ATL: EX-Tropical Depression FIVE - Discussion

[JonathanBelles]

Third heavy rain squall moving through here...lots of heavy rain so far today
and more expected with more squalls developing...

Yep! I wanted to mention that I am seeing a lot of close lightning strikes, but the thunder is more muffled. Lightning in itself is significant, although how much i'm not sure.

[Ivanhater]

[HURAKAN]

this system has evolved pretty fast

[Stormcenter]

Looking at that radar loop would make you think 94L was headed northward right into
the FL. west coast.

[Frank2]

this system has evolved pretty fast

Yes, I agree - it appears to be drifting northward, too...

Perhaps a TD later this evening - we'll see (I'll have to see what Max says at 6 on Local 10)...

In fact, for folks outside the area who might want to see his comments later this evening, click on:

http://www.justnews.com/hurricane2010/index.html

Frank

[bayouself]

Definetely see the rotation here:

http://www.intellicast.com/Local/WxMap.aspx?location=USLA0101&weather=hdRadarSmoothPaletteA

[Weather Watcher]

I have a question?

According to the wunderground... http://www.wunderground.com/tropical/tr ... ml#a_topad

the Hurricane hunters found winds at 35 mph wouldn't this make it a td?

Steve

[ROCK]

agree....got to be because its on the back side of the ULL.....dont you hate developing systems in the shadow of a ULL...ugh

[HurrMark]

Yeah, I think this is probably a TD right now...although it probably is not on the precipice of becoming a storm (maybe 30 mph).

[Lowpressure]

I have a question?

According to the wunderground... http://www.wunderground.com/tropical/tr ... ml#a_topad

the Hurricane hunters found winds at 35 mph wouldn't this make it a td?

Steve

Highly dependent of how high the plane was flying and if they found a closed LLC. There is always a standard percentage reduction based on flight level.

[Stormcenter]

This is from this afternoon's NWS discussion out of N.O. It makes one "think" that 94L will not be classified a TD at 4:00pm.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
315 PM CDT TUE AUG 10 2010

.SYNOPSIS...
A WEAK 1011 MB SURFACE LOW IS LOCATED OVER THE SOUTHEASTERN GULF OF
MEXICO. A 1016 MB HIGH IS CENTERED OVER THE WESTERN ATLANTIC WITH
THE RIDGE AXIS EXTENDING ACROSS THE NORTHERN GULF COAST. PARTLY
CLOUDY SKIES HAVE ALLOWED TEMPERATURES TO RISE INTO THE MID 90S
ACROSS MUCH OF THE AREA WITH HEAT INDEX VALUES CURRENTLY IN THE
105 TO 108 RANGE.

&&

.SHORT TERM...
ALL EYES REMAIN ON THE LOW PRESSURE SYSTEM IN THE SOUTHEAST GULF
AS IT SLOWLY BECOMES MORE ORGANIZED. THERE ARE A FEW OUTLIERS...
BUT THE MODELS ARE GENERALLY IN GOOD AGREEMENT CONCERNING THE
TRACK OF THIS SYSTEM...WITH THE MOST LIKELY PATH TAKING THE SYSTEM
NORTHWESTWARD INTO THE NORTH CENTRAL GULF OVER THE NEXT TWO
DAYS. THE LOW SHOULD MOVE INLAND OVER SOUTHEAST LOUISIANA BY
THURSDAY MORNING.

CONCERNING THE EVENTUAL INTENSITY...WHILE THE SYSTEM STILL NEEDS
TO MOVE OVER A LARGE PORTION OF WARM GULF WATERS...IT IS
FORECAST TO MOVE RATHER QUICKLY AND WILL ONLY HAVE ABOUT 48 HOURS
TO STRENGTHEN BEFORE IT MOVES INLAND. THIS WILL LIMIT ITS
POTENTIAL INTENSITY AND IN FACT NONE OF THE MODELS FORECAST IT TO
STRENGTHEN BEYOND A MODERATE TO STRONG TROPICAL STORM.

REGARDLESS OF WHETHER OR NOT THE SYSTEM INTENSIFIES AND BECOMES A
TROPICAL STORM...THE LOCAL AREA WILL FEEL AT LEAST SOME EFFECTS OF
THIS SYSTEM. EXPECT INCREASED CHANCES OF RAIN...STRONGER WINDS AND
ELEVATED TIDES. THE CURRENT FORECAST IS CALLING FOR 3 TO 5 INCHES
OF RAIN THROUGH FRIDAY WITH ISOLATED HIGHER AMOUNTS POSSIBLE...AS
WELL AS WINDS IN THE 15 TO 20 MPH RANGE WITH HIGHER GUSTS...AND
TIDES 2 TO 3 FEET ABOVE NORMAL. IF THE STORM INTENSIFIES AND
BECOMES A TROPICAL STORM...ALL OF THESE NUMBERS WILL INCREASE AT
LEAST SLIGHTLY.

[Aric Dunn]

Looking at that radar loop would make you think 94L was headed northward right into
the FL. west coast.

well I mentioned this earlier but there is a lot of vorticity with the MLC and most of the convective mass is associated with the MLC and the southerly flow is very much stronger than the westerly and NW. this is causes a similar phenomenon and a top when you first spin it.. it makes circles before staying in place... The LLC is too weak and not defined enough and convection is increasing away from the weak LLC so all this vorticity and convection is pulling on it and will eventually if enough convection develops with the MLC the LLC will consolidate under it and the whole thing will complete this "cyclonic loop" type motion. This will be the time when strengthening could occur.

just a note: the fluid dynamics that are behind the formation of tropical systems are not simply basic dynamics but have many parallels.

[brunota2003]

I have a question?

According to the wunderground... http://www.wunderground.com/tropical/tr ... ml#a_topad

the Hurricane hunters found winds at 35 mph wouldn't this make it a td?

Steve

Highly dependent of how high the plane was flying and if they found a closed LLC. There is always a standard percentage reduction based on flight level.

They are currently trying to close off the circulation, and then they'll probably make a couple passes to see exactly how well defined it is. Right now, it appears to be too broad for an upgrade.

[Ikester]

Definitely not a storm. With a pressure of only 0082, the winds would not be high enough to justify such an upgrade...weak depression, yes. Keep in mind that air goes from the mountain to the valley. If your valley isn't very low, then the air will not be transported in very quickly. Not to mention, this is a HUGE circulation. Gonna take a while.

[BigA]

I think what we're seeing drifing northward is a sort of extraneous MLC. Per recon and buoy data, the LLC (at this time still ill defined) is farther west. IMHO I think it will concentrate tonight around 25 north, 84-85 west.

[JonathanBelles]

Seems to me that this either is a tropical depression or will be by tonight. The only reason I resist is that it still is quite broad, but with the proximity to land, I think it should be numbered. Recon supports although it is weak. If we can get a couple good bursts of storms over the center, 94L should tighten up.

[Ikester]

Moment of truth is approaching. To upgrade or not to upgrade? The decision has probably been made by the NHC. Word should be out in about 15 min...

[Aric Dunn]

there was a 40mph wind reported SW of Key west and Cman station...says non t'storm wind gust...

[dixiebreeze]

Seems like the NHC should at the least issue a tropical disturbance alert to the gulf coast states if it doesn't update. I have a hunch not many folks are taking this seriously enough

[Sanibel]

Obvious improvement in structure and cyclogenesis.


The motion of the radar bands could be caused by the ULL and not be a true reflection of surface movement.