ATL: BERTHA - Post-Tropical - Discussion

[NDG]

Some of the strongest winds reported:

Conditions at: TIST (ST THOMAS (KING), VI) observed 1600 UTC 02 August 2014
Temperature: 26.0°C (79°F)
Dewpoint: missing
Pressure (altimeter): 30.01 inches Hg (1016.3 mb)
Winds: from the SE (140 degrees) at 28 MPH (24 knots; 12.5 m/s)
gusting to 43 MPH (37 knots; 19.2 m/s)
Visibility: 2.00 miles (3.22 km)
Ceiling: 2200 feet AGL
Clouds: scattered clouds at 1700 feet AGL
broken clouds at 2200 feet AGL
overcast cloud deck at 4100 feet AGL
Weather: RA (rain)
METAR text: TIST 021553Z 16027G38KT 3SM BR SCT017 BKN026 OVC060 27/ A3000 RMK AO2 PK WND 16038/1546 TWR VIS 10 RAE25B45E53 SLP161 P0004 T0267
Conditions at: TIST (ST THOMAS (KING), VI) observed 1553 UTC 02 August 2014
Temperature: 26.7°C (80°F)
Dewpoint: missing
Pressure (altimeter): 30.00 inches Hg (1016.0 mb)
[Sea-level pressure: 1016.1 mb]
Winds: from the SSE (160 degrees) at 31 MPH (27 knots; 14.0 m/s)
gusting to 44 MPH (38 knots; 19.8 m/s)
Visibility: 3 miles (5 km)
Ceiling: 2600 feet AGL
Clouds: scattered clouds at 1700 feet AGL
broken clouds at 2600 feet AGL
overcast cloud deck at 6000 feet AGL

[Hammy]

NHC says this has a closed circulation? Wow. Yawn. NEXT.

Actually the advisory clearly states that they're having a difficult time finding one.

[NDG]

What's been happening with Bertha is that it keeps getting decoupled every time it's weak LLC starts growing in height by shear, just like yesterday morning it happened this morning. Over all it still has a strong vorticity and it will not degenerate into a wave.

[cycloneye]

Nothing resembeling a closed LLC.

[Frank2]

I had to double check the METAR terminology in the St. Thomas ob - 3SM BR means visibilty 3 statute miles in mist...

[pgoss11]

2 PM Advisory still saying it's a tropical storm. I'm very surprised by this as it's very hard to even see the center even with the exact coordinates.

[Sanibel]

The SCAT is notorious for missing weak systems in the Zone.


The tiny displaced center burst is over Puerto Rico dumping rain.

[NDG]

Very interesting, all of reporting stations along the southern coast of PR winds have switched from the south, LLC could be reforming over Mona's pass or just north of it later tonight.

[Hammy]

If you look -very- closely you can see a faint westerly component to the low clouds on high-resolution visible just east of the Dominican Republic coast.

[Blown Away]

If you look -very- closely you can see a faint westerly component to the low clouds on high-resolution visible just east of the Dominican Republic coast.

Yes, I see that... Not sure if it's part of the circulation or some vortex shooting West...

[AJC3]

If you look -very- closely you can see a faint westerly component to the low clouds on high-resolution visible just east of the Dominican Republic coast.

I don't see it at all anymore.

I looked at high res visible imagery overlaid on a 1 degree LALO grid very closely, and observed the motion of low cloud elements around eastern Hispanola and to the south and southwest of PR as they've peeked out from behind the convective debris. There is no longer any semblance of any westerly component to the motion of these clouds. The best you have now is a due south motion in the area south of PR. Thus, it appears that this is (and likely has been for some time) an open t-wave.

That having been said, with the system slowing it's forward speed and beginning to turn over the next two days, that process, in and of itself, will increase the likelihood of a fairly quick return of some ground-relative westerly component to the wind flow - not to mention the improvement in organization that will occur as the system moves by Hispanola and into an increasingly favorable large scale environment.

Thus, even though it appears to have opened up, I feel pretty strongly that this is temporary.

[SeGaBob]

Saw this in the forecast discussion for my area today...


.SHORT TERM /SUNDAY THROUGH TUESDAY/...
00Z/02 GFS...00Z/02 NAM AND 12Z/01 ECWMF ARE IN REASONABLE AGREEMENT
THAT A BROAD AND PERSISTENT DEEP-LAYERED TROUGH WILL PREVAIL OVER
THE EASTERN UNITED STATES...WITH A DEEP SUB-TROPICAL MOISTURE
REMAINING OVER THE AREA WITH PWATS REMAINING NEAR OR GREATER THAN 2
INCHES...NEAR THE 75TH PERCENTILE FOR EARLY AUGUST. DISCOUNTED 00Z
NAM SOLUTION SURFACE FEATURES WHICH WEAKENED BERTHA AND INTENSIFIED
AN AREA OF LOW PRESSURE NORTHWEST OF BERTHA SUNDAY NIGHT OFF THE
EAST COAST OF FLORIDA. ALTHOUGH SOME OF THE OTHER MODELS HINT AT A
WEAK AREA OF LOW PRESSURE OFF THE EAST COAST OF FLORIDA/GEORGIA AT
THE SAME TIME...DO NOT FEEL THAT THE NAM SOLUTION IS REASONABLE AND
IGNORED IT.

[Hammy]

I'm thinking Gabrielle last year may be a good comparison the way things are going now, and interestingly in the same location, and it seems pretty much a given that it will degenerate to a wave for at least a day or two then reform further north.

I'm wondering as well, given the storm has gone a bit on the eastern side of the model envelope (as opposed to going over Hispaniola) if this could mean a stronger than expected system down the road as far as later model runs go.

[cycloneye]

Plane is going west north of DR trying to find a LLC.

[pgoss11]

What is everyone thinking? Downgrade at 5PM advisory?

[SeGaBob]

I'm guessing they'll leave it up one more advisory for continuity and take it down at 11pm if there is still no LLC.

[tolakram]

live visible: http://wwwghcc.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20CONUS&lat=18&lon=-65&info=vis&zoom=1&width=1000&height=800&quality=95&type=Animation&palette=ir1.pal&numframes=30

It certainly looks to these untrained eyes like something is forming just W/NW of PR. Speed up this 30 frame loop.

[tolakram]

saved radar loop

[Alyono]

near NW Puerto Rico is where I am monitoring

[wxman57]

2 PM Advisory still saying it's a tropical storm. I'm very surprised by this as it's very hard to even see the center even with the exact coordinates.

The NHC won't likely downgrade a system that is impacting land. Clearly, though, Bertha is a tropical wave.