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Atlantic Tropical Action 2011 - Part II


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Although this is in the long range and has high uncertainty, I would watch the July 10-17 time frame over the Atlantic basin. Paul Roundy's plots have been projecting a well-resolved Kelvin wave passage across the basin around July 10-12. This combined with the projected favorable and substantial-amplitude MJO phase 1-2 should result in significantly higher-than-climo TC genesis probs. This method seemed to work fairly well with the genesis of Arlene, as several of us zeroed in on the correct general time frame 10+ days in advance.

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Looking ahead to later next week, the TW current near 54W is chugging W and should enter the Caribbean later in coming weekend. While shear is too high for any development, conditions should improve in the Western Caribbean later next week as the wave enters the Western Basin. This will coincide well with a favorable Kelvin wave/MJO as we head toward the 10th...

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Although this is in the long range and has high uncertainty, I would watch the July 10-17 time frame over the Atlantic basin. Paul Roundy's plots have been projecting a well-resolved Kelvin wave passage across the basin around July 10-12. This combined with the projected favorable and substantial-amplitude MJO phase 1-2 should result in significantly higher-than-climo TC genesis probs. This method seemed to work fairly well with the genesis of Arlene, as several of us zeroed in on the correct general time frame 10+ days in advance.

ECMWF reduce shear across the Carribien signifigantly by day 7. Most global models are explicitly showing storms well in advence as well as some extra Phantomcanes now but I assume they could miss one occasionally.

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I dont really see any tropical activity for at least the next week, but thats not unusual for this time of year

Despite favorable upward motion phases, I sort of agree. Hints on the models, but nothing semi-concrete like we had with Arlene from a week or more out, and nothing looks too promising on satellite.

But, most of the models aren't even out to mid-month. I get thinking about Bertha, which was looking nice about July 4th weekend even before it was classified, so I look to Africa for good waves even if the MDR isn't usually favorable yet.

I've been kind of hoping for an EC threat about the third week of July to make the conference memorable. Steve is going, and we wouldn't want a Gulf storm while he is away.

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Convection continues with the tropical wave in the Eastern Caribbean, although the models don't really do much with it, outside of some vorticity from the GFS that spins off north of Hispaniola beyond 48 hours. Shear is expected to drop quite significantly over the next 48 hours in the Eastern Caribbean, but this feature might be stuck in the shear axis with the TUTT feature further NW by then.

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The wave that was mentioned earlier has increased in convection over night and a TUTT to the NW is creating a highly sheared Central Caribbean. We'll see what happens as shear looks to relax in the Western Caribbean in a few days...

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

800 AM EDT SAT JUL 2 2011

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

SHOWERS AND THUNDERSTORMS OVER THE LEEWARD ISLANDS...VIRGIN

ISLANDS...PUERTO RICO...THE DOMINICAN REPUBLIC...AND THE ADJACENT

WATERS OF THE CARIBBEAN AND THE ATLANTIC ARE ASSOCIATED WITH A

TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL TROUGH. UPPER-LEVEL

WINDS ARE NOT FAVORABLE FOR DEVELOPMENT...AND THERE IS A LOW

CHANCE...NEAR 0 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL

CYCLONE DURING THE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...

LOCALLY HEAVY RAINS AND GUSTY WINDS ARE EXPECTED TO SPREAD WESTWARD

ACROSS THE CENTRAL CARIBBEAN SEA...HAITI...AND EASTERN CUBA DURING

THE NEXT DAY OR TWO.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$$

FORECASTER BEVEN

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Local HGX office doesn't like the Euro, in regards the 500 mb low it forecasts to develop in the Gulf which would eventually improve rain chances for our drought stricken area, but anytime one sees almost a closed low off Florida in July, eyebrows are raised...

With the 24 hour time steps, I can't positively trace this back to the zero calorie lemon, it could come up from Central America. Almost looks like a combo package.

BTW, at 10 days this feature is entering the Atlantic South of Hatteras per the Euro...

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HPC Update:

IN REGARDS TO TROPICAL WEATHER...ENOUGH 00Z GLOBAL ENSEMBLE

MEMBERS WERE SPLAYED OUT ALONG AN ELONGATED AXIS ACROSS/AROUND THE

FLORIDA PENINSULA NEXT WEEKEND TO DEPICT A RETROGRADING INVERTED

TROUGH ACROSS THE SUNSHINE STATE/EASTERN GULF OF MEXICO/WESTERN

SUBTROPICAL ATLANTIC LATE IN THE PERIOD. THIS FEATURE IS THE

NORTHERN PORTION OF A TROPICAL WAVE CURRENTLY LOCATED NORTH OF

PUERTO RICO WHICH IS EXPECTED TO MOVE INTO A MORE FAVORABLE UPPER

LEVEL ENVIRONMENT DURING THE MEDIUM RANGE PERIOD AS IT APPROACHES

THE FLORIDA PENINSULA.

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It's still early on, but this weak lemon resembles the TCG of Franklin (2005) where a strong tropical wave ran into a TUTT feature which helped to enhance convection before it moved out, where shear lessened enough for development. I'm more optimistic with this lemon than the NHC considering the favorable phase of the MJO which might provide enough divergence aloft to keep this feature convectively active until it finds a more favorable environment.

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Some better looking waves coming across Africa. Shouldn't be long before we have to start watching those with nore interest.

If it was CV season, the wave approaching the CV would probably be too far North to be interesting in North America. But it isn't, and that is a sweet looking wave.

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Looking at my new favorite model product, which somewhat resembles TPW, which has worked pretty well the last couple of years since a local KHOU forum point pointed it out, is the 700 mb theta-e, well, 12Z and 18Z GFS suggest impressive leaving Africa in a week.

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There is still a little bit of vorticity north of Hispaniola this morning, but instead of the upper level low moving out, it moves over the system over the past 24 hours, keeping upper level winds far too unfavorable for organization for now. The ECWMF does show some sort of hybrid low pressure forming off the Outer Banks very late in the forecast period that seems related to the vorticity that is currently associated with the former lemon disturbance.

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