ATL: ISAAC - Post-Tropical - Discussion

[tolakram]

These large pictures are from ftp://goes.gsfc.nasa.gov/pub/goeseast/overview2/vis/

Note not all the images contain the entire area.



Large section of areas in front and behind (96L) 94L: http://img803.imageshack.us/img803/3777/zzoverview1.jpg

[gatorcane]

well all we need and have needed for the pasy 24 hours is convection. its rather strange there is none. plenty of moisture sal is not bad. May just need to slow down some.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Aric there is alot of SAL surrounding the system still looking at the latest VIS loops. That is still keeping this system at check. SSTs start to warm a good amount a bit further west. Plus I notice that the ULL to the NW is pushing SW and clearing out the SAL. Conditions do look good for this thing to take off west of 65W, as long it is stays away from land.

[Gustywind]

20/1145 UTC 15.7N 44.8W TOO WEAK 94L
20/0545 UTC 14.9N 42.1W TOO WEAK 94L

[Weatherboy1]

It really is all just about convection over the center at this point. Everything else is in place for a TD to be declared -- IF we finally get some storms firing over the center and building, I think the NHC will give this puppy a number. I also think that will happen very soon as the low is progressing over warmer and warmer waters with each move west. It's also worth noting that SHIPS (and now the HWRF in its last run) are showing some decent intensification down the road.

[tolakram]

Looking here: http://rammb.cira.colostate.edu/product ... r=AL942012



Center scooting away from convection, as per most systems in this area.

[Aric Dunn]

well all we need and have needed for the pasy 24 hours is convection. its rather strange there is none. plenty of moisture sal is not bad. May just need to slow down some.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Aric there is alot of SAL surrounding the system still looking at the latest VIS loops. That is still keeping this system at check. SSTs start to warm a good amount a bit further west. Plus I notice that the ULL to the NW is pushing SW and clearing out the SAL. Conditions do look good for this thing to take off west of 65W, as long it is stays away from land.

[img]http://img706.imageshack.us/img706/3678/visl820.jpg[/mg]

yes there is sal around but it is less than it has been for the last few weeks by far and around 94l is lower than with the two previous systems it well away from the center.

[Stormlover2012]

this is going to be a slow process

[Weatherboy1]

Aric - Good point about the SAL issue. I think that's why we're seeing more intermittent convection firing with 94 than the earlier systems that came through this area. As SSTs warm up, and the SAL issue becomes less of a problem, I think this system could fire up pretty quickly, especially if it stays in the NE Caribbean far enough away from South America. Definitely keeping an eye on this one, especially now that some of the intensity guidance (SHIPS, HWRF) is more bullish on development late in the period.

[cycloneye]

Let's see if bouy 41041 that 94L will move thru soon provides some valuable information later today.

http://www.ndbc.noaa.gov/station_page.php?station=41041

The center of 94L was 80 miles to the north-northeast of buoy 41041 at 9 AM AST and the buoy recorded SSW winds of 16 mph. It'll be interesting to see if the winds go W at 10 am AST.

[Blown Away]

Center scooting away from convection, as per most systems in this area.

Yes, but over the past few hours the center went from mostly exposed to being slightly covered by the convection ball to the SE. We will have to see over the next few hours if this recent convection is the beginning of Isaac or maybe Joyce!

[wxman57]

There isn't any question of an LLC. The issue has been lack of deep convection persisting near the LLC. It needs that convection near the center to persist for a number of hours before the NHC will upgrade it. Could be this afternoon.

[cycloneye]

There isn't any question of an LLC. The issue has been lack of deep convection persisting near the LLC. It needs that convection near the center to persist for a number of hours before the NHC will upgrade it. Could be this afternoon.

You think that even if the LLC is not fully under the convection,they will upgrade?

[OuterBanker]

BTW, it has slowed slightly. 20 to 25 yesterday, 17 to 22 today.

[wxman57]

There isn't any question of an LLC. The issue has been lack of deep convection persisting near the LLC. It needs that convection near the center to persist for a number of hours before the NHC will upgrade it. Could be this afternoon.

You think that even if the LLC is not fully under the convection,they will upgrade?

I wouldn't think they'd upgrade without convection over the center.

[HurrMark]

BTW, it has slowed slightly. 20 to 25 yesterday, 17 to 22 today.

Nope, that's in knots...speed is about the same.

1. A TROPICAL WAVE AND A LOW PRESSURE AREA LOCATED ABOUT 1100 MILES
EAST OF THE LESSER ANTILLES CONTINUES TO PRODUCE SHOWER AND
THUNDERSTORM ACTIVITY. ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR A
TROPICAL DEPRESSION TO FORM DURING THE NEXT DAY OR SO AS THIS LARGE
DISTURBANCE MOVES WESTWARD AT 20 TO 25 MPH. THIS SYSTEM HAS A HIGH
CHANCE...80 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS. INTERESTS IN THE LESSER ANTILLES SHOULD MONITOR THE
PROGRESS OF THIS SYSTEM.

[wxman57]

Note that I just measured a 3-hr speed of that LLC at 24.4kts. From 15.6N/44.16W at 1015Z to 15.7N/45.4W at 1315Z. That's 73.3NM in 3 hrs, or 24.4kts.

No question is moving quite fast now. That's why it's out-running the convection. Seven sped up to over 30 kts in 3-6hr movements as it approached the Lesser Antilles. That's what destroyed the LLC.

[TheBurn]

13:00 UTC RGB / Natural Color

[SouthDadeFish]

Winds at buoy 41041 are out of the SW at about 10 knots:

http://www.wunderground.com/MAR/buoy/41041.html

Current Weather/Wave Observations
Air Temperature: 76° F
Humidity: 100
Wind direction (W Dir): SW (215 - 224 Degrees)
Wind Speed (W Spd): 9.7 kts (11.2 mph)
Wind Gust (W Spd): 11.7 kts (13.4 mph)
Dominant Wave Period (DWP): 8 sec
Dominant Wave Height (DWH): 5.58 ft
Dominant Wave Range (DWR): exactly 5.6 ft
Wind Wave Period (WWP): 4 sec
Wind Wave Height (WWH): 1.64 ft
Wind Wave Range (WWR): 0.82 - 2.46 ft
Wave Swell Period (WSP): 8 sec
Wave Swell Height (WSH): 4.92 ft
Wave Swell Range (WSR): 4.10 - 5.74 ft
Atmospheric Pressure (AP): 29.88 in
Updated: 1:50 PM GMT on August 20, 2012

[canes04]

The overall size of this system is amazing. It will need to slow down to develop further.

[Bocadude85]

There isn't any question of an LLC. The issue has been lack of deep convection persisting near the LLC. It needs that convection near the center to persist for a number of hours before the NHC will upgrade it. Could be this afternoon.

What are your thoughts on this system wxman57? track and intensity?