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

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

Share this Blog
3
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1741 - 1691

Page: 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 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35Blog Index

1741. bappit
I think we are alone wunder kid.
Member Since: Posts: Comments:
WOW GUYS ORANGE ALERT 30% WOW WOW WOW Sorry about this I just came back from town
Member Since: Posts: Comments:
1739. bappit
Cool stuff. On page 5608:

Meteorological charts displaying Earth-relative streamlines are a standard tool in the forecasting industry, but generally provide a misleading picture of actual flow kinematics, or Lagrangian displacement of air, in propagating tropical waves. These maps typically display an upright omega pattern in the lower troposphere straddling the wave’s trough axis. In fact the omega pattern is often upside-down in the translating frame, with separatrix orientation to the north. In other cases, the separatrix is oriented to the east or west (or both). To the extent that horizontal advection explains the topology of streamlines, and therefore indicates where air in the closed gyre has detached from, it is firmly established in our 55 cases that air at 600 hPa is not derived from or being exchanged (by resolvable motions) with distant points to the south. For the most part, this is also true at 850 hPa. Rather, it is coming from (or previously associated with) air to the east, north or west of the gyre center. This result is probably the most important take-home message for operational purposes and weather briefings.


Member Since: Posts: Comments:
1738. bappit
I've reached page 5597 of "Tropical Cyclogenesis in Tropical Waves". (It starts on page 5587 of volume 9, 2009, of Atmospheric Chemistry and Physics.)

They start talking about shear and start sounding like (global warming, hack, coff) skeptics at an Wunderground Forecasters' convention. They note that:

It is widely appreciated, especially by forecasters, that strong vertical shear is inimical to genesis. This fact is thought to account for the reduction of Atlantic hurricanes in warm ENSO events, as the eastern Pacific “warm pool” forces upper-level westerlies over the Caribbean (Gray, 1984a, b; Goldenberg and Shapiro, 1996). Although reasons suggest themselves, none are entirely convincing.

Later on:

It is well-known that vertical shear can be detrimental to hurricane intensification; the strongest and most circularly symmetric storms have little environmental shear or shear tendency. It is precarious, however, to take whatever mechanisms are responsible for the effects of shear on hurricane-strength vortices and assign them to the pre-depression stage.

Also:

Forecasters’ experience notwithstanding, there is no reason to think that genesis is optimized in exactly zero vertical shear. If it were, the fact that easterly-wave amplitudes maximize near the altitude of AEJ maximum (~600 hPa) would be convenient to the marsupial paradigm because wave + mean vertical shear is zero at this altitude, by definition. We suspect that the role of vertical shear in the marsupial paradigm [and they would suggest in reality as well] is more subtle and may (in some cases) facilitate refraction of the waves, without affecting adversely their embedded deep convection.
Member Since: Posts: Comments:
Quoting FloridaHeat:
testing testingQuoting StormW:
The most likely place we may see this develop, is going to be closer to 35-40W.

Out until later this evening.
thanks storm
Member Since: Posts: Comments:
Quoting donna1960ruled:
This season is over. The Saharan dust has clearly negatively interacted with a strong bilateral onus that has predebentured the GVS (Greenland Vertical Syndrome). Ira Geer spoke to this at Brockport University last year.

Lots of tropical meteorologists will be joining the ranks f the unemployed momentarily. See you all next year!!!


People like this make me laugh. POOF.
Member Since: Posts: Comments:
NEW BLOG!
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1733. xcool
new blog
Member Since: Posts: Comments:
1732. Patrap
Hey..expert tropical observers..


NEW Blog Posted..!

LOL

Maybe try the directory instead of digging a trench in ones f-5 key
Member Since: July 3, 2005 Posts: 426 Comments: 128871
901L is farther north. The northeast component of the convection is where there is more of the spin referred by Masters.
Member Since: Posts: Comments:
There is a huge surge of mositure associated with this wave which NHC probably factored in in going up to 30%.......As long as the dust travels in tandem with the wave, and it appears to out in front of it, dry air might not be an impediment in the short-term.
Member Since: Posts: Comments:
Quoting itrackstorms:
ORANGE ALERT!



A TROPICAL WAVE JUST WEST OF THE CAPE VERDE ISLANDS IS BEGINNING TO
INTERACT WITH AN ELONGATED AREA OF LOW PRESSURE LOCATED ABOUT 500
MILES TO ITS WEST. ALTHOUGH THIS ENTIRE AREA OF DISTURBED WEATHER
REMAINS DISORGANIZED...SHOWER AND THUNDERSTORM ACTIVITY HAS
INCREASED DURING THE DAY. CONDITIONS APPEAR FAVORABLE FOR SOME
SLOW DEVELOPMENT AS THE DISTURBANCE MOVES SLOWLY WESTWARD...AND
THERE IS A MEDIUM CHANCE...30 PERCENT...OF TROPICAL CYCLONE
FORMATION DURING THE NEXT 48 HOURS.

Will 90L be re-activated? Or will they number it as 91L?
Member Since: July 7, 2010 Posts: 0 Comments: 5694
NEW BLOG!!!
Member Since: Posts: Comments:
1727. Becca36
New Blog!!
Member Since: Posts: Comments:
I see that our feature in the Atlantic has been upgraded to orange or a 30% chance. Satellite images suggest that this area is accompanied by an area of broad low pressure. Convection associated with it has also organized throughout the day. I would be surprised if this feature doesn't get designated 91L later today.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
TAFB Experimental Gridded Marine Forecast

Wind 8AM EDT Aug 6





Pressure


Member Since: Posts: Comments:
Maybe we'll get two systems out of this area. One from ex-90L, another from the wave behind it.
Member Since: Posts: Comments:
90L is a lot stronger today. 91L is helping the development instead of the SAL.
Member Since: Posts: Comments:
1722. NASA101
Quoting Levi32:
Strange now they deactivated the invest and yet raised the chances of development.


..Well I assume they'll designate this with Invest 91L...
Member Since: Posts: Comments:
Quoting mfaria101:

29? good genes I guess..Lol
My daughters 22 so I guess you can take that as a compliment


thanks :)
Member Since: Posts: Comments:
1720. Levi32
Strange now they deactivated the invest and yet raised the chances of development.
Member Since: November 24, 2005 Posts: 635 Comments: 26661
Quoting KEEPEROFTHEGATE:


to be honest 03 i had high expectations for this season
along with a lot of others
but something is not right
can not put my finger on it
but something is just not allowing systems to organize normally
every system struggle so far
except alex when making landfall
i am waitin to see if a more normal pattern
sets up for august
to confirm if season is to be
what has been expected
iam focusing on
the 15th to 20th
time frame in august
to see if i can see
what iam looking for


Such poetry! Here's mine:

I also had high expectations,
Then watched as the season progressed.
I've viewed everybody's frustrations--
Especially the tropic-obsessed.

We've studied each blob in the ocean;
We've analyzed models like geeks;
We've worried at each little motion...
Complaining "No cyclone!" for weeks.

But then I remember: it's early!
To downcast, it's really too soon:
One mustn't get sullen and surly;
There've never been seven by June.

So listen: the atmosphere's humming;
The season is starting. Just wait.
I promise the storms are a-comin'
(Just pray they don't come to your state.)

;-)
Member Since: November 8, 2009 Posts: 4 Comments: 13579
Quoting cirrocumulus:
The ITCZ doesn't matter to 90L. It's well north now.


90L is gone. The system would now be "91L" as 90L got absorbed by another, more potent wave.

It is also very far south, and if it were to go due west, hypothetically, it would impact with land.
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting CybrTeddy:


I like seeing fish storms, out to sea and not hurting nobody. Storms like Bill, Fred, ect. That way we can observe a Hurricane's beauty on satellite without having to worry about who's under it.

Reality is most of the time someone is under it.
Most make some kind of landfall. Even ones that go out to sea can catch boats out or at least disrupt them.
Member Since: Posts: Comments:
CybrTeddy: Did I call it or what? I beat NOAA by about ten minutes!
Member Since: Posts: Comments:
Quoting extreme236:
The pouch-analysis is on break or the info will be delayed today and tomorrow, however they did post this:

Special note: 17Z 31 July: Possible new pouch invest PGI23L ~51W
Anti-cyclone has developed there IMO.
Member Since: Posts: Comments:
Why did they deactivate 90L?

Are they about to re-classify it as 91L?
Member Since: Posts: Comments:
But remember to pace ourselves.....There will be lots of code oranges in September........ :)
Member Since: Posts: Comments:
They should reclassify 90L now that it's 'upgraded'.
Member Since: Posts: Comments:
1710. NASA101
Quoting Levi32:


Thank you :)

I am just a high school graduate who wants to get into Meteorology. I have no colors to display yet.


Only a high school graduate...hard to believe!? Well, I am learning some from your comments and videos! Keep it up!
Sounds like NHC just upgraded that area around 35W - 8N to 30%
Member Since: Posts: Comments:
OR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

1. A TROPICAL WAVE JUST WEST OF THE CAPE VERDE ISLANDS IS BEGINNING TO
INTERACT WITH AN ELONGATED AREA OF LOW PRESSURE LOCATED ABOUT 500
MILES TO ITS WEST. ALTHOUGH THIS ENTIRE AREA OF DISTURBED WEATHER
REMAINS DISORGANIZED...SHOWER AND THUNDERSTORM ACTIVITY HAS
INCREASED DURING THE DAY. CONDITIONS APPEAR FAVORABLE FOR SOME
SLOW DEVELOPMENT AS THE DISTURBANCE MOVES SLOWLY WESTWARD...AND
THERE IS A MEDIUM CHANCE...30 PERCENT...OF TROPICAL CYCLONE
FORMATION DURING THE NEXT 48 HOURS.

2. A TROPICAL WAVE LOCATED OVER THE CENTRAL CARIBBEAN SEA CONTINUES TO
PRODUCE LIMITED SHOWER AND THUNDERSTORM ACTIVITY...AND DEVELOPMENT
OF THIS SYSTEM APPEARS LESS LIKELY BEFORE IT MOVES INTO CENTRAL
AMERICA IN A COUPLE OF DAYS. THERE IS A LOW CHANCE...10
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES WESTWARD AT ABOUT 15 MPH.
Member Since: April 1, 2010 Posts: 9 Comments: 2699
1708. A4Guy
code orange!
Member Since: Posts: Comments:
The ITCZ doesn't matter to 90L. It's well north now.
Member Since: Posts: Comments:
ORANGE ALERT!



A TROPICAL WAVE JUST WEST OF THE CAPE VERDE ISLANDS IS BEGINNING TO
INTERACT WITH AN ELONGATED AREA OF LOW PRESSURE LOCATED ABOUT 500
MILES TO ITS WEST. ALTHOUGH THIS ENTIRE AREA OF DISTURBED WEATHER
REMAINS DISORGANIZED...SHOWER AND THUNDERSTORM ACTIVITY HAS
INCREASED DURING THE DAY. CONDITIONS APPEAR FAVORABLE FOR SOME
SLOW DEVELOPMENT AS THE DISTURBANCE MOVES SLOWLY WESTWARD...AND
THERE IS A MEDIUM CHANCE...30 PERCENT...OF TROPICAL CYCLONE
FORMATION DURING THE NEXT 48 HOURS.
Member Since: Posts: Comments:


Pat, ima take your advice on that fresca.
Member Since: July 8, 2005 Posts: 259 Comments: 24251
Quoting ho77yw00d:


lol oh well... maybe he was hoping I was a dude who knows


Zing!...
Member Since: Posts: Comments:
Thats a mean looking train starting.



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
Member Since: Posts: Comments:
1702. Patrap
.."it's So Fluffy"..!!!
Member Since: July 3, 2005 Posts: 426 Comments: 128871
Another item of note for the upcoming season is the general position of the A-B high. It is close to "settling" in for the peak months and right now it seems to favor a bee-line from Africa to the Greater Antilles. That "higher" trajectory so to speak is also consistent with Cold Phase Enso conditions which increase the threat to the US East coast by about 16%. Everyone from the Greater Antilles to the Gulf/Florida and East Coast will at risk this year. It's just a matter of the steering currents and general position of the high/trof as each individual storm approaches over the next two months..........It's going to be a long and potentially destructive season this year but where the landfalls might occur will not be known until it actually unfolds.
Member Since: Posts: Comments:
1700. xcool
omg blog about go crazy
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
i can see the blog header
on dec 1st 2010
"WORLDWIDE HURRICANES KILLED OFF BY G.W."


Ugh, don't go there, lol
Member Since: Posts: Comments:
Quoting Levi32:


I screen cast using screencast-o-matic


Thank you. :)
Member Since: April 1, 2010 Posts: 9 Comments: 2699
ORANGE ALERT
Member Since: Posts: Comments:
Quoting CybrTeddy:
AND
THERE IS A MEDIUM CHANCE...30 PERCENT...OF TROPICAL CYCLONE
FORMATION DURING THE NEXT 48 HOURS.


Can u post an img?
Member Since: April 1, 2010 Posts: 9 Comments: 2699
1695. Levi32
Quoting Snowlover123:


Levi, just curious, what program do you use to put your graphs on Youtube?


I screen cast using screencast-o-matic
Member Since: November 24, 2005 Posts: 635 Comments: 26661
AND
THERE IS A MEDIUM CHANCE...30 PERCENT...OF TROPICAL CYCLONE
FORMATION DURING THE NEXT 48 HOURS.
Member Since: July 8, 2005 Posts: 259 Comments: 24251
1693. Levi32
Quoting NASA101:


Great video! What's your background Levi..just curious?
I have Doctorate in Astrophysics but have a real interest in tropical weather! :)


Thank you :)

I am just a high school graduate who wants to get into Meteorology. I have no colors to display yet.
Member Since: November 24, 2005 Posts: 635 Comments: 26661
30% on 90L.
Member Since: July 8, 2005 Posts: 259 Comments: 24251
Quoting ho77yw00d:


Thanks, I am almost 29 and all I was doing was answering a question... geez some people are so uptight in this blog!

29? good genes I guess..Lol
My daughters 22 so I guess you can take that as a compliment
Member Since: Posts: Comments:

Viewing: 1741 - 1691

Page: 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 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Partly Cloudy
56 °F
Partly Cloudy