due west. Looking for the VDM...

yes even sub15N imo

[Aric Dunn]

I don't see this at 16N...this is much closer to 15N at this point, moving almost due west. Looking for the VDM...

yes even sub15N imo

unfortunately there is still multiple vorts and so the mean center of all them will be used and thats where the nhc has it.

[Aric Dunn]

so far one vort ( weak) at about 15.65N 66.45W per recon

[Shuriken]

Interesting stuff at noon today: a couple of shallow outflow boundaries have formed on the east side, and, contrary to what you might expect, will actually assist an intensification trend later this afternoon. How, you ask: answer, by lifting easterly inflow above the surface boundary layer, it can really rocket into the 700mb circulation friction-free.

[KWT]

Yep if it does still have struggles with its centers, then tracking the motion and its exact direction is abit of a fools game really!

[tropicwatch]

I don't see this at 16N...this is much closer to 15N at this point, moving almost due west. Looking for the VDM...

yes even sub15N imo

unfortunately there is still multiple vorts and so the mean center of all them will be used and thats where the nhc has it.

It will be nice once Isaac gets organized. Then it will take a lot of the guess work out of its position, movement and future track. Unfortunately that also means whatever is in its path, takes a hit from a stronger system.

[Shuriken]

unfortunately there is still multiple vorts and so the mean center of all them will be used and thats where the nhc has it.

I would argue that 16N is not a mean center (that would require another one at 17N to balance out the mid-level one at or below 15N).

LOCATION...16.0N 66.4W
ABOUT 165 MI...255 KM S OF SAN JUAN PUERTO RICO
ABOUT 275 MI...445 KM SE OF SANTO DOMINGO DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES

I'm not seeing any indication of WNW movement in the dominant mid-level center (which is still around 14.8-15Nish) at this time, nor do I see any indication that a northern outlier surface vortex is poised to take over dominance.

[BigB0882]

Yes, clearly focusing on a center and exact movement is a pointless game right now.

[Aric Dunn]

unfortunately there is still multiple vorts and so the mean center of all them will be used and thats where the nhc has it.

I would argue that 16N is not a mean center (that would require another one at 17N to balance out the mid-level one at or below 15N).

LOCATION...16.0N 66.4W
ABOUT 165 MI...255 KM S OF SAN JUAN PUERTO RICO
ABOUT 275 MI...445 KM SE OF SANTO DOMINGO DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES

I'm not seeing any indication of WNW movement in the dominant mid-level center (which is still around 14.8-15Nish) at this time, nor do I see any indication that a northern outlier surface vortex is poised to take over dominance.

[img]http://img269.imageshack.us/img269/3036/nonamed.png[/mg]

mid level is not at the surface thus you cannot compare the surface vort locations to the midlevel.

[Shuriken]

mid level is not at the surface thus you cannot compare the surface vort locations to the midlevel.

I know, but one should observe that Isaac's mid-level circulation has been its dominant axis for a day now, with a succession of short-lived weak surfaces vortexes orbiting north of it.

In the past, the NHC has made allowances for this type of storm behavior, and IMO should account for it again by center-fixing at the mid-level.

(Katrina in the Bahamas is a classic case of a southwest-inclined mid-level center dominating over a northwest-inclined surface feature. nascent-eyewall CBs gaining height steered different, and blew the pants off all the models predicting recurve up the east coast.)

[SouthDadeFish]

It looks like the mid level center is slowly creeping north towards the mean low level center. It appears they are trying to become stacked. I think this is one of the reasons the system has slowed down today as the circulation centers are tugging on each other. (Just my opinion)

[KWT]

Looks like recon has found a decent vortex at 15.5/6N, winds shoot up in the eastern part to 41kts at flight level, a tight looking wind field and importantly pressure shoots up 2-3mbs in a short distance.

Whether or not this is just another strong eddy I don't know, but it matches the best rotationg seen thus far.

[HurrMark]

Looks like recon has found a decent vortex at 15.5/6N, winds shoot up in the eastern part to 41kts at flight level, a tight looking wind field and importantly pressure shoots up 2-3mbs in a short distance.

Whether or not this is just another strong eddy I don't know, but it matches the best rotationg seen thus far.

That sounds about right...I would tag this at 15.3 or 15.4, but it's hard to tell just from satellite. Recon will tell all...