TD 2 nearly dead; African disturbance 90L gathering strength

By: Dr. Jeff Masters , 2:38 PM GMT on August 13, 2009

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Tropical Depression Two is near death, but is still worth watching. The dry, Saharan air to the north and west of the depression, combined with moderately high levels of wind shear of 15 - 20 knots, have almost completely destroyed all of TD 2's heavy thunderstorms. Satellite loops of the storm show a well-formed circulation, but almost no heavy thunderstorm activity.

Wind shear over TD 2 is expected to remain in the modereate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C three days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that TD 2 will not be able to intensify quickly, and some of the models indicate the TD 2 may get destroyed in the next day or two. However, several models still predict TD 2 will become a tropical storm. The HWRF model predicts TD 2 will become a hurricane five days from now, but this seems unlikely given the dry air and relatively high wind shear affecting the storm.


Figure 1. Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).

African tropical wave 90L
A strong tropical wave with a large circulation and plenty of heavy thunderstorm activity is a few hundred miles south of the Cape Verdes Islands, off the coast of Africa. NHC dubbed this disturbance 90L this morning. This morning's QuikSCAT pass shows that 90L has a very large circulation, and top winds of about 30 mph. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are in two major bands, to the north and to the south of the center. There is no heavy thunderstorm activity near the center yet, and this would have to happen before 90L can be named Tropical Depression Three. Water vapor imagery shows that since 90L is forming several hundred miles south of the dry air of the Saharan Air Layer (SAL), the storm should not be affected by dry air and dust as much as Tropical Depression Two has been. Wind shear is about 20 knots over 90L, and is forecast to remain in the moderate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days, which are high enough above the 26°C threshold for tropical cyclone formation to allow some slow development to occur. The GFS and ECMWF models continue to predict the development of this wave, though they are now less aggressive about intensifying it than they were in earlier runs. The consensus among the reliable HWRF, GFDL, GFS, and ECMWF models is to bring 90L to point near or just north of the northernmost Lesser Antilles Islands 6 - 8 days from now. The storm could be at hurricane strength by then, as forecast by the SHIPS intensity model.

I'll have an update Friday morning.

Jeff Masters

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An anticyclone has developed over 90L which should aid in upper level divergence and outflow which should cause the low to strengthen,deepen,and allow convection to form...
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Article in today's paper about the mess in Taiwan - they might be doing something horrible to the weather bureau for 'not predicting the typhoon'- not fair for those guys :(

http://www.smh.com.au/world/typhoon-victims-tell-the-president-to-get-moving-20090813-ejwn.html
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Quoting rxse7en:
Are TD2 and 90L developed enough for a slight Fujiwhara effect? Perhaps TD2 will start a more southerly track if it's not absorbed?


CMC was actually showing both storms nearing hurricane strength and merging in the CATL a few days ago (which I and pretty much everybody else on here made fun of), they're probably too far apart and since they're heading in roughly the same direction at about the same speed any interaction would be at most minimal.
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Over my life of watching Tropical Storms And Hurricanes, One thing is consistant, Weather can and will always suprise you. Its always changing. I give props to the people that put the time in forecasting storms to save lives.
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1726. amd

Quoting DM21Altestic:

2007 in particular was most notorious for the "certain kinds of caster"

*wishcaster - the art of wishing a storm to develop or hit a certain landform

*downcaster - the art of wishing a storm to dissipate, triggering the anger of wishcasters

*fishcaster - the art of wishing a CV storm to go out to sea and not hit the United States or land masses points southward, triggering the anger of westcasters

*westcaster - the art of wishing a storm (usually a CV storm) to go west and miss the chance to go out to sea, and instead hit land (possibly the United States).

*eastcaster - the art of wishing a storm (generally a Gulf storm) to bend further to the right. This was seen with Fay (2008).

*northcaster - the art of wishing a storm to miss the Yucatan Peninsula and instead go through the Yucatan Channel and miss the land masses to the west and east, seen with Emily and Wilma (2005) and Dean (2007).


yep, that year was full of 'casters, especially with Karen and Dean.
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Quoting Prgal:

I dont mind a tropical storm, but I dont want another David, Hugo or Georges. No way!


Jean wasnt any fun either no light or water for 5 days
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We are doing better this year, but are slipping back onto the drought monitor map. Reservoirs never fully recovered. We still rely on tropical systems and haven't seen anything in the past two years...
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1722. rxse7en
Quoting SavannahStorm:
Anyone that takes the GFS out 160+ hours as a fact obviously hasn't been paying attention. GFS has shown 90l to hit everything from Texas to Nova Scotia, and it changes each run. Despite the assertions of a certain someone, nothing is set in stone- nothing.

Give the system about 4-5 days, then we'll have a much better idea of where it is going once it reached the Antilles.
Wish I still had my "Set in stone" graphic from five years ago :D
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Quoting sky1989:
Like Louisanaboy, I hope that this storm stays away from all landmasses. But like Weather456 says, whatever this storm does it completely out of our control. Whatever we want it to do, or whatever we think it will do does not affect what will actually happen. We must continuously monitor what is going on, and always be prepared for the worst.

On a sidenote.
Reducing Greenhouse gas emissions in the first place, would help to prevent such super forces.
For example, more Co2 emission means hotter oceans.

Now, i agree it's out of human control.
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No problem, mel. How's SoCal? It's been monsoon season here, it has rained every afternoon, heavily, for the past 2 months.
Member Since: September 22, 2005 Posts: 18 Comments: 2343
Quoting MississippiWx:
Not sure how much there is to this, but the area north of the DR is very interesting to watch on visible satellite right now.

Visible


What's even more interesting about this area is how it appears to have a low shear environment and possible an upper high, allowing ventilation (outflow) in all directions. I have a feeling this will dissipate overnight, but you never know this time of year.
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1716. rxse7en
Are TD2 and 90L developed enough for a slight Fujiwhara effect? Perhaps TD2 will start a more southerly track if it's not absorbed?
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Quoting leftovers:
i fricken mad sure my computer is old but it was running perfectly until i clicked on this site now its screwed. before you all cash your check think about it it is characters like mind that got hurt by your failure to keep your systems clean enjoy your vacations
What are you talking about now?
Quoting SavannahStorm:
Anyone that takes the GFS out 160+ hours as a fact obviously hasn't been paying attention. GFS has shown 90l to hit everything from Texas to Nova Scotia, and it changes each run. Despite the assertions of a certain someone, nothing is set in stone- nothing.

Give the system about 4-5 days, then we'll have a much better idea of where it is going once it reached the Antilles.


Thank you for being a voice of reason, Savannah!
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Not sure how much there is to this, but the area north of the DR is very interesting to watch on visible satellite right now.

Visible
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Quoting DDR:
Good evening all.
456,any decent rain yesterday?
I'm getting too much rain in my area,When the itcz settles over in August its not nice.


yes, it rained heavy all last night. Was very refreshing since nights here can be warm.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1709. Prgal
Quoting Relix:
TD2 is fighting the good fight! I wouldn't mind a minimal TS here in PR to be honest =P. 40MPHs. Quick passing. Bring a thrill or two. Anything beyond TS is not welcome here in PR though! shoo shoo sho!

I dont mind a tropical storm, but I dont want another David, Hugo or Georges. No way!
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1707. JRRP
114
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1706. DDR
Good evening all.
456,any decent rain yesterday?
I'm getting too much rain in my area,When the itcz settles over in August its not nice.
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1704. Relix
TD2 is fighting the good fight! I wouldn't mind a minimal TS here in PR to be honest =P. 40MPHs. Quick passing. Bring a thrill or two. Anything beyond TS is not welcome here in PR though! shoo shoo sho!
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Quoting stormpetrol:
Slowly but surely former td2 is showing signs of regeneration , looks as though shear might have lighten up a bit ahead of it.

as I said we go to bed knowing TD2 is a remnant low we wake up and at 5am newly re-born TD2
Member Since: June 13, 2009 Posts: 2 Comments: 12712
the "wish" part --- In order not to be called a wish/down/west/north/florida/etc caster... you have to just state facts. Once you start giving any type of opinion you become a caster

many of the models are now showing a strong mid to upper level trough over the SEUS in that time frame which could potentially steer what is 90L away from the Eastern seaboard depending on the timing of the trough some models predict the trough could come in soon enough to turn 90l out to sea....Happy?
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TD 2

Member Since: July 24, 2005 Posts: 407 Comments: 19076
1700. sky1989
Quoting SavannahStorm:
Anyone that takes the GFS out 160+ hours as a fact obviously hasn't been paying attention. GFS has shown 90l to hit everything from Texas to Nova Scotia, and it changes each run. Despite the assertions of a certain someone, nothing is set in stone- nothing.

Give the system about 4-5 days, then we'll have a much better idea of where it is going once it reached the Antilles.


Amen to that!
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1699. fire635
Quoting DM21Altestic:

How is it downcasting to wish a storm to miss the United States and other land masses?


the "wish" part --- In order not to be called a wish/down/west/north/florida/etc caster... you have to just state facts. Once you start giving any type of opinion you become a caster
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No ill wishes on anyone, GOM, EC, or otherwise, but I'm still up here watching with interest and doin' my rain dance.
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you know... it really makes no big difference if this thing becomes a depression today, tomorrow, or saturday. It most, most, most likely will become a depression, so let's just watch and wait for the NHC to call it instead of being so concerned about when the NHC decides it's time to label it a TD :) Enjoy the show.
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1695. rxse7en
Quoting louisianaboy444:
They might call you a troll next.

lol i have been posting valuable information on this blog for 5 years i'm no where near a troll but let them call me what they like sometimes you just have to be the better person and look the other way...i call them like i see them and all i'm saying is that the models are showing more of a chance that this storm could miss the U.S all together and i think that is good news but i could be wrong...
Nah, you're right. How can people not getting hurt and property damaged be a bad thing?
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1694. Walshy
Winter Weather Advisory

Statement as of 2:47 PM MDT on August 13, 2009

... Winter Weather Advisory in effect from 6 PM Friday to noon MDT
Saturday for elevations above 5500 feet in Glacier National Park...

The National Weather Service in Great Falls has issued a Winter
Weather Advisory for snow... which is in effect from 6 PM Friday
to noon MDT Saturday for elevations above 5500 feet in Glacier
National Park.

One to two inches of early season snowfall is expected at
elevations above 5500 feet along going to the sun Road in Glacier
National Park Friday night and Saturday morning. Peaks above 7000
feet could receive as much as 6 inches of snow.

Marias Pass... which is at an elevation of about 5200 feet along U.S.
Highway 2... is not expected to receive accumulating snowfall. This
advisory is specifically addressing going to the sun Road and the
high country of Glacier National Park and nearby portions of the
Continental Divide.

Precautionary/preparedness actions...

A Winter Weather Advisory for snow means that periods of snow
will cause primarily travel difficulties. Be prepared for snow
covered roads and limited visibilities... and use caution while
driving.

For specific Road and travel conditions in Montana... dial 5 1 1.
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Anyone that takes the GFS out 160+ hours as a fact obviously hasn't been paying attention. GFS has shown 90l to hit everything from Texas to Nova Scotia, and it changes each run. Despite the assertions of a certain someone, nothing is set in stone- nothing.

Give the system about 4-5 days, then we'll have a much better idea of where it is going once it reached the Antilles.
Member Since: September 22, 2005 Posts: 18 Comments: 2343
1691. WxLogic
18Z GFS running... So far is has less intense system, but strong enough nonetheless. As we know weaker system tend to head further west than stronger ones. We shall see how the trough is depicted in this run.
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They might call you a troll next.

lol i have been posting valuable information on this blog for 5 years i'm no where near a troll but let them call me what they like sometimes you just have to be the better person and look the other way...i call them like i see them and all i'm saying is that the models are showing more of a chance that this storm could miss the U.S all together and i think that is good news but i could be wrong...
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1689. sky1989
Like Louisanaboy, I hope that this storm stays away from all landmasses. But like Weather456 says, whatever this storm does it completely out of our control. Whatever we want it to do, or whatever we think it will do does not affect what will actually happen. We must continuously monitor what is going on, and always be prepared for the worst.
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If currents trend continue my opinion is that we'll have a designated depression by this time on Saturday.
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Quoting Weather456:


My day been busy and it will get so as 90L evovles.

I'm expecting a TD between Friday and Sunday.
thanks weather i am also monitoring the situation does not look good for the northern leeward islands
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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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