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EPAC Tropical Action 2012


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Hey, Phil--

It's interesting how relevant this post of yours (from over a week ago) is:

Oh I agree... I'm just saying the synoptic pattern isn't that unfavorable for recurvature in May/Early June since you can still oftentimes get cutoff lows near Baja California. The main difference is the sea surface temperatures aren't supportive for a tropical cyclone above 15 degrees north so you probably won't get many substancial tropical cyclone landfalls.

The forecast for soon-to-be Bud nicely illustrates your point. The forecast track-- turning the cyclone NE and accelerating it-- is normally what I expect to see in October. But, as you say, it can also happen early in the season.

And, as you point out, the issue as Bud approaches the coast will be SSTs, which-- even that deep in the tropics-- still aren't that warm.

In any event, while 90E has some potential to become a TC, its already near the stable air located just to its northwest, and the system in general will probably have a short lifespan before its killed off by cold SSTs. Things become more favorable in the latter half of the month, where the ECMWF is suggesting some development beyond the day 5 range near the Gulf of Tehuantepec. I think that period will be a lot more interesting to watch.

Yep-- and TD 2E has formed right on time.

Kudos to ya. ;)

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Hey, Phil--

It's interesting how relevant this post of yours (from over a week ago) is:

The forecast for soon-to-be Bud nicely illustrates your point. The forecast track-- turning the cyclone NE and accelerating it-- is normally what I expect to see in October. But, as you say, it can also happen early in the season.

And, as you point out, the issue as Bud approaches the coast will be SSTs, which-- even that deep in the tropics-- still aren't that warm.

Yep-- and TD 2E has formed right on time.

Kudos to ya. ;)

Thanks Josh... while not a slam dunk by any means yet, I think the digging trough in the southwest United States beyond 72 hours should be more than enough of a weakness to pull TD 2E into the Mexican coastline.

lol @ the 12z Euro

Haha, didn't see that one coming. One thing that will have to be watched however, and the ECMWF highlights this problem, is that if the system moves too slowly, it may miss the weakness in the subtropical high in the 72-120 hour period. If the storm hasn't made landfall by day 6-7, the ECWMF suggests that a weak NE/SW oriented 500 hPa ridge will force the storm back slowly to the southwest. It is certainly an unorthodox solution, and my hunch is that its not likely to verify considering the strength of the trough in the Western United States, but still something worth keeping in the back of your mind if Bud ends up proving to be a slow mover.

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The models generally seem to be in OK agreement Re: a recurve to the NE-- although it's interesting that the GFS is also showing an about-face near the coast, like the 12Z Euro:

post-19-0-77378000-1337632580_thumb.gif

And the Ukie... thank god for the NGFDL and NOGAPS

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By the way, the track discussion is interestin':

THERE IS CONSIDERABLE CHANGE IN THE MODELS ON DAYS 4 AND 5...WITH THE 12Z GFS AND ECMWF SUGGESTING THAT THE CYCLONE MAY NOT BE FULLY PICKED UP BY A DEEPENING LONGWAVE TROUGH OVER THE WESTERN UNITED STATES...AND INSTEAD SLOWS DOWN AND STALLS VERY NEAR THE MEXICAN COAST. THE GFDL AND HWRF CONTINUE TO SHOW THE SYSTEM PLOWING NORTHEASTWARD ACROSS MEXICO...AND THOSE SOLUTIONS ARE DISREGARDED. THE NHC TRACK FORECAST SHOWS THE CYCLONE DECELERATING AS IT APPROACHES THE COAST OF MEXICO...ENDING UP ALONG THE COAST ON DAY 5.

Kinda lame. The GFDL/HWRF scenario is way hawter from a chase perspective.

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92E appears to be on the way after a long week of model teasing. A nice moisture envelope surrounds a future Bud. It does appear it will be a rather tight and small cyclone with some rapid IR potential the next 48 hours or so. While climo suggests nothing special, these small compact micro canes tend to throw a curveball or two. We will see.

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TS Bud has formed-- which is cool-- but the forecast is a buzzkill. Basically, all the models turn it NE toward the MX coast, but one camp accelerates the cyclone ashore whereas the other camp (GFS, Euro) decelerates and weakens it. The NHC has gone with the second camp, showing Bud unraveling to a TS well before reaching the coast.

Tingle cancel.

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TS Bud has formed-- which is cool-- but the forecast is a buzzkill. Basically, all the models turn it NE toward the MX coast, but one camp accelerates the cyclone ashore whereas the other camp (GFS, Euro) decelerates and weakens it. The NHC has gone with the second camp, showing Bud unraveling to a TS well before reaching the coast.

Tingle cancel.

post-19-0-64430400-1337677996_thumb.gif

Well it's a start though. The EPAC may be the region to focus on this year anyways.

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Some EPAC trivia-TS Bud in 2000 (a June storm) also moved northward and in mid June its moisture remnants moved into SE AZ triggering severe boomers and the earliest start to the monsoon on record. June 2000 wound up as the wettest June in living memory in Cochise County with rainfall totalling about 1000% of normal.

Steve

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Naked swirl alert... :lol:

The underperforming nature of this system thus far might be able to be explained by a Kelvin wave. I want to post an interesting graphic from Mike Ventrice's page which shows the subsidence phase of a Kelvin wave is in the process of traversing over the TC Bud. The interesting thing about this graphic is that its using Velocity Potential within the Kelvin wave band so this will accurately capture the upper level component of a Kelvin wave.

20p8o3o.gif

The red and blue contours represent convectively suppressed and convective active phases of the Kelvin wave. The vectors noted ar the 200 hPa wind anomalies with precipitation in mm/day noted from TRMM. The one thing you notice right away is the the distinct wind circulation associated with the supressed convective phase of the Kelvin wave. The typical convectively coupled Kelvin wave structure looks like this.

2vshvrk.png

Where there is strong convergence in the low levels that leads the stronger upper level divergence that occurs aloft. The suppressed phase works much in the same way, with divergence first observed in the low levels leading the upper level convergence. It is actually the convergent flow aloft that has lead to the increase in easterly shear over Bud (as seen in the graphic) that wasn't really accurately forecasted. In addition, the convergence aloft certainly is not favorable for convective enhancement as the signal moves overhead, so Bud, while not struggling convectively currently, may still not be producing as much convection around its core than it otherwise would be able to.

My best guess is that once the convergence moves directly overhead and shifts beyond TC Bud, we may see a brief period where the shear relaxes and intensification is observed. However, its also likely that westerly wind shear will increase on the backside of this convergent flow and then curtail development. Overall though, I think tomorrow will be Bud's best chance to develop. Whether or not RI occurs will likely determine if Bud can become a hurricane or not.

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