Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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Active tropical wave in the central Atlantic near 13.5N 37.5W at 01/15Z moving west at 20mph. A strong upper level ridge continues to build westward over and ahead of the system. SSTs about 28C. System should continue westward, perhaps even a little south of due west, over the next 3 or 4 days through an area of light wind shear. Conditions seem favorable for additional slow development as the system moves westward. Something to keep a close eye on this week.
ED
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Ed in Va
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Looks like we're seeing a definite pattern, with this, Dean, and Felix all heading in the same direction. Way too early to speculate, but when was the last time we had two years in a row without a U.S. landfalling hurricane? Anyone got a link...I looked, but couldn't find one.
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Survived Carol and Edna '54 in Maine. Guess this kind of dates me!
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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The Unisys link should give you what you are looking for:
Unisys Tropical Page
(The answer is 2000-01)
ED
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typhoon_tip
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Suspect this thread will eventually need to get bumped to the Main Page agenda...
Firstly, in case anyone is wondering: The models may not pick up on this disturbance very well. I'd count on disappointment if you are hoping to see multiple contours of MSLP modeled illustration at anytime soon.
Just as was the case with Felix and the differences between Felix and Dean's seeds, there is no certainty that the genesis phase of the any given TCs life will even been seen. Dean was, Felix on the other hand had a labored appearance in the models at best. In fact, a few models may be retarded on Felix's intensity as it gains longitude, for that matter...constantly playing catch-up for those models that are still a bit behind what is already verifying... (55kts, not bad).
But, as far as 98L goes, currently, visible imagery provides a rather conspicuous cyclonic gyre along the TW axis, and of course, it is plainly obvious that convection has increased signficantly in the last 12 hours. This system actually maintained a tiny convective plume during its entire voyage, which really came off of Africa slightly N of its previous siblings. One of my personal druthers with these things is that I really like to see the convection more than the turning... I have seen large dry TWs with clear rotation trundle the entire distance of the Atlantic Basin and never do diddly, about as often as I have seen small convective sneaky entities wind up TCs.
The dry air that has been plaguing the 25N/30-60W regions of the Basin is also showing the presents of this TW now, having a surrounding circumvallate of increased theta-e now seen in vapor imagery.
http://www.ssd.noaa.gov/goes/east/catl/wv-l.jpg (I would have just posted the image but it blocks to largely)
The upper air analysis looks a little shaky with some ESE shear in the area as of this morning. However, out ahead of the TW conditions improve quite a bit, with generally a lighter easterly component in the 300mb and 200mb levels... This means that as TW enters that region, its relative shear (environmental wind speed - minus system forward speed) drops off; and if convection is on-going, that would induce a more radial outflow in that type of antecedent environment. This better environment can be seen in the 200mb streamline analysis...
http://www.nhc.noaa.gov/tafb/QHQA17.jpg
which shows what a appears to be a very enhanced divergence and a COL coupled between approximately 45 and 50W, by 15N, due in the path of 98L's current trajectory. This is important because the modeling of the at 300mb for this region is showing this to be in no hurry to decay in structure. Should a fledging TC or TD get up underneath that it would easily tap into those favorable mechanics and probably get a pretty good assist.
All together, I think there is definitely potential for this system to develop further.
Edited by typhoon_tip (Sat Sep 01 2007 01:19 PM)
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punkyg
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Now can some tell me if theres convection over 98L's low or is it displace to the west of the low?
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typhoon_tip
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Quote:
Now can some tell me if theres convection over 98L's low or is it displace to the west of the low?
Yes,
currently convection is successfully produced but is being displaced west, away from the preceived axis of weakly closed surface circulation...
Wind overlay out of TPCs satellite division shows a fairly strong shear environment still in the area, which of course is also supported by the fact that we can visibly see the activity blowing toward the west.
Can never be certain exactly when this will relax but the better hope for 98L is for it to move west toward the divergence noted earlier in this thread... Lighter upper air winds that are parting company would prove a much healthier environment for development. Until that happens, I would not think this would do anything very quickly so long as the upper level east-southeasterly jet of 20 to 25kts persists.
Every season it seems there is at least one fighter.
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Clark
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Likely dealing with either the African easterly jet, the Saharan Air Layer-induced easterly jet, or some combination thereof right now. Still, when it approaches 50W, it'll likely be in a more favorable environment and primed for further development then.
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Edited by typhoon_tip (Sat Sep 01 2007 04:33 PM)
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typhoon_tip
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Mm, indeed. Have not seen a lot of that out there in recent days, but there we have it.
This entity has an interesting structure at this hour... Strong convection in a small area persists, very near the central axis of the close circulation.. Believe it or not, so long as that is the case there is latent heat being converted to mechanical wind field energy...
Edited by typhoon_tip (Sat Sep 01 2007 04:34 PM)
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Clark
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That convection is likely going to help tighten up the broad, elongated, ENE-WSW oriented circulation associated with the storm, even given the shear in place. From there, the circulation/wind can draw those fluxes from the ocean's surface and start to build a tropical cyclone. Fairly classic case of the early steps of a developing tropical cyclone, even if it doesn't develop due to the shear and/or the occasional dry air burst.
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punkyg
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When will 98L enter lower shear?
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Clark
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Perhaps in another day or so, as it moves further from Africa. Dry air and its associated mid-level jet actually likely aren't at play here; it's been low-level stability rather than dry air that have kept 98L from amounting to much before now, upon closer inspection.
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Current Tropical Model Output Plots
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typhoon_tip
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98L is far from unworthy to discussion... There is a potent little vortex relative to what convection is occasionally fighting shear in the SW quadrant. When the shear relaxes, this system may very well lurch into a development phase... Said shear is still modeled to relax, and, the system its self is moving slowly west and away from the axis of upper level easterlies.
But, agreed, the system off the SE U.S. Coast is an important feature to monitor. I have put together an entry and placed it over in the 2007 Storm Forum. It does not say anything spectacular but is an attempt really to raise awareness and discuss some factors that may lead to development.
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madmumbler
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Those latest 98L model tracks I'm seeing are a little...confusing to say the least. Gives new meaning to the term "spaghetti" models!
Is there any idea of a timeframe when we might see a "make or break" time for 98L? Or is it a system we should just sit tight and watch because no one honestly has an idea what it's going to do?
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Lesli in SWFL.
Friends help you move. Real friends help you move bodies.
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typhoon_tip
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Quote:
Those latest 98L model tracks I'm seeing are a little...confusing to say the least. Gives new meaning to the term "spaghetti" models!
Is there any idea of a timeframe when we might see a "make or break" time for 98L? Or is it a system we should just sit tight and watch because no one honestly has an idea what it's going to do?
More like the 2nd question.. The fact that it has a rigorous low level circulation as discerned by high res visible imagery, and occasionally bursts convection over the SW quadrant suggests it is not a dead subject matter. Assuming the shear ever relaxes, this could resume a generation phase rather quickly..
So...yes indeed: A hurry up and wait scenario..
Also, regarding the models...I would not put too much stock in the modeling of these systems when they are in genesis phase. Fwiw, also, to exemplify much of this... Felix was not seen by the majority of guidance for most of the time and still, even now some guidance are only grudgingly admitting there is even anything there... Yet, we have a major hurricane with superior structure, as evidenced by multiple data sources.
I think the stunningly brilliant performance with Dean has folk's model expectations ratcheted up a tad but in reality...these models are not really that good in the genesis phases of TC growth.. They do better once the systems are already in play and can situate physically in initializations -- even then, the longer term model results would more likely do worse than they did with Dean. Dean's handling, overall, was a bit of a positive performance anomally.
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Camirudi
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Sorry for asking a question and not posting a meaningful comment...
I've been curious the past couple of days watching 98L on the "Rainbow" view from the ssd.noaa.gov site...It seems like (at times) that convection seems to be 'firing up' from a central location that does not drift west west with time...For example, on the loop from 19:15 to 2:15 tonight (http://www.ssd.noaa.gov/goes/east/carb/loop-rb.html)
there seems to be a "hot spot" near 11N 40W where convection is firing up from a source of energy that appears ~stationary (almost like looking at vis sat of the smoke trail from widfire)...What causes this perception when looking at this loop? In this loop, Felix has gained almost 2.5o longitude yet this "hotspot" near 11N 40W appears ~ stationary...Is the wave moving that slow or is there something else causing this perception from the "Rainbow" loop...
Thanks in advance for any explanations...
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punkyg
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Hey beautiful people  , i just looked at 98L this morning and she looks better interms that she isn't being sheared as bad as yesterday. yes her center is still exposed, but i expect her to get it covered.
now that the wind shear has relaxed lets get to talking about when she is gonna develop.
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typhoon_tip
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Quote:
Hey beautiful people , i just looked at 98L this morning and she looks better interms that she isn't being sheared as bad as yesterday. yes her center is still exposed, but i expect her to get it covered.
now that the wind shear has relaxed lets get to talking about when she is gonna develop.
As most are likely aware, has dropped the Invest status on this feature. However, I am still observing a rather obvious circulation on-going and the UL winds have become a little less hostile. So we may not be done with this yet.
Stay tuned!
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