Little change to TD 7; 93L may develop off the coast of Africa

By: Dr. Jeff Masters , 1:57 PM GMT on August 10, 2012

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Tropical Depression Seven continues westward across the central tropical Atlantic with little change in appearance. Looking remarkably like the tropical depression that became Tropical Storm Ernesto last week, TD 7 has a limited region of heavy thunderstorms, as seen on satellite loops. A large amount of dry air to the west and north is visible on water vapor satellite loops, and this dry air is interfering with TD 7's heavy thunderstorms. Wind shear is a light 5 - 10 knots, which is favorable for intensification. Ocean temperatures are 26.5°C, which is a bit on the cool side, but these temperatures are 0.5° warmer than on Thursday. Winds at the Middle Atlantic buoy 41041 peaked at 29 mph, gusting to 38 mph, at 1:50 am EDT this Friday morning, when the center of TD 7 passed about 40 miles to the south. TD 7 will pass about 60 miles south of buoy 41040 near midnight tonight. The first hurricane hunter mission into TD 7 is scheduled for Saturday morning.


Figure 1. Morning satellite image of TD 7.

Forecast for TD 7
TD 7 formed about 400 miles east-northeast of where Ernesto became a tropical depression, as seen on our wundermap. Atmospheric and oceanic conditions are currently quite similar to what Ernesto experienced, and I expect TD 7 will struggle with dry air like Ernesto did. The SHIPS model predicts that shear will remain light through tonight, then rise to the moderate range on Saturday, when the storm will encounter upper-level southwesterly winds associated with a trough of low pressure. However, ocean temperatures will warm to 28°C, which may partially counteract the increase in shear, as far as maintaining a favorable environment for development. Dry air and shear may be significant enough to destroy TD 7 on Sunday, as predicted by the GFS and ECMWF models. These models tried to kill off Ernesto in a similar situation last week, so I am inclined to believe TD 7 will survive for the coming five days, but struggle. The official NHC forecast of a 45 mph tropical storm moving through the Lesser Antilles Islands Saturday night and Sunday is a reasonable one.


Figure 2. Morning satellite image of Invest 93L.

93L
A strong tropical wave in the far Eastern Atlantic that emerged off the coast of Africa Thursday night was designated Invest 93L by NHC. In their 8 am Tropical Weather Outlook, NHC gave 93L a 50% chance of becoming a tropical depression by Sunday morning. Satellite loops show a pronounced spin to the atmosphere at mid levels, but little in the way of heavy thunderstorm activity. The latest Saharan Air Layer Analysis from the University of Wisconsin shows that while the atmosphere immediately surrounding the disturbance is moist, there is a large area of dry air from the Sahara to the west and north. This dry air will be a significant impediment to development during the coming week. The ECMWF model shows some weak development of 93L over the coming week, and predicts a general west-northwesterly track. The storm may be something Bermuda needs to be concerned about in eight or so days.

I'll have a new post this afternoon.

Jeff Masters

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Quoting AussieStorm:


Here is all of August 2005. Not many comments for each blog.


Thanks for the link, Aussie. Very interesting reading!

Lindy
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BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1014 AM EDT FRI AUG 10 2012

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
EASTERN SUSSEX COUNTY IN CENTRAL DELAWARE...
THIS INCLUDES THE CITY OF GEORGETOWN...

* UNTIL 1115 AM EDT

* AT 1012 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORMS AND A LEADING GUST FRONT CAPABLE OF PRODUCING
DAMAGING WINDS IN EXCESS OF 60 MPH. THEY WERE LOCATED ALONG A
LINE EXTENDING FROM LEWES TO GUMBORO...OR ALONG A LINE EXTENDING FROM
13 MILES EAST OF GEORGETOWN TO 16 MILES SOUTH OF GEORGETOWN...AND MOVING
EAST AT 20 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
CAPE HENLOPEN STATE PARK AND DAGSBORO AROUND 1025 AM EDT...
REHOBOTH BEACH AND DAGSBORO AROUND 1030 AM EDT...
SELBYVILLE AROUND 1040 AM EDT...
MILLVILLE AROUND 1045 AM EDT...
BETHANY BEACH AROUND 1055 AM EDT...
BETHANY BEACH AROUND 1100 AM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IF YOU ARE IN ITS PATH...PREPARE
IMMEDIATELY FOR DAMAGING WINDS...LARGE HAIL...AND DEADLY CLOUD TO
GROUND LIGHTNING. PEOPLE OUTSIDE SHOULD MOVE TO A SHELTER...
PREFERABLY INSIDE A STRONG BUILDING BUT AWAY FROM WINDOWS.

IN ADDITION TO DAMAGING WINDS...FREQUENT CLOUD TO
GROUND LIGHTNING IS OCCURRING WITH THIS STORM. MOVE INDOORS
IMMEDIATELY! REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE
ENOUGH TO BE STRUCK BY LIGHTNING.

IN ADDITION TO DAMAGING WINDS...HEAVY RAIN WILL OCCUR
WITH THESE STORMS AND CAUSE LOW-LYING AND POOR DRAINAGE FLOODING.

PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.



LAT...LON 3845 7559 3884 7531 3885 7522 3879 7515
3879 7511 3881 7510 3880 7508 3867 7505
3862 7505 3861 7504 3845 7504 3844 7505
TIME...MOT...LOC 1414Z 269DEG 18KT 3876 7516 3846 7540



MPD
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting hurricanealley:


Get Grothar on here now!


Why? Has he been around since the founding of this country? lol.
Member Since: June 16, 2005 Posts: 0 Comments: 1325
06Z GFS: There isn't a whole lot to track for the next 15 days! WOW
The same for 00z EURO for the next 10 days!

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Quoting AussieStorm:
Goodnight all. My bed is super hot with my electric blanket on at super high.

GFS has 93L doing this....

SE of Bermuda
..nite aussie
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting TropicalAnalystwx13:
Still feel like writing a blog. Will do it when I get home this afternoon.

US History is boring...


Get Grothar on here now!
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Quoting angiest:


I wonder if that blob in the Caribbean will get a mention in the TWO sometime soon. This chart shows it in an area of possible development.
..i sure hope so, if this IS going into the gulf..people need to know about it early on
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Goodnight all. My bed is super hot with my electric blanket on at super high.

GFS has 93L doing this....

SE of Bermuda


loop
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Quoting GeoffreyWPB:
TD 7...



Is it just me or does TD7 already look more like a tropical wave than a TD?
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Quoting LargoFl:
..I could be wrong but I think its a cold front moving across the US


Yeah, one slow moving cold front
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Quoting LargoFl:


I wonder if that blob in the Caribbean will get a mention in the TWO sometime soon. This chart shows it in an area of possible development.
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I come here to follow the weather because it's the most informative site I know of.

I'm located in Lafayette LA and so far this year has been a bust. Don't get me wrong, I don't like damage to anyone's home, property, but I am fascinated with storms. It's so interesting to watch them develop.

Does anyone see a storm hitting the Gulf this year? I see this TD-7 is heading pretty much where Ernesto hit but could it make any turn Northerly at all before it hits land? Haven't had any real activity since 09 here.
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Quoting JTDailyUpdate:


Yeah, glad I don't live in New Jersey, they are getting hammered.
..yeah some real bad storms looks like..and..on a friday too, i know they are pissed
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting sar2401:


That's a weird disconnected blob of thunderstorms over SE Alabama. It formed last night and hasn't moved much since. Anyone have a clue on what the focusing mechanism is for it?
..I could be wrong but I think its a cold front moving across the US
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting TropicalAnalystwx13:
Still feel like writing a blog. Will do it when I get home this afternoon.

US History is boring...


Nah, US history is actually very interesting. Unfortunately, a lot of history teachers make it boring.
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Quoting LargoFl:
.........................................wow the northeast is going to have a rough day or two


Yeah, glad I don't live in New Jersey, they are getting hammered.
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TD 7...

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........................................gee thats a huge blob below Cuba..maybe thats what is going to move into the gulf?
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting LargoFl:


That's a weird disconnected blob of thunderstorms over SE Alabama. It formed last night and hasn't moved much since. Anyone have a clue on what the focusing mechanism is for it?
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Still feel like writing a blog. Will do it when I get home this afternoon.

US History is boring...
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Member Since: August 6, 2011 Posts: 4 Comments: 38446
Here's a joke I thought I tell to you all..Warning it's really bad..


When the continent of north America first formed what did the Atlantic and Gulf tell Florida?..

Watch out we got you surrounded!!.(Get it you know like what a police officer tells a suspect...)
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Quoting bappit:

No, no, no. The low level circulation is the engine that drives the storm since this layer is in contact with the ocean surface. The mid levels are about 12000 to 18000 feet, 700 mb and 500 mb. 50000 feet is well above the mid level circulation.

The low level circulation is disrupted by large bodies of water? How?


You are correct. I was using a typical thunderstorm as a model rather than a tropical storm, which probably did more to confuse than help. Low level circulation in thunderstorms is typically disrupted when it crosses a large lake and sucks in cooler water. Obviously, that's not the case with a tropical storm over the ocean. Since the remnants of Ernesto are over land, it seemed like a better analogy for the storm in question.
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.........................................wow the northeast is going to have a rough day or two
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting sar2401:
On the ant model front, we've had a huge increase in new fire ant mounds over the past 10 days here in central Alabama. I have no idea if there's a correlation with tropical storms but, not only are there more mounds, the little suckers really bite faster and sting more than usual. They are riled up about something.
..............nature is giving us the warning, its up to us to listen huh
Member Since: August 6, 2011 Posts: 4 Comments: 38446
Nice blob in the caribbean.If it persist then we may need to watch it.All though shear is high in the caribbean and Gulf right now.

If T.D 7 can continue to blow up convection around it's center Gordon may come later today.
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Because 10August12pmGMT's 13.7n48.0w was re-evaluated&altered to 13.6n48.6w at ~1pmGMT

Derived from (NHC) ATCF data for TropicalDepressionSeven for 10August12pmGMT:
MinimumPressure increased from 1008millibars to1009millibars
MaxSusWinds held at 30knots(35mph)56km/h
Vector changed from 266.8*West@19.1mph(30.7km/h) to 270.3*West@25.8mph(41.5km/h)

POS-Trinidad :: GND-Grenada :: BGI-Barbados :: SLU-St.Lucia

The easternmost dot on the kinked line is where 92L became a LOw again
The westernmost dot on the kinked line is where 92L became AL07
The next dot to the right is where AL07 became TD.7
The easternmost dot on the longest line is TD.7's most recent position

The longest line is a straightline projection through TD.7's 2 most recent positions to its closest approach (within 18miles or 29 kilometres) to a coastline
9August12pmGMT: AL07 had been headed for passage over SangreGrande (rightPOSdumbbell)
9August6pmGMT: TD.7 had been headed for passage over GrantleyAdamsInternationalAirport (bottomBGIblob)
10August12amGMT: TD.7 had been headed for passage over Bathsheba (middleBGIblob)
10August6amGMT: TD.7 had been headed for passage over HighCliffPoint (topGNDdumbbell)
10August12pmGMT: TD.7 was heading for passage over LittleBay in ~1day1hour from now (when this comment was posted)

Copy&paste pos-10.595n61.023w, bgi,13.09n59.457w,13.198n59.488w, gnd-12.191n61.602w, slu, 12.1n31.2w- 12.7n32.5w- 13.3n33.9w- 13.9n35.4w- 14.1n37.0w- 14.1n38.5w- 13.9n40.0w- 13.7n41.7w, 13.7n41.7w-13.7n42.9w, 13.7n42.9w-13.7n44.6w, 13.7n44.6w-13.6n46.3w, 13.6n46.3w-13.6n48.6w, 13.6n46.3w-13.31n59.579w into the GreatCircleMapper for a larger-scale map and other information
The previous mapping for comparison
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This season is set to explode. Batten down the hatches and nobody do anything stupid. NBC news has been doing a lot more in their climate and TS/Hurricane discussions. A new reality may well be setting in on what climate change is doing and how expensive it really is. Brian Williams is my favorite for nightly news. I get my news from dozens of sources, but nightly news is still one of them. Glad to see NBC and some other outlets taking weather and climate more seriously. As TWC has shown, extreme weather is a money maker. As NCstorm said yesterday, while none of us would ever wish the big one on even our enemies; we all are here to watch to see and wonder at the monsters of nature and what they are capable of.
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Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting Coastalgramps:
The Fireants are going nutz in my yard this week. Maybe they know something we don't know. Or it could be all the rain we have had lately.
Where are you located?
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On the ant model front, we've had a huge increase in new fire ant mounds over the past 10 days here in central Alabama. I have no idea if there's a correlation with tropical storms but, not only are there more mounds, the little suckers really bite faster and sting more than usual. They are riled up about something.
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A lot of moisture will be streaming into Florida today and tomorrow...

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Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting floridaboy14:
another mexico storm -__- man this season so far is a snooze. where are the beautiful cape verdes?


The season will become more entertaining for you, trust me.
Member Since: June 16, 2005 Posts: 0 Comments: 1325
THE ONLY ENVIRONMENTAL PARAMETER THAT APPEARS IDEAL FOR STRENGTHENING IS THE SEA SURFACE TEMPERATURE.

Interesting statement given the fact that they are calling for a tropical storm before it reaches the Antilles and throughout the period........They are putting a lot of faith in the SST's......... :)
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Quoting bappit:

No, no, no. The low level circulation is the engine that drives the storm since this layer is in contact with the ocean surface. The mid levels are about 12000 to 18000 feet, 700 mb and 500 mb. 50000 feet is well above the mid level circulation.

The low level circulation is disrupted by large bodies of water? How?

I'm with bappit on this one... the post he quoted is all kinds of wrong, on several points.
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Member Since: August 6, 2011 Posts: 4 Comments: 38446
Meantime, it's yet another day of recordbreaking heat in parts of Europe. The focus today is on Spain, which is seeing many daily and monthly high temperature records being set, in addition to at least a few all-time heat records for individual stations. Madrid (LEMD), for instance, reached 108 degrees today, which, if verified, is the city's all-time record high.
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Quoting sar2401:


Low level circulation is the disturbance in the atmosphere caused by a organized storm from the surface up to about 5,000 feet. Upper level circulation is the "engine" of a storm that pulls in warm, moist air and helps to feed it down to the lower levels, and can extend upward to as high as 50,000 feet. You can see the same thing with individual thunderstorm cells. The low level circulation can get disrupted by surface features like mountains or large bodies of water. As long as the upper level circulation continues, the thunderstorm can regenerate at the surface when conditions improve. Training thunderstorms often exist because, although low level circulation gets disrupted, enough upper level circulation remains intact to regenerate the storms at the surface when the conditions improve. That's the mechanism that may (or may not) allow Ernesto to regenerate a surface low when it reaches the Pacific.

No, no, no. The low level circulation is the engine that drives the storm since this layer is in contact with the ocean surface. The mid levels are about 12000 to 18000 feet, 700 mb and 500 mb. 50000 feet is well above the mid level circulation.

The low level circulation is disrupted by large bodies of water? How?
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Quoting WDEmobmet:


Yes, in fact it happened yesterday with TD7

LOL. I mean a real reversion rather than a fat fingered error.
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132. 7544
is that blob below cuba moving north tia

bahama blob blowing up
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Quoting Msdrown:


AussieStorm: Yes that is the report that backed his article. With this I can find his artcle but I really like this report. Thanks very much. After I have a chance to digest it more I will probably have some questions to bounce off of you and others.

You mean, I have to read it also. oh man, home work. I'm way to old for that. lol
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Member Since: August 6, 2011 Posts: 4 Comments: 38446
Quoting washingtonian115:

I figured it was a typo initially, I was just messing with you. Hence the ;) at the end.
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Quoting jeffs713:

Could you please share your ability to time-travel? ;)
Quoting washingtonian115:

2010 also had a lot of recurves for a La nina year..
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Well, no Ernesto in the Eastern Pacific. If the system regenerates, it will have a new name.
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BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1039 AM EDT FRI AUG 10 2012

THE NATIONAL WEATHER SERVICE IN TALLAHASSEE HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
SOUTHEASTERN LANIER COUNTY IN SOUTH CENTRAL GEORGIA...
EASTERN LOWNDES COUNTY IN SOUTH CENTRAL GEORGIA...

* UNTIL 1130 AM EDT

* AT 1037 AM EDT...THE NATIONAL WEATHER SERVICE HAS DETECTED A LINE
OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN
EXCESS OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING
FROM 9 MILES NORTH OF DASHER TO LAKE PARK...OR ALONG A LINE
EXTENDING FROM VALDOSTA TO LAKE PARK...AND MOVING EAST AT 25 MPH.

TREES OR POWER LINES HAVE BEEN BLOWN DOWN IN
JEFFERSON...BROOKS...AND LOWNDES COUNTIES WITH THESE STORMS.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
NAYLOR...STOCKTON AND GREENWOOD

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IF YOU ARE IN ITS PATH...PREPARE
IMMEDIATELY. PEOPLE OUTSIDE SHOULD MOVE INSIDE A STRONG BUILDING BUT
AWAY FROM WINDOWS.



LAT...LON 3084 8301 3084 8308 3081 8310 3079 8313
3063 8313 3062 8314 3062 8318 3063 8324
3092 8326 3098 8297 3087 8297
TIME...MOT...LOC 1439Z 263DEG 21KT 3087 8321 3062 8317



42-DVD
Member Since: August 6, 2011 Posts: 4 Comments: 38446
ok 11am advisory for TD7 is out and is moving a little faster as expected no TS watches yet forecast track further W and drops the intensity abit again
though I say TD7 should start to slow down near 60W shear should not be too much of a problem yes I still expect it to get sheared abit dry air I don't think will be too much of a problem either
and because the models I think are overhyping the dry air and shear that intensity gone out of wack maybe when HH flys models and NHC gets a better idea and also I think NHC has the track going too far S from day 3, 4, and 5
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Quoting washingtonian115:
2012 also had a lot of recurves for a La nina year..

Could you please share your ability to time-travel? ;)
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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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