ATL: TROPICAL DEPRESSION BONNIE - DISCUSSION

[KWT]

As I said in the chat room I'm not sure the surface obs from PR would actually show any developing LLC...

The reason I say that is take a look at the MLC on radar, and note that westerly winds extend to just offshore PR then quickly flip to the easterlies...now I'd assume if there is a surface circulation it'd follow a similar presentation, esp if its simply a weak developing system. The fact the more established MLC doesn't extend onshore to PR, not sure whether the surface obs would be totally useful in this situation given the system is quite small in terms of where the tighter region of circulation is at least at the mid levels.

ps, I'm not saying I think there is an LLC by the way, just that the obs may not be totally useful if there is a small circulation developing thats all, I think there is nothing at the surface just yet even if the MLC is decent.

[tronbunny]

Based on the graphic posted by Vortmax1, I have to ask, does that arrow indicate that the Mid-Atlantic High is moving ENE?

[Dean4Storms]

If that MLC and associated convection continues overnight it has a shot at earlier than expected development. As mentioned the shear is there but it is not so strong to keep a closed LLC from forming IMO given deep convection.

[Blown Away]

Does it reach Florida? I know it's not yet and may not become an "it", but does the disturbance make it in this direction or get driven farther north?

Don't get me wrong I never rule out curving before SFL but the forecasted high seems to be enough to steer 97L west of Florida into the GOM. I still don't think 97L makes it past 85W.

[clfenwi]

00Z best track

AL, 97, 2010072000, , BEST, 0, 190N, 658W, 25, 1014

[Blown Away]

If that MLC and associated convection continues overnight it has a shot at earlier than expected development. As mentioned the shear is there but it is not so strong to keep a closed LLC from forming IMO given deep convection.

The best part is the MLC is improving by the minute and 97L is moving slowly so we will be able to watch it on the radar for a while!

[tolakram]

Latest Radar:

[KWT]

The convective coverage is decreasing a little though from radar, so whilst it is developing quite a decent MLC now, the fact convective coverage is going down isn't best thing for a developing system, though its probably related to the D-min.

Also tolakram that shows how the westerly midlevel winds are just clipping PR's northern coast, note the showers on the eastern tip are moving slowly WSW again as the system lifts a little to the north.

[LSU2001]

Blown Away, could you expound on your not west of 85 west prediction? Do you think there is going to be a weakness in the ridge that will allow this to ride around into the panhandle?
Thanks,
TIm

[Gustywind]

LATEST

[Aric Dunn]

just to re-state .. there is no evidence including but not limited to surface obs indicating any surface circ.. and actually obs show east winds blowing all the way through the system.... the radar presentation is a small MSC and it needs more time to develop.. dont expect much of anything tonight or tomorrow.. if convection continues to maintain ( it really needs to expand) then we should begin to see pressure falls and a possible LLC sometime after that.. right now no pressure falls and all we have is a boundary interaction and a very very very weak MLC ... but it has improved all day and needs to continue..

[Recurve]

ECHO TOPS



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I think the appearance of an "MLC" may be deceiving...more of a bow echo in convection.

[Blown Away]

00Z best track

AL, 97, 2010072000, , BEST, 0, 190N, 658W, 25, 1014

Right about there?

[Gustywind]

LATEST

Looks like two twaves in one given its amazing size and its convective activity. More showers are falling here in Guadeloupe.

[KWT]

just to re-state .. there is no evidence including but not limited to surface obs indicating any surface circ.. and actually obs show east winds blowing all the way through the system.... the radar presentation is a small MSC and it needs more time to develop.. dont expect much of anything tonight or tomorrow.. if convection continues to maintain ( it really needs to expand) then we should begin to see pressure falls and a possible LLC sometime after that.. right now no pressure falls and all we have is a boundary interaction and a very very very weak MLC ... but it has improved all day and needs to continue..

Yeah I do agree with this, though I think the MLC is actually not in bad knick, though of course there have been stronger ones in the past but its ok.

Probably looking at another 24-36hrs if it maintains its current presentation, the problem is as you allude to its losing convection steadily which is sure suggestive that its not quite there yet, probably related to a decrease in upper divergence.

[cycloneye]

Right about there?

BA,a tad to the left but otherwise is perfect.

[MiamiHurricanes10]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org. For Official Information please refer to the NHC and NWS products.

Latest Update

An area producing disorganized showers and thunderstorms lacking a low level circulation was designated invest 97L earlier today. Latest long-range radar loops from San Juan, Puerto Rico indicate that this system does however have a well-defined mid-level circulation. Also noted, this mid-level circulation is surrounded by a large amount of strong thunderstorms which in turn may help that mid-level circulation work its way down to the lower levels and then consequently to the surface. Surface pressures across Puerto Rico remain relatively high, in the 1012-1013mb threshold with no significant drops noted over the past 3 hours. Thunderstorm activity with this area remains enhanced by the diffluent flow aloft courtesy of a TUTT low, although the TUTT low is helping the system in developing convection, it is also hurting it by causing 20-30 knot shear throughout much of the northern, western, and eastern quadrants. This system will continue to move off towards the west or west-northwest over the next several days possibly bringing strong thunderstorm activity and gusty winds to Puerto Rico, Hispañiola, Cuba, the Bahamas, and Florida. Any development of 97L will likely take place once it passes to the west of the TUTT low in a couple of days once it is around the far western Bahamas region. At the moment I think there is a high chance that 97L will become the season's 3rd tropical depression. Interests aforementioned should monitor the progress of 97L very closely.


Figure 1. Latest water vapor satellite image of 97L. Note that some dry air is being entrained in the western and northern quadrant of 97L.

MiamiHurricanes10

[Blown Away]

Blown Away, could you expound on your not west of 85 west prediction? Do you think there is going to be a weakness in the ridge that will allow this to ride around into the panhandle?
Thanks,
TIm

JMHO only, I believe 97L has been moving slower than predicted and the ridge that will be building in will begin to break down late this week and I don't think 97L will be past 85W before it begins to recurve. I also go with climatology that suggests 97L won't shoot west across the GOM. Just my amateur opinion!

[Nimbus]

The system is drying up quite a bit tonight, maybe the mid level circulation is displaced east?

[LSU2001]

Cool thanks a bunch for your response,
Tim