ATL: OPHELIA - Extratropical - Discussion

[Vince_and_Grace_fan]

Convection is increasing again, and somewhat deeper than earlier, so it may be classifiable now. The ASCAT pass at 0:24 UTC showed some unflagged 35-40 kt vectors and a separated, compact center, so it possible a weak tropical storm now.

[Vince_and_Grace_fan]

Surpisingly the HWRF and HMON became very bullish and now both strengthen the cyclone into a hurricane in the second part of the next week.

Maybe the GEM will be right as consistently shows this since 2 days?

[Vince_and_Grace_fan]

Fresh ASCAT, it shows some 35+ kt vectors north of the center which are not unflagged.

[CyclonicFury]

If this had persistent convection around its center it would have been Ophelia.

[CrazyC83]

Stranger things have happened...remember Grace 2009, or Vince 2005?

[CrazyC83]

If this was close to land, I think we would have Tropical Storm Ophelia right now. But in the land of only fish, there is no need to force an upgrade on a marginal situation.

[CyclonicFury]

The Euro and GFS no longer kill this quickly. The Euro actually strengthens it between 48 and 96 hours, and at 96 hours it shows 91L down to 1006 mb. The GFS is also trending stronger in the medium range. I think 91L has more time to develop than indicated in the NHC's TWOs, conditions don't really appear to change much based on the latest SHIPS guidance.

[Kazmit]

Still 70%/70%. Not very far off from being named, but would probably be very short-lived if it were named anyway.

[Sciencerocks]

Being sheared or far away isn't good scientific reasoning not to upgrade. Upgrade Cindy that never had convection over its LLC and not something else isn't dealing with science. Science is based on concise theory and fact.

[Dean_175]

Being sheared or far away isn't good scientific reasoning not to upgrade. Upgrade Cindy that never had convection over its LLC and not something else isn't dealing with science. Science is based on concise theory and fact.

Yeah but convection is very sparse. Still not well defined enough to upgrade-though it has had more convection near the LLC for the past few hours.

Convection is not deep nor organized enough for it to be classified as tropical, and it doesn't really have the presentation of a subtropical system either. It could still go either way, or not develop at all.

[CyclonicFury]

Convection beginning to increase in the past few frames. In my opinion this should be Ophelia now, but NHC is likely waiting for convective persistence.

[Dean_175]

If they don't declare it at 2am, they will likely reduce the probability of formation.

It has a shallow warm core and is producing around 40-45kt in the NW quadrant-- the shower activity is just not well defined-though may have become slightly more organized tonight. It is a system that is very borderline.

EDIT: In the past 3 -5 hours, convection has become much better defined. I think we could see Tropical Storm Ophelia at the next update at 8am--and I do think tropical vs. subtropical given the satellite presentation (possibly showing the beginning of a CDO), distance from center of max winds, and lack of a well defined upper level low, even though thermal wind analysis using (the previous) GFS run shows shallow warm core.

[EquusStorm]

Yup... this latest convective burst could be the tipping point for this. I imagine they would make sure it lasts for a few hours before pulling the trigger, but the 2am TWO should at least make note of this recent improvement. That surface low has been quite vigorous and persistent, and it'd be nice to see it get a name if it can hold on, haha. I'm quite fond of these late season, far-flung baroclinic transition sub/tropical cyclones, myself.

[Dean_175]

If they don't declare it at 2am, they will likely reduce the probability of formation.

It has a shallow warm core and is producing around 40-45kt in the NW quadrant-- the shower activity is just not well defined-though may have become slightly more organized tonight. It is a system that is very borderline.

EDIT: In the past 3 -5 hours, convection has become much better defined. I think we could see Tropical Storm Ophelia at the next update at 8am--and I do think tropical vs. subtropical given the satellite presentation (possibly showing the beginning of a CDO), distance from center of max winds, and lack of a well defined upper level low, even though thermal wind analysis using (the previous) GFS run shows shallow warm core.

Actually they increased to 80 percent.


It sounds like they are waiting for the convection to continue before upgrading.

well-defined low pressure system located over the subtropical
Atlantic Ocean about 800 miles southwest of the Azores is producing
winds to near gale force. Although the low is being affected by
strong upper-level winds, shower and thunderstorm activity has been
persisting near and to the east of the center during the past
several hours. If this activity continues, a tropical or
subtropical cyclone could form later today. The low is forecast
to drift northward today and then move slowly toward the
east-southeast through the middle of the week. Additional
information on this system can be found in high seas forecasts
issued by the National Weather Service.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...80 percent.

[Dean_175]

Yes^^

The very latest GFS run (00Z 10-09) has it sticking around even longer than the last. Showing a path that would be very interesting (if it verifies)- GFS moves it in a full and slow circle, towards the SE , and then slowly to the NW again. That would depend on what happens with it's interaction with a (model) frontal system that would influence that region of the Atlantic late in the week---the old GFS run has it possibly sheared apart and degenerating into an open trough, the new run has it interacting with it- but then pushed south again by the Azores high and re-intensifying.

[bob rulz]

Would be surprised if this wasn't Ophelia at 5am. Looks better than it has at any point.

[EquusStorm]

That convective burst appears to not only be a good bit more persistent than the last few, but now almost directly over the LLC, with additional development to the SW on the last frame. It honestly looks like a very compact little CDO, with a near circular appearance and cyclonic turning becoming evident. It should meet the criterion for a classified system if the current convective coverage persists until the next advisory package time at 5AM. Upper level winds have certainly increased but on the shear map and from what I can see on satellite, they aren't explicitly prohibitive of this right now.

[Dean_175]

That convective burst appears to not only be a good bit more persistent than the last few, but now almost directly over the LLC, with additional development to the SW on the last frame. It honestly looks like a very compact little CDO, with a near circular appearance and cyclonic turning becoming evident. Despite the strong upper level winds now, it should meet the criterion for a classified system if the current convective coverage persists until the next advisory package time at 5AM.

Yes,

and does anyone have any idea what actually caused the convection to suddenly flare over the LLC?

The SSD has finally listed it on their tropical products page -- with a Dvorak T number....it is considered a T1.0 (normally would indicate winds of 30mph or lower--but scatterometry shows winds of 40-45kt)---but this is due to it being the first given T number for the system.

This (Dvorak classification) along with the statement below indicates they are thinking it is tropical vs subtropical.

"REMARKS...INVEST HAS TAKEN ON A TROPICAL APPEARANCE AND THE PREVIOUSLY
EXPOSED WELL DEFINED CENTER HAS MOVED UNDERNEATH THE CONVECTION. DT OF
2.0 IS BASED ON TIGHTLY DEFINED LL CLOUD LINES AND A CENTER UNDERNEATH A
SMALL COLD OVERCAST. MET IS 1.5 AND PT IS 2.0. FT IS BASED ON CONSTRAINTS
THAT LIMIT THE FT OF THE FIRST TROPICAL CLASSIFICATION TO A 1.0. "

[talkon]

The latest BT now has Seventeen, but the strength is reduced to 30 knots and it's still a LO.

AL, 17, 2017100906, , BEST, 0, 309N, 400W, 30, 1008, LO, 34, NEQ, 0, 0, 0, 0, 1015, 180, 30, 0, 0, L, 0, , 0, 0, SEVENTEEN, M, 0, , 0, 0, 0, 0, genesis-num, 036, TRANSITIONED, alC12017 to al172017,

[Sciencerocks]

With ascat showing 35-40 knt winds...I'd say that is the intensity they should set it.