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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Quoting msgambler:
YAY, another worthless poll

Hey.. I just want to know what people think so far..
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Quoting superweatherman:
This Hurricane season they are going to be:
A.10-14 storms
B.14-18 storms
C.18-22 storms
D. Over 22 name storms


B.
Member Since: July 8, 2005 Posts: 259 Comments: 24575
Quoting superweatherman:
This Hurricane season they are going to be:
A.10-14 storms
B.14-18 storms
C.18-22 storms
D. Over 22 name storms


B - C
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1438. OneDrop
Hollywood, looks look T storms already building here in northeast broward, how is it down by southeast broward
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Quoting superweatherman:
This Hurricane season they are going to be:
A.10-14 storms
B.14-18 storms
C.18-22 storms
D. Over 22 name storms


What comes before A?
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1436. STXpat
A. Psuedo B.Solar C.Trajectory ?
Member Since: September 18, 2008 Posts: 0 Comments: 36
YAY, another worthless poll
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1434. bappit
Yep, just blobs. No vortical hot towers out there. :)
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i just moved to fl and my neighbor has me all freaked about hurricanes so i did research and found this website
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This Hurricane season they are going to be:
A.10-14 storms
B.14-18 storms
C.18-22 storms
D. Over 22 name storms
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Well, I see that Dr. Carver was right and I90 didn't survive...
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1430. Drakoen
Quoting AllStar17:


What do you think of this analysis?
Visible Loop


That's what I am seeing on RGB imagery as well. Looks like a broad area of low pressure. Convection is flowing cyclonic towards the surface trough axis. It still appears that the two disturbances have yet to phase.
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1429. bappit
Cool stuff.

Hmmmm, downdrafts apparently are an important positive component in TC genesis--besides the negative signal given by arc clouds. In reviewing prior research the authors comment:

The rotational confinement of these gust front boundaries appears important for sustained deep convective activity within the MCV embryo and surface spin-up. Even when gravity waves and gust fronts are not fully contained, they can be expected to play an important role in convective triggering along developing vortical boundaries in the proto-storm.

Haven't heard about vortical hot towers from people on the blog. Cool stuff.
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Quoting Orcasystems:


Yes yes yes.. what did I do :(
I really never know where to start...LOL
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Quoting msgambler:
Orca, Orca, Orca


Yes yes yes.. what did I do :(
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting FloridaHeat:
i am new to the blog and dont know how to do an avatar


It is probably in the que to be approved first.
Member Since: October 1, 2007 Posts: 81 Comments: 26516
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pressure here in swfl is 1011.7mb,if that puts things in perspective....
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Orca, Orca, Orca
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Be back in a bit.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting aquak9:


you're a bald gray guy??
LOL.
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1420. bappit
... multiple pathways to genesis exist. Four plausible pathways identify one or more of the following as key ingredients: (i) tropical waves, (ii) monsoon troughs, (iii) extratropical disturbances and (iv) topographic flows. For each pathway we can imagine a theoretical paradigm that provides conceptual stepping stones along the path. In tropical waves, a sweet spot for development evidently exists along the wave, associated with a region of low pressure in the lower troposphere. Having such a sweet spot does not guarantee genesis, of course ...

It will be shown here that for storms originating in tropical waves, the synoptic wave itself plays a vital role in the near-surface circulation. In our proposed tropical-wave scenario the relevant theoretical paradigm is the formation of a closed proto-vortex within the wave in the lower troposphere and subsequent eddy shedding whereby the vortex, energized further by deep convective heating, becomes detached from the wave and begins to control its own destiny. In what follows we refer to this sequence of events as the marsupial paradigm.

Our series on TC genesis, of which this paper is the first, addresses the tropical wave pathway and variations thereof (easterly wave propagation, tropical depression disturbances, instability of the ITCZ, and trapped equatorial modes) and the ability of these disturbances to create a closed gyre or “pouch” and subsequently within the pouch, a proto-vortex or “embryo” favorable for hurricane formation.


What the heck is a trapped equatorial mode?
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i am new to the blog and dont know how to do an avatar
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Quoting FloridaHeat:
is my avatar working now
Nope. Keep trying. Someone else with more knowledge will have to tell you how to put it up.
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Quoting AllStar17:


Isn't that what we are talking about?
Yes, there was just some confusion earlier.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Nada out there... just blobs



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting MiamiHurricanes09:
Pressures ranging from 1012-1007mb according to all the ship observations around there.

As a side-note, I wouldn't be surprised to see the tropical wave in between 35W-40W get tagged an invest later this evening.



Isn't that what we are talking about?
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Quoting GeoffreyWPB:


All that orange reminds me...3 months til Halloween!


Member Since: October 1, 2007 Posts: 81 Comments: 26516
Pressures ranging from 1011-1009mb according to all the ship observations around there.

As a side-note, I wouldn't be surprised to see the tropical wave in between 35W-40W get tagged an invest later this evening.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
1412. aquak9
Quoting FloridaHeat:
is my avatar working now


you're a bald gray guy??
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1411. NASA101
Quoting jasoniscoolman2010xx:
look Floater - Visible Loop you see a spin at 34 west and 9 north.


YUP, the spin is pretty obvious on visible satellite - and also getting more organized with convection - I see something forming here!!
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Quoting jasoniscoolman2010xx:
look Floater - Visible Loop you see a spin at 34 west and 9 north.


Yes, but it is very broad. It needs to tighten and organize before we get too concerned about a tropical cyclone forming.
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Quoting Neapolitan:
Another look at the Cauldron of Mexi--er, Gulf of Mexico:

Double, double, toil and trouble

Original image


All that orange reminds me...3 months til Halloween!
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Quoting CybrTeddy:


Looks about right to me.


I think it is SLOWLY getting better organized / re-organizing.
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Quoting StormW:


Getting ready to head to Busch Gardens!
Enjoy yourself.
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Quoting CyclonicVoyage:
One last note.

Seems as if the surface trough is catching back up to the wave to it's west. Allstar's assessment is a reasonable one. That would be the best shot is for the surface trough to regen the surface low.
Exactly.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting FloridaHeat:
is my avatar working now


I dont see it
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Quoting CyclonicVoyage:
One last note.

Seems as if the surface trough is catching back up to the wave to it's west. Allstar's assessment is a reasonable one. That would be the best shot is for the surface trough to regen the surface low.


Well, I can see a sfc. low forming where you said. It does appear the spin is getting better defined.
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Quoting AllStar17:


What do you think of this analysis?
Visible Loop


Looks about right to me.
Member Since: July 8, 2005 Posts: 259 Comments: 24575
One last note.

Seems as if the surface trough is catching back up to the wave to it's west. Allstar's assessment is a reasonable one. That would be the best shot is for the surface trough to regen the surface low.
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is my avatar working now
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If you start to see the "feeder band" to the south of the broad circulation start to wrap around, you'll know its organizing. Not showing that yet, though.
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1398. bappit
Relevant to monsoon-casters:

But for TC genesis, environmental conditions in the monsoon trough (McBride and Zehr, 1981) appear favorable over a larger area, providing a diverse set of flow configurations in the lower troposphere (shear line, confluence, gyre; Ritchie and Holland, 1999) and making the role of tropical waves (with their sweet spot) more challenging to ascertain – although precursor waves can be seen in many of these cases. Genesis by spontaneous aggregation (now a popular subject of research: e.g., Emanuel and Nolan, 2004; Nolan et al., 2006; Held, 2007; Borth, 2007; Schecter and Dunkerton, 2009) may be regarded as a limiting case of the monsoon trough pathway in which no particular region is favored, but conditions are rendered more favorable, e.g., by cranking up the underlying SST. In the real world, spontaneous aggregation is likely nature’s last resort. En route to storm formation, the tropical atmosphere almost always provides a sweet spot or more extensive region favorable to genesis.
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Quoting CyclonicVoyage:


Very possible. My opinion is 9.8N 36W

Gotta run, this is going to need some time to percolate for sure. It will drive ya batty trying to sort this one out right now.
LOL. That's very close to where the mid-level vort max is located.

Have a great day!
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting AllStar17:


What do you think of this analysis?
Visible Loop



THANKS...
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1395. DDR
Good morning
Showers here along the northern range in Trinidad,22.2 inches in rain in the past month and its pouring outside.
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Quoting MiamiHurricanes09:
Indeed. Telling from the location of the strongest 850mb vorticity, an area of low pressure may be trying to develop near 10N and 31W. However with all that latent heat being released by the convection to its west we might end up with several vorticies.



Very possible. My opinion is 9.8N 36W

Gotta run, this is going to need some time to percolate for sure. It will drive ya batty trying to sort this one out right now.
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Quoting texwarhawk:


Where can I find the sat image with the vorticity overlay?
Scroll down to the map that is titled "Invest Products". Click the "invest" you want to view and on from there.

CIMSS PREDICT
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Another look at the Cauldron of Mexi--er, Gulf of Mexico:

Double, double, toil and trouble

Original image
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Quoting AllStar17:


What do you think of this analysis?
Visible Loop
Definitely has acquired some banding, and where you put the circle looks about right to me. Good call there.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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