Invest 94L,Near Windwards-Discussions

[Sanibel]

On the other hand, people like myself who called for direct development of this system will be lucky if it forms. It has very poor structure and convection and the circulation it is embedded in has a "V" shape like a wedge to its NW in a very elongated pattern. This is a seriously lacking disturbance. I think it will form because it has managed to stay alive in very unfavorable conditions of dry air, crushing ridge, and probably horizontal subsidence. That said, the center is still ill-defined and poorly convected.

I suspect we'll see this storm get it together as it hits SST's where that becomes inevitable.

[Blown Away]

Still has a nice overall spin.
http://www.ssd.noaa.gov/goes/east/tatl/loop-vis.html

[vaffie]

I think it could easily develop. And the fact that it's not developing immediately is actually a bad sign for folks in the US, since it's more likely then to be weaker at first and thus have it's track miss Central America and head for the Gulf. So I would definitely not write this off. You can see very nice spiral bands in the vicinity of it's LLC right now on the latest infrared. I would not be surprised at all if some time later today or tonight as it crosses the 50th parallel, a blow-up of convection occurs at the center and rapid progression to TD and TS start to take place. Good vorticity. Decreasing shear. Warming sea surface temperatures. Right part of the season. Not too far south or too far north. I think it's got a strong chance. And frankly, when the NHC says conditions will improve, more than half the time, they do so quite dramatically.


http://weather.msfc.nasa.gov/GOES/goeseasthurrir.html

[x-y-no]

BAMS continues to be well north of the main cluster of model tracks. We should know today if this isn't totally off-base regarding the strength of the low-level ridging.

CONU has shifted substantially south since 0Z.

[Sanibel]

95L could pull this one unlike Dean. The flow 95L is embedded in is rocketing south - which is probably the sign of a weakness this time.

[wxman57]

I disagree with several of the above posters writing off 94L, but I do agree with the NHC. The official forecast as stated by the NHC is for environmental conditions to become more favorable for development. I'll go with the official forecast and say 94L is not dead and has a chance for development as we near September 1st.

I'm not sure if you were referring to my post that I didn't expect any development over the next 2-3 days, but I'm not saying it's dead, just that the best chance of development may be in the 4-6 day time frame when it reaches the central and western Caribbean as opposed to the next few days.

[skysummit]

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1015 AM EDT WED 29 AUGUST 2007
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 30/1100Z TO 31/1100Z AUGUST 2007
TCPOD NUMBER.....07-097

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (NORTH OF THE BAHAMAS)
FLIGHT ONE
A. 30/1800Z
B. AFXXX 01FFA INVEST
C. 30/1500Z
D. 29.0N 76.5W
E. 30/1730Z TO 30/2200Z
F. SFC TO 10,000 FT

FLIGHT TWO
A. 31/0600Z
B. AFXXX 02FFA CYCLONE
C. 31/0200Z
D. 28.0N 76.0W
E. 31/0500Z TO 31/0900Z
F. SFC TO 10,000 FT

2. SUCCEEDING DAY OUTLOOK: CONTINUE 12 HRLY FIXES IF
SYTEM NORTH OF THE BAHAMAS REMAINS A THREAT.
POSSIBLE LOW LEVEL INVEST NEAR 13N 58W AT 31/1800Z.

[Fego]

Can a system like Invest 94L be weakening but at the same time lowering its mb?. Right now the Navy page shows a 1009 mb (11N-46.9W). Yesterday the TWD (8:05 p.m.) had it with 1010mb and that was 1 mb lower than the previuos TWD (2:00 p.m.).

Here is the Navy link:
http://tcweb.fnmoc.navy.mil/tc-bin/tc_home.cgi

Besides, already is not classified as 'too weak':

29/1115 UTC 11.2N 44.8W T1.0/1.0 94L
29/0615 UTC 11.7N 42.8W TOO WEAK 94L.
Again, can be weakening no matter those facts?

[Fego]

I disagree with several of the above posters writing off 94L, but I do agree with the NHC. The official forecast as stated by the NHC is for environmental conditions to become more favorable for development. I'll go with the official forecast and say 94L is not dead and has a chance for development as we near September 1st.

I'm not sure if you were referring to my post that I didn't expect any development over the next 2-3 days, but I'm not saying it's dead, just that the best chance of development may be in the 4-6 day time frame when it reaches the central and western Caribbean as opposed to the next few days.

I am sure he was not referring to your post. My guess it was the Derek Ortt post, if I'm not wrong. Here is Derek's post:
"
I am seeing 94L slightly less organized this morning, just spit out a MASSIVE outflow boundary and I no longer see any signs of a surface circulation
chances of development just went down to close to nothing during the next couple of days
probably time to start focusing on the next system, as this one just blew itself up from the looks of morning visibles.
I am seeing 94L slightly less organized this morning, just spit out a MASSIVE outflow boundary and I no longer see any signs of a surface circulation chances of development just went down to close to nothing during the next couple of days probably time to start focusing on the next system, as this one just blew itself up from the looks of morning visibles."
.

[wxman57]

"Strength" is not just determined by the central pressure, it's a function of that pressure vs. the environmental pressure around 94L. As 94L moves farther west it is moving into a region of lower environmental pressures. This would lead to a slightly decreased pressure gradient (i.e. weakening) even with a lower central pressure.

Besides, the central pressure estimates are just that - estimates. Margin for error could be a few millibars.

Can a system like Invest 94L be weakening but at the same time lowering its mb?. Right now the Navy page shows a 1009 mb (11N-46.9W). Yesterday the TWD (8:05 p.m.) had it with 1010mb and that was 1 mb lower than the previuos TWD (2:00 p.m.).

Here is the Navy link:
http://tcweb.fnmoc.navy.mil/tc-bin/tc_home.cgi

Besides, already is not classified as 'too weak':

29/1115 UTC 11.2N 44.8W T1.0/1.0 94L
29/0615 UTC 11.7N 42.8W TOO WEAK 94L.
Again, can be weakening no matter those facts?

[Fego]

Well, thanks. As I say, every day you learn something.

[Dynamic]

Can a system like Invest 94L be weakening but at the same time lowering its mb?. Right now the Navy page shows a 1009 mb (11N-46.9W). Yesterday the TWD (8:05 p.m.) had it with 1010mb and that was 1 mb lower than the previuos TWD (2:00 p.m.).

Here is the Navy link:
http://tcweb.fnmoc.navy.mil/tc-bin/tc_home.cgi

Besides, already is not classified as 'too weak':

29/1115 UTC 11.2N 44.8W T1.0/1.0 94L
29/0615 UTC 11.7N 42.8W TOO WEAK 94L.
Again, can be weakening no matter those facts?

As my better understand, those numbers in bold are the estimate intensity using the Dvorak technique. The current numbers above are displaying an increasing trend from Too Weak to a full T-Number in the last hours. The system looks in the satellite to have a mean wind speed of 25Kts and their current intensity match with this classification. Based on this the system has a better classification now than 6 hours ago. Let see if this trend continue.

[windstorm99]

Jeff Masters thoughts on 94L....

A tropical wave midway between Africa and the Lesser Antilles (94L) has changed little since yesterday. QuikSCAT data from 4:47am EDT this morning shows a poorly organized system with a weak, elongated circulation. Top winds were 25 knots (29 mph). Visible satellite loops show a limited amount of disorganized thunderstorm activity. Wind shear is a favorable 5-10 knots over 94L, and should not be a problem for it until Friday or Saturday. By then, 94L will be moving through the Lesser Antilles Islands, and may encounter high wind shear if it is far enough north to feel the winds of an upper-level low pressure system that will be just north of Puerto Rico.

The presence of a large, dusty area of dry air surrounding its north side is the main thing holding back 94L. This dry air is being sucked into the circulation and is interfering with the storm's organization. When the dry air encounters a thunderstorm inside 94L, this denser dry air gets incorporated into the thunderstorm's downdraft, accelerating the downdraft, and creating arc-shaped surface cumulus clouds that mark the downdraft's position as it spreads out along the ocean surface (Figure 1). The presence of these arc-shaped surface clouds is usually a good sign that a storm is struggling with dry air and will not intensify significantly for at least the next 12 hours.

Water vapor satellite loops of the region show that 94L has not significantly moistened its environment. As the storm continues further west, it should be able to gradually do so, allowing it more of a chance to get organized. The system should track through the Lesser Antilles Islands on Friday, which is the earliest day I expect it could become a tropical depression. None of the reliable computer models make a believable forecast showing 94L developing into a tropical depression before it reaches the Lesser Antilles. The GFDL develops 94L into a tropical storm once it makes it into the central Caribbean south of the Domincan Republic, and this is a believable forecast, if 94L hangs together and makes it into the central Caribbean. The Hurricane Hunters are on call to investigate 94L on Friday.

[Derek Ortt]

the Dvorak estimates are subjective, so even though T numbers may go one way, the storm could be going the other

[Sanibel]

Everyone watching it knows if it refires it has something. I think we're all waiting for a refire. Maybe tonight, maybe tomorrow.

[HURAKAN]

Tropical Weather Outlook


Statement as of 11:30 am EDT on August 29, 2007

For the North Atlantic...Caribbean Sea and the Gulf of Mexico...

A tropical wave located about 900 miles east of the Windward Islands
is producing showers and thunderstorms. Although this activity is
currently disorganized...environmental conditions are expected to
gradually become more favorable for development as the system moves
westward at 15 to 20 mph.

An area of disturbed weather over the western Atlantic is primarily
associated with a non-tropical low centered about 260 miles
southeast of Charleston South Carolina. Upper-level winds could
become a little more favorable for development during the next few
days...and an Air Force plane is ready to investigate the system on
Thursday...if necessary. The low is expected to drift southward.

Showers and thunderstorms primarily located over the Yucatan
Peninsula are associated with a tropical wave. This activity is
expected to move over the Bay of Campeche during the next day or so
and will be monitored for any signs of development.

Elsewhere...tropical cyclone formation is not expected during the
next 48 hours.

$$

Forecaster Avila/Blake

[Anthonyl]

Actually Sanibel it's already beginning to re-fire.

[skysummit]

Actually Sanibel it's already beginning to re-fire.

Not shooting out outflow boundaries to the north it isn't.

[alienstorm]

You can now see the LLC at 10.8N 45.7W, however, it still looks very disorganized.

[CrazyC83]

I think this is about 36 to 48 hours from becoming TD6 or TD7 at this rate.