Little change to 90L; new African tropical wave is worth watching

By: Dr. Jeff Masters , 8:53 PM GMT on July 30, 2010

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Invest 90L is a tropical wave in the eastern Atlantic near 10N 33W with a very limited amount of heavy thunderstorm activity but a decent amount of spin. It does not have a well-defined surface circulation, and has shown little change in organization today. CIMMS wind-shear analyses show a low amount of wind shear (5 - 10 knots) over 90L, and sea surface temperatures are a record warm 29°C. The wave currently is in a moist environment and is not being affected by the dry Saharan Air Layer (SAL) to its northwest. The disturbance has moved far enough away from the Equator to leverage the Earth's spin to help it develop. The Saharan Air Layer with its dust and dry air lurks just to the north of 90L, but the SHIPS model predicts 90L will remain far enough from the dry air over the next five days so that it will not interfere with development.


Figure 1. Afternoon visible satellite image from 2pm EDT 7/30/10 of the relatively tiny 90L, and the large new tropical wave that moved off the coast of Africa yesterday.

Forecast for 90L
One factor inhibiting development of 90L this week will be the Madden-Julian Oscillation (MJO.) The MJO currently favors downward motion over the tropical Atlantic, which will act to decrease the chances of tropical storm formation. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased.

Perhaps the main factor interfering with 90L's development will be the presence of the large tropical wave to the east of 90L that moved off the coast of Africa yesterday. This new wave is large enough and close enough to 90L that it will probably begin to dominate regional weather patterns this weekend, stealing away 90L's inflow of low-level moist air. The new wave may also act to bring sinking air over 90L that will tend to suppress 90L's thunderstorm activity. It may turn out that the new wave will also steal some of 90L's spin, and end up being a threat to develop itself later on this weekend.

The latest 8am EDT (12Z) model runs for 90L show very little in the way of development of the storm. The predominant track forecast takes 90L into or just north of the northern Lesser Antilles Islands about 6 - 8 days from now. Looking at climatology based on research done by Dr. Bob Hart at Florida State University,, 90L has a 19% chance of developing into a tropical cyclone by 2pm Sunday. NHC is putting these odds at 20%. Dr. Hart also has an experimental product showing that historically, about 30% of all tropical cyclones that develop at 90L's current position eventually hit land as a hurricane. Of course, 90L is not yet a tropical cyclone, and I think that the large tropical wave off the coast of Africa will kill 90L this weekend.

Tropical wave in the eastern Caribbean
A tropical wave in the eastern Caribbean, south of the Dominican Republic, is moving west at 15 - 20 mph with no signs of development. The wave is under a high 20 knots of wind shear, due to strong upper-level westerly winds from an upper level low centered north of Puerto Rico. This shear is expected to remain remain high through Saturday. By Sunday, when the wave will be approaching Nicaragua, the wave will be far enough away from the upper level low that shear should fall to the moderate range, 10 - 20 knots. Some development is possible on Sunday, but the wave will have only about a 1-day window to develop before its westerly motion brings it inland over Nicaragua on Monday. NHC is giving this wave a 10% chance of developing into a tropical depression by 2pm Sunday.

Extreme cold records for 2010
In my post yesterday, I reported that fourteen countries had set their all-time hottest temperature record this year. I neglected to mention that one country has also set its coldest temperature in recorded history mark in 2010. Guinea had its coldest temperature in its history on January 9, 2010, when the mercury hit 1.4°C (34.5°F) at Mali-ville in the Labe region. Of the 229 countries with extreme coldest temperature records, 14 of these records have occurred in the past ten years (6% of all countries). There have been five times as many (74) extreme hottest temperature records in the past ten years (33% of all countries.) My source for extreme weather records is Chris Burt, author of Extreme Weather.

New study finds huge drop in the plants that form the base of the oceanic food chain
A study published this week in the journal Nature documents that microscopic marine phytoplankton, which form the basis of the marine food chain, have declined by 40% globally since 1950. Joe Romm at climateprogress.org discusses the implications, using this headline:

Scientists may have found the most devastating impact yet of human-caused global warming — a 40% decline in phytoplankton since 1950 linked to the rise in ocean sea surface temperatures. If confirmed, it may represent the single most important finding of the year in climate science.

I plan to discuss this paper next week.

Next update
I'll have an update this weekend, probably by 8pm EDT Saturday.

Jeff Masters

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And he was a NWS & NHC forecaster
so it does involve the tropics
Member Since: Posts: Comments:
Quoting Bipartisanship:
hi centix, good to see you on so early today.
Which means I may not be around late. Thanks.I keep thinking the tropics are going to surprise us and something will spinup in area we are not watching currently.
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90L turns into Tropical Storm Colin by 162 hours north of Puerto Rico, note the closed isobar with the wind barbs indicating winds in excess of 35 knots along with a closed low.


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Quoting Orcasystems:


Why do you type in bold asking... when you could type normally in Google and get the answer?


It was a joke but I guess that went right over your head Mr Personality :)
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Quoting earthlydragonfly:


I believe that it is the other way around... Lower intensity which will keep the storm further south because of the Coriolis effect


Huh?
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Quoting Hardcoreweather2010:
Why does Bobby Hebert have a box and what does it have to do with the tropics ?


Why do you type in bold asking... when you could type normally in Google and get the answer?
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Quoting Hardcoreweather2010:
Why does Bobby Hebert have a box and what does it have to do with the tropics ?


its Paul Hebert
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Quoting Orcasystems:
Model shift to the South (again) and a decrease in Intensity (again)



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI


I believe that it is the other way around... Lower intensity which will keep the storm further south because of the Coriolis effect
Less intensity less rotation of the storm the less net effect that the rotation of the earth will turn the storms direction to the north then north east.
Member Since: July 1, 2005 Posts: 10 Comments: 1683
I hope that they run the HWRF and GFDL at 18z or 00z.
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Why does Bobby Hebert have a box and what does it have to do with the tropics ?
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GFS going a little bit more aggressive in the 18z run. Note that 90L develops an area of low pressure (1011mb) when it's over the U.S Virgin Islands.

GFS 18z 144 hours.

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Quoting MiamiHurricanes09:
I would include jeffs713 in that mix.


yea that jeff is ok
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As long as INvest 90L's circulation remains trackable and intact, it will stay Invest 90L.

If 90L's circulation tracks under the other waves convection, it will remain 90L.

If 90L's circulation dissipates and one forms under the other wave, it will become Invest 91L.
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124. xcool



Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting will45:


yea me too
I would include jeffs713 in that mix.
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I'm waiting for the season to really begin. I'm surprised with such an active season fore-casted we only had a tropical depression and a minimal tropical storm this July. There's still a chance for August and September to be crazy active, but it needs to start now. Besides, I think I'm going crazy with nothing substantial to track and having to deal with weak invests that fluctuate so much.
Member Since: Posts: Comments:
Quoting FLdewey:
Can I refill your eggnog for you?

Get you something to eat?

Drive you out to the middle of nowhere and leave you for dead?


No thanks, but th anks...I think. lol.
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Quoting Orcasystems:


The only 2 Jeff's I pay attention to are Dr Masters and DestinJeff(for the humour).


yea me too
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Quoting will45:
Orca hide those models before Jeff gets back in here lol


The only 2 Jeff's I pay attention to are Dr Masters and DestinJeff(for the humour).
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Quoting CybrTeddy:
Return of the.. MJO?


That area of Upward MJO in that are of the EPAC has developed before there during downward pluses in the Atlantic. Unless you see something different this time around?
Member Since: September 6, 2009 Posts: 2 Comments: 3710
Quoting ElConando:


It is apparent that 90L will fall to the have behind it. Unless it starts to race off to the west. It has no shot of developing. On the other hand there is not much to stop the development of the wave behind it imo.
Agree. I think NHC just started putting everything at 20% coming off African coast. Why they expaned area east. This is time of year system could develop almost anywhere. I'm sure we will have something by end of next week.
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113. xcool


18z gfs
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Orca hide those models before Jeff gets back in here lol
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Levi, do you think the wave behind 90L gets tagged as 91L and they drop 90L? Or regardless, 90L stays?
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Quoting Orcasystems:


I have heard other people say the same thing about you :)


Oh BURN!, wait, that's... me :o
Member Since: September 6, 2009 Posts: 2 Comments: 3710
Quoting Levi32:


Like PRweathercenter said, it's an area of thunderstorms along the tail of an old front getting draped down in the area. It doesn't look like a threat to develop into anything tropical.

Oh OK.
Member Since: July 7, 2010 Posts: 0 Comments: 5626
Quoting Orcasystems:
Model shift to the South (again) and a decrease in Intensity (again)



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI


It is apparent that 90L will fall to the have behind it. Unless it starts to race off to the west. It has no shot of developing. On the other hand there is not much to stop the development of the wave behind it imo.
Member Since: September 6, 2009 Posts: 2 Comments: 3710
Quoting Bipartisanship:
Thanks, doc, i too expecta threater to form, ^_^. THANK GOD.


Are you already back again?!?!
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Quoting ElConando:
No one posted new blog in there. I had no idea I was talking to myself...


I have heard other people say the same thing about you :)
Member Since: Posts: Comments:
Model shift to the South (again) and a decrease in Intensity (again)



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
Member Since: Posts: Comments:
Quoting ElConando:
No one posted new blog in there. I had no idea I was talking to myself...

MH09 did ya must have missed it
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Quoting Levi32:


Like PRweathercenter said, it's an area of thunderstorms along the tail of an old front getting draped down in the area. It doesn't look like a threat to develop into anything tropical.


yea i told them in the other blog it was spinning the wrong way lol
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No one posted new blog in there. I had no idea I was talking to myself...
Member Since: September 6, 2009 Posts: 2 Comments: 3710
I am here... lol
Member Since: July 3, 2010 Posts: 0 Comments: 427
Quoting WeatherNerdPR:

Levi, can you tell me what is that area of Cloudiness North of the Bahamas?


Like PRweathercenter said, it's an area of thunderstorms along the tail of an old front getting draped down in the area. It doesn't look like a threat to develop into anything tropical.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting PRweathercenter:
I've never seen this blog so quite before....


they are probably still in the old blog.
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Quoting MiamiHurricanes09:
I'm going with tropical depression on Sunday. Monday sounds like a safer bet, but I'll take my chances. :)


I'm with you on that. Might be wrong but I think its plausible. Will check in later.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Have a good one people!!
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So we had it backwards, the wave will disrupt 90L and may steal the spin.
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I've never seen this blog so quite before....
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Area Forecast Discussion
Issued by NWS San Juan, PR

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27


000
FXCA62 TJSJ 301912
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
312 PM AST FRI JUL 30 2010

.SYNOPSIS...GENERALLY FAIR WEATHER IS EXPECTED ACROSS THE LOCAL
ISLANDS THROUGH THE UPCOMING WEEKEND WITH LIMITED AFTERNOON
CONVECTION EXPECTED TO DEVELOP EACH AFTERNOON OVER THE INTERIOR
AND WESTERN SECTIONS OF PUERTO RICO. INCREASING MOISTURE AND
INSTABILITY ARE EXPECTED BY EARLY NEXT WEEK...WITH AN INCREASE IN
SHOWER ACTIVITY EXPECTED FOR LATE MONDAY AND TUESDAY...AND A
POTENTIALLY STRONG TROPICAL WAVE EXPECTED TO REACH THE LOCAL
ISLANDS BY WEDNESDAY OR THURSDAY.

&&

.DISCUSSION...A TROPICAL WAVE PASSING SOUTH OF THE LOCAL ISLANDS
IS HAVING LITTLE IMPACT ON THE LOCAL WEATHER AS DRIER AIR HAS
ADVECTED ACROSS THE REGION AND A STRONG SUBSIDENCE CAP HAS KEPT
SHOWER ACTIVITY TO A MINIMUM ACROSS THE LOCAL ISLANDS TODAY.
CONTINUED GENERALLY DRY AND FAIR WEATHER IS EXPECTED TO PREVAIL
THROUGH THE UPCOMING WEEKEND...WITH AN ISOLATED SHOWER OR
THUNDERSTORM POSSIBLY BREAKING THROUGH THE CAP ACROSS WESTERN
SECTIONS OF THE ISLAND DURING THE AFTERNOON HOURS EACH DAY.


THE TUTT LOW TO OUR NORTHEAST IS EXPECTED TO RETROGRADE WESTWARD
EARLY NEXT WEEK...WITH A LOW LEVEL TROUGH OR REFLECTION OF THIS
TUTT EXPECTED TO BRING AN INCREASE IN MOISTURE ACROSS THE VI AND
SECTIONS OF PUERTO RICO BY MONDAY AFTERNOON AND TUESDAY. THE MOST
INTERESTING FEATURE OVER THE NEXT SEVEN DAYS IS THE POTENTIALLY
STRONG TROPICAL WAVE...THAT AT THIS TIME HAS A LOW CHANCE OF
DEVELOPING INTO A TROPICAL CYCLONE...EXPECTED TO REACH THE LOCAL
ISLANDS TOWARD THE MIDDLE TO END OF NEXT WEEK. STILL MUCH
UNCERTAINTY...BUT EITHER WAY...EXPECT A SIGNIFICANT INCREASE IN
SHOWER AND THUNDERSTORM ACTIVITY ACROSS THE LOCAL ISLANDS BY NEXT
WEDNESDAY OR THURSDAY AS THIS WAVE APPROACHES THE LOCAL ISLANDS.

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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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