Little change to 90L; new African tropical wave is worth watching
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
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AOI
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TS BUSTED FORECAST ALIBI
Zing!...
Pat, ima take your advice on that fresca.
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.
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.
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%
Are they about to re-classify it as 91L?
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.
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.
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.)
;-)
thanks :)
..Well I assume they'll designate this with Invest 91L...
Wind 8AM EDT Aug 6
Pressure
Will 90L be re-activated? Or will they number it as 91L?
NEW Blog Posted..!
LOL
Maybe try the directory instead of digging a trench in ones f-5 key
People like this make me laugh. POOF.
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.
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.
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