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Atlantic Tropical Action 2013


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Is it just me, or is 92L looking increasingly like a subtropical cyclone on satellite?  Large, increasingly curved band of convection well NE of the center, with a defined low level circ pretty well collocated with an upper level cold core low?

Different evolution. Low level low had tropical origins, and had the final kick to finally form an LLC with yesterday's day time heat convection over land. ULL moved in from the NE...it's moving rapidly SW, and if it can keep moving swiftly in that direction, conditions would enhance in a couple of days in the W/SW GoM.

 

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Erin might have actually ended up being pretty useful in the grand scheme of things. 

 

The EATL is remarkably clear of SAL

 

attachicon.gifsplitE.jpg

 

Agree. Erin's taking the bullet for the barrage of upcoming African waves. I recall back in August 2004 after Danielle and Earl, there was a big wave that left Africa that everyone assumed would be "Frances", but it never developed but allowed a moist pattern for what would become Hurricane Frances.

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Different evolution. Low level low had tropical origins, and had the final kick to finally form an LLC with yesterday's day time heat convection over land. ULL moved in from the NE...it's moving rapidly SW, and if it can keep moving swiftly in that direction, conditions would enhance in a couple of days in the W/SW GoM.

 

attachicon.gifwv-animated.gif

Yeah, I wasn't necessarily trying to imply that it formed in a subtropical manner - more just commenting on its appearance in satellite.

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Yeah, I wasn't necessarily trying to imply that it formed in a subtropical manner - more just commenting on its appearance in satellite.

Gotcha...In that case I agree with you.

 

Currently the long wave trough is digging around the Mississippi basin, keeping steering currents very light where 92L is, hence little movement is expected for the next 24 hours. Depending if it can completely break the ridging to the north of 92L or not, is how much Nerly component to it's translational movement it will get. 12z Ukie and 12z GFS just dig it enough to split the Sonoran/Bermuda ridges and slowly move 92L to the NW and N, before the trough lifts off and handles the steering currents to the Sonoran ridge, which turn 92L to the W and WSW landfalling between the C and S Texas coast. More troughing, farther north, less troughing, then west it is.

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Is it just me, or is 92L looking increasingly like a subtropical cyclone on satellite?  Large, increasingly curved band of convection well NE of the center, with a defined low level circ pretty well collocated with an upper level cold core low?

 

 

How can 92L develop on its own with an upper level low so close?  More likely is that the upper low starts taking on more tropical characteristics ala a subtropical.  That takes time and I'm not sure it gets there before "landfall".  May be close though.

 

 

Yeah, I wasn't necessarily trying to imply that it formed in a subtropical manner - more just commenting on its appearance in satellite.

 

Basically what happened was that the upper level low that had been shearing the system yesterday has now moved on top of the llc (which is MUCH better defined today), resulting in a vertically stacked cyclonic vorticity profile often consistent with initial subtropical development. This evolution is pretty unusual for August, although not unheard of. As long as the circulation can remain reasonably well defined, we should start to see convection pulsing as convection moistens the atmosphere near the llc and diabatic outflow form the convection destroys what remains of the upper-level vortex. 

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Something interesting happened today. Our WSI system is receiving a track for Invest92. Support confirmed that this is data coming from the NHC and they are working to find out why we are getting it. This is NOT an official forecast and there is no indication when it may have been made but I thought I would post it just for fun.

 post-209-0-31179800-1376677979_thumb.png

 

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Something interesting happened today. Our WSI system is receiving a track for Invest92. Support confirmed that this is data coming from the NHC and they are working to find out why we are getting it. This is NOT an official forecast and there is no indication when it may have been made but I thought I would post it just for fun.

RT @NHCDirector: .@wxbrad Experimental in-house NHC track/intensity forecasts for disturbances not intended for public release.
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Something interesting happened today. Our WSI system is receiving a track for Invest92. Support confirmed that this is data coming from the NHC and they are working to find out why we are getting it. This is NOT an official forecast and there is no indication when it may have been made but I thought I would post it just for fun.

 attachicon.gifSpaghetti Tropical Tracker 2.png

 

 

I noticed this yesterday on the track at http://www.ral.ucar.edu/hurricanes/realtime/plots/northatlantic/2013/al922013/track_early/aal92_2013081512_track_early.png

 

Almost posted on it. It's since been removed in later tracks.

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There is no convection to maintain the low level swirl of 92L, and the divergence/convergence couplet is East of the swirl, suggesting that storms may not be in a hurry to fire up.

 

So shouldn't this fill rather quickly nefore the ULL can shift far enough away to provide favorable ventilation?

 

/just asking

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I noticed this yesterday on the track at http://www.ral.ucar.edu/hurricanes/realtime/plots/northatlantic/2013/al922013/track_early/aal92_2013081512_track_early.png

 

Almost posted on it. It's since been removed in later tracks.

 

The experimental six/seven day track was put in with the guidance last year before they found out and put a quick halt to it.

 

Snippet from last year -

 

For the first time, the National Hurricane Center plans to develop six- and seven-day track forecasts for an entire storm season. It also plans to do a better job keeping them secret, as they leaked out to the public last year, cutting the experiment short. “We weren’t able to button them up; people were finding them,” said James Franklin, the center’s top hurricane specialist.

 

On writing advisories for invests/disturbances -

 

The hurricane center was less successfulicon1.png when, for the first time last year, it attempted to write advisories for disturbances on an experimental basis. Franklin said it was difficult to predict their track and intensity. “That wasn’t surprising, because those systems aren’t well defined. You don’t have a center, and you don’t always know where it is,” he said, adding that forecasters hope to do better this year.

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There is no convection to maintain the low level swirl of 92L, and the divergence/convergence couplet is East of the swirl, suggesting that storms may not be in a hurry to fire up.

 

So shouldn't this fill rather quickly nefore the ULL can shift far enough away to provide favorable ventilation?

 

/just asking

Looks to me like there is increasing low level turning closer to the convection, and that initial naked swirl that moved off the Yucatan is dropping SW in the low level flow and weakening.

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Looks to me like there is increasing low level turning closer to the convection, and that initial naked swirl that moved off the Yucatan is dropping SW in the low level flow and weakening.

It looks like that to me as well...but it's a painfully slow process. Mid level energy is also stronger and better colocated with the low level vorticity. Shear has been decreasing as well. Models are, for the first time in a long time in a much better consensus about the track, heading it toward the C/S TX coast.

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OK, now that I am staring at my ADD high display resolution visible loops, I can see a strong signs of mid level circulation Northeast of the dying swirl, and hints 92L may also be developing a new LLC.

 

 

Which I'd assume would favor the North Central Gulf.

 

 

Off the Momo and Popo Playa Party Plaza on the beach.  A tropical storm might have made my wife want to leave early anyway (not that a mere TS could hurt anything there), but every day I check the 16 day GFS total rainfall at 0Z and 12Z, and with few exceptions, not more than 1.5 inches in over two weeks.  Depressing.

 

But I can't stay depressed, I keep seeing signs of a potential East Gulf/Florida/Southeast landfall pattern and maybe a Caribbean cruiser pattern beginning of September, if we can just get the storms in place.

 

 

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Mid level center not looking shabby near 22N and 90.5W on last of visible images.  Doesn't show up quite as well on IR.

 

Trip to Galveston deferred, we finally got a decent thunderstorm, and its over Southern metro, and traffic would be a bear.  Small tree limbs down in the yard, best t-storm all year.

 

Never been at the Popo Playa Party Plaza with a cyclone in the Gulf,  not at all sure 92L will ever be a cyclone, but this is the closest we'll come this year.  To being in Galveston with a TC in the Gulf.  Don't want to rule out the changing early Autumn pattern season when something could sneak into our side of the Gulf, because I'd never hear the end of it on the odd chance something did.  If it can get semi-coherent while still South of 26N it has a chance to be a depression.

 

I'm assuming the 18Z SHIPS intensity of about 50 knots at landfall near the border is a reasonable number if it does become a coherent TC soon.  I still don't have a good feel for whether this is a sheared mess in a couple of days or becomes a tropical storm.  Not sure if it will be able to wrap in stronger storms forming over the Yucatan, or if those will disrupt organization until they weaken after dark.

 

Unrelated, yesterday, some of the less reliable global guidance were picking up on wave that had a nice low level signature but was convectively challenged.  A burst of convection caught my attention today, but it is several degrees East of the potential system.Has a bit more convection today (near NOAA logo).  JB tweeted about it today.  He hasn't tweeted about 92L lately. GFS & Euro not impressed.  Today's unreliable guidance, Canadian develops quickly and fishes, Navy tries to develop, land interaction issues but a obvious wave approaching Miami in a week.  CIMSS, low level vort, but still tied to ITCZ, ok upper convergence/lower divergence but some Easterly shear, and if it doesn't separate from the ITCZ, it will hit South America.  Low confidence, but closer than anything still over Africa.

 

Erin also catching my attention, she isn't going down w/o a fight per IR imagery

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post-138-0-01021600-1376699086_thumb.jpg

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:P

 

I'd go with the northern end of those plots...Matagorda to South Padre Island.

 

 

The starting point for the models appears to be the convectionless swirl, if a new center is forming to the Northeast, and everything else was the same (which it might not be), the guidance would be too far South, and extreme Northern Mexico to near Matagorda would be closer.  Assuming a new center doesn't form close enough to the trough to head more Northwards towards Louisiana.  And the CIMMS steering suggests initial position will affect direction.

 

I think Louisiana is still a viable option, although shear is forecast to be more hostile for anything getting much North of 25N.   Not to cite the new 0Z NAM as tropical guidance, but it splits 92L into two separate weak lows within a day

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