ATL: MATTHEW - Ex-Tropical Storm - Discussion

[HURAKAN]

1st visible (well, half) lol

[KWT]

I wouldn't get too worried just yet about any impacts alot down the line because this system could quite easily spend a few days overland and barely be a system at all once it emerges and be very large, so we just as easily be dealing with a TD towards Florida as we could a 3/4!

This is why this set-up is so interesting and so tough to make a decent call with.

[ColinDelia]

Agreed KTW. This is just a whole lotta unknown at this point

[I Scream Cone]

yes, but with the SST's as hot as they are, it would not take much time over water to become monstrous. Hope for the best, prepare for the worst.

[HURAKAN]

Latest

[GCANE]

Very unstable air this morning.

CAPE at 4000.

LI's around -5.

http://www.ssd.noaa.gov/goes/flt/t3/loop-wv.html

Great fuel to fire this up.

[cycloneye]

Up to 80%

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT THU SEP 23 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON RECENTLY
DOWNGRADED TROPICAL DEPRESSION LISA...LOCATED ABOUT 350 MILES
WEST-NORTHWEST OF THE CAPE VERDE ISLANDS.

THUNDERSTORM ACTIVITY HAS CONTINUED TO INCREASE AND BECOME BETTER
ORGANIZED THIS MORNING IN ASSOCIATION WITH A VIGOROUS LOW PRESSURE
SYSTEM LOCATED OVER THE SOUTH-CENTRAL CARIBBEAN SEA. ENVIRONMENTAL
CONDITIONS ARE GRADUALLY BECOMING MORE FAVORABLE FOR DEVELOPMENT...
AND THIS DISTURBANCE COULD BECOME A TROPICAL DEPRESSION LATER TODAY
AS IT MOVES WESTWARD AT AROUND 15 MPH. AN AIR FORCE RESERVE
RECONNAISSANCE UNIT AIRCRAFT IS SCHEDULED TO INVESTIGATE THE SYSTEM
LATER THIS MORNING. THERE IS A HIGH CHANCE...80 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
REGARDLESS OF DEVELOPMENT...THIS DISTURBANCE HAS THE POTENTIAL TO
PRODUCE HEAVY RAINFALL OVER PORTIONS OF CENTRAL AMERICA IN A COUPLE
OF DAYS.

[cyclonic chronic]

C.NASA'S GOLBAL HAWK WILL FLY A 26 HR MISSION INTO THIS
AREA DEPARTING 23/1500Z. OPERATING FL 580-650.

[HURRICANELONNY]

I think they'll find a depression. Center around 13n 75w.

[cycloneye]

11:45z

[Vortmax1]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MELBOURNE FL
411 AM EDT THU SEP 23 2010


THE FORECAST FOR WED-THU CONTINUES TO BE VERY LOW CONFIDENCE. THE
00Z RUN OF THE GFS AND ECMWF DRIFT A TROPICAL SYSTEM OUT OF THE
NORTHWEST CARIBBEAN AND INTO FLORIDA ON THU. I HAVE FOLLOWED THE
MODELS HANDLING OF THIS POTENTIAL SYSTEM FOR MORE THAN 10 DAYS AND
HAVE SEEN ALL KINDS OF SOLUTIONS. THE BOTTOM LINE IS THAT THERE IS
NO WAY TO HANG YOUR HAT ON ANY ONE MODEL OR SOLUTION WHEN THE
TROPICAL SYSTEM HAS NOT EVEN FORMED YET. OFTEN THESE KINDS OF
SYSTEMS HANG OUT IN THE NORTHWEST CARIBBEAN FOR AWHILE BEFORE
LIFTING NORTH. THEREFORE WILL FAVOR A CONTINUATION OF MOIST
SOUTHEAST FLOW AND KEEP POPS AT 40 PERCENT DURING THIS TIME
PERIOD...UNTIL THE SYSTEM DEVELOPS AND THE MODELS GET A BETTER
HANDLE ON THINGS.

[Blown Away]

The NHC stated there is a vigorous low, so I think they have a defined area to base model runs on. If 95L were to effect Melbourne it would be more than 7 days away, so yes I agree with not hugging models.

[HURAKAN]

Loop - http://rammb.cira.colostate.edu/ramsdis ... asec4ir204

a monster in the making

[HURRICANELONNY]

Totally agree with that discussion. I've said that many times. Models are a joke until we have Matthew.

[Comanche]

Anyone care to tackle this?



Regardless of heat content, this is at May levels, way below climo and from what I gather, is an impeding factor for this.

http://onlinelibrary.wiley.com/doi/10.1 ... 4/abstract

Excerpt- "it would appear difficult for cyclones or anticyclones of any reasonable size to develop significantly in low latitudes, with the exception of cyclones in a vertically unstable atmosphere."

I know this was a ways back, and I didn't read through all the intervening pages, but I might be able to comment just a bit on this.

Please understand, I've only just skimmed the paper. However, I am familiar with the ideas presented. First note that the paper was published in 1950, back when our understanding of synoptic-scale weather systems was still limited. Sumner was arguing based on the energy available in the thermodynamic instability of the atmosphere alone, without really considering the additional energy source of the underlying surface (in the case of tropical cyclones, the warm ocean). Our understanding of synoptic-scale systems (both extra-tropical and tropical) has progressed in leaps and bounds since then. Specifically, in the case of tropical cyclones, it is now understood that tropical cyclones indeed derive most of their energy from the latent and sensible heat fluxes from the underlying ocean surface. Vertical thermodynamic atmospheric instability does play a role, but it is this air-sea interaction that really fuels the storm. Consider the following, somewhat-layman-readable article by Kerry Emanuel:

ftp://texmex.mit.edu/pub/emanuel/PAPERS ... y_2006.pdf

The basic idea is that a hurricane acts is a heat engine which makes use of the thermodynamic disequilibrium between the atmosphere and ocean to drive its "motor", which is the kinetic energy of the winds. The increased low-level winds increase the flux of heat and moisture from the ocean surface by agitating the surface (waves and spray), which increases the kinetic energy of the winds again, and so on in a positive feedback cycle. Eventually, in an ideal setting, a steady state is reached in which the dissipation of kinetic energy by turbulence and surface friction balances the amount of power generated by the thermodynamic energy flux, which leads to Emanuel's famous Maximum Potential Intensity (MPI) index (http://wxmaps.org/pix/hurpot.html).

Obviously, the real-world scenario is more complicated, but the above mechanism captures the essence. In the real world, you have vertical wind shear which disrupts the heat engine cycle by weakening the "ascent leg" of the Carnot cycle, and by allowing dry mid-tropospheric air into the inner core, which dilutes the warm core by evaporation and mixing. Also, the vertical thermodynamic instability, discussed in the Sumner paper linked above, can help by "priming the pump", but it is not actually necessary to sustain a tropical cyclone once it gets going: in effect, the flux of heat and moisture from the ocean surface creates the needed vertical instability on a large scale -- in this case, simply parcel theory-derived calculations of instability (i.e. CAPE) don't really apply.

That's my quick take on the question. Let me know if anything is unclear or if there are any questions. I must also point out again that I'm really not as much a TC expert as I am a midlatitude severe storm guy, and my knowledge of the most recent research developments in tropical cyclones is somewhat limited (btangy, where are you ).

I cannot thank you enough for this explanation, it was one of those things that you look at, and nobody seems to know what to make of. Case in point, the question has been asked many times on this site without acknowledgment..........until now. Again, thank you!

[HURAKAN]

Latest

[cycloneye]

12z Best Track

AL, 95, 2010092312, , BEST, 0, 135N, 748W, 30, 1007, LO

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 010.invest

Changed from Disturbance to Low.

[wzrgirl1]

What does CA interaction imply?

[Vortmax1]

Comanche ...I'm glad to see you received a response to your question.
And thank you for posting it here. I hadn't read back too far yet.

[tolakram]

Looks like today is the day we get some development. Let's hope this is more clear cut than some of the models are hinting at and this gets torn up inland.