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Tropical Storm Isaac, Part 1: Moving Through The Eastern Caribbean Sea


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i'm thinking it'll delay the start, not dissipate this system but i do like the convective trend. just would like it to fill in a bit more. and as well, that dry patch to the northeast of the convection does make me wonder how fast it'll develop before this system makes it to the leewards. the environment looks better west of the leewards than east.

This, and then some. The central convective burst is seriously expanding with each new frame.

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i'm thinking it'll delay the start, not dissipate this system. but i do like the convective trend. just would like it to fill in a bit more. and as well, that dry patch to the northeast of the convection does make me wonder how fast it'll develop before this system makes it to the leewards. the environment looks better west of the leewards than east.

Yup, I think we'll see diurnal cycling until it can sufficiently moisten it's environment in a couple days, fairly standard for tropical cyclones attached to a SAL outbreak.

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BULLETIN

TROPICAL DEPRESSION NINE ADVISORY NUMBER 1

NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012

500 AM AST TUE AUG 21 2012

...NINTH DEPRESSION OF THE SEASON FORMS EAST OF THE LESSER

ANTILLES...TROPICAL STORM WARNINGS AND WATCHES ISSUED...

SUMMARY OF 500 AM AST...0900 UTC...INFORMATION

----------------------------------------------

LOCATION...15.2N 51.2W

ABOUT 715 MI...1150 KM E OF THE LEEWARD ISLANDS

MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H

PRESENT MOVEMENT...W OR 270 DEGREES AT 20 MPH...32 KM/H

MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES

WATCHES AND WARNINGS

--------------------

CHANGES WITH THIS ADVISORY...

THE METEOROLOGICAL SERVICE OF BARBADOS HAS ISSUED A TROPICAL STORM

WARNING FOR DOMINICA.

THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WARNING FOR

GUADELOUPE...DESIRADE...LES SAINTES...MARIE GALANTE...AND ST.

MARTIN.

THE GOVERNMENT OF ANTIGUA HAS ISSUED A TROPICAL STORM WARNING FOR

ST. KITTS...NEVIS...ANTIGUA...MONTSERRAT...AND BARBUDA.

THE GOVERNMENT OF CURACAO HAS ISSUED A TROPICAL STORM WATCH FOR

SABA...ST. EUSTATIUS...AND ST. MAARTEN.

THE GOVERNMENT OF ANTIGUA HAS ISSUED A TROPICAL STORM WATCH FOR THE

BRITISH VIRGIN ISLANDS.

A TROPICAL STORM WATCH HAS BEEN ISSUED FOR PUERTO RICO...VIEQUES...

CULEBRA...AND THE U.S. VIRGIN ISLANDS.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...

* DOMINICA

*GUADELOUPE...DESIRADE...LES SAINTES...MARIE GALANTE...AND ST.

MARTIN

* ST. KITTS...NEVIS...ANTIGUA...MONTSERRAT...AND BARBUDA

A TROPICAL STORM WATCH IS IN EFFECT FOR...

* SABA...ST. EUSTATIUS...AND ST. MAARTEN

* BRITISH VIRGIN ISLANDS

* PUERTO RICO...VIEQUES...CULEBRA...AND THE U.S. VIRGIN ISLANDS

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE

EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE

POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR

PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.

DISCUSSION AND 48-HOUR OUTLOOK

------------------------------

AT 500 AM AST...0900 UTC...THE CENTER OF TROPICAL DEPRESSION NINE

WAS LOCATED NEAR LATITUDE 15.2 NORTH...LONGITUDE 51.2 WEST. THE

DEPRESSION IS MOVING TOWARD THE WEST NEAR 20 MPH...32 KM/H...AND

THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT COUPLE OF

DAYS. ON THE FORECAST TRACK...THE CYCLONE SHOULD MOVE THROUGH THE

SOUTHERN LEEWARD ISLANDS AND NORTHERN WINDWARD ISLANDS WEDNESDAY

AFTERNOON...AND EMERGE OVER THE EASTERN CARIBBEAN SEA BY THURSDAY

MORNING.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER

GUSTS. STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...AND

THE DEPRESSION IS EXPECTED TO BECOME A TROPICAL STORM LATER TODAY.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB...29.74 INCHES.

HAZARDS AFFECTING LAND

----------------------

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH THE WARNING

AREA BY WEDNESDAY AFTERNOON...MAKING OUTSIDE PREPARATIONS DIFFICULT

OR DANGEROUS.

RAINFALL...TOTAL RAIN ACCUMULATIONS OF 4 TO 8 INCHES ARE POSSIBLE

OVER THE NORTHERN WINDWARD ISLANDS AND THE LEEWARD ISLANDS.

SURF...DANGEROUS SURF AND RIP CURRENT CONDITIONS WILL AFFECT THE

WINDWARD ISLANDS AND THE LEEWARD ISLANDS DURING THE NEXT COUPLE OF

DAYS. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER OFFICE FOR

MORE INFORMATION.

NEXT ADVISORY

-------------

NEXT INTERMEDIATE ADVISORY...800 AM AST.

NEXT COMPLETE ADVISORY...1100 AM AST.

$$

FORECASTER STEWART

TROPICAL DEPRESSION NINE TROPICAL CYCLONE UPDATE

NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012

510 AM AST TUE AUG 21 2012

...TROPICAL STORM WARNING ISSUED FOR ANGUILLA...

THE GOVERNMENT OF ANTIGUA HAS ISSUED A TROPICAL STORM WARNING FOR

ANGUILLA.

$$

FORECASTER STEWART

post-32-0-60875100-1345539184_thumb.gif

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I'm more conservative than Stewart's forecast of a near-major hurricane by day 4.

Given the residual dry air, very large circulation size, fast forward motion and strong low-level easterlies all the way to the e. Caribbean, along with the reluctance of the global and mesoscale models, I don't see much likelihood of this becoming a hurricane until it gets west of about 70W. I'd favor gradual strengthening the next few days.

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I'm more conservative than Stewart with a near-major hurricane by day 4.

Given the dry air, very large circulation size, and the reluctance of the global and mesoscale models, I don't see much likelihood of this becoming a hurricane until it gets west of about 70W. I'd favor gradual strengthening the next few days.

Makes sense. What do you think of the track, Justin?

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I would edge a little south of NHC's track (about 50 miles s. of Haiti and ending up somewhere between Jamaica and the s. coast of eastern Cuba by day 5) especially given the rapid organization and vertical coupling occurring in the past 6 hours, which means TD9 will be influenced less by low-level flow and more by the WSW-ENE oriented mid-level ridge.

Makes sense. What do you think of the track, Justin?

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Ok, start throwing the hot dogs at me, but this looks like a rapid development of a legit CDO, that looks like it's already starting to rotate. Not 100% on this, especially given the history of entanglement with SAL, however TPW imagery did indicate that 09L was starting to insulate or surround its center with high PWAT air.

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Ok, start throwing the hot dogs at me, but this looks like a rapid development of a legit CDO, that looks like it's already starting to rotate. Not 100% on this, especially given the history of entanglement with SAL, however TPW imagery did indicate that 09L was starting to insulate or surround its center with high PWAT air.

OK, let me be the first... :weenie:

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I would edge a little south of NHC's track (about 50 miles s. of Haiti and ending up somewhere between Jamaica and the s. coast of eastern Cuba by day 5) especially given the rapid organization and vertical coupling occurring in the past 6 hours, which means TD9 will be influenced less by low-level flow and more by the WSW-ENE oriented mid-level ridge.

OK, cool-- thanks, Justin.

OK, let me be the first... :weenie:

I liked your thoughts. :)

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Ok, start throwing the hot dogs at me, but this looks like a rapid development of a legit CDO, that looks like it's already starting to rotate. Not 100% on this, especially given the history of entanglement with SAL, however TPW imagery did indicate that 09L was starting to insulate or surround its center with high PWAT air.

latest72hrs.gif

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Ok, start throwing the hot dogs at me, but this looks like a rapid development of a legit CDO, that looks like it's already starting to rotate. Not 100% on this, especially given the history of entanglement with SAL, however TPW imagery did indicate that 09L was starting to insulate or surround its center with high PWAT air.

It can be called a CDO since that's what it is, it's central, it's dense, and it's overcast :P

As far as the jargony use of CDO which implies that it won't collapse for awhile since it's well developed, I gotta disagree, we're still in peak diurnal convective max territory and I expect this convection to wane, one of the first bursts in days afterall.

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You looked at the image URL didn't you. :P Yep. Ernie 2006. Struggled its whole life and just never got organised and in the end, its most lasting legacy was a rain maker for the Carolina,VA,MD & VA. I have no reasoning, it just sticks out in my mind as a kind of "I've seen this movie before" deal.

Ernesto 2006 may not have been consequential but for a "mere" Tropical Storm he was King of the Jungle.

When dusk turned into evening here on Cape Fear, our gentle breeze rose to a brisk wind. As darkness entrenched itself moderate showers turned to relentless heavy windswept rain. Then around midnight or a bit thereafter, Ernesto's 70mph eye wall rolled over us. Howling winds raked the trees, torrents of rain fell, and "blue flashes" began appearing. Off went the power.

I always laugh inside when I see someone "poo pooing" a storm because it's not big enough or strong enough; as if they have so much personal experience with the eyes of tropical cyclones sweeping through their back yards; especially those away from the immediate coast.

Wilmington, North Carolina experienced the full brunt of three eye walls (Charley 75mph, Ernesto 70mph, and Ophelia 80mph) in just the last eight years. With two of them the calm centers (Charley - midday, and Ernesto - midnight) passed directly overhead; Ophelia crawled along the coast pummeling us all day long.

Okay, none of those were monsters (thankfully,) but in the real world of people's back yards, these type storms (as direct hits) are far from everyday weather; they're "memorable" in every way to all who experience them.

At times I sense the difference between being a "weather geek" and a "news geek" gets lost. Not every hurricane savages a city upon landfall. So what? How does this diminish the awe of actually experiencing one of these tropical beasts?

Hurricanes are effectively coastal storms; just like nor'easters. Compare the difference between being on the New England coast during a high-end nor'easter with being a hundred miles inland. Night and day, right? The same goes for hurricanes. When you live on the coast -- and take a direct hit, there's no such thing as a "small hurricane." That it doesn't decimate the town is irrelevant; it's still a mighty and memorable storm for those who experience it.

Sorry to ramble on so... I guess I'm just trying to remind people to be more appreciative of all hurricanes and not to dwell so constantly on the historic ones that are so few and far between. The grandeur of nature doesn't require news headlines.

ERNESTO 2006:

TropicalStormErnesto2006.gif

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Ok, start throwing the hot dogs at me, but this looks like a rapid development of a legit CDO, that looks like it's already starting to rotate. Not 100% on this, especially given the history of entanglement with SAL, however TPW imagery did indicate that 09L was starting to insulate or surround its center with high PWAT air.

The middle-mid-level center and the upper-mid-level center are obviously misaligned by 2 angstroms, and inspection of satellite imagery clearly reveals an oxygen molecule and a nitrogen molecule that do NOT have a water vapor molecule between them, only 100 miles from the upper-low-level center.

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Members,

We realize the great potential with Tropical Depression 9 and staff has been proactive in discussing what needs to be done for any expected additional traffic for the Tropical threads. We know the unique situation with this potential in that it could affect the Republican National Convention, but we ask that NO politics be discussed in this forum. None. We have already begun to see this and we ask that it stop immediately.

When conditions warrant, we will go into a storm mode phase where we put in additional temporary moderators and regular staff patrols threads much more frequently. Also, during this period, normal warnings and actions resulting from not adhering to regular and storm mode rules are more severe including: suspension with no warning for 24 hours or throughout the entire storm, being limited to 5 posts per day or even banned. We want to keep these threads informative and clutter free so everyone can enjoy them. To avoid any of the aforementioned actions, simply keep on topic. That's it. You'll see a banner at the top of the board when storm mode is declared. For now, let's keep the politics out of this and discuss the potential with TD 9.

If you have any questions about any of this, PM any moderator or admin. Thanks everyone.

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Looking at first few frames of vis loop, just as it looks like cloud tops are warming a bit (I have SSD loops up in IR and vis), a little tower just East of apparent LLC casting a shadow.

Euro ensembles from Alan Huffman's model page suggests at least one member close to New Orleans, a week out, not going 100% on Florida. If Adam or one of the othe rpro-mets who see individual Euro ensemble members could comment, I'd be most appreciative.

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Looking at first few frames of vis loop, just as it looks like cloud tops are warming a bit (I have SSD loops up in IR and vis), a little tower just East of apparent LLC casting a shadow.

Euro ensembles from Alan Huffman's model page suggests at least one member close to New Orleans, a week out, not going 100% on Florida. If Adam or one of the othe rpro-mets who see individual Euro ensemble members could comment, I'd be most appreciative.

Still a wide spread, from the Bahamas to Houston. The mean is still in the Eastern Gulf.

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First light visible suggests the center is on the northern edge of the waneing convection. It's still a bit hard to conclusively prove this and there may have also been a center relocation overnight. Well know for sure with a few more satellite frames. Those that are rooting for a stronger system will want to see this stay farther south.

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From what I can tell, the MLC and LLC aren't perfectly aligned at this time. The LLC seems to be on the northern end of the convection (near the new burst), while the strong MLC is to the WSW.

One could argue there is a very slight WSW component, but I won't touch that.

The disturbance depression as a whole is in pretty decent shape for now. If this can maintain convection and get that LLC to align, then this should have no trouble becoming a tropical storm today. Seems to have sufficiently modified the dry air that was eating it.

GOES11452012234rp6ou3.jpg

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FWIW the euro ensembles are like the op,but then deviate and are a bit further west in the Gulf.

Yeah, still a lot of spread with this thing. I'm not locking anything up at this point, despite the fact I favor the Eastern Gulf. For those of you looking at the Euro ensemble mean though, realize that the lower heights in the Western Gulf after D10 are skewed by the storms that haven't made landfall yet. Better than 80% of the members have landfall by D10.

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