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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Quoting Acemmett90:

now im nervous and you should be to i hope i goes poof but i know that wont happen


Nervous? Please, its a just an INVEST. Quit being the JFV Jr. Team and look at the facts. The storm, not even a depression, is still thousands of miles away
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By the by... France and Germany have gotten out of their respective recessions.

Good news.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Quoting HurricaneKyle:


So are Delta II launches with GOES satellites. I believe that correlates some. :)


I heard about this on the radio. This has nothing to do with satellites. When a hurricane hits the coast, it mixes up the dirt. So by taking core samples from the coasts, you can see how often hurricanes hit. Therefore, because there has not been much mixage in the lower levels, this has been the most active period in a long time.
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Waiting on the speciality models on 90L...
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Quoting FloridaTigers:
Interesting BBC article: http://news.bbc.co.uk/2/hi/science/nature/8197191.stm

Hurricanes in the Atlantic are more frequent than at any time in the last 1,000 years, according to research just published in the journal Nature.

too bad there is no way for them to know that with even 90% certainty.

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Quoting FloridaTigers:
Interesting BBC article: http://news.bbc.co.uk/2/hi/science/nature/8197191.stm

Hurricanes in the Atlantic are more frequent than at any time in the last 1,000 years, according to research just published in the journal Nature.


So are Delta II launches with GOES satellites. I believe that correlates some. :)
Member Since: August 10, 2009 Posts: 3 Comments: 672
Quoting StormW:
TROPICAL WEATHER SYNOPSIS /TD2/INVEST 90L/SYNOPSIS AUG 13, 2009 ISSUED 10:40 A.M. EDT


Thank you for this: "The other thought is...the possibility of development in the GOMEX could exist...I say COULD...not definite."
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90L is enormous compared to T.D. 2. I think it could really turn ugly as it starts out over the Atlantic with all that warm water.
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Due to 90L's size its going to take some time for TD status,as angular momentum and conservation of energy will take her awile to get going.

A Storms size is usually determined at Genesis..Small remain small to a extent,and Large do the same.
A cat 3 Large storm can do much more damage and overall Impact than a Cat 4-5 Smaller storm as a rule too.
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Quoting Acemmett90:

and pretty fast for a massive storm
yeah, you would think that what happend in the last hour would take about 15 hours for a storm of that proportion.
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Interesting BBC article: http://news.bbc.co.uk/2/hi/science/nature/8197191.stm

Hurricanes in the Atlantic are more frequent than at any time in the last 1,000 years, according to research just published in the journal Nature.
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273. jasoniscoolman10
Quoting jasoniscoolman10:
Storm Relative 16km Microwave-Based Total Precipitable Water Imagery
Is that yellow comma at about 35W 15N'ish, showing the dry air (relative to surrounding environment) that has wrapped around #2?
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Quoting CaneWarning:


I think the GFS is more about track instead of intensity at this time. Correct me if I'm wrong.


good point. My point was more of a point that said... "THEY HAVE IT AS ANA."
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Quoting Acemmett90:
not good see below
so now it has 3 bands and convection over the center, looks like it is intensifying quite rapidly, imo.
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Quoting leftovers:
almost everyone ate crow the their td 2 forecast


this is why I don't make forecasts... just observe on what is going on.
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Quoting hurristat:


They have it at 1000 mb in the last frame...


I think the GFS is more about track instead of intensity at this time. Correct me if I'm wrong.
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Quoting weatherwatcher12:

I believe K-Man said that it is just upper diffluence caused by interaction with the ULL
correct
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Quoting Patrap:
12 Z GFS Model run loop


They have it at 1000 mb in the last frame...
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Quoting Vortex95:


That disurbance bears some watching but that blow up is a bit disorganised.

I believe K-Man said that it is just upper diffluence caused by interaction with the ULL
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Quoting Patrap:
12 Z GFS Model run loop


Thank you!
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Quoting SomeRandomTexan:
I may be eatig crow later but I don't think the area of interest in the Bahamas will amount to much... If anything were to happen it would take quite a bit of time.. the is currently no vorticity in the area and the ULL interacting with it should keep in in check.. jmho
i agree its just going to be a rain maker for us in south Florida which is well welcomed.
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308. JRRP
Quoting CaneWarning:


Can someone please post the GFS images to the blog? I am unable to access most of the websites from work. Thanks.

Link
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A few thoughts on TD 2 and 90L.

TD 2 is crippled. Though it's thrown up a nice thunderstorm cell, the circulations is elongating east to west. At this point the system is hours away from opening up into a wave unless the thunderstorm activity somehow manages to increase further in size and duration. To do that TD 2 would have to fight through moderate shear, relatively low heat content, and a ton of dry air around it. The NHC made the right call by keeping a 25kt TD through the entire forecast, even though the odds of that happening are nil. In fact, the only thing I can see potentially working in TD 2's favor is its small size. (If that's actually a positive at this point)

On to 90l, The system is a big sloppy disorganized mess right now. That's not to say it can't get its act together in the next 24 hours, but for the moment, the invest is too disorganized to really ramp up. Mind you, in this case the large size will help insulate the system from some of the dry air, T numbers are sitting at 1.0, but until the dry slot in the center of the system is taken care of, the invest will be very slow to develop.
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12 Z GFS Model run loop
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GFS predicts the formation of a tropical depression tomorrow
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I may be eatig crow later but I don't think the area of interest in the Bahamas will amount to much... If anything were to happen it would take quite a bit of time.. the is currently no vorticity in the area and the ULL interacting with it should keep in in check.. jmho
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Quoting Vortex95:


It means that TD2 is no longer in a weakening state but either stable or slowly strengthening one.

Thank you
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Checking in briefly.
9oL is one ENORMOUS system.
I hope never to see that consolidate into a smaller, more organised entity.
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Quoting Weather456:


the last I check yea. I'm going to look at the 12z gfs


Can someone please post the GFS images to the blog? I am unable to access most of the websites from work. Thanks.
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02L.TWO, TRACK_VIS, 13 AUG 2009 1430Z

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Quoting Acemmett90:

it looking bad for us in fla but good for it
FYI, the current movement of the Bahamas AOI is WNW, so it looks like SFLA will get some well needed rain by Sunday, btw im saying what the the noon news just said in there weather outlook.
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Hi everyone,

Anything new on the possible GOM potential coming up this weekend or so?
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Quoting Vortex95:


Have the models kept their "monster" storm prediction?


the last I check yea. I'm going to look at the 12z gfs
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If 90L forms quickly, its intensification will likely create shear for anything in the surrounding environment (a.k.a. TD2 or what is left of it). It has happened many times that the larger and more energetic of two systems in close proximity ended up basically eating the other, or vampirizing it if you will, by shearing the lesser system's convection toward itself. TD2 may be trying to mount a comeback with this burst of moderate convection, but if it doesn't bulk up very fast, it's going to be history.
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Quoting wunderkidcayman:
Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
weakening flag and rapid dissipation flag all OFF


What do those mean exactly?
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Quoting wunderkidcayman:
Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
weakening flag and rapid dissipation flag all OFF


Mainly because it cannae weaken much more than it has already, and if it dissipated... that's hardly rapid.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Official NAVY Tropical Page
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288. 7544
Quoting Progster:
Link

Sat presentation of wave/CB cluster N of Haiti is improving rapidly...Surface pressures remain high in the area, but shear is decreasing.


yeap if it holds to the bahammas could this one try to develope tia ive been watching
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Quoting HurricaneKyle:


Unfortunately, an anti-cyclone is moving along with 90L, protecting it against shear.
yup, so that means 90L has a big body guard that will protect him like this one:
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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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