Tropical Tidbits from the Tundra

Dolly Review; A look at the next few weeks

By: Levi32, 5:28 AM GMT on July 24, 2008

Dolly has been downgraded to a tropical storm over south Texas with 70mph winds, and a pressure of 981mb. Dolly has been slow to weaken even 11 hours after landfall. This is partly due to the flat terrain of southern Texas, but mainly it's because the upper-level conditions over Dolly finally came into perfect shape AFTER she made landfall. The ULLs which had plagued Dolly's western and southern sides, blocking off her outflow channels, are gone, leaving a perfect anticyclone over Dolly. This resulted in Dolly's structure actually improving after landfall. Had this happened 24 hours ago, we would be seeing a Category 3 or 4 hurricane making landfall in Texas. We are very lucky that this did not happen, and it is a lesson in intensity forecasting: NEVER IGNORE ULLs.....lol. My personal landfall intensity forecast was a little on the high side at 105mph. I made this forecast 2 days before landfall, but Dolly's actual intensity was 95-100mph, borderline Cat 1/2. The NHC, on the other hand, did a pretty good job on Dolly's intensity, forecasting a high end Cat 1 most of the way.

The NHC also did a spectacular job on Dolly's track forecast, especially from 4-5 days out, when they nailed a south Texas landfall. Later on they ended up being a little too far south, but with a coastline shaped the way it is along the Texas/Mexico border, an error of even a few miles can make a huge difference in landfall location, so the NHC did a very good job. My landfall forecast from 3 days out was for a landfall between Brownsville and Corpus Cristi, Texas. I never got the guts to narrow it down any further due to Dolly's unpredictable movements just prior to landfall, but I stuck with that forecast for the full 72 hours before landfall, and it turned out alright. I know it's nothing to brag about, but Dolly was my best ever forecasted storm here on WU in my 4 years here, so I'm happy.

Texans and Mexicans, however, are not very happy, as they are getting absolutely dumped on by Dolly's heavy rains. Radar estimates show a swath of 20+ inches of rainfall along the track of the southern eye wall, where Dolly's most intense winds and rain were located. Luckily, this swath remained north of the Rio Grande River Valley, where the most catastrophic damage would have occured, but severe flooding is still going to be a major problem in southern Texas. Dolly's slow movement towards the west at 6mph is what has allowed this much rain to fall, and Dolly will continue to unload on south Texas and northern Mexico over the next 2 days as she gradually moves off to the west and dissipates.

On to other things. Former Invest 97L, west of the Cape Verde Islands, has lost its designation due to low expectations for development. Low SSTs and dry air are, for the moment, choking this system off. However despite appearances, this system has actually dragged a huge mass of moisture off of Africa and into the eastern Atlantic, and the system will be moving back over warm SSTs supportive of development in a couple days. For now the system is a low threat, but I am not writing it off just yet. Little sneakers like this system can slip under the ridge in the central Atlantic and develop on the other side where conditions are more favorable, and can end up threatening the US down the road. Right now if this system developed into a TC it would most likely recurve, but you gotta keep an eye on the ones that lay low and creep across.

Of potentially more interest is the wave SE of former 97L, just coming off the coast of Africa. This wave is at a much lower latitude, and therefore will be moving over much warmer SSTs over the next few days. As I mentioned before, ex-97L brought lots of moisture off Africa, and this will help moisten the environment ahead of this next wave. The only model which really shows this wave is the GFS, which keeps the system an open wave as it moves into the Caribbean in a week or so. Again this could be another wave that waits until later to develop, like the wave that spawned Dolly, so keep an eye on it.

Aside from these 2 waves mentioned above, the African wave train has quieted down a bit, and the entire eastern and central Atlantic are under a huge area of subsidence. The reason for this is the MJO:
The big upward motion pulse we have had this July is gone, and we are now in the next phase of the cycle, where areas of downward motion (brown lines) will dominate most of the Atlantic over the next 2-3 weeks. That said, these pulses of downward motion aren't horribly strong, so it is not out of the question for us to get 1 or 2 developments during the first half of August. In fact it is important to keep in mind that the MJO doesn't necessarily guarantee an abundance or a lack of developments, but it can make it easier or more difficult for storms to form. Hurricane Emily of 2005, developed into a Category 5 hurricane during a downward MJO pulse, so don't count anything out. Instead of one wave right after another off the African coast, we will get one big one at a time spread out over several days, which will need to be monitored. The next upward motion pulse is due to arrive in the Atlantic right at the peak of the hurricane season; late August through early September. We have already had an above-average July, and I expect the real track race for this season will begin in late August, where the real meat of the 2008 hurricane season awaits us. If this month has been any indication, we've got a long way to go.

We shall see what happens!

Updated: 5:29 AM GMT on July 24, 2008

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Dolly close to landfall

By: Levi32, 2:53 PM GMT on July 23, 2008

Hurricane Dolly update 1pm Eastern Time Wednesday 7-23-08:

Dolly has reached peak intensity, and recon reports a 3mb pressure rise in the last 2 hours. However, the winds continue to remain the same if not increasing a little as they continue to catch up with the pressure drop from earlier when Dolly rapidly intensified. The eye is pretty much closed again, although weakly, and is contracting. Dolly is taking steps to survive and maintain intensity as long as she can but she's run out of time. She's moving over cooler, shallower waters near the coast and is probably upwelling a bunch now too, along with dry air intake after being near land so long. Dolly should remain a Category 2 until landfall though. Unfortunately none of this really has any affect on the copious rainfall amounts which will fall over northern Mexico and southern Texas as Dolly crawls westward, and major flooding is a distinct possibility. Frictional effects helped Dolly's move north. The jut of land near the border caused the west side to weaken which pinwheeled her north, but now that the coast curves to the left it allows Dolly to move more west. SW eye wall, the worst part of the storm, is moving over South Padre island and Port Isabel right now, and Dolly will be making landfall near Port Mansfield during the next 90-120 minutes. Thoughts and prayers are with the people in the path of this storm.

11am update:
Dolly put on a burst of rapid intensification early this morning, which is what I feared. Pressure has now leveled off it would seem at 964mb. Winds are only just now starting to catch up with the pressure but the NHC is calling Dolly a Cat 2. Earlier the 20 mile-wide eye was closed, but radar shows the northern wall eroding, either from dry air or an EWRC, it remains to be seen which. My intensity forecast from the last 2 days would seem to be dead on for 105mph Cat 2 with sub-970mb pressure. This is not a good thing for Texas, but Dolly is moving over a slice of cooler waters just off the coast which may help weaken her just before landfall, although she is taking her sweet time about moving inland. Dolly is crawling NNW at under 5mph according to radar, and will now make landfall in Texas, not Mexico. I don't expect much more strengthening to occur before landfall, and it looks like weakening might actually ensue shortly, which is good news for Texas. Unfortunately all this slow movement is prolonging the heavy rains as well, which will cause flooding problems. Dolly is a small storm though, and her rainfall isn't as bad as some hurricanes. We will see how long Dolly stays over water, and if it is a good or bad thing for her to stay longer. Thoughts and prayers are with all in Dolly's path. Stay safe!


Dolly Radar imagery:



Dolly NHC forecast track and warnings:


Dolly visible satellite imagery (click for loop):


Dolly model tracks:

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Updated: 5:13 PM GMT on July 23, 2008

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Hurricane Dolly prepares to make landfall

By: Levi32, 5:19 PM GMT on July 22, 2008

Dolly Update 2am Eastern Time Wednesday 7-23-08:

Hurricane Dolly is slowly...ever so slowly...organizing and strengthening off the Mexican coast. Deep convection has finally wrapped all around the center, which is evident in both satellite and radar imagery. The eye is formed but ragged, and recon reports have showed that the pressure has leveled off at 982mb and refuses to budge, and they haven't found any winds above minimal hurricane force. Dolly has been wobbling in a general NW direction over the last 8 hours, and this motion should continue through this afternoon. At this time it is still unclear whether Dolly will make landfall in extreme NE Mexico or southern Texas. All will depend on her final movements over the next 8-12 hours. Dolly may even stall under weak steering currents during this time, further prolonging landfall. At this point Dolly may not be able to get past Cat 1, but I do expect slow strengthening right up until landfall. My forecast was for landfall between Brownsville and Corpus Cristi as a Cat 2 with winds of 105mph. Even if it ends up wrong, a forecast is a forecast, and I have stuck by it for 3 days. Dolly ain't done yet, so we shall see what happens! Stay safe out there all in the path of Dolly, thoughts and prayers are with you.

8pm EST update:
Dolly is continuing to slowly organize this evening. She is still having core issues, but deep convection has wrapped around most of the center, with a small lack on the east side, where what would be the eye wall is still open. The eye went back to an undefined mess a few hours ago, but Brownsville radar shows well-established core thunderstorms around the north and west sides of the center. Outflow is still having major issues on the southern semicircle due to the ULL in the Bay of Campeche, but continues to expand in the other quadrants. Despite Dolly's somewhat ragged appearance, the hurricane hunters have reported a steadily falling pressure throughout the day, which is now down to 982mb. Winds are still at 65kts so far; minimal hurricane intensity. My forecast still looks good to me. Radar is continuing to show a more northward track than the NHC is predicting, and I'm still calling for a landfall as a Category 2 hurricane with 105mph winds between Brownsville and Corpus Cristi, Texas. Again the major problem with Dolly will be the excessive rainfall, not the winds. up to 15 inches of rain is expected over parts of Texas and Mexico, so people should be prepared for possible major flooding.

3:30pm update:
Dolly continues to slowly build her core this afternoon. The west and southern sides of the eye wall have had trouble closing off due to dry air, but that should slowly fade in the coming hours. Dolly's outflow continues to expand nicely with the exception of the NW quad where you can see a "flat" appearance on satellite imagery, as if it is running into a wall. This is due to an ULL over Texas which is moving westward, but in the process impeding some of Dolly's outflow. However, the environment remains very conducive for further strengthening, and as soon as Dolly's eye becomes established, I think we will see a steady strengthening trend ensue. Recon has found a continually dropping pressure, which is now down to 988mb. Hurricane-force winds have yet to be found, but I expect the winds will catch up to the pressure soon enough.

Dolly continues to slow down as well, and a more northward component has been noted in radar imagery out of Brownsville this afternoon. This is exactly what I have expected over the past few days, and I am still calling for a landfall between Brownsville and Corpus Cristi as a Cat 2 with 90kt(105mph) winds.

1pm update:
Tropical Storm Dolly is getting her act together this morning. After struggling with some dry air from the Yucatan, her core is finally taking shape, with a broken 20nm-wide eye. Her pressure is 991mb, winds 70mph, and she has FINALLY slowed down to 11mph towards the NW. Outflow continues to expand in all quads, including the southern side, which was struggling yesterday due to the weak ULL moving off to the south, which maintained its affect on Dolly longer than anticipated. Dolly is now in a very conducive environment for strengthening, with warm SSTs and a healthy anticyclone over the top of her. Right now she's just about ready to hit hurricane strength, and I expect steady intensification to continue right up until landfall. The final landfall intensity remains a bit of a problem. We still don't know exactly how long Dolly is going to remain offshore, now that she has slowed down and begun to turn to the north a little bit. I'm not one to change my forecasts unless I really feel the need to, and I'm not about to start here. 3 days ago I forecasted a Cat 2 with a small possibility of a Cat 3. The chances of Dolly having time to become a major hurricane are slim at the moment, but I think a Cat 2 is still definitely possible, and I am going to go with 90kts(105mph) for my final landfall intensity.

Who's she gonna hit? Well the models have for the most part come into good agreement with the NHC on a hit near or around the Texas/Mexico border. The models still differ on speed a little bit, and a couple still try to turn Dolly further north along the Texas coast. The problem with forecasting the track is the fact that Dolly is slowing down as she nears the periphery of the high that is currently steering her. This high is weakening and sliding east due to a trough over the Great Lakes pushing southward. I believe this is going to allow Dolly to turn a little more to the north than the NHC is indicating. Yesterday I said landfall between Brownsville and Corpus Cristi, and again I'm not about to change it unless I have to, so I'm still going with that this morning.

Regardless of where Dolly makes landfall, a large area from northern Mexico to southern Texas are going to get lots of rain, which is needed in some places, but severe flooding is a big concern. The Rio Grande River Valley is at the most risk, and the NHC's current path would mean a drastic flooding event in that area. Everyone in the warning areas issued by the NHC should be prepared for a hurricane hit in the next 24-36 hours. No matter where Dolly's exact landfall is, many people will get heavy weather from this system, so be prepared.

We shall see what happens!

Dolly Radar imagery:



Dolly NHC forecast track and warnings:


Dolly visible satellite imagery (click for loop):


Dolly model tracks:

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Elsewhere in the Atlantic:

Bertha is just about gone....FINALLY!! Lol. Cristobal is done strengthening, and will move out to the NE, potentially affecting Newfoundland, but shouldn't be a major problem.

The biggest story besides Dolly over the next week is going to be the gigantic wave coming off the African coast in the next day or so. This wave is very vigorous and the NHC has already labeled it as an orange(20-50%) risk for development even though it's still over mainland Africa. This system could develop into a tropical depression very quickly after emerging off the coast, and this system should be in the vicinity of 20n 60w in about a week. Can't even think about potential land impacts yet until we actually get a named storm, if we get one, and then we can start looking at the pattern. Right now all focus is obviously on Dolly, but don't let this one slip under your radar during the next few days.

Updated: 6:38 AM GMT on July 23, 2008

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Dolly update 1pm EST Tuesday

By: Levi32, 5:18 PM GMT on July 22, 2008

Tropical Storm Dolly is getting her act together this morning. After struggling with some dry air from the Yucatan, her core is finally taking shape, with a broken 20nm-wide eye. Her pressure is 991mb, winds 70mph, and she has FINALLY slowed down to 11mph towards the NW. Outflow continues to expand in all quads, including the southern side, which was struggling yesterday due to the weak ULL moving off to the south, which maintained its affect on Dolly longer than anticipated. Dolly is now in a very conducive environment for strengthening, with warm SSTs and a healthy anticyclone over the top of her. Right now she's just about ready to hit hurricane strength, and I expect steady intensification to continue right up until landfall. The final landfall intensity remains a bit of a problem. We still don't know exactly how long Dolly is going to remain offshore, now that she has slowed down and begun to turn to the north a little bit. I'm not one to change my forecasts unless I really feel the need to, and I'm not about to start here. 3 days ago I forecasted a Cat 2 with a small possibility of a Cat 3. The chances of Dolly having time to become a major hurricane are slim at the moment, but I think a Cat 2 is still definitely possible, and I am going to go with 90kts(105mph) for my final landfall intensity.

Who's she gonna hit? Well the models have for the most part come into good agreement with the NHC on a hit near or around the Texas/Mexico border. The models still differ on speed a little bit, and a couple still try to turn Dolly further north along the Texas coast. The problem with forecasting the track is the fact that Dolly is slowing down as she nears the periphery of the high that is currently steering her. This high is weakening and sliding east due to a trough over the Great Lakes pushing southward. I believe this is going to allow Dolly to turn a little more to the north than the NHC is indicating. Yesterday I said landfall between Brownsville and Corpus Cristi, and again I'm not about to change it unless I have to, so I'm still going with that this morning.

Regardless of where Dolly makes landfall, a large area from northern Mexico to southern Texas are going to get lots of rain, which is needed in some places, but severe flooding is a big concern. The Rio Grande River Valley is at the most risk, and the NHC's current path would mean a drastic flooding event in that area. Everyone in the warning areas issued by the NHC should be prepared for a hurricane hit in the next 24-36 hours. No matter where Dolly's exact landfall is, many people will get heavy weather from this system, so be prepared.

We shall see what happens!



Dolly NHC forecast track and warnings:


Dolly visible satellite imagery (click for loop):


Dolly model tracks:

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Elsewhere in the Atlantic:

The biggest story besides Dolly over the next week is going to be the gigantic wave coming off the African coast in the next day or so. This wave is very vigorous and the NHC has labeled it as an orange(20-50%) risk for development. This system could develop into a tropical depression over the next few days, and this system should be in the vicinity of 20n 60w in about a week. Can't even think about potential land impacts yet until we actually get a named storm, if we get one, and then we can start looking at the pattern. Right now all focus is obviously on Dolly, but don't let this one slip under your radar during the next few days.

Updated: 5:20 PM GMT on July 22, 2008

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Dolly to threaten Texas

By: Levi32, 5:28 PM GMT on July 21, 2008

Update 7pm Eastern Time:

Dolly is slowly organizing this afternoon. Convection is increasing around the center and the wind field has tightened up a bit according to the recon. As of this writing the recon also just found a pressure reading of 998mb, 6mb lower than the last vortex message 3 hours ago. Dolly is running out of time to become a formidable hurricane though. If she doesn't slow down within 12 hours she's not going to be able to get any stronger than a Cat 1, which is good news for the Texas/Mexico coast. The reason for this is 2-fold. The faster she goes, obviously the less time she has before landfall, hence less time to strengthen. The other reason is that a fast-moving system has a hard time organizing because the low-level center tends to outrun the convection, making it hard to consolidate a CDO over the center. Therefore Dolly will have to slow down before she can attain hurricane status. A lot will have to do with her track before landfall too. If she continues on this beeline for the Rio Grande River, I don't think she'll make it past Cat 1. If she slows down and tries to curve more north though, towards Texas, then there is still a threat for a ramp up to Cat 2 or 3. I don't expect any rapid intensification from Dolly until she slows down. If she does slow down though expect her to try to ramp up quickly. She's got everything going for her except her own impatience to get ashore, and she's organized enough now that she could explode at any time once she slows down enough. Everyone on the Mexican and Texas coasts should continue to keep a close eye on Dolly. My track ideas below remain the same.

Previous Update:
Tropical Storm Dolly's surface circulation has finally stopped playing cat and mouse with us. Last night the center relocated under the mid-level circulation, which was much further to the north. As a result, Dolly only barely passed over the NE tip of the Yucatan, and is now in the GOM off the northern coast of the peninsula. Dolly still has sustained winds of 50mph, pressure of 1007mb, and moving WNW at 18mph. Convection has been impressive over the last 24 hours, but circulation problems yesterday inhibited any strengthening of the system. Right now Dolly looks like half of a storm, with no convection south of the center at this time, and the ULL to the SW is still having an influence, giving the southern side of Dolly a flat appearance, instead of the nice rounded look that healthy storms have.

That said, the ULL is rapidly dropping away to the SW, leaving a building anticyclone over the top of Dolly in its wake, which is expanding the outflow in all quads except the SW, and causing the whole storm to expand. This is a classic setup for strengthening in the GOM, and in about 24 hours I think we will be looking at hurricane Dolly. Right now Dolly is still too close to the Yucatan, drawing in dry air and still getting rid of the ULL. Once Dolly gets some room to breathe over the open water she is going to take off, and she forms a solid core, steady intensification should occur. The NHC agrees with this, and forecasts Dolly to be a borderline Cat 1/2 at landfall in extreme southern Texas. I think this will be a Cat 2 and possibly 3. Dolly doesn't have all that much time to strengthen into a major hurricane, but we don't know for sure exactly how much time she'll have at the end, so it's hard to say right now. Dolly will also have to slow down before major organization can occur, and she is forecast to do that within the next 24 hours, so we'll see how it goes. There are plenty of warm deep waters (28-29c) in the path of Dolly, which would support a major hurricane.

Where oh where will Dolly go? Actually we have a fair idea with this system. The models are in close agreement on a continued WNW/NW motion towards the Texas/Mexico border. The models have been slowly trending north over the last several runs, and the majority, including the NHC, now forecast a curve to the north during the last 24 hours and a landfall somewhere in southern Texas. What will be steering Dolly over the next 3 days is an upper-level high over the GOM and southern US. 2 things are going to contribute to Dolly's potential curve to the north before landfall. One, the high's western edge lies over the western gulf. This means that Dolly will eventually slow down as steering currents become weaker near the edge of the high, and Dolly may start curving north around this edge right at the last minute before landfall. The 2nd thing, which we can see in our Water Vapor loop, is a trough over the Great Lakes starting to dig southward over the eastern US, and will start to weaken the high over the GOM. There were already a couple kinks in this high to begin with, and all this will help Dolly inch her way northward. Also the stronger Dolly gets, the harder she will try to find a break in the high. One last interesting thing to note is that climatology shows that all the July tropical storms that passed near Dolly made landfall in the US, and only one in Mexico. I don't know what this map will look like once Dolly becomes a hurricane, but it is interesting.

Ok, so who should be prepared? Anyone from the northern Mexican coast to Houston, Texas. Dolly's movements during the last day before landfall are still quite uncertain, as well as her intensity, so we can't focus on any one area for impact potential. Everyone on the Texas coast and northern Mexican coast, especially near the Rio Grande River, should be prepared for a potential major hurricane hit in 60-84 hours. No need to panic, there's still plenty of time to narrow down Dolly's final landfall. I myself am putting Dolly somewhere between Brownsville and Corpus Cristi, which I will narrow down as time goes on and we get a better handle on the situation. Be prepared, stay safe, and listen to the NHC and your local weather office.

We shall see what happens!



Dolly visible satellite imagery (click for loop):


Dolly model tracks:

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Elsewhere in the Atlantic:

Bertha is just about gone....FINALLY!! Lol. Cristobal is done strengthening, and will move out to the NE, potentially affecting Newfoundland, but shouldn't be a major problem.

The biggest story besides Dolly over the next week is going to be the gigantic wave coming off the African coast in the next day or so. This wave is very vigorous and the NHC has already labeled it as an orange(20-50%) risk for development even though it's still over mainland Africa. This system could develop into a tropical depression very quickly after emerging off the coast, and this system should be in the vicinity of 20n 60w in about a week. Can't even think about potential land impacts yet until we actually get a named storm, if we get one, and then we can start looking at the pattern. Right now all focus is obviously on Dolly, but don't let this one slip under your radar during the next few days.

Updated: 10:54 PM GMT on July 21, 2008

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Cristobal not a big threat; but Dolly is another story

By: Levi32, 11:02 PM GMT on July 20, 2008

Tropical storm Cristobal is slowly moving NE close to the outer banks of North Carolina. Convection had completely gotten de-coupled from the COC yesterday, and is only just now starting to consolidate closer to the center, but it's pretty much too late for Cristobal. He may strengthen as he moves out to sea but he is no major threat to any land areas, and in fact is bringing beneficial rainfall to the Carolinas.

As I expected, 94L was finally named TS Dolly this morning after a recon found a defined surface circulation. However, in the 5pm discussion this afternoon the NHC said that the recon reported a less-well defined circulation. I believe this may be being caused by the COC trying to relocate to the northeast. Right now the center is displaced SW of the mid-level center and the main area of deep convection. However visible imagery this afternoon shows the COC trying to jump NE into a new burst of convection. The mid-level center is still very defined , and it will be interesting to see which center wins the battle, as it will have an effect on Dolly's track. I think Dolly may have time to strengthen to maybe a 50kt system before hitting the Yucatan, and then little change in intensity during the crossing, maybe some slight weakening. The ULL that has been producing wind shear over Dolly is rapidly dropping away to the SW and weakening as it goes. This means that Dolly will end up being under a nice upper-level anticyclone over the Gulf of Mexico. This, and 28c SSTs, should contribute to strengthening. The NHC is calling for a TS most of the way and then Cat 1 at landfall on the Mexican coast, but personally I think this is going to be a solid Cat 2 in the gulf.

So who will Dolly honor with her presence? Well the models are in great agreement for the first 48 hours, bringing Dolly over the Yucatan and eastern Bay of Campeche. This track could be shifted slightly to the north if the center ends up relocating NE, but for now the track for the next 2 days looks pretty solid. Beyond that the models diverge and have been jumping back and forth between a Mexico landfall and a southern Texas landfall. I am in close agreement with the NHC forecast for a landfall just south of the Rio Grande River, however it's really still too far out to speculate on the landfall location. The upper-level high over the GOM will be weakening over the next few days as a long-wave trough digs southward over the Great Lakes. The western periphery of this high also lies over the western GOM. All of this means that Dolly will slow down under weaker steering currents after her crossing of the Yucatan, and it is possible that she could end up moving further north than the models are anticipating at this point. Everyone on the Mexican coast and southern Texas coast should closely monitor Dolly over the next few days.

Elsewhere in the Atlantic, Bertha is moving out, but we have a new puppy to watch, and it's a big puppy. A new wave emerging off Africa, and this one is a monster and will probably develop over the central Atlantic. Don't let this one slip by your radar while we focus on stuff close to home. Too early to speculate on anything with this system but it could be in the vicinity of 20n 60w within a week. Keep an eye out for it.

We shall see what happens!

Cristobal radar imagery:


Cristobal visible satellite imagery (click for loop):


Cristobal model tracks:

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Dolly visible satellite imagery (click for loop):


Dolly model tracks:

Updated: 11:54 PM GMT on July 20, 2008

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Cristobal.......and Dolly?

By: Levi32, 11:07 PM GMT on July 19, 2008

First of all Bertha is back at hurricane status yet again, but is finally showing signs of extratropical transition, and will continue to head out over the north Atlantic posing no threat to anybody.

Tropical Storm Cristobal is located about 100 miles off the NC coast after making a jog to the north this afternoon, bringing him much closer to land. Cristobal has winds of 45mph with a pressure of 1005mb, moving NE at 6mph. This movement is expected to continue over the next several days, and Cristobal may pose a threat to the NC outer banks. Upper-air conditions are fairly ideal for development, and Cristobal is sitting over the gulf stream, where plenty of warm water resides. It would seem that all systems are go, but Cristobal's convection remains quite modest and the system is not really strengthening at this point, with the exception of continued organization of the spiral bands. I believe this is due to dry air being pulled into Cristobal by his own circulation off of the continent. The NW quad has been void of convection from the beginning, and there is a lot of dry air over the land. At this point Cristobal isn't able to overcome this, and until he can, he will remain no stronger than a 45kt system. However, residents in North Carolina should continue to monitor this system very closely, because if Cristobal does overcome the dry air before going out to sea, he could crank up really fast before anyone realizes it. Such is the nature of home-grown developments, we saw it with Humberto last year. For now Cristobal will hopefully be beneficial if he can spread some much-needed rain over the area, which probably won't be much unless he makes landfall.

Our other system, 94L, is still fighting for life in the Caribbean. This system WAS a tropical depression 2 days ago, by definition, and it was an incredible feat that it pulled that off. Since then the circulation has become open once again, but the mid-level circulation is still kicking nicely. Convection has managed to remain healthy and is now consolidating over the mid-level center, which was placed further north of the surface center. 94L has been fighting wind shear due to an ULL to its northwest, but this ULL is now weakening and shear over 94L is under 20 knots now. Eventually this ULL will pull out, providing a much nicer environment for 94L to develop in as it moves into the western Caribbean and GOM.

At this point I don't believe 94L has time to amount to very much before hitting the Yucatan Peninsula, but that's actually a bad thing. When a strong hurricane moves over the Yucatan Peninsula and emerges again over the GOM, the core gets significantly weakened. However, the outer bands of the storm stay over water the whole time. So when the storm moves back over water, what happens is the outside of the storm is in better shape than the core, and a competition between the outer bands and the heart of the system takes place. As a result most major hurricanes never regain their former glory after crossing the Yucatan. Recently, Hurricanes Wilma and Emily of 2005 are good examples of this, as well as Isidore of 2002. But a weaker system of weak TS status or under doesn't have a well set-up core yet, and is far less affected by the journey across the Yucatan than a hurricane is. Therefore 94L may not amount to much prior to hitting the Yucatan, but once it emerges in the GOM we have to watch out, because we will probably have a Cat 1, 2, or 3 hitting the Mexican coastline in 5 days.

Yeah I said Mexico....but Texas needs to watch this very closely as well. The ridge isn't horribly strong north of 94L, and the western periphery is sitting right over the western gulf. A lot of 94L's future track will depend on where it hits the Yucatan, where it exits the Yucatan, and how fast it gets there. A long-wave trough will be digging down into the eastern United States in 3-4 days, which will further weaken the ridge. Some models have 94L making landfall on the western side of the gulf already by this time, so it might not matter, but we will have to see how fast 94L really moves over the coming days. Model consensus has 94L going into Mexico on both coastlines, with the exception of the GFDL and HWRF which continue to be the northerly outliers, taking 94L through the Yucatan Channel and into Texas. The latest GFDL run and the CMC closely agree on a hit to the Mexico/Texas border as a major hurricane, but it's too early to speculate on these solutions. Right now we have to watch and wait. Interests in Texas and Mexico should closely monitor this system.

Cristobal radar imagery:


Cristobal visible satellite imagery (click for loop):


Cristobal model tracks:

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Invest 94L visible satellite imagery (click for loop):


Invest 94L model tracks:


Updated: 11:11 PM GMT on July 19, 2008

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94L and 96L developing

By: Levi32, 5:21 PM GMT on July 18, 2008

Again my apologies for being absent over the last week. Things have been so crazy.

We have a very active Atlantic Ocean this morning. Bertha refuses to go away, and is becoming a pain to have on the map lol. Fortunately she is finally moving NE and will eventually transition to extratropical and exit the picture forever. She is no threat to any land areas anymore.

Close to home we have Invest 96L about 80 miles northeast of Jacksonville, Florida. We knew this system was going to be a problem because the trough over the eastern seaboard split and left a piece behind over the NE gulf. This piece has moved across Florida and now sits off the SE coast. With all respect to the NHC, and in all honesty, this system is a TD no questions asked. It has closed rotary circulation with plenty of convection which is now spreading over the COC. By definition it's a TD, I don't care what anyone says. As I already said convection is looking healthy and is currently spreading over the COC as it organizes. This system is under weak steering currents and will drift NNE following the gulf stream over the next few days. This gives it plenty of time to ramp up and I think we could possibly be dealing with a borderline hurricane off the NC coast in 2-3 days. Needless to say all interests on the SE coast need to keep a close eye on this system, which I will be monitoring very closely over the next few days.

Next we have 94L in the central Caribbean, which is also being a stubborn little creature. After fighting injections of dry air and constant wind shear, this little system has maintained excellent convection over the last 24 hours, which this morning is starting to organize into bands, and yes this is already a TD. The circulation IS CLOSED, with 20-knot west winds south of the center over a large area with 35-knot winds north of the center. What more can you ask for, it's a TD or TS already. It will be interesting to see which of these invests gets named Christobal first. The NHC doesn't seem to be in a hurry to name either of them lol. Anyway, 94L will be moving WNW over the next several days, and once it gets into the western Caribbean, the environment will greatly improve, allowing for some significant development.

But who cares if it's a wave or a Cat 5? All that matters is where it's going right? lol...ok well the ridge to the north isn't all that strong over the western Caribbean/GOM...so 94L is going to slowly turn WNW over the next 48 hours. Beyond this point the models diverge a bit. The GFDL and HWRF curve 94L drastically to the north taking the system through the Yucatan channel and into the central gulf. The other models shove 94L right into the Yucatan and out the other side into the BOC. Honestly I think this is going to be a close call. The ridge really isn't that strong over that area and there will be a couple kinks in it as 94L moves through. I believe this will allow 94L to move a little NW before hitting the northeast tip of the Yucatan, and then it will cruise across the gulf in a NW or WNW direction. It is way too early to speculation about landfalls here, the system isn't even named yet, and it's just too far out to know much. At this point I think Texas will definitely have to keep an eye on this one, as well as the Mexicans on both coastlines.

We shall see what happens!

Invest 96L radar imagery:


Invest 96L visible satellite imagery (click for loop):


Invest 96L model tracks:

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Invest 94L visible satellite imagery (click for loop):


Invest 94L model tracks:


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Bertha re-strengthening

By: Levi32, 5:57 PM GMT on July 09, 2008

I apologize the last couple days suddenly got really busy and I haven't had time to post. I don't have time for an in-depth update but here's what I had time to come up with this morning.

Hurricane Bertha is furthering her reputation for resilience in the face of semi-hostile conditions, restrengthening this morning after a major weakening period yesterday due to dry air and some wind shear. The outflow has begun to expand to the west, convection is firing in symmetrical fashion around the core, and the eye has appeared once again. Bertha now looks like she's back at Cat 2 status, after dropping to a minimal Cat 1 yesterday. Warm SSTs and low wind shear could allow Bertha to strengthen further today, and she has a chance to hit major hurricane status again over the next 2 days. By Friday, Bertha will be moving into SSTs below 26c, and should weaken gradually back down to TS status by the weekend.

Obviously Bertha is recurving, and I was wrong about her making the 70w line before doing so. This shows not only my lack of experience and expertise, but also how difficult track forecasting can be for computer model and human alike. Bertha apparently has felt the weakness in the ridge much more than anyone anticipated, which was probably due to the fact that she bombed out into a major hurricane. My forecast was based on my intensity forecast for Bertha to remain a TS until she was past 60w, due to the dry air and wind shear combining to keep her at bay. Obviously I was again wrong, and Bertha strengthened beyond what any of us had thought possible, becoming the 6th strongest early season hurricane on record. As I said throughout my forecasts, a weaker system would be likely to slip under the weakness and get further west, and a hurricane would probably feel the weakness more. This is what happened when Bertha bombed out, she became more appealing to the trough, so she turned north and didn't look back.

Steering currents are going to remain weak around Bermuda over the next few days, keeping Bertha at a slow pace northwestward. As I said a few days ago, the shortwave coming off the east coast is not going to get her, and she will be trapped under the ridge for a while, left to meander around. This means that Bertha could go practically any direction during this time, and Bermuda should keep a close eye on Bertha. The NHC and most of the computer models currently have her going east of the island, but this is not a guarantee, and she should be watched closely. In about 6 days Bertha will finally be swept out to sea for good by a longwave trough coming across off the eastern seaboard, and the historic adventure of Hurricane Bertha will come to an end.

We shall see what happens!

Floater visible satellite:


^click for loop^

NHC 5-day forecast:


Model track guidance:


GFS ensemble track guidance:



Model intensity guidance:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Updated: 6:22 PM GMT on July 09, 2008

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Bertha strengthening

By: Levi32, 1:18 AM GMT on July 07, 2008

Tropics update 10pm EST 7-6-08:

Tropical Storm Bertha has become much better organized throughout the course of the day. Convection has increased considerably over the COC, outflow and spiral banding have improved, and recent microwave overpasses reveal an eye forming, which could be seen on visible satellite imagery earlier. The NHC has put Bertha's intensity at 50kts, which with all due respect is way off. Bertha is a Cat 1 hurricane right now strengthening over the warming SSTs in front of her. The feedback cycle has reached the point where Bertha can sustain her own levels of moisture, effectively fighting off the dry air to her west and southwest. I expect Bertha to continue slowly strengthening over the next 24 hours, after which time she will encounter a branch of the sub-tropical jetstream, resulting in southwesterly shear. Based on how Bertha has dealt with environmental hurdles so far, I don't expect this shear to weaken Bertha, but rather halt intensification temporarily. After Bertha clears the shear she will probably resume intensification as she moves over increasingly warm waters of the southwest Atlantic. Beyond this point we don't know much about what conditions will be like, so it's too soon to speculate on Bertha's intensity. Obviously as time goes on we will get a better idea of how things will play out intensity-wise.

Time for everyone's favorite part of Bertha's adventure. Where is this stubborn young lady headed? Well as always the models are still quite spread out. They have made a small shift north today, with the exception of the GFS. The NHC has shifted their track north accordingly, as they usually do, and they now have Bermuda in the the 4-5 day cone of error. Now we can't go bouncing around with the models as if we're being lead by leashes. Models are not our masters lol. While the model consensus should definitely be taken into account, we have to look deeper than the supercomputer's calculations.

As we have already previously discussed, there is a weakness in the Bermuda High at about 50w, which Bertha is currently moving under. This weakness is tugging a little bit on Bertha, and she is moving more WNW today than west. However, this weakness is on its way out of the picture, so the high will be building back in over the next day or so. I expect Bertha to turn back to a slightly north of due west course as this occurs. Notice how little this weakness is affecting Bertha in reality, when several days ago the models thought it would be enough to recurve Bertha. This just shows how wrong the models can be and how much they flop around.

Now Bertha's next obstacle will be the long-wave trough currently sitting over the eastern US. This trough will create another weakness in the high, and this is where things get messy. Most of the models are recurving Bertha into this weakness, but a couple are still sticking to the south. The GFS over the last few runs has been consistently bringing Bertha north towards the trough, but then the trough leaves and the high tries to build back in, trapping Bertha off the southeastern US coast. Now the GFS is always going to be the GFS....so it brings a second trough and takes Bertha out after a few days of meandering around. As I said this whole thing is very messy.....and it's still too far out to say where Bertha is going to go, and the US isn't off the hook yet. I have a feeling the GFS is correct in trapping Bertha under the high with weak steering currents, and she will have to meander her way around off the SE coast for a while. Bertha's exact location when she enters this area will be critical in determining whether she eventually gets pulled out to sea, or comes back towards the coast as the high builds in over top.

For right now I still think Bertha is going to go south of the current NHC track, and south of most of the models. Her forward motion hasn't slowed yet, meaning the high isn't breaking down, and I think she will continue this west to WNW motion for a couple more days at least, even despite the fact that she is turning into a stronger, deeper storm, which can be steered by the upper-level flow. Again it's too early to assume anything. It's a very interesting situation, and I have a feeling it will be a great learning experience for us all.

We shall see what happens!

Floater visible satellite:


^click for loop^

NHC 5-day forecast:


Model track guidance:


GFS ensemble track guidance:



Model intensity guidance:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Tropical disturbances:

None at this time. The area of disturbed weather over the western GOM will not develop due to the new TD in the eastern Pacific. Western Caribbean is also quiet, but both these areas have to be watched through July 20th. The wave behind Bertha hasn't amounted to anything so far, but there are more waves to follow coming off Africa, and at least one more of these has a good chance of developing under this MJO pulse, so keep an eye out to the east. Just for fun I'll mention that if any of these waves coming off Africa develop in the next week, they will take a much more southerly path than Bertha did, probably through the Caribbean.

Updated: 2:02 AM GMT on July 07, 2008

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Bertha continues to challenge forecasters

By: Levi32, 4:03 PM GMT on July 05, 2008

Tropics update 11:30am EST:

TS Bertha has changed little in intensity overnight. Cooler SSTs have prevented much strengthening over the last 24 hours, and the storm looks much the same as it did yesterday. By tomorrow Bertha will have moved back over SSTs of 26c, and up to 28c by Monday or Tuesday. Looking at our trusty water-vapor loop, we notice a couple things. First we notice the ULL along 50w 35n. This is the ULL that the models first thought would cause enough weakness in the Bermuda High to recurve Bertha right away. This is no longer an option, as Bertha continues to move due west at 20mph, which shows strong steering currents under a building high pressure area, meaning Bertha is not getting ready to recurve anytime soon. When or if Bertha does recurve, look for the storm to slow down as steering currents weaken on the periphery of the high. Ok, so this ULL will not be instigating a recurve, and will be pulling out over the next few days, but that doesn't mean it doesn't play a part in Bertha's adventure. A piece of the ULL is going to kind of stay behind along with a branch of the sub-tropical jetstream over the next 4 days. This will be causing some rough shear to impact Bertha after she gets to warmer SSTs, probably in the 20-30kt range. The 2nd thing we notice on our water-vapor loop is all the dry air to the southwest and west of Bertha. If you haven't noticed already, Bertha's SW quadrant is completely void of clouds. This is due to dry air entrainment, and this dry air will continue to be a problem until Bertha reaches about 60w. Why all the dry air when there didn't seem to be that much before? The answer is the MJO. Right now the two big upward motion (rising air) pulses are centered over the EPAC/GOM/W. Carib and the eastern Atlantic/west Africa. When air goes up, it has to go down somewhere else to keep the equilibrium. So in between these pulses of upward motion is an area of strong downward motion (sinking air) over northern South America and the central Atlantic. All these factors are going to inhibit strengthening of Bertha over the next 4-5 days, which is actually a bad thing. Remember that a weaker system is less likely to be steered by high-altitude winds, and will not feel weaknesses in the high as easily as a stronger system. The NHC brings Bertha to a hurricane by day 4, and I am not sure I agree with this. I think Bertha will struggle to achieve hurricane intensity until she's past 60w, when I believe conditions will become more conducive for strengthening.

So.....where the heck is she gonna go?? Good question. As I said, the ULL is no longer going to recurve Bertha, but it could still pull on her a little bit. The GFS is shifting back and forth a little bit with the last few runs, and currently favors a NW track for a time due to the ULL's influence before turning Bertha back towards the west, and then recurving her off the eastern seaboard. Lots of this morning's models have shifted north of the NHC track, with the exception of the UKMET and NOGAPS. The GFS ensembles continue to stay well south of the main GFS model, which is interesting. The ECMWF now completely loses Bertha, for whatever reason, maybe shear or something. So anyway Bertha will make it past monster number 1. Number 2 is the longwave trough that will be over the eastern US by the time Bertha makes it into the SW Atlantic. Uncertainty is extremely high here. The GFS has fluctuated back and forth from a CONUS landfall to trapping Bertha under the high and eventually recurving her. At this point it's still too far out to tell, and most everything depends on Bertha's track prior to 60w longitude. However, the reality is, that just like I said a while back, a recurve is far from a lock here, and the US could end up being threatened. I stressed this a few days ago, and the similarities to 1996 Bertha are huge in terms of timing, potential track, and Bermuda High setup. Again we can only watch, wait, and see at this point. We will have a better grasp on things after we see where Bertha is and how strong she is when she crosses 60w. If there's any one rule in Meteorology, it's to be ready for anything.

We shall see what happens!


Floater visible satellite:



^click for loop^

NHC 5-day forecast:


Model track guidance:


GFS ensemble track guidance:



Model intensity guidance:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Tropical disturbances:

None really....former 93L has pretty much fizzled, but the western Caribbean and GOM still need to be closely watched over the next 10 days as upper-level conditions slowly improve with the MJO pulse moving through.

The GFS is still forecasting a TD to form from the next wave just exiting Africa. This will have to be watched closely as the MJO pulse will probably be giving us at least one more storm out of this burst. There isn't much I can tell you about this wave at this time, except that if it does develop it will be taking a much more southerly track than Bertha is currently taking. Don't let it sneak up on us while all eyes are on Bertha =)

Updated: 4:06 PM GMT on July 05, 2008

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Bertha's adventure begins------couple sneaks trying to play tricks?

By: Levi32, 5:32 PM GMT on July 04, 2008

Tropics update 1pm EST:

Tropical Storm Bertha has strengthened slightly overnight, although I don't quite see why. Right now the storm resembles an egg...lol...with the storm getting elongated south to north. This appearance is due to the cool SSTs (under 26c) to Bertha's west and north. In this visible image you can see a stratocumulus cloud deck northwest of Bertha marking the stable air over the cool water. Bertha has begun to move over this area, and as a result the west and northwest sides of the storm are void of convection, giving it an elongated look. Bertha will have to transverse cool waters for about 2 days before they warm back up, and during that time I don't expect any strengthening to occur, in fact slight weakening is definitely possible. The deep convective pattern is currently disorganized, but overall Bertha has put herself together very nicely with well-defined spiral bands and good outflow in the eastern and southern semicircles. I expect Bertha to slightly weaken today and tomorrow as she transverses cooler waters, followed by more slow strengthening in the warmer waters of the central Atlantic. This closely resembles the NHC's intensity forecast.

So what's up with track? Well, the GFS has joined the westcaster party over the last couple runs, having Bertha miss the first weakness in the high and cruise just north of the islands. This is what I have expected from the beginning, the GFS tends to over-exaggerate weakness in the Bermuda High, and with Bertha to remain weak over the next few days, I just don't see the ULL picking her up this early. We now have the ECMWF, UKMET, NOGAPS, and the GFS all forecasting a westerly path north of the islands. The CMC follows this idea until it bombs Bertha into a Cat 2 NE of Puerto Rico, which causes Bertha to recurve abruptly as she suddenly becomes more appealing to the trough. My reasoning has not changed, and I believe that a weak Bertha depicted by most of the models will slip under the ULL/trough in the central Atlantic. Therefore I think Bertha is going to escape monster number 1 in her adventure.

We now have to start thinking about monster number 2. This monster takes the form of a long-wave trough over the eastern seaboard about a week from now. The ECMWF brings Bertha dangerously close to the US before recurving her into this trough. The GFS almost recurves Bertha, traps her under the high yet again as the trough leaves, and then slowly moves her north until the next trough picks her up. Now again the GFS has issues transfering heat from the tropics to the mid-latitudes, and tends to over-exaggerate troughs in the east. The ECMWF has Bertha following her namesake's path in 1996 almost dead on until she gets close to the east coast. Again, just as before, this is all speculation, and we won't have a good idea of how things will look for at least several days. However, the reality is that a recurve is just simply not locked in yet, although at this time it appears likely at some point. Down the road Bertha may decide to follow her ancestor's footsteps to the US, and the pattern is very much the same now as it was in '96. I must stress that I am not making a forecast here, just an observation, and it is still a wait, watch, and see game until we can get a better grasp on how things will play out during the next several days. Are you ready for an adventure?

We shall see what happens!

Floater visible satellite:



^click for loop^

NHC 5-day forecast:


Model track guidance:


GFS ensemble track guidance:



Model intensity guidance:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In other news, a tropical disturbance south of the Dominican Republic, former invest 93L, remains disorganized this morning, but 850mb vorticity is showing a vigorous little circulation still intact. Wind shear is still running over 30 knots in the western and central Caribbean, and at this time I don't think this system is a threat to develop. However this will have to be watched as it may sneak up on us later on as it moves west into the Gulf of Mexico. I will say again that this entire area has to be watched very closely over the next 2 weeks as the MJO pulse moves in and upper-level conditions become more conducive for home-grown development. Models have been toying with the idea of a low forming in the western GOM and moving into the Texas area some time in the next week. This is definitely a possibility worth monitoring, we saw how much activity has spun up in the eastern Pacific, and all that activity is going to be moving into the southwestern GOM and western Caribbean.

Also....we have another African wave that I think is gonna sneak up on us over central Africa. This wave is coming off in 2 days and the GFS is developing it over the last 2 runs and taking it through the Caribbean behind Bertha. I believe that this is going to be a real threat for development as it comes across with the MJO over the eastern Atlantic, and with the pattern the way it is this next system will try to sneak through the Caribbean and cause some fun and games in the Gulf of Mexico. Keep an eye to the sky folks! Hurricane season is upon us.

Updated: 7:47 PM GMT on July 04, 2008

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Bertha makes history; 93L fighting

By: Levi32, 5:18 PM GMT on July 03, 2008

Tropical Storm Bertha:

The NHC has named 92L Tropical Storm Bertha, the first tropical cyclone ever to form east of 34w during early July in recorded history. As a result there is no climatology to follow whatsoever lol. The system is getting better organized with consolidating thunderstorms near the center with spiral bands forming, and good outflow. However, Bertha is about to move over an area of cool SSTs near or below 26c, which I believe will halt any further intensification beyond about 40 knots. This area can be seen on visible imagery as an area of stratocumulus clouds northwest of Bertha, indicating stable air over the cooler water. The NHC is forecasting gradual intensification to a 55-knot TS in 5 days, which I agree with but I think she will be slightly weaker than that.

The models are still trending towards recurving Bertha, but this is by no means locked in stone yet. The ECMWF can't make up its mind as to whether it wants a weaker westward system or an eager eastward system. The UKMET and CMC continue to show a weaker system tracking further west, and are the southerly outliers. The GFS and company, GFDL, and the HWRF, all forecast recurvature in the central Atlantic due to a weakness created in the high by an ULL currently sitting in the central Atlantic. However, the GFS has major issues with transfering heat from the tropics to the mid-latitudes, and tends to over-exaggerate weaknesses in the Bermuda High. I have also noticed that the GFS is splitting the energy with Bertha, sending one piece to the northern islands and the other piece out to get trapped under the high in the central Atlantic as the ridge builds back in the wake of the ULL, and then eventually recurve. To me all this barks uncertainty, and a lot of this is going to come down to how strong Bertha is during the next week, as a weaker system has a greater chance of slipping under the high without getting picked up by the ULL. The NHC has chosen a forecast track which is a consensus of the major models, which also shows recurving.

For now it's still watch, wait, and see. Bertha's movement over the next 24 hours will be a good indicator of whether she is following the model consensus or not. Her strength should also be closely monitored, as this is the most important factor in determining her future track.






Bertha visible floater loop


Bertha IR Floater loop

Dvorak Intensity Estimates for Bertha

NHC latest Bertha public advisory

NHC latest Bertha forecast discussion


Invest 93L:

Our "little invest that could", 93L, is currently fighting for its life in the eastern Caribbean. 30-knot shear is affecting the system strongly now, but its making a valiant effort to maintain convection over a weak LLC. The TUTT responsible for the shear will be clearing out over the next couple days, relaxing the upper-level winds and giving 93L another shot, if it survives until then. Even if 93L is mostly destroyed, any remnant at all will have to be watched closely as it moves into the western Caribbean or GOM. The MJO pulse is moving into that area and anything could ignite when the upper-level winds become favorable, so this system will have to be watched closely.

We shall see what happens!



^Click for loop^

93L IR floater loop



Tropical Atlantic Bouy reports, plots, and maps

Atlantic forecast models


EUMETSAT satellite imagery

CIMSS Atlantic upper-level winds and derived analysis


National Hurricane Center

SSD Dvorak Intensity Estimates

CIMSS Dvorak Intensity Estimates


SSD tropical formation probability and other maps

Navy Tropical Cyclone Page

NASA High-resolution GOES Satellite Imagery


North Atlantic WV Loop (The Big Picture)

CIMSS Atlantic MIMIC-TPW product
(water vapor content)

Permalink

92L slowly organizing

By: Levi32, 4:09 AM GMT on July 01, 2008

Tuesday Evening Update: 92L is slowly becoming better organized today, continuing to sustain heavy convection throughout the diurnal minimum. The diurnal max tonight will be interesting to watch, and tomorrow will mark 24 hours that 92L has been over water. This is a large system, and I expect only gradual development at first. As expected, the models are all jumping around. While it is still too early to get a handle on what the future track of 92L might be, a feature that will play a critical part is already evident. An upper-level low is located at about 29n 49w, which can be seen on water-vapor imagery. This ULL will be meandering around in the middle of the Bermuda High for several days, and could instigate a weakness in the high strong enough to pull 92L northward. This is where the models diverge. The 0z run of the ECMWF draws 92L northward but then builds back the ridge turning the system westward once again in 10 days. The 12z run of the CMC this morning echoes this solution, although far more pronounced with WSW movement in 5 days. However, the 12z run of the ECMWF this morning now follows more in line with the GFS, sending 92L out into the middle of nowhere to get trapped underneath the high and eventually recurve. Part of why the ECMWF may be showing this is because it gets really aggressive in intensifying 92L into a strong hurricane by the time it reaches the central Atlantic, and the stronger the system, the more likely that it will get pulled north by any weakness in the ridge. The GFS has major issues transferring heat from the tropics to the mid-latitudes, and routinely tries to recurve most Cape Verde storms. Again, we will just have to watch and see how these factors play out. First we need to see if 92L even develops during the next few days, and if it does, its strength will play a large role in its track. My opinion is that this will eventually become Bertha down the road, possibly within the next couple days. My thinking from early this morning is still pretty much the same, so I will leave that post below.

We shall see what happens!

Previous update Tuesday morning:

After a very quiet June, the MJO pulse has moved to our side of the world, and is setting up favorable conditions for possible TC development in the month of July. The two main areas of upward motion are currently in the EPAC/GOM/Caribbean and the eastern tropical Atlantic. Currently there are no threat areas in the GOM or the Caribbean waters. Most of the action from the MJO pulse is focused on the EPAC with Boris, Christina, and 96E, for now. During the next couple weeks this action will move eastward and we will have to start keeping our eyes on the GOM and Caribbean for possible development.

Turning our eyes to the east, we have a vigorous tropical low/wave complex over western Africa which will emerge over the Atlantic Ocean sometime during the next 24 hours. The GFS has been forecasting development with this system for more than a week, and the rest of the global models are now unanimously calling for development as soon as the system reaches water. SSTs are nice and warm near the African coast at about 28c. Further west the water cools a bit north of 10n, and a developing storm system could have to move over a small area of SSTs below 26c(solid yellow represents 26c) before moving on to warmer waters west of 40w. Upper-level winds are gradually becoming more favorable for development in the EATL, and an anticyclone has already started to develop above the African wave. The Saharan Air Layer (SAL) as always will be an issue to consider. There were a couple major dust storms in June, but since then the SAL has been decreasing in the eastern Atlantic, and shouldn't be as suppressing as it normally is, though it will still have to be watched.

What chances do I give this system of developing? I hate probabilities with a passion...because in my opinion they are not real forecasts. I would like to see this system over water for at least 24 hours before I decide whether I think it's gonna develop, although if the models are right it could beat me to it before I've forecasted it lol =). For now I am going to move on assuming that it WILL develop.

So what's in store for the future of a developing tropical cyclone in the eastern Atlantic during the next week? Well, as I've already mentioned conditions are mostly favorable east of 50w. Right now a TUTT(Tropical Upper-Tropospheric Trough) is hanging out north of the islands and extends down into the Caribbean, creating strong wind shear that would probably rip apart any tropical cyclone attempting to advance west. You can see it on this map. Look for the cluster of cyan 50+ knot wind barbs(flags with triangles) near and east of Puerto Rico. Those barbs represent strong upper-level winds on the SE side of the TUTT. The GFS is forecasting this TUTT to start to lift out to the north in about a week, which is when our little system will be advancing on the area. It remains to be seen how things will play out then. Obviously we will get a better handle on it in the coming days.

The future track of a Cape Verde system is always a very challenging thing. The Bermuda/Azores high has been strong and extending west over the eastern seaboard of the United States so far this Summer, but the models are hinting at a trough possibly setting itself up over New England in the coming weeks, which would serve to weaken the western periphery of the Bermuda High. A developing system coming through the central Atlantic would probably have a hard time making it to the US coast in this scenario if the system passes north of the Antilles Islands. The GFS has been back and forth between fishy storm and GOM/eastern Seaboard landfall, which is to be expected. Also keep in mind that it is a fairly huge feat for a Cape Verde hurricane passing north of the Caribbean to make it all the way to the US. It doesn't happen every day, but we all know what happened to Florida in 2004. Again this is something that we will get a better grasp on as time goes on.

Regardless of whether this system develops or not, the MJO pulse will be around for the next 20 days or so, and the African wave train will be throwing many bullets into the Atlantic that will need to be monitored. As I mentioned before the GOM and Caribbean will also have to be watched for development closer to home in the next 2 weeks as the waves that don't develop in the EATL make their way west into the Caribbean and regenerate under the area of upward motion, just as they are doing right now in the eastern Pacific. We shall see what happens!





92L visible floater loop


92L IR Floater loop

Tropical Atlantic Bouy reports, plots, and maps

Atlantic forecast models


EUMETSAT satellite imagery

CIMSS Atlantic upper-level winds and derived analysis


National Hurricane Center

SSD Dvorak Intensity Estimates

CIMSS Dvorak Intensity Estimates


SSD tropical formation probability and other maps

Navy Tropical Cyclone Page

NASA High-resolution GOES Satellite Imagery


North Atlantic WV Loop (The Big Picture)

CIMSS Atlantic MIMIC-TPW product
(water vapor content)

Updated: 9:32 PM GMT on July 01, 2008

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About Levi32

Levi Cowan has been tracking tropical systems since 2002, and is currently working on his bachelor's degree in physics at UAF.

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