Two African waves worth mentioning

By: Dr. Jeff Masters , 3:51 PM GMT on July 18, 2009

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There are two African tropical waves worth mentioning today, though neither looks particularly threatening. A tropical wave near 12N 45W, about 1200 miles east of the Lesser Antilles Islands (97 L), is moving west at 15 - 20 mph. This wave is now surrounded by an area of very dry air from the Sahara Desert. The dry air has disrupted most of the wave's heavy thunderstorm activity, and will continue to make it difficult for this system to develop over the next 2 - 3 days. Wind shear is a modest 10 knots over the disturbance, and should remain in the moderate 10 - 15 knot range over the next 2 - 3 days. Thereafter, shear is expected to rise to 20 - 30 knots. This morning's QuikSCAT pass showed no evidence of a surface circulation, and only a modest wind shift associated with 97L. The National Hurricane Center is giving this system a low (less than 30% chance) of developing into a tropical depression in the next 48 hours.

A second tropical wave now approaching the northern Lesser Antilles Islands is under 30 knots of wind shear, and has little prospect of development due to the high shear. However, the wave will bring heavy rain to the islands over the next two days.

None of the computer models are forecasting tropical storm development over the next seven days, and I don't expect either of the two African waves mentioned today to develop over at least the next three days.


Figure 1. Current satellite image of African wave 97L, 1200 miles east of the Lesser Antilles Islands.

I'll have an update Sunday afternoon.
Jeff Masters

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18Z GFS starting to lock more and more into a Bahama to E FL coast low development... this time taking it straight up the US E Coast... compared to the last run (12Z) in has trended W in the later period.

Due to current southern location of the current tropical disturbances I would go with a more S and W track of this possible disturbance next week until I see a different behavior that would change my though. I still believe like before that this would be moving right through the Greater Antilles if not a bit further south hugging the coast before starting to turn NW/N/NE due to the split trough that most models are forecasting to be in place in the C GOM.
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Quoting stormpetrol:
I'm going out a limb here , I think by Friday next week , we'll have a named system in the Atlantic/Caribbean, yep I guess in my 44 years I've eaten alot more contaminated things than crow LOL! By the way well done or medium well will do.
With Hell Sauce of course.
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I'm going out a limb here , I think by Friday next week , we'll have a named system in the Atlantic/Caribbean, yep I guess in my 44 years I've eaten alot more contaminated things than crow LOL! By the way well done or medium well will do.
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It's storming here in Lake Worth.
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take about a cold snap brrr

take a look at some of the Windchill


Saturday Night
Chance of Snow. Overcast. Low: -83 °F . Wind West 17 mph . Chance of precipitation 20% (trace amounts). Windchill: -104 °F .

Sunday
Scattered Clouds. High: -52 °F . Wind SW 24 mph . Windchill: -117 °F .

Sunday Night
Scattered Clouds. Low: -90 °F . Wind WSW 13 mph . Windchill: -126 °F .

Monday
Partly Cloudy. High: -56 °F . Wind SW 20 mph .

Monday Night
Chance of Snow. Overcast. Low: -88 °F . Wind NNW 6 mph . Chance of precipitation 20% (trace amounts). Windchill: -110 °F .

Tuesday
Chance of Snow. Overcast. High: -50 °F . Wind West 11 mph . Chance of precipitation 20% (trace amounts). Windchill: -117 °F .

Tuesday Night
Overcast. Low: -77 °F . Wind SW 15 mph . Windchill: -113 °F .

Wednesday
Partly Cloudy. High: -58 °F . Wind West 17 mph . Windchill: -137 °F .

Wednesday Night
Overcast. Low: -86 °F . Wind WSW 11 mph . Windchill: -101 °F .

Thursday
Chance of Snow. Overcast. High: -50 °F . Wind NW 13 mph . Chance of precipitation 20% (trace amounts). Windchill: -101 °F .

Thursday Night
Overcast. Low: -97 °F . Wind NNW 11 mph .

Friday
Overcast. High: -58 °F . Wind SW 26 mph . Windchill: -133 °F .

Friday Night
Overcast. Low: -81 °F . Wind NW 8 mph . Windchill: -101 °F
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HIGH SEAS FORECAST

.ATLC TROPICAL WAVE FROM 11N62W TO 21N60W MOVING W AT 18 KT.
FROM 13N TO 20N BETWEEN 55W AND 63W NE TO E WINDS 20 KT. SEAS
LESS THAN 8 FT. WINDS AND SEAS HIGHER IN SCATTERED SQUALLS AND
TSTMS WITHIN 180 NM TO 240 NM E OF WAVE.

.24 HOUR FORECAST TROPICAL WAVE FROM 23N67W TO VICINITY MONA
PASSAGE. WITHIN 240 NM E OF WAVE E TO SE WINDS 20 TO 25 KT. SEAS
8 TO 10 FT. WITHIN 120 NM W OF WAVE NE TO E WINDS 20 KT. SEAS 8
TO 10 FT IN E SWELL.

.48 HOUR FORECAST NORTHERN PORTION OF TROPICAL WAVE FROM S OF
24N NEAR 73W. FROM 18N TO 24N BETWEEN WAVE AND 66W E TO SE WINDS
20 TO 25 KT. SEAS 8 TO 10 FT. WITHIN 120 NM W OF WAVE NE TO E
WINDS 20 KT. SEAS 8 TO 10 FT IN E SWELL.
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Something is bound to form into a cyclone soon. While it is too early to been seen if this activity produces any names, it seems the EPAC activity has transferred into Atlantic activity. EPAC had Blanca, Carlos, and Dolores.....maybe it is the Atlantic's turn now
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Quoting GeoffreyWPB:
Here we go again in Lake Worth.



Yup.
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Quoting reedzone:
Looks like land will be the main reason for no development of any of the wave, the 18Z GFS tries to get it goes until it hits Puerto Rico and Hispaniola. It will take time for anything to get going even hours after crossing rough territory. This is another reason why models don't develop anything until after it gets NORTH of the Bahamas.



Very true
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Link
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Here we go again in Lake Worth.

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Quoting wunderkidcayman:
where is the center of pre-98l
It looks to me around 62w and 15n but I could be wrong.
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A circulation,whether at the surface or mid-level is evident west of the Leewards already in the Caribbean,..the Blow up of Convection is east of it.

Floater 1 - Visible Loop
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OR maybe something like Tropical Storm Tammy could happen where it forms right off of Florida and pushes west into the state due to the high. Anything is possible in all reality. This is why I am watching both areas.
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spinning
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where is the center of pre-98l
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thunderstorms are trying t redevelop around ex97L
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Quoting Weather456:


Overcast, with mainly mid-level clouds. maximum gust today 32 knots and about 1/2 a inch of rain in intermediate showers. I have a PWS you can check out at WU. I'm actually at the office since we may experience flooding of that kind of rain approaches.
Thanks.
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Just put any Zip or Location in the Box at the top of every wu-page for a City Forecast or current conditions.


Vostok, Antarctica -67 F




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Looks like land will be the main reason for no development of any of the wave, the 18Z GFS tries to get it goes until it hits Puerto Rico and Hispaniola. It will take time for anything to get going even hours after crossing rough territory. This is another reason why models don't develop anything until after it gets NORTH of the Bahamas.
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Quoting stormdude77:
It's raining here in Barbados....outside is very ''still''
Looks like you have quite a bit of rain heading your way.
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Quoting Weather456:


That's just the Antilles blob. Since much of the energy appears to remain along the Northern Island chain over the next few days. As for ex-97L, the probability of 1 inch or more is 50% and thats later this week Thur-Fri.

ok. thanks
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Patrap:
Current Conditions

St Kitts Wu-page


Basseterre, Saint Kitts (PWS)
Updated: 7 min 55 sec ago
Scattered Clouds
81.9 °F
Scattered Clouds
Humidity: 82%
Dew Point: 76 °F
Wind: 9.0 mph from the East
Wind Gust: 23.0 mph
Thanks. Just curious since he seems to be the closest to the blob right now.
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It's raining here in Barbados....outside is very ''still''
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Quoting stormwatcherCI:
Weather456 what's the current conditions in St Kitts ?


Overcast, with mainly mid-level clouds. maximum gust today 32 knots and about 1/2 a inch of rain in intermediate showers. I have a PWS you can check out at WU. I'm actually at the office since we may experience flooding of that kind of rain approaches.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Year of shear.
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Current Conditions

St Kitts Wu-page


Basseterre, Saint Kitts (PWS)
Updated: 7 min 55 sec ago
Scattered Clouds
81.9 °F
Scattered Clouds
Humidity: 82%
Dew Point: 76 °F
Wind: 9.0 mph from the East
Wind Gust: 23.0 mph
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Quoting weatherwatcher12:

So we are not going to get much from the Antilles blob and ex-97L


That's just the Antilles blob. Since much of the energy appears to remain along the Northern Island chain over the next few days. As for ex-97L, the probability of 1 inch or more is 50% and thats later this week Thur-Fri.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Weather456 what's the current conditions in St Kitts ?
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Quoting Weather456:


Yep but not much, a max of 10 mm per day expected for the island over the next day and 2.

So we are not going to get much from the Antilles blob and ex-97L
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting hunkerdown:
Could you please be more clear :)


The northern portion of the wave over the Lesser Antilles with break off and move north of the Lesser Antilles. Wind shear will be unfavorable in the Bahamas. South Florida should see some increased rain chances. The wave will interact with a frontal boundary and there may be a small window of oppurtunity for a subtropical cyclone to form. I'm not bought on a purely tropical system.

The GFS shows most of the energy going into the northern portion of the system while the southern portion, convection-less, travels through the Caribbean. There is a chance that ex-97L maybe be able to catch up and potentially do something in the Caribbean as conditions aloft will be favorable 2-3 days from now.
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Quoting BurnedAfterPosting:


you are going to confuse people if you keep calling it 97L when it is no longer an invest


Absolutely,..those kinda hanging on Posts of a Deactivated system just confuses folks,one could easily add,former 97L
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Floater 1 - Visible Loop

.A TROPICAL WAVE HAS JUST ENTERED THE FAR EASTERN
CARIBBEAN SEA...AND IS ALONG 62W MOVING W NEAR 18 KT. THE WAVE
WILL MOVE ACROSS THE REMAINDER OF THE EASTERN CARIBBEAN TONIGHT
THROUGH SUN REACHING THE CENTRAL CARIBBEAN NEAR 70W AS IT
SLOWS DOWN SOME BY EARLY MON...NEAR 75W MON NIGHT...NEAR 80W
TUE...NEAR 84W ON WED AND NEAR THE YUCATAN PENINSULA AND BELIZE
ON THU.
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Quoting reedzone:
Guys, I'm still calling it 97L lol, I know it's been de-activated, but I'm giving it 14 more hours, basically DMAX tonight.


you are going to confuse people if you keep calling it 97L when it is no longer an invest
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Quoting weatherwatcher12:

Anything in store for Jam


Yep but not much, a max of 10 mm per day expected for the island over the next day and 2.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Guys, I'm still calling it 97L lol, I know it's been de-activated, but I'm giving it 14 more hours, basically DMAX tonight.
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Quoting Patrap:
97L..LOL..one bubble..


lol
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Quoting Weather456:
Interesting, here's the 72 hrs forecast, northern energy breaks off the northern section of the wave. regardless of develops increase moisture heads west towards the Bahamas, Cuba and possibly, FL.


Anything in store for Jam
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Thats a good read,tyvm
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This is the latest from the NHC :SYNOPSIS...A TROPICAL WAVE HAS JUST ENTERED THE FAR EASTERN
CARIBBEAN SEA...AND IS ALONG 62W MOVING W NEAR 18 KT. THE WAVE
WILL MOVE ACROSS THE REMAINDER OF THE EASTERN CARIBBEAN TONIGHT
THROUGH SUN REACHING THE CENTRAL CARIBBEAN NEAR 70W AS IT
SLOWS DOWN SOME BY EARLY MON...NEAR 75W MON NIGHT...NEAR 80W
TUE...NEAR 84W ON WED AND NEAR THE YUCATAN PENINSULA AND BELIZE
ON THU. A SECOND TROPICAL WAVE CURRENTLY OVER THE CENTRAL ATLC
IS FORECAST TO REACH THE EASTERN CARIBBEAN BY EARLY TUE...TO
NEAR 68W BY EARLY WED...AND TO NEAR 73W ON THU. TRADE WINDS WILL
FLUCTUATE IN RESPONSE TO PASSAGE OF THE WAVES. HIGHEST WINDS AND
SEAS EXPECTED MAINLY ACROSS N PORTIONS OF THESE TROPICAL WAVES.
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Interesting, here's the 72 hrs forecast, northern energy breaks off the northern section of the wave. regardless of develops increase moisture heads west towards the Bahamas, Cuba and possibly, FL.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
97L..LOL..one bubble..
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Quoting reedzone:
Well 97L still has very good structure with one bubble of convection that is very slowly growing. Like I said, I'm giving it 14 more hours (basically till Sunday morning) to regenerate. It's moving into a moist environment and shear is decreasing where it's tracking. As for the wave near the Islands, it could be tagged by either Sunday or Monday, depends really when the wind shear gets to marginal at best which all models show today. Drakeon made a good point on the "possible East Coast system". I just got done looking at the cyclone phase maps and while most have it as a warm core symmetrical system, all of the models show a shallow cored system which means it's a possible "Subtropical System". Although I love to track those, they look so awesome on satellite, Gustav (2002) was the best one I've seen so far. So lets take it day by day and watch BOTH 97L and wave and see what they can do. No doubt, alot of moisture is heading to the East Coast regardless of any development.


It is not 97L anymore
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If any one is making decisions outta here,well...at least theres not a 25 knt wind anywhere to blow them away,..LOL
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Well 97L still has very good structure with one bubble of convection that is very slowly growing. Like I said, I'm giving it 14 more hours (basically till Sunday morning) to regenerate. It's moving into a moist environment and shear is decreasing where it's tracking. As for the wave near the Islands, it could be tagged by either Sunday or Monday, depends really when the wind shear gets to marginal at best which all models show today. Drakeon made a good point on the "possible East Coast system". I just got done looking at the cyclone phase maps and while most have it as a warm core symmetrical system, all of the models show a shallow cored system which means it's a possible "Subtropical System". Although I love to track those, they look so awesome on satellite, Gustav (2002) was the best one I've seen so far. So lets take it day by day and watch BOTH 97L and the Tropical Wave and see what they can do. No doubt, alot of moisture is heading to the East Coast regardless of any development.
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So…97L has been deactivated, and yet some bloggers don’t believe it…and 98L has not been officially designated, yet some bloggers attest that it has. Just affirms that this is an entertainment blog, not meant to make any decisions concerning real-time threatening storms that may affect your part of the world.
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On the Convective Blow up..


A TROPICAL WAVE EXTENDS ALONG 21N58W 15N61W TO 10N62W MOVING
W NEAR 18 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER
MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. WATER VAPOR IMAGERY INDICATES THE WAVE IS BEGINNING TO
MOVE BENEATH AN UPPER LEVEL RIDGE ACROSS THE ERN CARIBBEAN AND
THE NRN PORTION OF THE WAVE IS COMING UNDER THE IMPACTS OF AN
UPPER LOW CENTERED NE OF PUERTO RICO NEAR 23N58W. UPPER LEVEL
DIFFLUENCE BETWEEN THESE TWO FEATURES ARE ENHANCING SCATTERED
MODERATE CONVECTION FROM 13N-18N BETWEEN 55W-62W.

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This is the last NWS discussion from Miami,fl


THE TROPICAL WAVE OVER THE WINDWARD ISLAND WILL BE MOVING WEST TO
NORTHWEST THIS WEEKEND AND INTO SOUTH FLORIDA AREA ON TUESDAY INTO
MIDDLE OF NEXT WEEK.
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Quoting Tazmanian:




its not 97L its called x-97L
Its actually called a tropical wave.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Drakoen:


Post 665, 668, and 691
Could you please be more clear :)
Member Since: August 15, 2008 Posts: 0 Comments: 2515

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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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