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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On the current path of motion, 97L is expected to enter the Carribbean in 36-48 hrs

48 hrs

Member Since: July 24, 2005 Posts: 407 Comments: 19076
had to leave @ 11pm last night and just got in and now able to check so what is going on with both our waves this early am?
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1648. surfmom
Morning - getting a jump start on the weather maps this morning....Wow Weather456 - you've got it all done for me.....NOT looking for a 'cane but a little wave action in the gulf would be nice..... haven't seen a groundswell in a verrrrry long time.
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Wave #1

NATIONAL WEATHER SERVICE MIAMI FL
333 AM EDT SUN JUL 19 2009

.DISCUSSION...WEAK SURFACE RIDGE OVER THE AREA SHOULD WEAKEN AND
MOVE NORTH OF THE AREA BY MONDAY TURNING THE WIND DIRECTIONS MORE
EASTERLY. A TROPICAL WAVE NEAR PUERTO RICO ATTM WILL CONTINUE
MOVING WEST AT 10 TO 15 KNOTS AND ARRIVE OVER SOUTHEAST FLORIDA
BY EARLY WEDNESDAY. MODELS CONTINUE TO SHOW THAT MOST OF THE
HIGHER MOISTURE WILL MOVE UP THE WESTERN ATLANTIC BUT THE SURFACE
WIND SHIFT TO THE SOUTHEAST WITH THE WAVE WILL SWING THROUGH THE
AREA ON WEDNESDAY. WITH THE HIGHER MOISTURE TO OUR EAST, PWAT`S
WILL REMAIN MOSTLY AT OR BELOW 2 INCHES OVER THE AREA BUT THE
MODELS ARE INDICATING AN INCREASE ABOVE 2 INCHES LATE IN THE WEEK.

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97L also has slowed down some, which should be an advanatge to it getting LLCC up and going.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
The disturbance heading due west straight for Barbados and the Windwards.


I noticed that earlier. That westward motion will allow it to avoid the 20 knots of shear to the north of it.
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Quoting jasoniscoolman09:
good morning everyone...x71L IS LOOKING BETTER NOW.


71? o_O
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Good ole morning shift. I see ex-97L likes the warmer waters...definitely is still a player. I would keep an eye on the wave at 65W too...even though it looks horrible now.

Enjoy the approaching work week...I'll be on vacation! :P
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The disturbance heading due west straight for Barbados and the Windwards.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Shortwave imagery revealed a broad circulation associated with ex-97L. I suspect if this continues through the day, it should be re-designated. Whether or not it is closed, QuikSCAT or visible should answer that.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1637. KC2NOLA
Greetings from NOLA.
456 your insights dealing with 97L have been pretty spot on.
I look forward to reading your thoughts. I am in no means up to most of the blogs education dealing with tropical weather, but I do love it and hope to learn more through you all.
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G'night all.
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Quoting facetracker:
It does look like the system to the north that is moving east is curling down and helping 97. is there a name for this?


Upper level low. DMAX is whats helping EX97L.
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It does look like the system to the north that is moving east is curling down and helping 97. is there a name for this?
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From one of the loops, it looks like 97L's t-storms are being helped in venting by what looks like a big upper low more north in the Atlantic. This is just my observation as a lay person. I'm an artist, not a weather man, although I do work in emergency management. It's interesting to watch and see how things develop in the tropics, although systems seldom affect this area (The Jersey Shore). Last year, we had Hanna, and earlier that summer, an outer rain band from Cristobal went right over our area, drenching us on what was predicted to be a sunny, weekend day. '06 we dealt with Ernesto. Cindy poured buckets on us in '05.
In '04, we felt the remants of Bonnie, Charley, Frances, Gaston, Ivan and Jeanne, like a tropical choo-choo train. '03 saw Isabel hit down to our south, but with a huge windfield expanding towards us. '99 saw Floyd, a 70 mph tropical storm, just downgraded literally a few minutes before it blew by, placing us in a dead calm for about an hour between torrential rain and serious wind. '96 saw Bertha, almost a Floyd, but not quite. '89 saw Hugo passing to our west. In'85 we had Gloria, right on our doorstep as a 'cane, as we did nine years earlier with Hurricane Belle in 1976. Both made "direct strikes", but not official landfall, and damage was light, but evident. That's all in my life span. My brother speaks of Donna in 1960, and lore is legendary of the '53 and '54 seasons around here, where I think we saw Connie, Diane, Hazel and maybe another come close our way enough to bring strong winds during that time. The '44 Great Atlantic Hurricane gave my community a very bitchy slap, 100 mile per hour winds, as did the '38 storm of immense fame, which did slightly less damage here. The last direct landfall on our state was a Category One Hurricane in 1903, putting us overdue for the once-in-a-hundred-year estimate of such happening. In 1821, a major hurricane, at least a three, possibly a four, hit Cape May and paralleled up the coast, which was not very populous at the time. We are fast approaching the once-in-200-year benchmark of the estimate of a major making Jersey landfall again. If it happened today as it did in 1821, damage would surpass Katrina because NJ is far more densely populated than the Gulf Coast, and we have many more houses built right up to sea, many with zero hurricane tolerance, except for the most modern structures. Combine that with the fact that such a repeat would put the storm into NYC, potentially crushing the all-important subway system, and disaster-like damage to Lower Manhattan world financial markets, already scarred from terrorist attacks, and the overall economy. I hope I am long dead before this "big one" comes our way! Peace to all the bloggers and God Bless.
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Divergence and Convergence have increased. Interesting.
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Good Night everyone
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Stormchaser2007:
DMAX is approaching and some may be surprised to what they wake up to tomorrow.



D-Max is very soon
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Stormchaser2007:
DMAX is approaching and some may be surprised to what they wake up to tomorrow.


I can just imagine how they will react
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Does this indicate a closed low?:
Member Since: May 16, 2009 Posts: 1 Comments: 1231
DMAX is approaching and some may be surprised to what they wake up to tomorrow.

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Quoting Stormchaser2007:


Should lift the TUTT out soon. Interesting.


And replaced by a ridge, but it comes back in 5 days

Member Since: July 24, 2005 Posts: 407 Comments: 19076
This buoy is close (14.477 N 53.008 W):
Wind Direction (WDIR): ENE ( 70 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 21.4 kts
5-day plot - Wind Gust Wind Gust (GST): 25.3 kts
5-day plot - Wave Height Wave Height (WVHT): 8.2 ft
5-day plot - Dominant Wave Period Dominant Wave Period (DPD): 7 sec
5-day plot - Average Period Average Period (APD): 5.5 sec
5-day plot - Atmospheric Pressure Atmospheric Pressure (PRES): 29.94 in
5-day plot - Pressure Tendency Pressure Tendency (PTDY): -0.05 in ( Falling )
5-day plot - Air Temperature Air Temperature (ATMP): 81.1 °F
5-day plot - Water Temperature Water Temperature (WTMP): 82.0 °F
5-day plot - Dew Point Dew Point (DEWP): 75.2 °F
5-day plot - Heat Index Heat Index (HEAT): 87.3 °F
Member Since: May 16, 2009 Posts: 1 Comments: 1231
I figured somehow ex97L would come back..
heavy convection firing off. Wonder if they will reactivate it.
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Quoting Weather456:
Notice the ridge rising from N South America



Should lift the TUTT out soon. Interesting.
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Quoting Weather456:


later this morning,


There goes the TUTT
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Notice the ridge rising from N South America

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Member Since: May 16, 2009 Posts: 1 Comments: 1231

Here it is
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Stormchaser2007:


Alright. So when do you think you'll have another discussion on Ex97L? Kinda interested in what you're thinking.


later this morning.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
NEW 850mb Vorticity has increased and is more organized.

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Quoting btwntx08:
aha tampa is wrong on shear lol


What else is new. I really never believe him on anything with the tropics. Tends to overreact allot.
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Quoting Weather456:
CIMSS issue times:

06Z - 3:40
09Z - 6:40
12Z - 9:40

and so on, and I and 40 minutes. Well thats normally timing.

so in 4 minutes we should have it
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Weather456:


Nope, on the Central Atlantic imagery if you overlay upper wids notice they are 5-10 knots from the NE. Not seeing any shear.


Alright. So when do you think you'll have another discussion on Ex97L? Kinda interested in what you're thinking.
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CIMSS issue times:

06Z - 3:40
09Z - 6:40
12Z - 9:40

and so on, and I and 40 minutes. Well thats normally timing.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Stormchaser2007:


Hm pretty accurate. Do you think shears enhancing the convection? Although I really dont see any shear.


Nope, on the Central Atlantic imagery if you overlay upper wids notice they are 5-10 knots from the NE. Not seeing any shear.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:


Yea I saw that but not sure what to make of the 5-10 knot winds I'm seeing. I'll wait for the shear maps to update for 06Z

Hopefully they will be issued soon
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting weatherwatcher12:

The NHC is saying something strange:
000
ABNT20 KNHC 190533
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN JUL 19 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE OVER THE EASTERN CARIBBEAN SEA IS PRODUCING
DISORGANIZED SHOWERS AND THUNDERSTORMS AS IT MOVES WEST-
NORTHWESTWARD AT ABOUT 15 MPH. WHILE RAINFALL ASSOCIATED WITH THE
WAVE MAY BE LOCALLY HEAVY AT TIMES...UPPER-LEVEL WINDS REMAIN
UNFAVORABLE FOR SIGNIFICANT DEVELOPMENT OF THE SYSTEM. THERE IS A
LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY ASSOCIATED WITH A TROPICAL WAVE LOCATED ABOUT
900 MILES EAST OF THE WINDWARD ISLANDS HAS INCREASED A LITTLE THIS
EVENING. HOWEVER...UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR
SIGNIFICANT DEVELOPMENT AT THIS TIME
. THERE IS A LOW CHANCE...LESS
THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN


Yea I saw that but not sure what to make of the 5-10 knot winds I'm seeing. I'll wait for the shear maps to update for 06Z
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
The NHC better pay attention:

11am Today by 456

Tropical Invest 97L

There has been little change to this tropical invest, as showers remain limited along a tropical wave near 41W. There continues to be excellent mid-low level turning along the wave axis, which is major thing, needed going into the Western tropical Atlantic. I suspect the wave to have the same effect as the current wave near the islands, where convection would suddenly increase. None of the forecast models develop this wave as yet.


Hm pretty accurate. Do you think shears enhancing the convection? Although I really dont see any shear.
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Quoting Weather456:
The NHC better pay attention:

11am Today by 456

Tropical Invest 97L

There has been little change to this tropical invest, as showers remain limited along a tropical wave near 41W. There continues to be excellent mid-low level turning along the wave axis, which is major thing, needed going into the Western tropical Atlantic. I suspect the wave to have the same effect as the current wave near the islands, where convection would suddenly increase. None of the forecast models develop this wave as yet.

The NHC is saying something strange:
000
ABNT20 KNHC 190533
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN JUL 19 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE OVER THE EASTERN CARIBBEAN SEA IS PRODUCING
DISORGANIZED SHOWERS AND THUNDERSTORMS AS IT MOVES WEST-
NORTHWESTWARD AT ABOUT 15 MPH. WHILE RAINFALL ASSOCIATED WITH THE
WAVE MAY BE LOCALLY HEAVY AT TIMES...UPPER-LEVEL WINDS REMAIN
UNFAVORABLE FOR SIGNIFICANT DEVELOPMENT OF THE SYSTEM. THERE IS A
LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY ASSOCIATED WITH A TROPICAL WAVE LOCATED ABOUT
900 MILES EAST OF THE WINDWARD ISLANDS HAS INCREASED A LITTLE THIS
EVENING. HOWEVER...UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR
SIGNIFICANT DEVELOPMENT AT THIS TIME
. THERE IS A LOW CHANCE...LESS
THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Morning Everyone and stormchaser, lol
Member Since: July 24, 2005 Posts: 407 Comments: 19076
The NHC better pay attention:

11am Today by 456

Tropical Invest 97L

There has been little change to this tropical invest, as showers remain limited along a tropical wave near 41W. There continues to be excellent mid-low level turning along the wave axis, which is major thing, needed going into the Western tropical Atlantic. I suspect the wave to have the same effect as the current wave near the islands, where convection would suddenly increase. None of the forecast models develop this wave as yet.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1602. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #30
TROPICAL DEPRESSION, FORMER MOLAVE (T0609)
15:00 PM JST July 19 2009
============================================

Subject: Tropical Depression Overland South China

At 6:00 AM UTC, Tropical Depression, Former Molave (994 hPa) located at 23.0N 111.0E is reported as moving west at 15 knots.

This is the final tropical cyclone advisory from the Japan Meteorological Agency
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Quoting weatherwatcher12:

I was being sarcastic lol :)

Oh, I figured that. I was agreeing with you that it wasn't being battered. Thanks.
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Quoting popartpete:
To me, it seems that 97l has really blossomed in the last few hours.

It's in a nice moist environment
Member Since: May 16, 2009 Posts: 1 Comments: 1231

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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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