95L growing more organized; Pakistan's Indus River flood peaking downstream

By: Dr. Jeff Masters , 2:23 PM GMT on August 21, 2010

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A tropical wave (Invest 95L) in the far eastern Atlantic about 350 miles southwest of the Cape Verdes Islands has become more organized this morning. Satellite loops show that the wave has some rotation, and heavy thunderstorm activity has increased in recent hours, after a period overnight with little change. Water vapor satellite loops show that there is some dry air to the north of 95L, but this dry air currently appears to be too far away to significantly interfere with development. The main impediment to development is the moderate 10 - 20 knots of wind shear over the system. The shear is forecast to remain in the moderate range through Monday, then decrease. This should allow 95L to develop into a tropical depression Monday or Tuesday. NHC is giving 95L a 30% chance of developing into a tropical depression by Monday morning. With 95L's recent increase in organization, these odds should probably be 50%.


Figure 1. Morning satellite image of 95L.

Forecast for 95L
A ridge of high pressure will force 95L to the west or west-northwest for the next five days, and the system should increase its forward speed from its current 5 - 10 mph to 15 - 20 mph by Monday. A series of two powerful troughs of low pressure are predicted to move off the U.S. East Coast next week and cross the Atlantic; these troughs should be able to pull 95L far enough to the northwest so that it will miss the Lesser Antilles Islands. If 95L stays weak or does not develop in the next five days, as predicted by the NOGAPS model, it has a chance of eventually threatening Bermuda. If 95L develops into a hurricane, as predicted by most of the computer models, it will probably recurve to the east of Bermuda and not threaten any land areas.

Elsewhere in the tropics
The ECMWF model is predicting formation of a tropical depression in the western Gulf of Mexico off the coast of Texas 6 - 7 days from now.

Pakistan's monsoon rains diminish; Indus River flood crest nears the coast
The flooding on Pakistan's largest river, the Indus, has slowly eased along the upper and middle stretches where most of the heavy monsoon rains fell in late July and early August. However, a pulse of flood waters from these heavy rains is headed southwards towards the coast, and flood heights have risen to near all-time record levels today at the Indus River gauge station nearest to the coast, Kotri (Figure 2.) The new flooding has forced the evacuation of an additional 150,000 people in Pakistan today. Flood heights at every monitoring station along the Indus have been the highest or almost the highest since records began in 1947. Fortunately, the monsoon has entered a weak to moderate phase, and heavy rain is not expected over the flood region over the next few days, according to the Pakistan Meteorological Department.


Figure 2. August flow rates along the Indus River, courtesy of the Pakistan Meteorology Department.

Some aid agencies helping with humanitarian crisis in Pakistan:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

Jeff Masters

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236. beell
Quoting atmoaggie:

What prog and storm said are true as well. There are 2 different things at play for this invest:
1. Upper level winds would affect a stronger system more, effectively drawing it north as a trough moves by
2. Beta effect drawing a larger system poleward, exclusive of steering winds.


95L does have some room for beta effect to provide latitude gain. More so in this system than others.

Add a touch of coriolis sauce.

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Member Since: July 6, 2010 Posts: 113 Comments: 32505
kman and storm concur..now I am perking up some...
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95L has now begun to organize after its convective wane last night. Looking at satellite imagery banding features are slowly beginning to develop. The overall structure of 95L also looks a bit more consolidated as well. The surface circulation is also getting better defined as noted on total percipitable water. 95L is also under the influence of the Madden-Julian Oscillation providing a moister environment for development. Currently I would give this area a 60% chance of developing into a tropical cyclone, however, it will take time and it may not become a tropical depression until Monday (conservatively).


Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting PanhandleChuck:


Glad to here that, I despise the fire ants that I have around here
Not sure why I don't have fire ants...

Could be due to the only 1 inch of top soil and all well-compacted clay around here. when using a post-hole digger, one "shaves" the clay. Tunneling in the stuff is probably impossible.

(I am in about the only place in SE LA that never was river delta/silt deposition.)
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Quoting kmanislander:


Yep. The next set will brush the NE islands.


Considering where the models are NOW, that's quite a big shift to the Left.
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Quoting StormW:
Standby for another left shift in model guidance.


Storm, don't do that!! You'll be called a wishcaster, west-caster, and those other things they call us people that look more at the pattern then forecast models. ;)
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Quoting atmoaggie:
Oddly, I don't have fire ants. Little black sugar ants that do bite, but is only slightly bothersome, thankfully, and no venom.


Oh my, poleward ants, mushrooms and hurricanes. I better get back to yard work, seems safer ;)

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hmnmm storm w interesting
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Quoting atmoaggie:

Beta, a mathematical notation, denotes the latitudinal variation of the Coriolis parameter or the latitudinal gradient of earth's angular speed. The Coriolis parameter, twice the component of the earth's angular velocity about the local vertical, has zero value at the equator, and becomes extreme at the pole (i.e., |1.4584E-4| radian per second). On the other hand, the beta parameter has a maximum value at the equator (i.e., 2.289E-11 per meter per second) and becomes zero at the pole.
...
The beta effect on a TC can be a function of the TC size, but not necessarily the TC intensity (DeMaria, 1985). When the TC size is small and the steering flow is moderate to strong (e.g., about 15 knots or 7.7 m/s), the direction of motion reflects the direction of the steering flow. When the TC size is large, the beta effect may have a major impact on the motion.

From here: http://www.nrlmry.navy.mil/~chu/chap4/se100.htm

Part of a most excellent resource: Tropical Cyclone Forecasters' Reference Guide


Thanks, atmo. Was about to post some dialogue from "Professor" character in a movie script I wrote. lol Yours is a better, more detailed explanation of the beta effect in a storm system. Great link, too!

Add: And thanks StormW and Progster! Slow to catch up with posts.:)
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Quoting StormW:
Standby for another left shift in model guidance.


Yep. The next set will brush the NE islands.
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Quoting StormW:
Standby for another left shift in model guidance.


Is this debate about WHEN it will recurve or IF?

Thanks.
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Quoting atmoaggie:
Well done! I have too many teeth to do an effective Arkansasan...
that's a common problem for people not from there...
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Quoting Hhunter:



that is old they olny update evere 6 too 8 hrs or so




here is the most newest one

95L is looking a lot better this AM then a few hrs a go


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Quoting atmoaggie:
Oddly, I don't have fire ants. Little black sugar ants that do bite, but is only slightly bothersome, thankfully, and no venom.


Do you want some? I'll give you mine.
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Quoting StormW:


Aye!


Hi again.

A well defined surface low is taking shape rapidly. As I said earlier today Monday ( daytime ) is a long way off for TD status given the increased pace of organization but Monday ( between midnight Sunday and sunrise Monday ) seems possible given what I am seeing out there now. Sunday evening also not out of the question IMO.
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Quoting ShenValleyFlyFish:
Pears to me theys tryin to say sumpin like a gyroskope. The faster you pull the string the better it stands up. You got a bigun like a hurrycane the faster you spin it the more it wants to go up to the north pole on acount of the earth spinnin under it and bein a gyro too or sumpin like that.
Well done! I have too many teeth to do an effective Arkansasan...
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Quoting atmoaggie:
Oddly, I don't have fire ants. Little black sugar ants that do bite, but is only slightly bothersome, thankfully, and no venom.


Glad to here that, I despise the fire ants that I have around here
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Quoting ShenValleyFlyFish:
Pears to me theys tryin to say sumpin like a gyroskope. The faster you pull the string the better it stands up. You got a bigun like a hurrycane the faster you spin it the more it wants to go up to the north pole on acount of the earth spinnin under it and bein a gyro too or sumpin like that.
thank ya Shen :)
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Quoting PanhandleChuck:


No, didn't hear that one... Did they get ya bad?
Oddly, I don't have fire ants. Little black sugar ants that do bite, but is only slightly bothersome, thankfully, and no venom.
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Quoting tkeith:
Arkansan (southern dialect)
Pears to me theys tryin to say sumpin like a gyroskope. The faster you pull the string the better it stands up. You got a bigun like a hurrycane the faster you spin it the more it wants to go up to the north pole on acount of the earth spinnin under it and bein a gyro too or sumpin like that.
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Member Since: July 6, 2010 Posts: 113 Comments: 32505
Quoting StormW:


Becuase closer to the surface, wind speeds move slower due to frictional forces. As one moves up through the atmosphere, wind speeds 9velocities) become faster. For instance, the predominate flow right now is east to west in the Atlantic. The weakness out by 55W is felt much stronger in the mid to upper level s of the atmosphere. As a strong builds, and gets stronger, the "center" gets steered higher up in the atmosphere...the stronger the storm, the deeper layer the steering becomes, as a hurricane, especially a major, extends very high in altitude. As the storm gets stronger, the actual flow of the storm itself becomes dominate, so the next "layer" up from there, where the storm circulation has no influence, is where the steering layer becomes.

This is why future Danielle, is more apt to "feel" the weakness from the (mid to upper trofs) that are forecast, if it becomes stronger, quicker. If it remains in shallow layer steering, it won't feel this weakness:

850-700


850-500


850-250


Ah yes, enlightenment. I had wondered about the layers as you mentioned, I had always thought about them being in a state of flux and not able to have a consistent effect on the steering of any system at any time and any place (where a system was). It is a complex issue, steering. Many factors and not all of them waving their hands and saying "Watch this"! As Dezi Arnez would say, "You 'splained it good".
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Quoting jason2010xxxx:
HOW IS THE FISH STORM DOING.



The fish are starting to swim in circles now.
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Quoting want2lrn:


Send it to me!


i wanna copy too!
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Quoting StormW:


Aye!
If this thing has trouble consolidating but spins up to a larger TS, beta could be important...
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Quoting WeatherfanPR:


This cyclone has 2 eyes. lol
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Quoting atmoaggie:
Remember that I had ants move into the blower motor of my car 2 weeks before Gustav hit LA?
(you know, the AC-on, ant-shower thing)


No, didn't hear that one... Did they get ya bad?
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Quoting KanKunKid:



Thanks Atmo aggie! Now that's more like it! Something I can sink my teeth into.
Thanks for that reference as well. Now I can throw away my dog-eared copy of "Tropical forecasting for dummies".


Send it to me!
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Quoting TropicalAnalystwx13:


Errr...


turns N after that at 150 hrs
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HOW IS THE FISH STORM DOING.

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Member Since: July 6, 2010 Posts: 113 Comments: 32505
Forget about the 06Z model runs. They don't initialize anywhere near where the current position is.

Waiting on the 12Zs.

Although, of some value for overall atmosphere.
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Quoting StormW:


That wasn't for you...the response you got from the blogger said that "nobody here is doing a great job forecastig"


I don't think the NHC are bad forecasters, they're just human like us :), with more knowledge on storms, sometimes makes bad judgement, but again.. human. I personally don't think 95L will ramp up too fast as models are showing, it's a monsoonal area of moisture. It took Alex 3-4 days to actually get going, so I'm agreeing with a westward steering for the next 48 hours. This should shift the models southwest somewhat in the next 24 hours. Observation, not a complete forecast ;)
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ACE is going to go up up up according to the 12z GFS with Danielle just meandering around...Shows her as a MH

Member Since: July 6, 2010 Posts: 113 Comments: 32505
Quoting StormW:


That wasn't for you...the response you got from the blogger said that "nobody here is doing a great job forecastig"


StormW,

Is it correct to say that this debate is more about WHEN 95L will recurve than IF?

Thanks.
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Quoting PanhandleChuck:


I hear ya bud, I just found it a little interesting.

Gustav did not make a direct impact here but it was close. The only thing we got was some gusty winds, big waves and some beach errosion
Remember that I had ants move into the blower motor of my car 2 weeks before Gustav hit LA?
(you know, the AC-on, ant-shower thing)
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Quoting Progster:


stronger systems go poleward because they tend to (a) travel toward areas of thinner atmosphere (think of the atmosphere as a tilted surface, thicker at the equator and thinner at the poles). and (b) are deflected poleward by Coriolis forces.


Its a force that considers the system as a whole. Think of a system as a vortex in a fluid. In the case of a hurricane, its sucking in mass at low levels, and pumping out mass aloft. To its south, the atmosphere is thicker. To its north, thinner. SO there's a already a bias to move north built in. Now the dynamics of the storm help determine its motion as well. Wherever, under a column of air from the surface to the top of the storm, its evacuating mass faster at the top than replacing it at the bottom, the surface pressure will fall. To keep its simple that generally happens over the NW quadrant of the low, and so promotes a northward bias in its track. The stronger the system gets, the more pronounced this effect is.
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Quoting HurricaneGeek:
Is this debate more about IF it will recurve or WHEN?

Because to me it seems we've got 15 people with 27 different opinions.
jajaja =)


Shear could impact 95L enough to keep it weak. Forward-speed could undermine convection... keeping 95L weak enough to miss the first trough.
Right now, it looks like a right-side of Bermuda track. But this is now.

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Quoting CosmicEvents:
There's no such thing as an ant-caster. The whole ant thing is just meant to draw anecdotal reports like yours, and for reporting, I thank you.
.
.
I've been keeping track of these anecdotal reports since LaDobeLady reported her ants in Houma, La., 10 days prior to Katrina's landfall...before Katrina even hit Florida. So far, I've found no to slim definite correlation...but we keep trying.


I hear ya bud, I just found it a little interesting.

Gustav did not make a direct impact here but it was close. The only thing we got was some gusty winds, big waves and some beach errosion
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Quoting KanKunKid:



Thanks Atmo aggie! Now that's more like it! Something I can sink my teeth into.
Thanks for that reference as well. Now I can throw away my dog-eared copy of "Tropical forecasting for dummies".

What prog and storm said are true as well. There are 2 different things at play for this invest:
1. Upper level winds would affect a stronger system more, effectively drawing it north as a trough moves by
2. Beta effect drawing a larger system poleward, exclusive of steering winds.
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Err...







Member Since: July 6, 2010 Posts: 113 Comments: 32505
Quoting TropicalAnalystwx13:


When :)


OK, that's what I was thinking. I like that 60/20 rule. Right now the center is at 10.6 and 31. That means we've got to go 9.4 more to the N and 29 to the W.
We shall see.
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Quoting atmoaggie:

Beta, a mathematical notation, denotes the latitudinal variation of the Coriolis parameter or the latitudinal gradient of earth's angular speed. The Coriolis parameter, twice the component of the earth's angular velocity about the local vertical, has zero value at the equator, and becomes extreme at the pole (i.e., |1.4584E-4| radian per second). On the other hand, the beta parameter has a maximum value at the equator (i.e., 2.289E-11 per meter per second) and becomes zero at the pole.
...
The beta effect on a TC can be a function of the TC size, but not necessarily the TC intensity (DeMaria, 1985). When the TC size is small and the steering flow is moderate to strong (e.g., about 15 knots or 7.7 m/s), the direction of motion reflects the direction of the steering flow. When the TC size is large, the beta effect may have a major impact on the motion.

From here: http://www.nrlmry.navy.mil/~chu/chap4/se100.htm

Part of a most excellent resource: Tropical Cyclone Forecasters' Reference Guide



Thanks Atmo aggie! Now that's more like it! Something I can sink my teeth into.
Thanks for that reference as well. Now I can throw away my dog-eared copy of "Tropical forecasting for dummies".
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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