New African disturbance 96L likely to develop

By: Dr. Jeff Masters , 2:55 PM GMT on September 07, 2009

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A tropical wave (96L) that emerged off the coast of Africa yesterday has organized rather quickly, and will likely become a tropical depression by Tuesday night. Satellite imagery from the European satellite shows a well-organized circulation, but not enough heavy thunderstorm activity near the center of circulation to be considered a tropical depression. The storm is far enough south that the dry air of the Saharan Air Layer is not a major impediment to development. Wind shear is moderate, 10 - 15 knots, and ocean temperatures are 1 - 2°C above the threshold needed for tropical cyclone formation.


Figure 1. Morning satellite image of 96L, off the coast of Africa. The remains of disturbance 95L, which are under 30 - 40 knots of wind shear, can be seen at upper left.

The forecast for 96L
Most of the models develop 96L, and the chances are that this disturbance will become Tropical Storm Fred later this week. The system will initially move west-northwest, but by Thursday, a strong trough of low pressure passing to 96L's north will pull the storm to the northwest, and may be capable of fully recurving the storm to the northeast. However, most of the models foresee that 96L will not move far enough north for this to happen, and that the storm will have to wait for the next trough of low pressure. With the steering pattern for this year continuing to feature plenty of deep troughs of low pressure moving off the U.S. East Coast, the odds of 96L making it all the way across the Atlantic to threaten land areas appear low. Still, much that is unexpected can and does happen in the world of tropical meteorology, and 96L bears watching.

North Carolina low
An area of concentrated thunderstorms has developed off the North Carolina coast in association with the remains of an old cold front. This system is under about 20 - 30 knots of shear, and is not tropical. However, it will bring heavy rain to eastern North Carolina today and Tuesday, as the storm slides north-northeastward along the coast.

I'll have an update Tuesday.

Jeff Masters

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000
WTNT32 KNHC 072034
TCPAT2
BULLETIN
TROPICAL DEPRESSION SEVEN ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009
500 PM AST MON SEP 07 2009

...NEW TROPICAL DEPRESSION FORMS IN THE FAR EASTERN ATLANTIC...

AT 500 PM AST...2100 UTC...THE CENTER OF TROPICAL DEPRESSION SEVEN
WAS LOCATED NEAR LATITUDE 12.5 NORTH...LONGITUDE 24.5 WEST OR ABOUT
160 MILES...255 KM...SOUTH OF THE SOUTHERNMOST CAPE VERDE ISLANDS.

THE DEPRESSION IS MOVING TOWARD THE WEST NEAR 16 MPH...26 KM/HR. A
TURN TOWARD THE WEST-NORTHWEST AND A SLIGHT DECREASE IN FORWARD
SPEED IS FORECAST DURING THE NEXT DAY OR TWO.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. STRENGTHENING IS FORECAST OVER THE NEXT COUPLE OF DAYS...AND
THE DEPRESSION IS EXPECTED TO BECOME A TROPICAL STORM TONIGHT OR
TUESDAY.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.

OUTER RAIN BANDS FROM THE DEPRESSION ARE EXPECTED TO CONTINUE TO
SPREAD ACROSS THE SOUTHERN CAPE VERDE ISLANDS TONIGHT...PRODUCING
LOCALLY HEAVY RAINFALL AND GUSTY WINDS.

...SUMMARY OF 500 PM AST INFORMATION...
LOCATION...12.5N 24.5W
MAXIMUM SUSTAINED WINDS...35 MPH
PRESENT MOVEMENT...WEST OR 280 DEGREES AT 16 MPH
MINIMUM CENTRAL PRESSURE...1005 MB

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 PM AST.

$$
FORECASTER BROWN
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000
WTNT22 KNHC 072033
TCMAT2
TROPICAL DEPRESSION SEVEN FORECAST/ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009
2100 UTC MON SEP 07 2009

TROPICAL DEPRESSION CENTER LOCATED NEAR 12.5N 24.5W AT 07/2100Z
POSITION ACCURATE WITHIN 35 NM

PRESENT MOVEMENT TOWARD THE WEST OR 280 DEGREES AT 14 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1005 MB
MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 12.5N 24.5W AT 07/2100Z
AT 07/1800Z CENTER WAS LOCATED NEAR 12.4N 23.9W

FORECAST VALID 08/0600Z 12.6N 26.5W
MAX WIND 35 KT...GUSTS 45 KT.
34 KT... 30NE 0SE 0SW 30NW.

FORECAST VALID 08/1800Z 13.0N 28.7W
MAX WIND 45 KT...GUSTS 55 KT.
34 KT... 45NE 30SE 30SW 45NW.

FORECAST VALID 09/0600Z 13.9N 30.5W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 20NE 15SE 0SW 15NW.
34 KT... 60NE 45SE 30SW 60NW.

FORECAST VALID 09/1800Z 15.1N 32.1W
MAX WIND 55 KT...GUSTS 65 KT.
50 KT... 30NE 20SE 0SW 30NW.
34 KT... 75NE 60SE 45SW 75NW.

FORECAST VALID 10/1800Z 17.6N 33.9W
MAX WIND 55 KT...GUSTS 65 KT.
50 KT... 30NE 20SE 0SW 30NW.
34 KT... 75NE 60SE 45SW 75NW.

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 225 NM
ON DAY 4 AND 300 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY

OUTLOOK VALID 11/1800Z 19.5N 34.5W
MAX WIND 50 KT...GUSTS 60 KT.

OUTLOOK VALID 12/1800Z 21.0N 34.5W
MAX WIND 45 KT...GUSTS 55 KT.

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 12.5N 24.5W

NEXT ADVISORY AT 08/0300Z

$$
FORECASTER BROWN
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NHC has issued Forecasts Advisories for TD 7 and TS Linda
Member Since: July 14, 2009 Posts: 51 Comments: 1731
Quoting cyclonekid:
Its possible
Quoting Ameister12:

I would think so.


looks like a TS already imo.
Member Since: April 29, 2007 Posts: 0 Comments: 7862
Quoting Weather456:
The non tropical low has dumped some heavy rains across South and North Carolina


It's not ending anytime soon.
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The non tropical low has dumped some heavy rains across South and North Carolina

Member Since: July 24, 2005 Posts: 407 Comments: 19076
ECMWF model not forecasting the wave behind 07L to become anything...ECMWF taking 07L out to sea.
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Quoting stormpetrol:
TS Fred by 11 tonight?

I would think so.
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Quoting stormpetrol:
TS Fred by 11 tonight?
Its possible
Member Since: July 14, 2009 Posts: 51 Comments: 1731
Member Since: July 24, 2005 Posts: 407 Comments: 19076
TS Fred by 11 tonight?
Member Since: April 29, 2007 Posts: 0 Comments: 7862
Quoting Weather456:


between 4:30 and 5:00

Probably gonna get the info at 4:45.
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Quoting stormpetrol:
Is Td/7, Fred going to be a westward traveler? Ensemble models would seem to think so.
If it stays weak like the GFDL is forecasting, then yes it will move W, if it intensifies like a lot of models are predicting 07L should curve out to sea.
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Quoting Ameister12:
It's getting close to 5pm, that's when we should get information from the NHC of 07L.


between 4:30 and 5:00
Member Since: July 24, 2005 Posts: 407 Comments: 19076
NOGAPS developing the wave behind 07L:


GFS has the wave behind 07L following 07L's path:


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It's getting close to 5pm, that's when we should get information from the NHC of 07L/96L.
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Quoting Levi32:
This is definitely gonna be Fred, I think a hurricane and possibly major hurricane during the course of this week and next week. It has the best opportunity of any Cape Verde system this year with a moist environment in front of it, but behind it comes another burst of dry air to shut things down again.


The models seem to be expecting the high moisture levels to remain stagnant over the area, especially as the MJO moves in. The NOGAPS is keeping SAL values low across the region.

Link

GFS 700mb RH
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Is Td/7, Fred going to be a westward traveler? Ensemble models would seem to think so.
Member Since: April 29, 2007 Posts: 0 Comments: 7862
The wave in back of 07L is producing strong convection but it is disorganized, models have been hinting for this to become our next TD but nothing too intense because of the presence of 07L.
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so td7 @ 5pm?
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In fact, TD 7 has three troughs to overcome, and the GFS has it meeting the 3rd one as a weak tropical cyclone. Actually the GFS weakens TD 7 beyond 1 week and turns it back west. In the image below, TD 7 is staring into the face of a strong front. We'll have to wait and see what unfolds.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
On water vapor imagery you can see that the cirrus outflow clouds are moving westward and are not being pulled northwestward. This is possibly a sign that it should continue westward for another day or two at the least.
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Quoting Weather456:


That is true - just becuz a hurricane is strong does not mean it will go north.

but Hurricane Ike was under different steering patterns.

In this case, if TD 7 strengthens, that increases the chance of curvature as the deep layer weakness is stronger.
correct, if it is not deep enough (strong) it will not feel the effects of the trough, but it is expected that this will probably become hurricane Fred, so right now a curvature is anticipated, but remember this is mother nature and no one on this earth can correctly and accurately predict the tropics.
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This is definitely gonna be Fred, I think a hurricane and possibly major hurricane during the course of this week and next week. It has the best opportunity of any Cape Verde system this year with a moist environment in front of it, but behind it comes another burst of dry air to shut things down again.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Yes, Weather456, that is true, but that weakness can change quickly. I believe that was the case with Ike last year.
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000
WHXX01 KMIA 071924
CHGE77
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1924 UTC MON SEP 7 2009

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

EAST PACIFIC OBJECTIVE AIDS FOR

TROPICAL CYCLONE LINDA (EP152009) 20090907 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090907 1800 090908 0600 090908 1800 090909 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 15.4N 126.7W 15.6N 128.1W 16.0N 129.1W 16.4N 129.9W
BAMD 15.4N 126.7W 15.6N 127.7W 15.9N 128.6W 16.4N 129.5W
BAMM 15.4N 126.7W 15.7N 128.1W 16.0N 129.3W 16.3N 130.4W
LBAR 15.4N 126.7W 15.7N 127.8W 16.2N 128.9W 17.1N 130.3W
SHIP 45KTS 52KTS 57KTS 58KTS
DSHP 45KTS 52KTS 57KTS 58KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090909 1800 090910 1800 090911 1800 090912 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 17.0N 130.8W 19.1N 132.6W 22.6N 133.3W 26.0N 133.1W
BAMD 17.2N 130.7W 19.9N 133.7W 24.0N 136.7W 27.3N 137.5W
BAMM 16.7N 131.6W 18.1N 133.6W 21.4N 135.5W 24.7N 136.7W
LBAR 18.1N 131.9W 21.8N 135.4W 26.1N 136.6W 29.2N 131.9W
SHIP 60KTS 52KTS 33KTS 0KTS
DSHP 60KTS 52KTS 33KTS 0KTS

...INITIAL CONDITIONS...
LATCUR = 15.4N LONCUR = 126.7W DIRCUR = 280DEG SPDCUR = 7KT
LATM12 = 15.3N LONM12 = 125.3W DIRM12 = 274DEG SPDM12 = 7KT
LATM24 = 14.8N LONM24 = 123.9W
WNDCUR = 45KT RMAXWD = 25NM WNDM12 = 30KT
CENPRS = 1000MB OUTPRS = 1006MB OUTRAD = 150NM SDEPTH = D
RD34NE = 50NM RD34SE = 30NM RD34SW = 40NM RD34NW = 60


LINDA is going up too 45kt
Member Since: May 21, 2006 Posts: 5091 Comments: 115131
Quoting Patrap:
Im so confused..is it 96L,0L7, 007,or TD-7..and should I sauce the Chicken again or start the wienies?

The Shrimps are beginning to Burl too.

Smells like a Holiday here.

Sounds more like your typical weekend, Pat. :D
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Quoting TheDawnAwakening:
I am not saying he will go south and west, nor am I not arguing that he will go north. I just see the possibility of a further south solution. Just because a system is stronger, does not mean it will go further north, case in point was Hurricane Ike last year.


That is true - just becuz a hurricane is strong does not mean it will go north.

but Hurricane Ike was under different steering patterns.

In this case, if TD 7 strengthens, that increases the chance of curvature as the deep layer weakness is stronger.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
This is what the 5PM advisory will look like (discount the coordinates, they are similar to the 5PM advisories but not exact)

Storm information valid as of: Monday, September 7, 2009 18:00 Z
Coordinates: 12.4N 23.9W (View Map or View Storm Centered Satellite Image)
Location: 176 miles (283 km) to the S (188°) from Praia, Cape Verde
Distance Calculator: How far away is this storm from me?
Pressure (MSLP): 1005 mb (29.68 inHg | 1005 hPa)
Sustained wind speed (1 min. avg.): 30 knots (35 mph | 15 m/s)
Member Since: Posts: Comments:
I am not saying he will go south and west, nor am I not arguing that he will go north. I just see the possibility of a further south solution. Just because a system is stronger, does not mean it will go further north, case in point was Hurricane Ike last year.
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Some heavy convective burst with TD 7 might bring it to Fred as early as tonight

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Also I see a way that 07L stays south it has more favorable conditions as well as less SAL to deal with. Will 95L did pave the way, it moved so far NW that it died out due to SAL and Wind shear, but 07L is much further south. If it can stay out of the reach of the troughs for now, it has a better chance to strengthen.
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oh no !! That Reed dude. the Westcaster is going to show up again. He will have this thing headed for New York. Good thing most of us ignore him.
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Yeah, I don't see TD7/Fred making too far west with this prolonged troughing pattern.
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Conditions at 41013 as of
(3:50 pm EDT)
1950 GMT on 09/07/2009:

Wind Direction (WDIR): ESE ( 120 deg true )
Wind Speed (WSPD): 7.8 kts
Wind Gust (GST): 9.7 kts
Wave Height (WVHT): 6.2 ft
Dominant Wave Period (DPD): 7 sec
Average Period (APD): 5.2 sec
Mean Wave Direction (MWD): SE ( 135 deg true )
Atmospheric Pressure (PRES): 29.79 in
Pressure Tendency (PTDY): -0.11 in ( Falling Rapidly )
Air Temperature (ATMP): 78.1 °F
Water Temperature (WTMP): 81.1 °F
Dew Point (DEWP): 73.0 °F
Heat Index (HEAT): 80.6 °F
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Quoting futuremet:
Good to see you cyclonekid
Good to see you too...been reading your blog a lot...love them...Great Job.
Member Since: July 14, 2009 Posts: 51 Comments: 1731
The circulations appeared almost stacked at this time. After looking at the -3 hours compared to the +3 hour shear maps from CIMSS I see that there was an upper level low to the southwest of 07L, but at the +3 hours it has weakened completely with a continued upper level anticyclone over the region with diffluent flow aloft signifying conditions favorable for strengthening although rapid intensification is unlikely for 25 knots in 24 hours given that SSTs are lower then the 29C threshold. Wind shear is dying down among the shear axis stretching SW to NE from the Caribbean Leeward Islands to the old disturbance 95L. Some regions are decreasing. Also divergence is kind of weak but they only sampled the western fringes of the cyclone.
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Quoting AussieStorm:

They taste great, barely any fat but only the hind legs can be eaten.
Just had a horrible, horrible image of a plateful of kangaroo buffalo wings. Carry on.
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Quoting Levi32:


An eye-like feature like that is more likely caused by dry air messing with its inner structure. Notice the stratocumulus field to the NW on that image. That's indicating a dry and stable airmass associated with cool SSTs. Strengthening of 15E is unlikely.

That makes since.
Bye the way, welcome back!
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Good to see you cyclonekid
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This is the 2nd of 2 frontal troughs expected in 1 week

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting WeatherStudent:
Afternoon, Drak! OMG!!!!!!!!!!!!!!! Levi32, welcome back. We've missed you terribly. Where have you've been? Is everything OK? I'm frolic to have you back. You're extraordinarily intellgent when it comes to the field of tropical meteorology. Anyways, thoughts on TD7?, my bud??? Yipers!!! :) You're back, yes!!!!!! :)


Hyper as ever I see WS....lol. If you read my parting blog my family has been doing a lot and with the school year starting I've been a bit too busy to write regular blogs. I'll be trying to stop by in here when I can.

As for TD 7 I have no disagreement with the thoughts in here. It's likely to eventually recurve. I'm more excited about the fact that we finally have a true Cape Verde system to watch in the eastern Atlantic. The only reason it's developing so nicely is because of the 2 waves in front of it that paved the way by moistening the atmosphere up. If it weren't for them the dominant dry air would kill 96L just like the other waves before it.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting futuremet:
It is still more likely that TD7 will recurve out to sea, as a series of trough will create weaknesses along the A/B high.

I just don't see how it can bypass such a weakness.



It can bypass it if the Azores high strengthens back in time, which is why the CMC and other models stalls it and moves it back west. One thing is for sure, the chance of a U.S. impact is low, for the model ensemble shows another prolonged troughing pattern.
Good Afternoon, futuremet.
Member Since: July 14, 2009 Posts: 51 Comments: 1731
We'll just have to wait and see how it unfolds
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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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