African tropical waves
An tropical wave near 12N 34W, a few hundred miles southwest of the Cape Verde Islands, has a pronounced surface circulation one can see in QuikSCAT satellite data from 3:52am EDT this morning. The amount of heavy thunderstorm activity has decreased since yesterday, and any development should be slow to occur. The thunderstorm activity associated with this wave was being enhanced yesterday by a process known as upper-level divergence. When the the winds at high levels diverge (blow outward from a common center), then air from the surface must rise to fill the vacuum created. As this surface air rises, the moisture in it condenses, fueling thunderstorms. Thunderstorms created by this mechanism make a tropical disturbance look more impressive than it really is. The wave has moved away from this area of upper divergence, reducing the amount of thunderstorm activity.
The large spiral of low clouds near 18N 45W surrounded by a large cloud of dry air and African dust continues to spin, but the thunderstorm activity near the center has dropped to nearly nil this morning. The wave is under a very favorable upper-level environment for development, with low shear and an upper-level anticyclone on top. However, water vapor satellite imagery shows that the air on all sides is very dry. The GFS model is showing that this wave will not be able to find a moister environment until Sunday at the earliest, when it may be near Puerto Rico or the Bahamas.
I'll be back late this afternoon with an update on Ernesto, John, Ioke, and the rest of the tropics.
Jeff Masters
Replies
7
SoWal ExpertAuthor
Posted by: JeffMasters, 5:01 PM EDT on August 30, 2006
African tropical waves
A tropical wave near 12N 36W, a few hundred miles southwest of the Cape Verde Islands, has changed little in organization today. Some slow development of this system is possible over the next few days.
The large spiral of low clouds near 18N 46W surrounded by a large cloud of dry air and African dust continues to spin, but the thunderstorm activity near the center remains near zero this afternoon. The wave has some potential for development if it can find a moister environment. This is not likely until Sunday at the earliest, when it may be near Puerto Rico or the Bahamas.
I'll be back Friday morning with a new update.
African tropical waves
A tropical wave near 12N 36W, a few hundred miles southwest of the Cape Verde Islands, has changed little in organization today. Some slow development of this system is possible over the next few days.
The large spiral of low clouds near 18N 46W surrounded by a large cloud of dry air and African dust continues to spin, but the thunderstorm activity near the center remains near zero this afternoon. The wave has some potential for development if it can find a moister environment. This is not likely until Sunday at the earliest, when it may be near Puerto Rico or the Bahamas.
I'll be back Friday morning with a new update.
Beach Lover
Beach Lover
What I thought was Invest 98 is actually Invest 90. Out ot the two 90 looks the best organized but 98 is having a blow up of showers.
SoWal ExpertAuthor
Posted by: JeffMasters, 10:27 AM EDT on September 02, 2006
NHC declares a new "invest" on tropical wave in Lesser Antilles
The tropical wave surrounded by a cloud of African dust and dry air that I've been commenting on ever since it left the coast of Africa, is now an official threat. NHC has designated this wave "Invest 99L" this morning. The wave is near 15N 61W, right on top of the Lesser Antilles Islands. It is surrounded by a large cloud of dry air and African dust, but has slowly been able to pump more moisture into its center each night over the past few days as thunderstorm development kicks up then dies away. The thunderstorm activity has picked up considerably this morning, the first time the disturbance has been able to build thunderstorms during the daytime hours. The disturbance is tracking west at 15 mph into a large upper trough of low pressure over Cuba and Hispaniola that is creating about 10-20 knots of shear over 99L. The trough is expected to weaken and move west over the next few days, potentially creating a low shear environment over most of the Caribbean. This could allow intensification of 99L into a tropical depression by Monday.
Figure 2. Preliminary model tracks for Invest 99L. These models are described at the NHC web site.
The mid-Atlantic tropical wave to watch
A tropical wave near 11N 39W, midway between Africa and the Lesser Antilles Islands, was declared "Invest 98L" last night by NHC. However, the wave no longer has a well-defined low level circulation. Instead, this disturbance has a long oval area of circulation extending across 10 degrees of longitude, from about 33W to 43W, as seen in a QuikSCAT satellite pass from 4:11am EDT this morning. The heaviest thunderstorm activity has shifted eastward several hundred miles since last night, from 40W to about 35W. It appears that if this disturbance develops, it will happen from this more easterly position. The model runs from last night and this morning (Figure 3) all used the more westerly position of 40W, so can be disregarded. The system is moving slowly west at 10 mph, and could be near or north of the Lesser Antilles Islands on Thursday. Wind shear over the system is low, 5-10 knots, and the wave is over warm SSTs of 83-86F (28.5-30 C). Wind shear is forecast to remain low over the next few days, and the system has the potential to become a tropical depression by Monday. A modest inhibiting factor might be the large area of dry air and African dust to the wave's north.
Figure 3. Preliminary model tracks for Invest 98L. These models are described at the NHC web site.
New wave coming off the coast of Africa
A strong new tropical wave is emerging from the coast of Africa today near the Cape Verde Islands. Some of the computer models continue to develop this wave into a tropical storm or hurricane by the middle of next week.
Which of these three waves should most concern us? Both the wave coming off Africa today and the one in the middle of the Atlantic--98L--will probably end up recurving out to sea. However, 99L is already in the Caribbean and is forecast to enter a low shear environment, so this is the one to be most concerned with.
Dr. Gray's September 1 forecast
The hurricane forecast team at Colorado State University headed by Phil Klotzback and Dr. Bill Gray issued their September forecast for Atlantic hurricane activity today. They predict 5 named storms, 3 hurricanes, and 2 intense hurricanes for September, which is about normal for that month. They predict an additional 2 named storms and one hurricane in October, and one named storm in November. This would give the hurricane season of 2006 total of 13 named storms, 5 hurricanes, and 2 intense hurricanes. An average season has 11 named storms and 6 hurricanes. They credited dry air from the Sahara and more El Nino-like conditions than expected for the lower than average hurricane activity observed in August. Prices of oil, natural gas, and heating oil futures fell on commodity markets by 1-3% on the news of the forecast. The Klotzbach/Gray team originally forecast that 17 named storms would form this year.
NHC declares a new "invest" on tropical wave in Lesser Antilles
The tropical wave surrounded by a cloud of African dust and dry air that I've been commenting on ever since it left the coast of Africa, is now an official threat. NHC has designated this wave "Invest 99L" this morning. The wave is near 15N 61W, right on top of the Lesser Antilles Islands. It is surrounded by a large cloud of dry air and African dust, but has slowly been able to pump more moisture into its center each night over the past few days as thunderstorm development kicks up then dies away. The thunderstorm activity has picked up considerably this morning, the first time the disturbance has been able to build thunderstorms during the daytime hours. The disturbance is tracking west at 15 mph into a large upper trough of low pressure over Cuba and Hispaniola that is creating about 10-20 knots of shear over 99L. The trough is expected to weaken and move west over the next few days, potentially creating a low shear environment over most of the Caribbean. This could allow intensification of 99L into a tropical depression by Monday.
Figure 2. Preliminary model tracks for Invest 99L. These models are described at the NHC web site.
The mid-Atlantic tropical wave to watch
A tropical wave near 11N 39W, midway between Africa and the Lesser Antilles Islands, was declared "Invest 98L" last night by NHC. However, the wave no longer has a well-defined low level circulation. Instead, this disturbance has a long oval area of circulation extending across 10 degrees of longitude, from about 33W to 43W, as seen in a QuikSCAT satellite pass from 4:11am EDT this morning. The heaviest thunderstorm activity has shifted eastward several hundred miles since last night, from 40W to about 35W. It appears that if this disturbance develops, it will happen from this more easterly position. The model runs from last night and this morning (Figure 3) all used the more westerly position of 40W, so can be disregarded. The system is moving slowly west at 10 mph, and could be near or north of the Lesser Antilles Islands on Thursday. Wind shear over the system is low, 5-10 knots, and the wave is over warm SSTs of 83-86F (28.5-30 C). Wind shear is forecast to remain low over the next few days, and the system has the potential to become a tropical depression by Monday. A modest inhibiting factor might be the large area of dry air and African dust to the wave's north.
Figure 3. Preliminary model tracks for Invest 98L. These models are described at the NHC web site.
New wave coming off the coast of Africa
A strong new tropical wave is emerging from the coast of Africa today near the Cape Verde Islands. Some of the computer models continue to develop this wave into a tropical storm or hurricane by the middle of next week.
Which of these three waves should most concern us? Both the wave coming off Africa today and the one in the middle of the Atlantic--98L--will probably end up recurving out to sea. However, 99L is already in the Caribbean and is forecast to enter a low shear environment, so this is the one to be most concerned with.
Dr. Gray's September 1 forecast
The hurricane forecast team at Colorado State University headed by Phil Klotzback and Dr. Bill Gray issued their September forecast for Atlantic hurricane activity today. They predict 5 named storms, 3 hurricanes, and 2 intense hurricanes for September, which is about normal for that month. They predict an additional 2 named storms and one hurricane in October, and one named storm in November. This would give the hurricane season of 2006 total of 13 named storms, 5 hurricanes, and 2 intense hurricanes. An average season has 11 named storms and 6 hurricanes. They credited dry air from the Sahara and more El Nino-like conditions than expected for the lower than average hurricane activity observed in August. Prices of oil, natural gas, and heating oil futures fell on commodity markets by 1-3% on the news of the forecast. The Klotzbach/Gray team originally forecast that 17 named storms would form this year.
Beach Fanatic
Beach Fanatic
Just pray it stays away from land but gives us beautiful swell!
Beach Fanatic
Surf's up!!!:clap_1:
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