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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Quoting blsealevel:


thank you

No prob.

I neglected to also bold the last portion: When the TC size is large, the beta effect may have a major impact on the motion.

This is a larger system.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
1534. xcool
move off forecast points .move west..
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting DestinJeff:
Ok. Now things get "interesting"



A leftward recurve? Ummm...
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Quoting plywoodstatenative:
Stormchaser2007 Whats the intensity on that system? with the graphic you posted


Category 3

The winds were in m/s so:

115-120mph
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1531. markot
its not moving wnw look at loops maybe slightly south of west.
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1530. Ryuujin
Quoting DestinJeff:
Ok. Now things get "interesting"



Destin, am I reading that right? Is that a turn back to the west on that model or am I completely off my rocker?
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ridge much stronger in western atlantic and low pressure has replaced high pressure over greenland.
Link
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Quoting atmoaggie:
Seems that this should be posted again...

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 can be interpreted as the local change of the vertical component of relative vorticity due to the product of the beta parameter and meridional wind speed, i.e., the beta term in the absolute vorticity equation. The equatorial beta effect causes a northern hemispheric TC to move toward the northwest with a speed about several degrees per day when the large-scale steering flow is absent (Rossby, 1948 and 1949; Kuo,1950; Kitade, 1980; Anthes,1982; DeMaria, 1985; Chan and Williams, 1987 and 1994; Fiorino and Elsberry, 1989; Smith, 1993; Wang and Li, 1994; Jones, 1995). In the Northern Hemisphere, the beta effect causes tropical cyclones embedded in the easterlies south of the subtropical ridge to move faster and slightly to the right of the steering flow. The beta effect also causes Northern Hemisphere tropical cyclones moving northwest tend to move faster and to the left of the steering flow, and tropical cyclones moving northeastward tend to move slower and to the left of the steering flow (Elsberry et. al., 1987).

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


thank you

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1526. markot
Quoting WeatherfanPR:
TD#6 is actually following the NHC projected track and moving wnw.
it is mloving west not wnw.
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1525. xcool
plywoodstatenative .ooh okay
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Stormchaser2007 Whats the intensity on that system? with the graphic you posted
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nm on that one xcool
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Quoting HurricaneSwirl:


He made an attempt at cleverness but sorta failed. He was getting at the fact that at max intensity it would not be called TD6 anymore, so he would go with B. But that doesn't make any sense, because if it attained B it wouldn't be called TD6 anymore.. you would go with A..
And so we debate common sense... Lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
1521. wxhatt
The GFS brings it quite close to New England around day 11.

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Quoting errantlythought:


Could we please quote this every hour or something?

Thanks, Levi.


Models underestimated the recurve of Colin, it got closer to Bermuda than originally expected. Colin was to the slight right of consensus.
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Seems that this should be posted again...

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 can be interpreted as the local change of the vertical component of relative vorticity due to the product of the beta parameter and meridional wind speed, i.e., the beta term in the absolute vorticity equation. The equatorial beta effect causes a northern hemispheric TC to move toward the northwest with a speed about several degrees per day when the large-scale steering flow is absent (Rossby, 1948 and 1949; Kuo,1950; Kitade, 1980; Anthes,1982; DeMaria, 1985; Chan and Williams, 1987 and 1994; Fiorino and Elsberry, 1989; Smith, 1993; Wang and Li, 1994; Jones, 1995). In the Northern Hemisphere, the beta effect causes tropical cyclones embedded in the easterlies south of the subtropical ridge to move faster and slightly to the right of the steering flow. The beta effect also causes Northern Hemisphere tropical cyclones moving northwest tend to move faster and to the left of the steering flow, and tropical cyclones moving northeastward tend to move slower and to the left of the steering flow (Elsberry et. al., 1987).

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
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting Hurricanes101:
1475. Couillon 11:31 PM GMT on August 21, 2010

It says at maximum intensity


He made an attempt at cleverness but sorta failed. He was getting at the fact that at max intensity it would not be called TD6 anymore, so he would go with B. But that doesn't make any sense, because if it attained B it still wouldn't be called TD6 anymore.. you would go with A..
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1516. xcool
no POLL for me
Member Since: September 26, 2009 Posts: 2 Comments: 15603
I believe it moves W then WNW-NW then get pushed back west. JMO
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1512. xcool
plywoodstatenative .huh?
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Looking at things, conservatively thinking I think 06L will peak at 120 mph. If conditions allow, 06L could peak at 140 mph.
Member Since: July 8, 2005 Posts: 259 Comments: 23012
xcool: Let me put it this way, you put that photo on the Eleven O clock news down here. I guarantee everyone at Publix and such like grocery stores will want to kill you for it.
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Quoting Couillon:
It says maximum intensity for TD#6.It will be TS,not TD,so B.Then new poll starts.


Talking about PGI34L
Member Since: July 6, 2010 Posts: 108 Comments: 30245
TD#6 is actually following the NHC projected track and moving wnw.
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Looks like we'll have to watch this wave as well.

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1505. xcool


td6.
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting DestinJeff:
Ok. Now things get "interesting"



ok, so is that going northerly and then going back south?
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Quoting TropicalAnalystwx13:


This thing probably wont recurve


Model consensus is consistently pointing towards a recurve east of Bermuda. Time will tell.
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Quoting Hurricanes101:
1475. Couillon 11:31 PM GMT on August 21, 2010

It says at maximum intensity
It says maximum intensity for TD#6.It will be TS,not TD,so B.Then new poll starts.
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TD#6 Cat 4-5 before its done in my opinion. Lets hope it goes N from now!
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Quoting plywoodstatenative:
Kristina, falling back on what you said. How will you take your crow?


Huh? I don't recall making any predictions...I'm confused now.
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1499. wxhatt
A rather healthy system depicted here by the GFS.

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1497. xcool
DestinJeff .ABOUT GETTING interesting"
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting DestinJeff:
Ok. Now things get "interesting"

Now that's very "interesting".
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting DestinJeff:
Ok. Now things get "interesting"



yes it will
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I believe this system will become a Low-end Category 4 at maximum intensity.
Member Since: July 6, 2010 Posts: 108 Comments: 30245
Quoting heretolearninPR:


Thank you Taz for a good laugh. As the season heats up we will have less and less time for the laughs.



welcome
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Quoting Stormchaser2007:
The super hi-res NCAR WRF develops TD6 into a powerful hurricane



On that topic i have one thing to say: Y I P E S!!!!!
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Quoting Tazmanian:



sorry am not going too elaborate evere thing i say


Thank you Taz for a good laugh. As the season heats up we will have less and less time for the laughs.
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1488. xcool
DestinJeff . WESTHWRF
Member Since: September 26, 2009 Posts: 2 Comments: 15603
1475. Couillon 11:31 PM GMT on August 21, 2010

It says at maximum intensity
Member Since: March 10, 2010 Posts: 1 Comments: 7233
Kristina, falling back on what you said. How will you take your crow?
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About JeffMasters

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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