Tropical Depression Five a heavy rain threat; the smoke clears in Moscow

By: Dr. Jeff Masters , 3:23 PM GMT on August 11, 2010

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Tropical Depression Five is currently weak and disorganized, but it has the potential to organize into a potent rain-maker that may bring extremely heavy rains to Louisiana, Mississippi, Alabama, and Georgia over the next four days. Outer rain bands from TD 5 are already affecting the New Orleans region, where as much as two inches of rain has fallen in isolated regions. TD 5 has only limited heavy thunderstorm activity at present, thanks to an infusion of dry air early this morning from an upper-level low pressure system over the Gulf of Mexico. However, TD 5 is steadily recovering from this blow, and water vapor imagery shows the atmosphere is moistening in the eastern Gulf of Mexico as TD 5 builds more heavy thunderstorms. Wind shear is currently a moderate 10 - 15 knots over TD 5, and water temperatures are very warm, 31°C. The Hurricane Hunters have left TD 5, and a new aircraft is scheduled to arrive this afternoon.


Figure 1. Morning radar image of TD Five from the New Orleans radar.

Forecast for TD 5
The latest SHIPS model forecast predicts that wind shear will drop to the low range, 5 - 10 knots, by tonight, and remain low for the remainder of TD 5's life. The main hindrance to development will be the current large, disorganized nature of the storm's circulation. Without a tight, well-defined center of circulation, it will take time for the storm to intensify, and I don't expect TD 5 will have time to become more than a 50 mph tropical storm. NHC is giving TD 5 just a 2% chance of reaching hurricane strength. The main threat from TD 5 will be rainfall. This is a slow-moving storm, and the steering currents pushing the storm towards the coast are expected to weaken Thursday and Friday. TD 5 will likely slow to a crawl on Thursday and Friday, moving at just 3 - 5 mph. This will allow the storm to dump very heavy rains in excess of eight inches in isolated regions.

93L
There is not much new to report on the tropical wave (Invest 93) in the middle Atlantic Ocean that has been close to tropical depression status for three days now. The disturbance has a well-defined surface circulation, but only a limited amount of heavy thunderstorm activity, thanks to dry air aloft and wind shear of 10 - 20 knots. Wind shear is expected to stay in the moderate range, 10 - 20 knots, over the next three days, which is low enough that 93L could become a tropical depression at any time during that period. NHC is giving 93L a 70% chance of developing into a tropical depression by Friday morning. The GFS, GFDL, and HWRF models predict 93L will develop, and the GFDL forecasts that the storm will become a hurricane. A strong trough of low pressure moving across the central Atlantic is recurving 93L to the north, and the system should only be a concern to shipping interests. None of the reliable computer models are forecasting tropical cyclone development in the Atlantic over the next seven days, other than for 93L.

Moscow's air clears, but it is still extraordinarily hot
A thunderstorm blew through Moscow early this morning, bringing a little rain and a very welcome shift of wind direction. The wind shift freed the city from the persistent wild fire smoke that had plagued the city for seven straight days. Temperatures at Moscow's Domodedovo airport hit 35°C (95°F) today, the 29th day in row that temperatures have exceeded 30°C (86°F) in Moscow. The average high temperature for August 11 is 21°C (69°F). Moscow's high temperatures have averaged 15°C (27°F) above average for the first eleven days of August--a truly extraordinary anomaly. There is some modest relief in sight--the latest forecast for Moscow calls for high temperatures of 30 - 31° (86 - 88°F) Thursday through Sunday. This is still 20°F above normal, but will be a welcome change from the extreme heat of the past two weeks. Long range forecasts from the ECMWF and GFS models show no major change to the ridge of high pressure locked in over Russia, for at least the next seven days. However, both models suggest that a trough of low pressure may be able to erode the ridge significantly 8 - 10 days from now, bringing cooler temperatures of 5°C (8°F) above average.

Next update
I'll have an update this afternoon between 3 - 4 pm EDT.

Jeff Masters

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TD5 continues to become better organized, still very broad but the rubber band look is now an oval look, symmetrical.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
I would be interested to see what the temp lapse rates are currently over the Atlantic.

Quoting KEEPEROFTHEGATE:



The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood. While six factors appear to be generally necessary, tropical cyclones may occasionally form without meeting all of the following conditions. In most situations, water temperatures of at least 26.5 °C (79.7 °F) are needed down to a depth of at least 50 metres (160 ft); waters of this temperature cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms. Another factor is rapid cooling with height, which allows the release of the heat of condensation that powers a tropical cyclone.High humidity is needed, especially in the lower-to-mid troposphere; when there is a great deal of moisture in the atmosphere, conditions are more favorable for disturbances to develop. Low amounts of wind shear are needed, as high shear is disruptive to the storm's circulation. Tropical cyclones generally need to form more than 555 kilometres (345 mi) or 5 degrees of latitude away from the equator, allowing the Coriolis effect to deflect winds blowing towards the low pressure center and creating a circulation. Lastly, a formative tropical cyclone needs a pre-existing system of disturbed weather, although without a circulation no cyclonic development will take place.
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Quoting stormpetrol:
has 93L split and become 2 separate entities?


Indeed it has.

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772. SLU
Quoting stoormfury:
although the ingredients in the MDR are all in place for an explosive season thereis something which i cannot fathom that is preventing all these invsets depressins or tropical storms from being properly organised and to prove the forecasters right. tropical meteorology after all is not that easy too many variables


Well coming into the season we thought it would be a season getting off to an explosive start but it looks like a season that will conform to climatology whereby most of the activity might occur from August 15th to October 15th similar to 1998 which is an analog year.
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Hey Storm or Levi..

Do u think this TD5 might be stalling or getting to that point? also I been looking at some models and some of them have td5 hit land then come back to the Gulf.. What do you both think the probability of that happening? thx if u do answer..

Sorry if i posted this again, but wasnt sure y'all saw it.
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Quoting StormW:


One way to tell (which is why I placed the "L" on the satellite pic) is if you go to the RGB loop, look at the lower cloud deck. Notice how the lower clouds over FL. are moving toward the NW, and then backing and coming down over LA. Then south of the system, you can see how they are coming up from the WSW. You can see where they"meet".

rgb loop



Thank you

Its little bits of education that you save and one day it all adds up.

I guess in your case you have a huge bank? LOL
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Member Since: July 14, 2009 Posts: 51 Comments: 1731
This is crazy... I really think this thing split in two. It looks like the old area of convection split off and developed its own surface low, and now the old LLC is firing up intensely. We could end up with two storms out of this one.

This visible loop is wild...
NOAA 93L Visible Floater
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Quoting stoormfury:
although the ingredients in the MDR are all in place for an explosive season thereis something which i cannot fathom that is preventing all these invsets depressins or tropical storms from being properly organised and to prove the forecasters right. tropical meteorology after all is not that easy too many variables



The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood. While six factors appear to be generally necessary, tropical cyclones may occasionally form without meeting all of the following conditions. In most situations, water temperatures of at least 26.5 °C (79.7 °F) are needed down to a depth of at least 50 metres (160 ft); waters of this temperature cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms. Another factor is rapid cooling with height, which allows the release of the heat of condensation that powers a tropical cyclone.High humidity is needed, especially in the lower-to-mid troposphere; when there is a great deal of moisture in the atmosphere, conditions are more favorable for disturbances to develop. Low amounts of wind shear are needed, as high shear is disruptive to the storm's circulation. Tropical cyclones generally need to form more than 555 kilometres (345 mi) or 5 degrees of latitude away from the equator, allowing the Coriolis effect to deflect winds blowing towards the low pressure center and creating a circulation. Lastly, a formative tropical cyclone needs a pre-existing system of disturbed weather, although without a circulation no cyclonic development will take place.
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Quoting KEEPEROFTHEGATE:
this one could be the one

CV AOI
img src="http://" alt="" />


CYCLONIC CONVECTION INVADING THE SOUTHERN SAHARA. OVER.
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Quoting Tropicsweatherpr:
Does anyone has a image or loop of inside Africa to see that wave that has been mentioned located in Central Africa?


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763. xcool
ALL models did good job on tD5 & rip td5
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Quoting btwntx08:
750:i wasnt angry there got a problem???


Please, try to keep the negativity off the blog...
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has 93L split and become 2 separate entities?
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IMO, subtropical hurricanes CAN develop. Hurricane Karl in 1980 developed from the center of a cold-core extratropical storm before turning subtropical.

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Quoting StormW:


I think it's gonna be close to the coast when it does. Looks like it's trying to slowly organize now...but being such a large circulation, it will take time to consolidate.


Thanks. If what Stormchaser81 is right with his graphic showing the center, it doesn't look that far off from the center (at least part of it) making landfall. Is his graphic accurate?
Member Since: September 25, 2007 Posts: 0 Comments: 207
this one could be the one

CV AOI
img src="http://" alt="" />
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Does anyone has a image or loop of inside Africa to see that wave that has been mentioned located in Central Africa?
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Quoting StormW:


The ULL has helped to pull in a lot of dry air.

Hard to say about whether or not another COC could form SE. Right now, that area appears to be mid level.


I keep waiting for that blow up in the SE to move, and maybe it is, but it looks like it's just sitting there...stubbornly refusing to tag along with the rest of that mess. ;)
Member Since: September 2, 2008 Posts: 0 Comments: 105
although the ingredients in the MDR are all in place for an explosive season thereis something which i cannot fathom that is preventing all these invsets depressins or tropical storms from being properly organised and to prove the forecasters right. tropical meteorology after all is not that easy too many variables
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Quoting JavPR:

it's been raining a lot for the past two days in Western PR...yesterday there were a big amount of thunderstorm activity....


The Central Atlantic Triangle is VERY apparent...and the system near 25N, 50W looks like Bonnie. WHY did the NHC downgrade it to medium-risk on the TWO?!
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Quoting cheetaking:
What the? Did 93L just split in two? I see a nearly-stationary area of intense storms under a weak LLC around 23N 58W, and a very well-defined but storm-deprived LLC headed northeast at 25.8N 50W.


Who knows, maybe a Fujiwara will occur, and one component will develop into a cat. 1 before hitting Greenland.
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Post 745...Why all the Anger?
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StormW. What is your take on the circulation just south of pensacola riding the coast. It appears to me judging by the flow around it that this is where a big fat L should be placed on the map....
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Hopefully I got this right, but this should clear things up for people if I got this right.

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Quoting cheetaking:
What the? Did 93L just split in two? I see a nearly-stationary area of intense storms under a weak LLC around 23N 58W, and a very well-defined but storm-deprived Low-Mid level swirl headed northeast at 25.8N 50W.


Storms are developing over the COC near 50W/28.5N. It is no longer storm deprived.
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742. SLU
Quoting ElConando:


I don't even know what to call it at this point but a very broad low. Dissipation seem fairly immanent to me as well.


I'll be embarrassed if they keep it as a TD at 5pm. lol
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Quoting btwntx08:

FORECASTER CANGIALOSI/WALTON

walton never heard of him before also way too consertative also i heard what ike ike not dumm gfs shows something u saw it wrong again


She
Corey Walton
Member Since: September 23, 2005 Posts: 15 Comments: 11341
739. JavPR

it's been raining a lot for the past two days in Western PR...yesterday there were a big amount of thunderstorm activity....
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Storm, Do you see TD5 pulling itself back together at all before landfall??
Member Since: September 25, 2007 Posts: 0 Comments: 207
Hey Storm or Levi..

Do u think this TD5 might be stalling or getting to that point? also I been looking at some models and some of them have td5 hit land then come back to the Gulf.. What do you both think the probability of that happening? thx if u do answer..
Member Since: Posts: Comments:
What the? Did 93L just split in two? I see a nearly-stationary area of intense storms under a weak LLC around 23N 58W, and a very well-defined but storm-deprived LLC headed northeast at 25.8N 50W.
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Quoting SLU:
This is certainly too weak to be called a TD based on the "hurricane manual". I'm definitely up for downgrading at 21z.



I don't even know what to call it at this point but a very broad low. Dissipation seem fairly immanent to me as well.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting angiest:


Rita didn't make landfall in Texas, but rather just across the border in LA. ;) And as stated, Ike was not technically a major.


Actually, Rita made landfall at the mouth of the Sabine River, the center of which is the border dividing Texas from Louisiana. Rita made landfall between Sabine Pass, Texas, and Johnson Bayou, Louisiana, at 02:38 CDT on September 24, 2005 as a Category 3 Hurricane with winds at 115 mph. It was directly on the border of the two states. I will agree Louisiana got the worst of it.
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Quoting StormW:
img src="
i think its just to hot sst's atomsphere too hot when something gives its going to be big
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Quoting Clearwater1:
The wave at approx 55 15n is firing off some convection and doesn't look that bad. Yellow circle, but who knows. 93L down to orange. . . one seems to be the worlds longest lasting invest. lol

I can see the 55w 15n wave going up to 20% at 8pm and possible invest status as convection is improving.
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Quoting StormW:
img src="Photobucket" alt="" />


Why is the COC is a pool of dry air? And could a new COC develop farther southeast as the current COC makes landfall in Louisiana?
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Quoting BahaHurican:
Kinda hard not to, given the ridiculous way rain falls in FL - 1 minute absolute dry, the next, the deluge that created the Flood.... lol


Yep have been in some bad ones in the past especially on the highway. One of the oddest adventures I had in a car dealing with rain was in a parking lot with poor drainage a couple years back. Not that there were any floating cars but lets just say some people had the brilliant idea of trying to a flooded parking lot doing 15 to 20mph and paid the price.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
728. SLU
This is certainly too weak to be called a TD based on the "hurricane manual". I'm definitely up for downgrading at 21z.

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Surface/Mid level circulation developing or reforming near 27.4N/84.6W. Convection is beginning to take more of a counter clockwise spin to it moving wnw now getting away from land and could rapidly develop given developing anticyclonic winds aloft, warm SSTs, a moistening environment and a strong mid to low level circulation developing, towards DMAX tomorrow morning, if it shows no signs by then, then its RIP TD5.
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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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