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Tropical Depression Don


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The 850mb vorticity max is definitely south of what the Euro has been forecasting it to be, and the model has it skirting the N coast of Hispaniola... I think it will try the Sern coast instead, plus E Cuba, before jogging more poleward while a weakness develops over FL, but with a rather strong ridge building back, a wave/cyclone in the S Central GOM aiming the W Gulf coast are my early thoughts.

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As for intensity, the Sern track is definitely better wrt shear... an ULL currently over Cuba will be backing W, leaving a more conducive upper level environment (not ideal either, but at least < 20kts of werly shear) over the currently hostile Caribbean. Obviously land interaction is the main factor here, so I don't think we'll have anything significant until (if) it reaches the GOM... unless it somehow avoids the Leeward islands.

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This one could be a fun one to track, one way or another. Certainly not an easy forecast.

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The invest, for now, is under a favorable upper level environment for further organization. There is a belt of westerlies to the north of the system ventilating it well and allowing for good large scale lift, and a small anti-cyclone over the system, keeping it in a lightly sheared environment.

However, strong low level easterly winds are evident over the eastern Caribbean, which will limit surface convergence and make it hard for a closed surface circulation to form in the near term as the system moves west of the islands.

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While some banding features are evident on microwave imagery, there does not yet appear to be a well defined surface circulation, which along with an unfavorable strong easterly flow over the eastern Caribbean does not support immediate development of 90L.

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A strong subtropical ridge north of the invest will likely keep the system on a WNWrly course over the next 2 to 3 days. So north of the islands is off the table. Given how little latitude the system has and the strength of the subtropical ridge, the system may be able to skirt just south of Hispaniola, although it will be close.

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By the end of the weekend into early next week, the heat ridge will shift back west towards the heartland, allowing a couple of shortwaves to round the ridge and carve out a short lived trough along the US east coast, which will weaken the subtropical ridge off the southeast coast. Given the ECM shows a clear southeast flow even at the surface, this should turn even a weak tropical system to the right, so a more northwestward motion days 3-5 could well cause our system to possibly graze southern Hispaniola and at least graze Cuba.

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In addition to land interaction over the next 3-5 days, 90L has a good chance of dealing with TUTT induced shear. Two TUTTs are located catty corner to each other, and as they slowly pull away from each other a belt of westerlies will likely remain between them, which 90L will eventually have to cross through. The above day 4 ECM image shows this well.

After about midweek however, 90L may emerge into a lower shear environment over the Gulf and resume a more westerly track as the strong heat ridge shifts towards the eastern US. Note how a weakening TUTT exists over the western Gulf that is still shifting west, with lighter upper level winds over the eastern Gulf/Florida area where 90L will likely be located in 6 days:

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I really doubt we see significant development before Wednesday. Too much possible land interaction and other factors such as TUTT related shear to limit the potential of this invest in the short term.

This wave will probably end up somewhere in the Gulf in 5 to 6 days given the unlikely prospects for significant deepening before then and strong ridge that will build back in over the eastern US before 90L moves into a more favorable environment, likely preventing another system that tracks northeast into the open Atlantic. The opportunity for development of 90L, while uncertain at this range, appears better over the Gulf starting Wednesday as the system slips under a large upper level ridge. Survival over the next 5 days will be key however.

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This invest is looking bad. Development chances down to 20% from 30%. There is another tropical wave east of this one that looks better. But tropics can always have surprises like people say. You never know what invest 90l could do. Thats why its need to be watched when it gets to the western carribean and GOM.

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12Z track and intensity guidance suggests a weak disturbance passing S of Hispaniola/Cuba and through the Yucatan Channel. SHIP does ramp up to 64 kts by hour 120, but without surface reflection and strong shear, that solution appears very unlikely. We will see.

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This invest is looking bad. Development chances down to 20% from 30%. There is another tropical wave east of this one that looks better. But tropics can always have surprises like people say. You never know what invest 90l could do. Thats why its need to be watched when it gets to the western carribean and GOM.

Agree. Andrew looked like decomposing hamburg north of PR in 1992. A couple days later, ....

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I still think this has a better than none chance at development in about 3 days over the Gulf.

Possible land interaction and TUTT induced shear will likely keep the system in check for the next 48-72 hours. However, even if the wave moves over land, it should remain trackable into the Gulf of Mexico, where it will have over 48 hours over warm waters and under an upper level anti-cyclone to get its act together before moving inland somewhere over the western Gulf.

The 0z GFS shows low shear beneath a large upper level anti-cyclone over the Gulf days 4-6:

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The ECM drastically weakened shear over the Gulf by hour 96 on its 12z run, and keeps this wave trackable as an area of increased vorticity until it runs the system into Texas at around 144 hours out:

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The islands won't destroy an open wave, they will simply keep it in check.

Perhaps I'm grasping for straws here, but the NHC may be trying to hint at down the road development between the lines:

DISORGANIZED SHOWERS AND THUNDERSTORMS OVER HISPANIOLA...PUERTO RICO...AND THE THE LEEWARD ISLANDS ARE ASSOCIATED WITH A TROPICAL WAVE OVER THE EAST-CENTRAL CARIBBEAN SEA. UPPER-LEVEL WINDS...AS WELL AS THE INTERACTION OF THE DISTURBANCE WITH THE LAND MASSES OF HISPANIOLA AND CUBA...ARE EXPECTED TO PREVENT SIGNIFICANT DEVELOPMENT OVER THE NEXT COUPLE OF DAYS AS THE SYSTEM MOVES TO THE WEST-NORTHWEST AT 15 TO 20 MPH. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. NEVERTHELESS...PERIODS OF LOCALLY HEAVY RAINFALL AND GUSTY WINDS CAN BE EXPECTED OVER PUERTO RICO AND HISPANIOLA THROUGH SUNDAY.
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^^^Yeah the only thing that could hinder development would be dry air if any at all is in the GOM. This system looks like it will really get going in the western carribean and Gulf of mexico unless land interaction and shear destroy this system over the next 48 hours. Im thinking dolly 2008 redux. lol

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Local KHOU-TV 11 forum pro-met WxMan57, who does tropical cyclone forecasting for private clients, does not rule out this developing once past land, so I'm up to glass one quarter full optimistic.

TC or not, we need the rain and it seems possible.

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90L actually doesn't look horrible today. Convection isn't particularly strong, but looking at visible loops there are signs of some sort of low level circulation near the southern edge of the convection, moving slightly north of due west:

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No doubt the invest will have to at least graze Hispaniola today and likely eastern Cuba tomorrow.

The invest is under 10-20 knots of shear, which is allowing for some marginal organization. It may actually split the stronger shear over the next couple of days, assuming the TUTT over the Yucatan channel continues to retrograde:

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Still think this one could end up developing down the road.

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^^^Yeah the only thing that could hinder development would be dry air if any at all is in the GOM. This system looks like it will really get going in the western carribean and Gulf of mexico unless land interaction and shear destroy this system over the next 48 hours. Im thinking dolly 2008 redux. lol

I'm so not on board with development of this thing. Even once in the gulf I doubt it has much of a chance, it will be clicking along pretty good on forward speed and it's not gonna dilly dally around the GoM. This thing is on life support now, not even a slight spin to it at all. My prediction this thing get to TD status at most before landfall in the GoM and even that is a long shot imo. How do you get Dolly 2008 analog from this thing anyways. I went and looked up Dolly and nothing about this system really makes me think Dolly. This thing is DoA, I can see some enhancing rains I'm sure but a Cat 2 Hurricane I think not.

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I can't find anything even showing this as an invest anymore. Am I missing something here?

no, you are not missing anything - no longer an invest, but still a wave & as a wave, it will be discussed in the TWO - currently tagged as 10% chance of developing in the next 48 hrs (that could mean greater than 5%, but less than 14%, since they tag it to the nearest 10 - that really po's ppl when they tag it as zero...)

a couple posters just explained it brilliantly to someone who had difficulty understanding on another board

a FOX hurricane blog out of Tampa explained it to their readers a few hours back as "This afternoon the National Hurricane Center stopped running computer forecast models on the system and so it is no longer considered a suspect area or invest area."

it reserves the right to come back tho... does anyone know, if it does, will it still be 90L ???

edit - correcting my math, it was past my bedtime...I should have said: (that could mean greater than 5%, but no more than 15%)

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It's still an invest, but when probabilities of cyclogenesis are low, no computing resources are wasted on it... it will still be 90L until you see it deactivated from here. Once it is deactivated, if it comes back to life, it is assigned a new code. Right now it's still entangled with E Cuba, and the mid level and low level vorticities are not vertically stacked... there will probably be some organization next 24hrs, which I think will be critical to assess if it will become anything... but upper level conditions are far from ideal.

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no, you are not missing anything - no longer an invest, but still a wave & as a wave, it will be discussed in the TWO - currently tagged as 10% chance of developing in the next 48 hrs (that could mean greater than 5%, but less than 14%, since they tag it to the nearest 10 - that really po's ppl when they tag it as zero...)

a couple posters just explained it brilliantly to someone who had difficulty understanding on another board

a FOX hurricane blog out of Tampa explained it to their readers a few hours back as "This afternoon the National Hurricane Center stopped running computer forecast models on the system and so it is no longer considered a suspect area or invest area."

it reserves the right to come back tho... does anyone know, if it does, will it still be 90L ???

It's still an invest, but when probabilities of cyclogenesis are low, no computing resources are wasted on it... it will still be 90L until you see it deactivated from here. Once it is deactivated, if it comes back to life, it is assigned a new code. Right now it's still entangled with E Cuba, and the mid level and low level vorticities are not vertically stacked... there will probably be some organization next 24hrs, which I think will be critical to assess if it will become anything... but upper level conditions are far from ideal.

I learn something new everyday on this board. Thanks folks!

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I'd love to be wrong, but outside the not particularly well regarded NAM, nothing, and even the NAM is weak. 1/16th glass full optimitistic, and even an enhancement in moisture and rain seems to be fading for Texas end of the weak.

Doesn't look officially deactivated, but not updated in almost a day, and as noted, no models run.

next.

ftp://ftp.nhc.noaa.gov/atcf/tcweb/

post-138-0-66968900-1311593884.jpg

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The only positive development re: 90L is that guidance did suggest a weakening TUTT and that is happening this morning. NHC saying 0% as of 8:00 AM so we'll see if deactivation happens before the day is done.

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