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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The Antarctic Oscillation (AAO), the southern hemisphere cousin and equivalent to the Arctic Oscillation (AO), is an excellent indicator during the southern hemisphere winter of what the AO will be doing during the following winter in the northern hemisphere. We are seeing the highest AAO ever recorded so far this winter, and this foreshadows a strong positive AO for this winter in our hemisphere.
Look at how low the surface pressures have been during the last 3 months south of 60S and how high they are in the subtropics. That is one heck of a pressure gradient and indicates an exceptionally strong jetstream and excessive storminess.
This is the same kind of thing that happens in the northern hemisphere when the Arctic Oscillation goes strongly positive, and we could see that this winter. This would go along with the extreme cold forecasted in the arctic this winter by the CFS and Japanese climate models, and if things set up right, could end up in one of the worst winters in decades for Alaska, western Canada, and perhaps even the Pacific Northwest may get in on some of the action.
same as always
wait watch see
352. Levi32 11:55 PM GMT on July 30, 2010
Thats a polite way of saying our winter is going to suck isn't it.
ugh... FIGURES.LOL
so tell me about this 90L
Heat advisory for tomorrow for Orange County, pretty unusual for upper 90s in central Florida. I saw this in the AFT discussion for NWS MLB:
THE MAIN STORY WILL CONTINUE TO BE THE HOT CONDITIONS DUE TO
EXPECTED LATE CONVECTIVE DEVELOPMENT. AFTER A REPORT FROM SEMINOLE
EM ABOUT INCREASED HEAT STRESS ADMISSIONS AT LOCAL EMERGENCY ROOMS...
HAVE LOOKED AT LOCAL HEAT ADVISORY ISSUANCE. A LOCAL CRITERIA FOR
A HEAT ADVISORY (2 DAYS OR MORE OF TEMPS IN THE UPPER 90S) WAS
ADDED AFTER THE 1998 HEAT WAVE WHEN HEAT INDICES DID NOT MEET
THRESHOLDS. HAVE HAD A FEW DAYS WITH UPPER 90S HIGHS IN METRO
ORLANDO SO HAVE DECIDED TO ISSUE A HEAT ADVISORY THERE.
LMAO, JFV and mojo shouldnt even be used in the same sentence becuz it will never happen. Unless he has a new shower curtain with Dora the explorer on it....
And seriously? I leave yall for 3 days and the crayons are gonna get busted out! lol.
Well I forget where you live, but globally yes it will suck. If you're in the southern and eastern US, not so much...should be far warmer than last winter. Remember we had a negative AO this past winter which drove all the cold air south, well this year if the positive AO pans out the cold air will be very intense but farther north and the jetstream will keep the subtropical portions of the continents flooded with warm air.
Yes, my daughter lives south of you and she has been tellin me how hot and dry it is over there. I read back in the blog from earlier today and saw you got hammered again because of your opinions. Dont let them bother you. I know in fact if your wrong you will be the first to say so!! You did well for my area this past winter Thanks
Great weather info., very interesting. I never knew how these things were interrelated!
Odd thing is it shows S Fla at just below average winter temps. LOL
Scientists may have found the most devastating impact yet of human-caused global warming %u2014 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.
Thanks, Jeff!
Looking forward to that.
Sorry, TX, FL, LA, MS, AL suffered in the winter of 2009-10. It is just your turn! Get ready it will be nasty!
Hey how are you doing today? weather 87 here in z-hills fl.
Funny what goes around comes around. If that verifies some bloggers are going to have a lot of fun this winter.
Equal and opposite gives a mean change of zero....hmm.
maybe i will take a break from the blogs this winter
lol
A breath taking 99F, dewpoint near 63F, Heat Index about 101F, a SW breeze at 10MPH.
Another "oven=like" day, with 7 days of 78-81F to 99-104F temps> Normal N TX Summer!!
That's false, actually.
Extremes beget extremes is a better way to put it. It doesn't balance because there is destruction involved with both extremes.
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