ATL: INVEST 91L - Discussion

[cycloneye]

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invest_al912008.invest
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200810191824
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INVEST, AL, L, , , , , 91, 2008, DB, O, 2008101918, 9999999999, , , , , , METWATCH, , AL912008
AL, 91, 2008101918, , BEST, 0, 176N, 869W, 25, 0, DB, 0, , 0, 0, 0, 0,

[CrazyC83]

Is the TD16 continued?

[cycloneye]

Is the TD16 continued?

No,is apart from 16.

[Just Joshing You]

I think this is separate from TD16.

[jinftl]

Excerpt from Dr. Jeff Master's blog...

An area of disturbed weather associated with a large area of low pressure has developed over the Western Caribbean Sea. This is not a reincarnation of Tropical Depression 16, but does have some of the moisture from that storm. The intensity and areal coverage of heavy thunderstorms in the disturbance has slowly increased over the past day.

Is the TD16 continued?

[Sanibel]

I'm looking at a long-range satellite loop (3 days) that clearly shows 16 moving into the East Pac. What's left in the NW Caribbean is some moisture that was following 16.

Agree. No doubt though this disturbance pulled in some lingering energy TD16 deposited in the monsoon trough feature in the area. It doesn't really matter since we now have a separate entity to track.


Perhaps this faster organization will allow the more east/stronger scenario to develop?

[cycloneye]

Not bad looking.

[Blown Away]

I'm looking at a long-range satellite loop (3 days) that clearly shows 16 moving into the East Pac. What's left in the NW Caribbean is some moisture that was following 16.

Agree. No doubt though this disturbance pulled in some lingering energy TD16 deposited in the monsoon trough feature in the area. It doesn't really matter since we now have a separate entity to track.
Perhaps this faster organization will allow the more east/stronger scenario to develop?

I think your right, looking at the deep BAM the stronger the system is the more east it will go.

[jinftl]

One thing for sure is that the water in the Bay of Campeche and most of the Gulf is still plenty warm. Most areas are still marginally favorable...at least able to sustain development until you get closer to the U.S. coast, where temps drops into the 70s (except the Florida peninsula which is still over 80 deg). Whether or not atmospheric conditions would be as favorable is another story.

[fci]

We're in the last couple of weeks or so to be very mindful of development in this area as it relates to Florida.

This is the area that some of the posters have been predicting would be an invest by the end of the weekend.

This time of year + W Carib = Pay close attention.

[kpost]

I looked it up in the tropical help section, i know these images are important but can not recall how, why or how to read them. All i do know is that something is definitely there and that others use these images so i posted them.

(if you can explain the divergence/convergence thing easily please PM me, thanks)

[MiamiensisWx]

I believe this system is on its way to TD classification within ~24-36 hours, although I'm leaning toward ~36 hours as a rough estimate. Visible satellite imagery depicts a well defined MLC and hints of an outflow channel (from a 250-300 mb trough) on the eastern semicircle. There is decent forced ascent in the vicinity, and there are two vorticity maximums in a broader region of 850 mb LL vorticity. Since the greatest convection is occurring near 85 W in the vicinity of the second vorticity maximum, it is plausible that a broad LLC may eventually develop in this vicinity.

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8vor4.html

http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

http://manati.orbit.nesdis.noaa.gov/storm_at_image21/latest_at_2.html

[MiamiensisWx]

I looked it up in the tropical help section, i know these images are important but can not recall how, why or how to read them. All i do know is that something is definitely there and that others use these images so i posted them.

(if you can explain the divergence/convergence thing easily please PM me, thanks)

Convergence denotes the accumulation of air within a particular locale, which results in a net inflow.

Divergence denotes the variations in wind speed at various atmospheric levels. It also denotes the movement of wind from one vicinity to another locale.

Vorticity denotes the amount of rotation in a horizontal plane. It is often a precursor to the development of surface lows, as well as low level circulations.

[jinftl]

This is a time of the year where the climatology seems particularly strong in indicating that a storm forming in the western caribbean will become a florida storm....given the steady progressions of troughs and fronts in late october, a recurve to the north and east would be hard to avoid....it is then more a question of the exact angle of approach, size, strength.

But climatology is not the final word on where a storm goes....outlier tracks do happen!

We're in the last couple of weeks or so to be very mindful of development in this area as it relates to Florida.

This is the area that some of the posters have been predicting would be an invest by the end of the weekend.

This time of year + W Carib = Pay close attention.

[CourierPR]

MiamiensisWx, your analysis is excellent and much appreciated.

[AJC3]

I looked it up in the tropical help section, i know these images are important but can not recall how, why or how to read them. All i do know is that something is definitely there and that others use these images so i posted them.

(if you can explain the divergence/convergence thing easily please PM me, thanks)

Convergence denotes the accumulation of air within a particular locale, which results in a net inflow.

Divergence denotes the variations in wind speed at various atmospheric levels. It also denotes the movement of wind from one vicinity to another locale.

Vorticity denotes the amount of rotation in a horizontal plane. It is often a precursor to the development of surface lows, as well as low level circulations.

Just to piggyback on what was said here...

Why are LL convergence and UL divergence important? Both lead to atmospheric ascent (rising air). When you have sufficient moisture/instability in the tropics, a low level focusing mechanism such as an incipient tropical disturbance, an area of synoptic ascent (via LL convergence/UL divergence or a combination of the two) will generally lead to persistent convection. Persistent convection leads to release of latent heat, which warms the column, spreads thicknesses and eventually lowers surface pressure - all the ingredients of TC development.

[kpost]

thank you MiamiensisWx
edited: to also thank AJC3
can convergence/divergence show shear?
my only concern would be if this system is only 100 miles or so from shore, how developed can it get before it hits land, and can't the land destroy it before it can hit the gulf and lower the chances for formation (or make it follow the BAMS and push through like TD16)? Yes i am -removed-, that it will NOT come near me or like accuweather (yes i know) keeps talking about it pushing through me (central Fl.) and nailing the east coast.

[jinftl]

As long as it doesn't re-emerge into the water...but there are many instances of storms/disturbances emerging off of the yucatan and strengthening...either for the first ime or regaining some portion of their former strength. Case in point...Wilma..she took quite a hit and weakened over the Yucatan but grew to a Cat 3 off of Florida.

thank you MiamiensisWx
can't the land destroy it before it can hit the gulf and lower the chances for formation.

[MiamiensisWx]

thank you MiamiensisWx
edited: to also thank AJC3
can convergence/divergence show shear?
my only concern would be if this system is only 100 miles or so from shore, how developed can it get before it hits land, and can't the land destroy it before it can hit the gulf and lower the chances for formation (or make it follow the BAMS and push through like TD16)? Yes i am -removed-, that it will NOT come near me or like accuweather (yes i know) keeps talking about it pushing through me (central Fl.) and nailing the east coast.

Although upper level divergence aids TCs' "ventilation" (and outflow channels), you're correct that it can also induce shear, ESPECIALLY if there is meager/scarce low level convergence. Excessive divergence and scarce low level convergence is detrimental to TCs' formation and intensity. The difference between UL divergence producing shear or "aiding" the TC can be also determined by the angle of the TC's movement in relation to the direction/strength of the upper level winds.

If this system moves over the Yucatan Peninsula, it would likely prevent the TC from entering the Gulf of Mexico as a purely tropical system, since baroclinic ascent (if I'm correct) will be occurring as the system moves over the Gulf of Mexico. Strong westerly wind shear south of a trough to the NW and north of a 250-300 mb (upper level) anticyclone in the Caribbean will likely result in a sheared "hybrid type"/subtropical system in the Gulf of Mexico (after its initial origination and development as a purely tropical system in the Caribbean).

Edit: The system will also be moving AGAINST the direction of the shear, which is a negative factor. Conversely, Wilma moved parallel to the upper level winds, allowing it to intensify prior to Florida landfall (via divergence aiding a poleward outflow channel).

[Tampa Bay Hurricane]

Thanks Miamiwx for your excellent analysis. I will be watching
this closely. Hopefully gulf shear should keep intensity in check.