ATL : INVEST 90L - DISCUSSION

[ConvergenceZone]

Judging from the early models they are expecting a TUTT to pull 90l north. That would be great if it got taken out by wind shear like Bonnie did.

Its hard to say where this area will roll up and decouple from the ITCZ. The Sooner it spins up the more time it will have effected by the deeper steering of the TUTT. Might be a fish but we often see early model runs that are too far right with the track.

The chance of a bonnie situation happening again, would be extremely slim. I can't remember the last time we had an ULL following along in close proximity in the same direction and speed as the tropical disturbance was. That doesn't happen very often.

[KWT]

Who knows BA, I don't have much faith in those sorts of forecasts this far out anyway to be honest with you. The ECM does dive the ULL SW towards where the wave would be but its too far out to have even small confidence on that.

Ivanhater, I wonder what those 10 dates where..hmmm

[cycloneye]

HPC's take

FOR THE TROPICS...A QUARTET OF SYSTEMS ARE FORECAST...WITH TWO IN
THE TROPICAL ATLANTIC AND TWO IN THE NORTHEAST PACIFIC. FOR YET
ANOTHER DAY...TPC AND HPC POINTS WERE QUITE SIMILAR AND A
COMPROMISE WAS AGREED TO WHERE MODERATE DIFFERENCES WERE SEEN.
THE CPC ANALOG COMPOSITE FOR THE END OF THE MEDIUM RANGE PERIOD
LINKS TO TEN DATES AS THE BEST MATCH TO THE EXPECTED PATTERN...AND
OF THOSE DATES...SIX CONTAINED A TROPICAL CYCLONE IN THE ATLANTIC
BASIN...FOUR OF WHICH WERE CENTERED IN THE WESTERN SUBTROPICAL
ATLANTIC WHERE THE WAVE NEAR 17 WEST LONGITUDE THIS MORNING IS
EXPECTED TO END UP BY NEXT THURSDAY.

ROTH/HEDGE

That may suggest the wave just of the African Coast now may be the dominant feature. (Discuss about that wave on the thread at Talking Tropics)

[KWT]

I'd imagine that will be the one that takes over but I'd imagine given the expected synoptic evolution they will probably keep 90L if they do decide to merge, because this one isn't going anywhere fast.

The fact this one has any turning at all though does make things more complicated, esp if the wave tries to form itself as well...no wonder its a complex evolution according to the models!

[Aric Dunn]

the thing here is that the two systems are already interacting and should continue too..

[Ivanhater]

[cycloneye]

Good image loop Ivan of the two features.

[HURAKAN]

Sit and wait! Nothing happening here soon.

[Cuber]

Hey peeps i'm back after 4 days with big troubles with my Internet...
I'm suprised to see that we have this pertubed area pretty south in latitude. Something to keep an eye on during the next couple of days...

Gusty ... be sure to stay safe ... you'll probalby experience this (and anything else this season) sooner than most of us

[Dean4Storms]

Just came to a halt, strange with it so close to the ITCZ. Clearly looks like 90L is on its way to becoming a TC!!

[KWT]

Yeah its slowing right down with convection just flaring up around it, just as the models and Aric D has called for all day.

Not likely to see much development till the wave comes along, after that and at least for the short term conditions look decent enough.

[cycloneye]

Look how weak is the steering in the ITCZ area. Once the wave behind kicks it, it will start to move more faster.

[SouthFloridawx]

Sit and wait! Nothing happening here soon.

Now you've ensured something happening...

[KWT]

Yeah Cycloneye that really does show why the models barely shift the convection, plus its just an ITCZ region of convection, the wave behind it will be what sets-up the extra spark from the looks of things.

[wxman57]

I think this one may have a fair shot at developing. I notice that convection is on the decrease over the past 6 hours or so, though. If you look at a WV loop you can see why. Earlier today, it was near the southeast side of a weak upper-level low center. But as the day progressed, it moved past the axis of the low center and out of the more favorable lift environment. The key over the next 24 hours is whether or not convection redevelops, perhaps with the addition of more energy from the east as some models suggest.

Could be a NE Caribbean threat around next Wednesday and a southeast U.S. threat the following weekend. Models do indicate a slowing of its forward speed near the Bahamas. Lots of uncertainty that far out.

[KWT]

Yeah I also agree with that Wxman57...the GFDL/HWRF is going mental in terms of strength with both models suggesting a major hurricane, and both models track NW but I think its way too agressive....

Wouldn't surprise me to see this one ultimatly being a Carolinas threat but we will see, long way to go yet.

The wave is key to helping to fire up the convection but I personally don't think it gets going too quickly, hence why I'm throwing out the GFDL/HWRF combo.

[cycloneye]

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT THU JUL 29 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND A FEW THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE ARE
MOVING ACROSS THE WINDWARD ISLANDS. THERE ARE NO SIGNS OF
ORGANIZATION AT THIS TIME...AND ANY DEVELOPMENT OF THIS SYSTEM
IS EXPECTED TO BE SLOW TO OCCUR AS IT MOVES GENERALLY WESTWARD AT
10 TO 15 MPH. LOCALLY HEAVY RAINS AND STRONG GUSTY WINDS COULD
AFFECT PORTIONS OF THE LESSER ANTILLES OVER THE NEXT DAY OR SO.
THERE IS A LOW CHANCE...10 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

AN AREA OF DISTURBED WEATHER IS LOCATED OVER THE EASTERN ATLANTIC
OCEAN ABOUT 650 MILES SOUTHWEST OF THE CAPE VERDE ISLANDS. THIS
SYSTEM SHOWS SOME SIGNS OF ORGANIZATION...AND SLOW DEVELOPMENT OF
THIS DISTURBANCE IS POSSIBLE DURING THE NEXT COUPLE OF DAYS AS IT
MOVES SLOWLY TOWARD THE WEST OR WEST-NORTHWEST. THERE IS A LOW
CHANCE...20 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN

[KWT]

Interesting to note the difference between the two areas highlighted, the NHC do seem to think slow development is possible which is obviously from the usual line of "development, if any"

The GFDL is pretty amazing, probably a major hurricane on that run, way too agresssive though it does show conditions aloft at least for a while.

BTW, who has the website link for the site that shows where similar storms have formed in this sort of location.

[cycloneye]

90L will be a tropical wave at 00z surface analysis

Interesting ITCZ discussion that clears more the features.

http://www.nhc.noaa.gov/text/refresh/MI ... 0004.shtml?

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 11N18W 9N25W 8N29W 8N33W 13N53W
11N64W. A SURFACE TROUGH AND ASSOCIATED 1010 MB LOW PRES
IS CURRENTLY EMBEDDED WITHIN THE ITCZ NEAR 9N31W IS GENERATING
SCATTERED MODERATE ISOLATED STRONG OF CONVECTION WITHIN 120 NM S
OF THE AXIS BETWEEN 31W AND 41W. HOVMOELLER DIAGRAMS...LONG
TERM SATELLITE IMAGERY AND SPECTRAL ANALYSIS SUGGEST THAT THIS
TROUGH IS ACTUALLY A TROPICAL WAVE AND WILL THEREFORE BE
INTRODUCED ON THE 00 UTC SURFACE ANALYSIS. SCATTERED MODERATE TO
STRONG CONVECTION IS NOTED WITHIN 120-180 NM N OF THE AXIS
BETWEEN 45W AND 57W.

[KWT]

Well that just makes things even more complicated, now we could possibly end up having two waves trying to interact, just gotta wonder whether they will mess up each others mid level turning?