An easterly wave that was "born" one week ago over the Ethiopian Highlands exited the African coast yesterday and quickly got organized. It's now just a couple hundred miles off the coast, halfway to the Cape Verde Islands at approximately 16N 21W. It has a 1006mb Low embedded within it, and is tracking W at 15kts. However, it is forecast to curve toward the WNW-NW and into higher shear and cooler water. The SST now is only around 26C, but could drop to 24C in the next couple of days. It would become TD5 or TS Edouard if it can strengthen before the environmental conditions deteriorate.
Please visit my tropical Atlantic headquarters.
30 July 2008
23 July 2008
Dolly making landfall...
Dolly has strengthened overnight, and is now just miles from the coast (at 16Z) and is a Category 2 hurricane... 85kts and 964mb. Though only 40 miles or so offshore, the eyewall (the engine that drives the rest of the machine) is still over very warm Gulf water. As such, the storm can still continue to strengthen while the entire western half of the storm is over land. The eye is presently located 40 miles ENE of Brownsville TX and is ~23 miles across.
Rainfall totals could reach one foot. Storm surge is in the 4-6 foot ballpark. It's still too early to know the full aftermath, as it's still in progress. Buoy 42020, offshore between Brownsville and Corpus Christi, is reporting 22' waves, and the worst is still coming.
It's moving very slowly (about 6kts) and is now heading nearly parallel to the coast, which means Dolly could still have several hours over water. If you navigate to the link below, you'll find links to radar loops, surface observations, and satellite imagery.
Hardly worth discussing, Cristobal is now a disorganized extratropical storm south of Newfoundland.
The easterly wave near the Cape Verdes has degenerated quite a bit and is now much less of a concern. It will be monitored for signs of redevelopment.
Please visit my tropical Atlantic headquarters.
P.S. You can all consider yourselves more educated than CNN, who claims that Dolly is the second storm of the Atlantic season. Hard to reach "D" after only two storms! Granted, it is the second HURRICANE, but not the second storm. Details, details....
Rainfall totals could reach one foot. Storm surge is in the 4-6 foot ballpark. It's still too early to know the full aftermath, as it's still in progress. Buoy 42020, offshore between Brownsville and Corpus Christi, is reporting 22' waves, and the worst is still coming.
It's moving very slowly (about 6kts) and is now heading nearly parallel to the coast, which means Dolly could still have several hours over water. If you navigate to the link below, you'll find links to radar loops, surface observations, and satellite imagery.
Hardly worth discussing, Cristobal is now a disorganized extratropical storm south of Newfoundland.
The easterly wave near the Cape Verdes has degenerated quite a bit and is now much less of a concern. It will be monitored for signs of redevelopment.
Please visit my tropical Atlantic headquarters.
P.S. You can all consider yourselves more educated than CNN, who claims that Dolly is the second storm of the Atlantic season. Hard to reach "D" after only two storms! Granted, it is the second HURRICANE, but not the second storm. Details, details....
22 July 2008
Cristobal heading out to sea, Dolly heading for land...
Cristobal is now east of Cape Cod, south of Nova Scotia, and is a 55kt tropical storm. It will continue heading generally eastward into the north central Atlantic and should only be a tropical system for another day or two.
Dolly, on the other hand, is of much greater concern. Over the last 18 hours, the huge rainband that was far removed from the center has dissipated in favor on centralized deep convection. This is the needed ingredient for strengthening: focusing the latent heating over the center. The latest intensity is 60kts and 991mb, and is getting closer to hurricane status every hour. It's also getting closer to landfall every hour... now just 200 miles southeast of Brownsville and heading NW at 10kts. Landfall is expected early tomorrow morning near Brownsville as a hurricane.
Intensity at landfall is a tricky thing... the storm is showing every sign of rapid intensification, and it's at the classic current intensity to begin RI. Vertical shear is basically negligible, and SSTs are 29C+. So the problem is how fast will Dolly intensify on its approach? NHC is forecasting landfall at 80kts, which is line with the model guidance, but models (and people) don't forecast RI well.
You can already see outer rainbands approaching the coast, and the eyewall is coming into view as well:
http://radar.weather.gov/radar.php?rid=BRO&product=N0Z&overlay=11101111&loop=yes
I will also keep a running loop of the short-range Brownsville radar at: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/dolly08/Dolly_22-23Jul08.gif
The latest watches and warnings for Texas and Mexico are plotted graphically at:
http://www.nhc.noaa.gov/storm_graphics/AT04/refresh/AL0408R+gif/
And the easterly wave that exited Africa yesterday is looking very impressive. It's now near the Cape Verde islands, and is consolidating its circulation. It has a 1009mb Low, and is moving W at 15kts. It is not forecast to intensify real quickly, but very gradually, and continue heading W-WNW.
Please visit my tropical Atlantic headquarters.
Dolly, on the other hand, is of much greater concern. Over the last 18 hours, the huge rainband that was far removed from the center has dissipated in favor on centralized deep convection. This is the needed ingredient for strengthening: focusing the latent heating over the center. The latest intensity is 60kts and 991mb, and is getting closer to hurricane status every hour. It's also getting closer to landfall every hour... now just 200 miles southeast of Brownsville and heading NW at 10kts. Landfall is expected early tomorrow morning near Brownsville as a hurricane.
Intensity at landfall is a tricky thing... the storm is showing every sign of rapid intensification, and it's at the classic current intensity to begin RI. Vertical shear is basically negligible, and SSTs are 29C+. So the problem is how fast will Dolly intensify on its approach? NHC is forecasting landfall at 80kts, which is line with the model guidance, but models (and people) don't forecast RI well.
You can already see outer rainbands approaching the coast, and the eyewall is coming into view as well:
http://radar.weather.gov/radar.php?rid=BRO&product=N0Z&overlay=11101111&loop=yes
I will also keep a running loop of the short-range Brownsville radar at: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/dolly08/Dolly_22-23Jul08.gif
The latest watches and warnings for Texas and Mexico are plotted graphically at:
http://www.nhc.noaa.gov/storm_graphics/AT04/refresh/AL0408R+gif/
And the easterly wave that exited Africa yesterday is looking very impressive. It's now near the Cape Verde islands, and is consolidating its circulation. It has a 1009mb Low, and is moving W at 15kts. It is not forecast to intensify real quickly, but very gradually, and continue heading W-WNW.
Please visit my tropical Atlantic headquarters.
21 July 2008
Bertha finally gone, Cristobal and Dolly form, new wave off Africa...
The final advisory was written on Bertha on Sunday morning. It's now an extratropical cyclone over Iceland. It was around for 17.25 days, the new longest-lasting July storm. It also set a record for furthest east formation in July. Bertha, with the help of the rest of the month, has elevated the 2008 season to the ranks of the 1916, 1926, 1933, 1961, and 2005 seasons so far. These were some of the most active seasons on record.
In what is rapidly starting to look like a substantial hurricane season, Cristobal formed from the disturbance that was located off the GA coast on Friday, and Dolly formed from what was the long-tracked easterly wave that was in the western Caribbean on Friday. Both are tropical storms now, and both are forecast to intensify.
Cristobal is located around 200 miles ENE of Cape Hatteras NC with an intensity of 55kts and 1000mb. It is forecast to strengthen slightly, perhaps to minimal hurricane, but head northeast toward Newfoundland by Wednesday. The satellite presentation is not so healthy. It has centralized cold cloud tops, but is very compact and sheared.
Dolly, on the other hand, looks more substantial. After watching it struggle for 10 days, it finally got named near the Caymans on Sunday at 12Z. It has since crossed the Yucatan Peninsula as a TS, and is now in the Gulf heading for southern Texas. It's a large system, but lacking centralized deep convection right now. All of the convection is in a hefty rainband wrapping 3/4 of the way around the center. Latest intensity is 45kts and 1005mb. It's heading WNW at a brisk 16kts, and landfall is expected on Wednesday as a fairly strong hurricane. Environmental conditions in the western Gulf would allow for rapid strengthening. A Hurricane Watch has been issued from Brownsville to Port O'Connor.
Lastly, a new very strong easterly wave is just exiting Africa and has the potential to develop quickly once over the ocean. There is a 1007mb Low embedded within a broad mid-level circulation centered near 15N 15W. The next number/name in deck is 5/Edouard.
Please visit my tropical Atlantic headquarters.
In what is rapidly starting to look like a substantial hurricane season, Cristobal formed from the disturbance that was located off the GA coast on Friday, and Dolly formed from what was the long-tracked easterly wave that was in the western Caribbean on Friday. Both are tropical storms now, and both are forecast to intensify.
Cristobal is located around 200 miles ENE of Cape Hatteras NC with an intensity of 55kts and 1000mb. It is forecast to strengthen slightly, perhaps to minimal hurricane, but head northeast toward Newfoundland by Wednesday. The satellite presentation is not so healthy. It has centralized cold cloud tops, but is very compact and sheared.
Dolly, on the other hand, looks more substantial. After watching it struggle for 10 days, it finally got named near the Caymans on Sunday at 12Z. It has since crossed the Yucatan Peninsula as a TS, and is now in the Gulf heading for southern Texas. It's a large system, but lacking centralized deep convection right now. All of the convection is in a hefty rainband wrapping 3/4 of the way around the center. Latest intensity is 45kts and 1005mb. It's heading WNW at a brisk 16kts, and landfall is expected on Wednesday as a fairly strong hurricane. Environmental conditions in the western Gulf would allow for rapid strengthening. A Hurricane Watch has been issued from Brownsville to Port O'Connor.
Lastly, a new very strong easterly wave is just exiting Africa and has the potential to develop quickly once over the ocean. There is a 1007mb Low embedded within a broad mid-level circulation centered near 15N 15W. The next number/name in deck is 5/Edouard.
Please visit my tropical Atlantic headquarters.
18 July 2008
Bertha still lingering, two other disturbances getting organized...
Bertha is still a tropical storm, and is now about 700 miles south of Newfoundland. The first advisory on Bertha was written on July 3, over two weeks ago! Phil Klotzbach here at CSU points out that this is now the longest-lived storm in the Atlantic since Alberto '00 at 15.25 days. It has smashed the record for longest-lived July storm.
Latest intensity is 55kts and 995mb and tracking NE at 16kts. It still has a very impressive satellite presentation, with a renewed attempt at forming an eyewall and eye. However, this last-minute perk comes a day or so before it encounters hostile shear and cold ocean temperatures. It should transition to an extratropical cyclone by the end of the weekend.
Elsewhere, things are getting active. The easterly wave I first mentioned 9 days ago and have been keeping you updated on (the one that recently passed by the Windwards) is now just north of western Venezuela and has a lot of deep convection near the center of the mid-level circulation. There is a 1008mb Low embedded in the convection. Given its location and potential for strengthening, the western Gulf coast has a very long-range heads-up (could be 6-7 days out... IF it makes it).
Closer to the US, there's a circulation with associated convection just offshore of Georgia. Conditions are also favorable for this to develop... a huge boost for it is its position directly over the warm Gulf Stream. You can see it from the Charleston SC long-range radar: http://radar.weather.gov/radar.php?product=N0Z&rid=clx&loop=yes
It is expected to basically track N-NE along the length of the east coast, which is dangerous if it decides to quickly strengthen!
The next names on the list are Cristobal and Dolly.
Please visit my tropical Atlantic headquarters.
Latest intensity is 55kts and 995mb and tracking NE at 16kts. It still has a very impressive satellite presentation, with a renewed attempt at forming an eyewall and eye. However, this last-minute perk comes a day or so before it encounters hostile shear and cold ocean temperatures. It should transition to an extratropical cyclone by the end of the weekend.
Elsewhere, things are getting active. The easterly wave I first mentioned 9 days ago and have been keeping you updated on (the one that recently passed by the Windwards) is now just north of western Venezuela and has a lot of deep convection near the center of the mid-level circulation. There is a 1008mb Low embedded in the convection. Given its location and potential for strengthening, the western Gulf coast has a very long-range heads-up (could be 6-7 days out... IF it makes it).
Closer to the US, there's a circulation with associated convection just offshore of Georgia. Conditions are also favorable for this to develop... a huge boost for it is its position directly over the warm Gulf Stream. You can see it from the Charleston SC long-range radar: http://radar.weather.gov/radar.php?product=N0Z&rid=clx&loop=yes
It is expected to basically track N-NE along the length of the east coast, which is dangerous if it decides to quickly strengthen!
The next names on the list are Cristobal and Dolly.
Please visit my tropical Atlantic headquarters.
Bertha still lingering, two other disturbances getting organized...
Bertha is still a tropical storm, and is now about 700 miles south of Newfoundland. The first advisory on Bertha was written on July 3, over two weeks ago! Phil Klotzbach here at CSU points out that this is now the longest-lived storm in the Atlantic since Alberto '00 at 15.25 days. It has smashed the record for longest-lived July storm.
Latest intensity is 55kts and 995mb and tracking NE at 16kts. It still has a very impressive satellite presentation, with a renewed attempt at forming an eyewall and eye. However, this last-minute perk comes a day or so before it encounters hostile shear and cold ocean temperatures. It should transition to an extratropical cyclone by the end of the weekend.
Elsewhere, things are getting active. The easterly wave I first mentioned 9 days ago and have been keeping you updated on (the one that recently passed by the Windwards) is now just north of western Venezuela and has a lot of deep convection near the center of the mid-level circulation. There is a 1008mb Low embedded in the convection. Given its location and potential for strengthening, the western Gulf coast has a very long-range heads-up (could be 6-7 days out... IF it makes it).
Closer to the US, there's a circulation with associated convection just offshore of Georgia. Conditions are also favorable for this to develop... a huge boost for it is its position directly over the warm Gulf Stream. You can see it from the Charleston SC long-range radar: http://radar.weather.gov/radar.php?product=N0Z&rid=clx&loop=yes
It is expected to basically track N-NE along the length of the east coast, which is dangerous if it decides to quickly strengthen!
The next names on the list are Cristobal and Dolly.
For the latest on the developing depressions in the Caribbean Sea and off the US east coast, please visit http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atlantic/
I added a feature for the batch of real-time images... in the visible and infrared floaters (bottom center and bottom right), you can view different storms by simply placing your cursor over the name of the one you wish to see. Clicking on one of the names will take you to the full-sized version of the image. The numbers are identified in the track plot (lower left of the page's images).
Please visit my tropical Atlantic headquarters.
Latest intensity is 55kts and 995mb and tracking NE at 16kts. It still has a very impressive satellite presentation, with a renewed attempt at forming an eyewall and eye. However, this last-minute perk comes a day or so before it encounters hostile shear and cold ocean temperatures. It should transition to an extratropical cyclone by the end of the weekend.
Elsewhere, things are getting active. The easterly wave I first mentioned 9 days ago and have been keeping you updated on (the one that recently passed by the Windwards) is now just north of western Venezuela and has a lot of deep convection near the center of the mid-level circulation. There is a 1008mb Low embedded in the convection. Given its location and potential for strengthening, the western Gulf coast has a very long-range heads-up (could be 6-7 days out... IF it makes it).
Closer to the US, there's a circulation with associated convection just offshore of Georgia. Conditions are also favorable for this to develop... a huge boost for it is its position directly over the warm Gulf Stream. You can see it from the Charleston SC long-range radar: http://radar.weather.gov/radar.php?product=N0Z&rid=clx&loop=yes
It is expected to basically track N-NE along the length of the east coast, which is dangerous if it decides to quickly strengthen!
The next names on the list are Cristobal and Dolly.
For the latest on the developing depressions in the Caribbean Sea and off the US east coast, please visit http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atlantic/
I added a feature for the batch of real-time images... in the visible and infrared floaters (bottom center and bottom right), you can view different storms by simply placing your cursor over the name of the one you wish to see. Clicking on one of the names will take you to the full-sized version of the image. The numbers are identified in the track plot (lower left of the page's images).
Please visit my tropical Atlantic headquarters.
16 July 2008
Bertha persists, new depression ready to form...
Bertha is still a strong 60kt tropical storm, now around for 13 days. It's located about 400 miles northeast of Bermuda. The forecast is to maintain this intensity, and continue heading generally eastward, then northeastward.
An interesting feature deserves to be pointed out... a cold SST wake left by Bertha. As a storm passes over a patch of ocean, it churns it up, and upwells cooler water from below. In some regions and times of the year, the "mixed layer" is very deep and it's hard to upwell cool water because it lies so deep. Other times, the sea surface temperature might be very warm, but the warmth doesn't extend very deep. It's in these cases that we typically see a dramatic cold wake. The wake can be exaggerated by slow storm motion (longer time to act), an intense storm (more vigorous churning), or a combination. Anyway, with that background in mind, check out this 2-week SST loop:
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/sectors/sst/coast15.php
(areas of persistent cloud-cover as shown as gray because SSTs couldn't be retrieved that day)
Also take note of the beautiful eddies and vorticies formed along the Gulf Stream. Some eddies are warm, some are cold... some rotate cyclonically, some rotate anticyclonically.
Elsewhere, the easterly wave I've been discussing each day is now located near 57W and is getting much better organized... it's about 100 miles east of the Windward Islands and moving W at 20kts. There is a broad mid-level circulation, and scattered deep convection with cloud tops hitting -70C. It's in weak-moderate northwesterly vertical wind shear, and SSTs are in the 28C ballpark. This is forecast to keep tracking W-WNW through the Caribbean and perhaps enter the Gulf of Mexico by early next week.
You can find a radar loop of pre-TD3 (?) from Martinique at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/cristobal08/Cristobal_16Jul08.gif
(I took the liberty of naming the loop after its likely future name...)
There's also a fairly well-organized wave south of Jamaica, heading toward Nicaragua. This system will also be watched closely for development, as it's in a favorable environment as well.
Please visit my tropical Atlantic headquarters.
An interesting feature deserves to be pointed out... a cold SST wake left by Bertha. As a storm passes over a patch of ocean, it churns it up, and upwells cooler water from below. In some regions and times of the year, the "mixed layer" is very deep and it's hard to upwell cool water because it lies so deep. Other times, the sea surface temperature might be very warm, but the warmth doesn't extend very deep. It's in these cases that we typically see a dramatic cold wake. The wake can be exaggerated by slow storm motion (longer time to act), an intense storm (more vigorous churning), or a combination. Anyway, with that background in mind, check out this 2-week SST loop:
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/sectors/sst/coast15.php
(areas of persistent cloud-cover as shown as gray because SSTs couldn't be retrieved that day)
Also take note of the beautiful eddies and vorticies formed along the Gulf Stream. Some eddies are warm, some are cold... some rotate cyclonically, some rotate anticyclonically.
Elsewhere, the easterly wave I've been discussing each day is now located near 57W and is getting much better organized... it's about 100 miles east of the Windward Islands and moving W at 20kts. There is a broad mid-level circulation, and scattered deep convection with cloud tops hitting -70C. It's in weak-moderate northwesterly vertical wind shear, and SSTs are in the 28C ballpark. This is forecast to keep tracking W-WNW through the Caribbean and perhaps enter the Gulf of Mexico by early next week.
You can find a radar loop of pre-TD3 (?) from Martinique at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/cristobal08/Cristobal_16Jul08.gif
(I took the liberty of naming the loop after its likely future name...)
There's also a fairly well-organized wave south of Jamaica, heading toward Nicaragua. This system will also be watched closely for development, as it's in a favorable environment as well.
Please visit my tropical Atlantic headquarters.
15 July 2008
Bertha moves out into the open ocean...
Bertha was a strong tropical storm when it passed over Bermuda Monday afternoon. The island got hit by the northwest eyewall, then spent a few hours in the calm eye, then got the southwest eyewall, which came with very heavy rain and 60+ kt gusts. Power was knocked out to thousands of people, and roads were flooded. However, it sounds like they faired pretty well, with minimal damage and no injuries or deaths.
I got a live report from a colleague, Rick Taft, who is vacationing in Bermuda. This was just prior to and during the first pass under the eyewall: "We have had tons of rain and gusty winds all day today. We've gone out in bathing suits several times to play in the pool during the stormy weather -- at times the pelting rain was painful! Lots of fun!" They were not near trees or anything dangerous, and there wasn't lightning, so I guess it's a nice way to pass time in heavy rain! Certainly a big difference between this rather weak storm and what the island experienced in Fabian '03.
The 24-hour meteogram from Bermuda can be found here:
http://weather.uwyo.edu/surface/meteogram/images/sfgrama.080715_0555.txkf.gif (english)
http://weather.uwyo.edu/surface/meteogram/images/sfgramm.080715_0555.txkf.gif (metric)
Note the dip in central pressure, along with the cloud cover decrease, wind shifts, etc all associated with the eye passage.
The storm is now well northeast (~200 miles) of Bermuda, and is tracking NNE at 10kts. The 15Z intensity estimate is 60kts and 995mb, nearly back to hurricane strength. Bertha is expected to re-attain hurricane strength today and tomorrow and slowly make its way generally eastward into the open ocean.
The easterly wave I discussed yesterday is now located near 48W and moving W at 15kts. There is still an embedded Low, but the system has not gotten any better organized. In the coming days, the environment will become more hostile, so its chances for getting named are shrinking.
Please visit my tropical Atlantic headquarters.
I got a live report from a colleague, Rick Taft, who is vacationing in Bermuda. This was just prior to and during the first pass under the eyewall: "We have had tons of rain and gusty winds all day today. We've gone out in bathing suits several times to play in the pool during the stormy weather -- at times the pelting rain was painful! Lots of fun!" They were not near trees or anything dangerous, and there wasn't lightning, so I guess it's a nice way to pass time in heavy rain! Certainly a big difference between this rather weak storm and what the island experienced in Fabian '03.
The 24-hour meteogram from Bermuda can be found here:
http://weather.uwyo.edu/surface/meteogram/images/sfgrama.080715_0555.txkf.gif (english)
http://weather.uwyo.edu/surface/meteogram/images/sfgramm.080715_0555.txkf.gif (metric)
Note the dip in central pressure, along with the cloud cover decrease, wind shifts, etc all associated with the eye passage.
The storm is now well northeast (~200 miles) of Bermuda, and is tracking NNE at 10kts. The 15Z intensity estimate is 60kts and 995mb, nearly back to hurricane strength. Bertha is expected to re-attain hurricane strength today and tomorrow and slowly make its way generally eastward into the open ocean.
The easterly wave I discussed yesterday is now located near 48W and moving W at 15kts. There is still an embedded Low, but the system has not gotten any better organized. In the coming days, the environment will become more hostile, so its chances for getting named are shrinking.
Please visit my tropical Atlantic headquarters.
14 July 2008
Bertha hitting Bermuda...
As I eluded to in my update LAST Monday, Bermuda should indeed being keeping a close eye on Bertha. As of now, they don't have a choice, the eyewall is right over the island. Though only a 55kt tropical storm as of this morning, it does have an intact and large eyewall.
You can view a longer, long-range radar loop at:
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/bertha08/Bertha_13Jul08.gif
and a shorter, short-range radar loop at:
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/bertha08/Bertha_14Jul08_short.gif
As of 15Z, the intensity is 55kts and 990mb, and heading N at 6kts. This very slow motion will leave Bermuda in tropical storm conditions for at least a day. Over the next few days, the storm will SLOWLY move northward, then NE. Intensity should remain nearly constant, with weakening a few days out once it gets over colder water. Bermuda is under a Tropical Storm Warning, and can expect 3-5" of rain, and large battering waves.
Bertha will easily be the longest-lived named storm during July in recorded history (back to 1851). It is also the 2nd longest-lived July hurricane. Truly a remarkable storm!
Elsewhere, one of the easterly waves I mentioned last week has gotten much better organized. It exited the African coast on Thursday, and is now located near 45W, traveling west at 15kts. It has an embedded 1008mb Low, and a healthy circulation. The next name/number on deck is 3/Cristobal.
Please visit my tropical Atlantic headquarters.
You can view a longer, long-range radar loop at:
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/bertha08/Bertha_13Jul08.gif
and a shorter, short-range radar loop at:
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/bertha08/Bertha_14Jul08_short.gif
As of 15Z, the intensity is 55kts and 990mb, and heading N at 6kts. This very slow motion will leave Bermuda in tropical storm conditions for at least a day. Over the next few days, the storm will SLOWLY move northward, then NE. Intensity should remain nearly constant, with weakening a few days out once it gets over colder water. Bermuda is under a Tropical Storm Warning, and can expect 3-5" of rain, and large battering waves.
Bertha will easily be the longest-lived named storm during July in recorded history (back to 1851). It is also the 2nd longest-lived July hurricane. Truly a remarkable storm!
Elsewhere, one of the easterly waves I mentioned last week has gotten much better organized. It exited the African coast on Thursday, and is now located near 45W, traveling west at 15kts. It has an embedded 1008mb Low, and a healthy circulation. The next name/number on deck is 3/Cristobal.
Please visit my tropical Atlantic headquarters.
11 July 2008
Recurvature expected soon for Bertha...
Bertha is slowly nearing Bermuda, but they should be spared from a direct hit, as a mid-latitude trough is coming to their rescue (not all models agree on this though). The trough would nudge Bertha northeastward, away from the island and out to higher shear and cooler water. As it approaches the island though, you can monitor it via radar: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/bertha08/Bertha_12Jul08.gif
As of this writing, only the outermost rainbands are within the radar's range.
The satellite presentation is certainly not as impressive as it had been in recent days. The inner core is somewhat disorganized, with a large ragged eye surrounded by a not-so-complete eyewall. However, outflow aloft is symmetric and healthy, the SSTs are around 28C, and there's presently very weak vertical wind shear.
As of 21Z today, the intensity is 80kts and 976mb, based on the first aircraft recon flight into the storm. It is tracking NNW at 4kts. Bertha should be near Bermuda for the next few days with such a slow motion.
A Tropical Storm Watch has been issued for the island.
The forecast is for continued slow erratic motion toward the NW-N, then tomorrow afternoon start heading N-NE. Intensity should remain nearly steady until the trough imposes stronger shear over the system. Even if it does end up passing very near or over Bermuda, it's not a terribly strong hurricane. Their last encounter was with Florence on 9/12/06 (CAT1), and then the infamous Fabian on 9/5/03 (CAT3).
Please visit my tropical Atlantic headquarters.
As of this writing, only the outermost rainbands are within the radar's range.
The satellite presentation is certainly not as impressive as it had been in recent days. The inner core is somewhat disorganized, with a large ragged eye surrounded by a not-so-complete eyewall. However, outflow aloft is symmetric and healthy, the SSTs are around 28C, and there's presently very weak vertical wind shear.
As of 21Z today, the intensity is 80kts and 976mb, based on the first aircraft recon flight into the storm. It is tracking NNW at 4kts. Bertha should be near Bermuda for the next few days with such a slow motion.
A Tropical Storm Watch has been issued for the island.
The forecast is for continued slow erratic motion toward the NW-N, then tomorrow afternoon start heading N-NE. Intensity should remain nearly steady until the trough imposes stronger shear over the system. Even if it does end up passing very near or over Bermuda, it's not a terribly strong hurricane. Their last encounter was with Florence on 9/12/06 (CAT1), and then the infamous Fabian on 9/5/03 (CAT3).
Please visit my tropical Atlantic headquarters.
10 July 2008
Bertha still heading toward Bermuda...
CAT1 hurricane Bertha is still heading northwest, and has undergone an eyewall replacement cycle today. In this cycle, a larger, weaker eyewall encircles the original smaller eyewall, chokes it off, and replaces it. In time, it too contracts, and during this process the storm would typically fluctuate in intensity (weaken during the new eyewall formation, and strengthen during the new eyewall contraction).
That said, the intensity estimate as of 21Z today is 75kts and 980mb. It's located about 400 miles southeast of Bermuda and tracking northwest at 9kts. It still has an open eye, and is in an environment favorable for strengthening, in addition to the eyewall cycle factor. Large-scale flow is becoming complicated, which means the track forecast is becoming less certain. Motion over the next few days should be generally NW to N, but slowing and becoming erratic. This puts Bermuda at risk for several days, not knowing if it will hit them or not. Bertha has already been around for one week, and probably will be for another week!
Please visit my tropical Atlantic headquarters.
That said, the intensity estimate as of 21Z today is 75kts and 980mb. It's located about 400 miles southeast of Bermuda and tracking northwest at 9kts. It still has an open eye, and is in an environment favorable for strengthening, in addition to the eyewall cycle factor. Large-scale flow is becoming complicated, which means the track forecast is becoming less certain. Motion over the next few days should be generally NW to N, but slowing and becoming erratic. This puts Bermuda at risk for several days, not knowing if it will hit them or not. Bertha has already been around for one week, and probably will be for another week!
Please visit my tropical Atlantic headquarters.
09 July 2008
Bertha on a comeback...
After the encounter with higher shear and drier air yesterday, Bertha is back to a more symmetric shape with an open eye. A microwave image (from SSM/I) at 0939Z this morning captured the eye reforming prior to it opening up in VIS and IR imagery. Another microwave-instrument-bearing satellite had an overpass at 0521Z and there was not an eye at that time. As of 15Z today, the intensity was estimated at 65kts and 987mb, a minimal CAT1 hurricane. However, since then, the presentation has improved noticeably, and I suspect that at the 21Z advisory, we'll see something more like 75kts, with a strengthening trend in the forecast.
The SST is presently 27.5C under the storm, and will hover around that temperature for the coming days. Vertical shear is southwesterly at ~15kts, which is moderate, but low enough to allow an eye to reform.
An interesting question remains... what about Bermuda? In 4-5 days (weekend-ish), it appears that Bertha will have a close encounter with the island. Just how close depends on the encroaching mid-latitude trough. It could be responsible for not only steering/recurving Bertha away from the island, but also shearing and weakening it beforehand. It will be a close call.
Elsewhere in the basin, there are easterly waves trekking across the deep tropics at about 50W, 35W, and 20W, none of which currently show signs of organization.
Please visit my tropical Atlantic headquarters.
The SST is presently 27.5C under the storm, and will hover around that temperature for the coming days. Vertical shear is southwesterly at ~15kts, which is moderate, but low enough to allow an eye to reform.
An interesting question remains... what about Bermuda? In 4-5 days (weekend-ish), it appears that Bertha will have a close encounter with the island. Just how close depends on the encroaching mid-latitude trough. It could be responsible for not only steering/recurving Bertha away from the island, but also shearing and weakening it beforehand. It will be a close call.
Elsewhere in the basin, there are easterly waves trekking across the deep tropics at about 50W, 35W, and 20W, none of which currently show signs of organization.
Please visit my tropical Atlantic headquarters.
07 July 2008
Bertha skips CAT2 and becomes first major hurricane of the season...
Since the previous advisory, Bertha intensified from 80kts (CAT1) to 100kts now (CAT3). The estimated minimum sea level pressure is 948mb, or 27mb lower than six hours ago!
This type of "Cape Verde storm" is atypical so early in the season. They happen, but this one stands out as being the easternmost formation prior to August 1. This would indicate a generally active season is in the making, since SST and shear are already favorable in this classically Aug-Sep formation zone.
Bermuda should still be keeping a close eye on this hurricane as the week progresses.
Please visit my tropical Atlantic headquarters.
This type of "Cape Verde storm" is atypical so early in the season. They happen, but this one stands out as being the easternmost formation prior to August 1. This would indicate a generally active season is in the making, since SST and shear are already favorable in this classically Aug-Sep formation zone.
Bermuda should still be keeping a close eye on this hurricane as the week progresses.
Please visit my tropical Atlantic headquarters.
Bertha now a strong Category 1 hurricane...
During the long holiday weekend, Bertha made some big jumps in organization, despite some cooler ocean temperatures and some dry air trying to wrap around the circulation. Earlier this morning (Monday), an eye formed and has remained open since then. The storm is now in a very favorable environment, and Bertha is forecast to continue intensifying. At 15Z today, the intensity estimate is 80kts and 975mb, nearly a CAT2 storm. It's still heading WNW at 13kts, basically identical to what it was 4 days ago. Location is 19.6N 51.3W, far away from any land.
Given the environment, it's likely that Bertha will become a CAT2 storm within a day, and perhaps even reach 100kts and make CAT3 status (that's a remote possibility). Large-scale steering flow is still WNW, but will become more NW by the middle of the week as the storm skirts around the subtropical High. Bermuda is under the gun by the end of the week, and should be watching this very closely. Right around this time however, Bertha could interact with a mid-latitude trough, which complicates the track and intensity forecast.
Please visit my tropical Atlantic headquarters.
Given the environment, it's likely that Bertha will become a CAT2 storm within a day, and perhaps even reach 100kts and make CAT3 status (that's a remote possibility). Large-scale steering flow is still WNW, but will become more NW by the middle of the week as the storm skirts around the subtropical High. Bermuda is under the gun by the end of the week, and should be watching this very closely. Right around this time however, Bertha could interact with a mid-latitude trough, which complicates the track and intensity forecast.
Please visit my tropical Atlantic headquarters.
03 July 2008
Bertha forms in the far eastern Atlantic...
The disturbance I mentioned yesterday southeast of the Cape Verdes was upgraded to TD2 early Thursday morning based on visible, infrared, and microwave satellite imagery/data. Then six hours later, it was upgraded to Tropical Storm Bertha based again on improved satellite presentation. At 15Z (11am EDT), TS Bertha was located at 13.3N 24.7W and moving WNW at 12kts. Intensity is estimated at 35kts and 1006mb.
This was extraordinarily well forecast; models had predicted this formation last week. One week ago, Bertha was a large convective complex over Chad and Sudan in central Africa. Even since yesterday at this time, it has gotten much better organized in terms of surface circulation and concentration of the deepest convection over the center. Cloud-top temperatures are persistently colder than -70C now.
The SSTs are a little on the cool side, around 26C, but sufficient for genesis and moderate strengthening. Vertical wind shear (defined as the vector difference between the low-level 850mb winds and the upper-level 200mb winds) is very low over the system, and should remain that way for at least the next few days. Overall, environmental conditions favor intensification and a gradual movement to the WNW.
Please visit my tropical Atlantic headquarters.
This was extraordinarily well forecast; models had predicted this formation last week. One week ago, Bertha was a large convective complex over Chad and Sudan in central Africa. Even since yesterday at this time, it has gotten much better organized in terms of surface circulation and concentration of the deepest convection over the center. Cloud-top temperatures are persistently colder than -70C now.
The SSTs are a little on the cool side, around 26C, but sufficient for genesis and moderate strengthening. Vertical wind shear (defined as the vector difference between the low-level 850mb winds and the upper-level 200mb winds) is very low over the system, and should remain that way for at least the next few days. Overall, environmental conditions favor intensification and a gradual movement to the WNW.
Please visit my tropical Atlantic headquarters.
02 July 2008
Possible Depression forming...
A well-organized tropical wave exited the African coast yesterday, and is now located just southeast of the Cape Verde islands. You can see its progress at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/hovmoller/atlantic/
A QuikSCAT pass from 07Z today showed a completely closed surface circulation, with some non-rain-contaminated vectors on the western half approaching the tropical storm threshold of 35kts. QuikSCAT is an active microwave scatterometer that is capable of determining the surface wind speed and direction.
http://manati.orbit.nesdis.noaa.gov/storm_at_image21/qscat08070217_92as.png
It is in an environment with little vertical wind shear, and sea surface temperatures (SST) are sufficiently warm... in the 27C ballpark.
Should it continue to organize, it would become TD2 then TS Bertha. [Arthur was already named in late May and was a short-lived storm that formed from the remnants of Alma in the eastern Pacific.]
In the longer term, this system should have a hard time making it too far west, so is likely not a threat to the US. It could however, become a strong TS or even a hurricane in the coming days.
For those of you who have joined this mailing list since last season, welcome! If you ever have any questions about the content of these updates, please ask!
Please visit my tropical Atlantic headquarters.
A QuikSCAT pass from 07Z today showed a completely closed surface circulation, with some non-rain-contaminated vectors on the western half approaching the tropical storm threshold of 35kts. QuikSCAT is an active microwave scatterometer that is capable of determining the surface wind speed and direction.
http://manati.orbit.nesdis.noaa.gov/storm_at_image21/qscat08070217_92as.png
It is in an environment with little vertical wind shear, and sea surface temperatures (SST) are sufficiently warm... in the 27C ballpark.
Should it continue to organize, it would become TD2 then TS Bertha. [Arthur was already named in late May and was a short-lived storm that formed from the remnants of Alma in the eastern Pacific.]
In the longer term, this system should have a hard time making it too far west, so is likely not a threat to the US. It could however, become a strong TS or even a hurricane in the coming days.
For those of you who have joined this mailing list since last season, welcome! If you ever have any questions about the content of these updates, please ask!
Please visit my tropical Atlantic headquarters.
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