Weather456's Tropical Weather Blog

Tropical Week

By: Weather456, 4:55 PM GMT on July 19, 2008

Recapping the Week....

Hurricane Bertha

Bertha left Bermuda and continued to chug its way across the Atlantic first towards the northeast, then southeast, then resumed her northeast motion. Bertha longevity made her the longest lived pre-August Atlantic hurricane on record and the longest July Atlantic cyclone ever. Bertha is also the longest lived tropical cyclone since Ivan 2004 and her ACE surpassed all storms in 2007 except Hurricane Dean. After remaining a somewhat anemic tropical storm, Bertha was upgraded to a hurricane a third time on Friday at very far latitude. She continues to remain a well-organized hurricane and is nearing her extratropical transition stage as indicated by QuikSCAT sea winds and the frontal band ahead to her left of motion. She is really a classic long-lived hurricane, and we've seen few since 2004.

goes-12 Visible of Hurricane Bertha

Tropical Depression Three

Tropical Depression Three formed off the SE US Coast late Friday night and strengthen early on Saturday. Currently the depression is remains fairly organized but injecting a good amount of continental dry air from the mainland and thus much of the western periphery is void of deep convection. Despite this, he remains a strengthening a depression and posed to come TS Cristobal in the next 24 hours. The depression is moving over warm sea surface temperatures and wind shear has weakened a bit to 10 knots and thus modest intensification is expected. The depression is on the western side of a deep layer ridge (Bermuda High) and thus a northeast motion is expected and this could bring it near the Outer banks of North Carolina as a modest to strong tropical storm.

Tropical Invest 94L

This feature never made it to TD status as it moved through the Tropical Atlantic early this week and the Eastern Caribbean later. Currently the system is producing vigorous convection on the Central Caribbean but a QuikSCAT passed this morning showed an open wave. The hurricane hunters are currently investigating the system. The system is embedded within the southwest flow of the Caribbean low level jet and thus a northwest motion is expected which should bring it near the Yucatan in a day or two. After which it would either enter the Bay of Campeche or the Gulf of Mexico which would leave anywhere from SE Mexico to SW Louisiana open.


Some of the global models are hinting more development off the coast of Africa as a strong tropical wave emerges over the next several days.

Goes-12 Visible of Tropical Depression Three and Invest 94L

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Active Tropics

By: Weather456, 10:57 PM GMT on July 14, 2008

Tropical Storm Bertha

Slow moving Bertha continues to rake the island of Bermuda with high winds, heavy rain and choppy seas. Many residents, despite warning were rescued after being caught in rip currents over the weekend.

Dangerous rip currents were occurring along the U.S. East Coast from the Carolinas through southern New England, according to the hurricane center. Officials said that may have contributed to at least one drowning Saturday along a New Jersey beach.

Bertha was swirling north at near 9 mph (15 kph). It was expected to bring 3-5 inches (8-13 centimeters) of rain to Bermuda. A turn to the northeast was expected Tuesday, with a turn to the east expected Wednesday.

Source: AP

Satellite loops of the slow storm showed improvements from the more anemic appearance a day ago and it is likely she will re-intensify into a hurricane. She is one of my favorite storms tracking since I began in 2002. Bertha will continue off towards northeast then curve towards the southeast. Afterwards she would resume her northeastward motion. This is mainly due to the steering flow Bertha is embedded in – that is – on the northern edge of an omega high.

Tropical Invest 94L

An area of low pressure in the central tropical Atlantic remains fairly organized despite decrease in the amount of convection. Compared to 24 hours and even 48 hours ago, the disturbance has organized a great deal. This area remains over warm sea surface temperatures, high humidity and low vertical wind shear and thus the formation of a depression in the next 24 hours remains fair. This area will continue off towards the west-northwest under the influence of the subtropical ridge. I am currently using synoptic forecasting techniques and discarding the models until the area fully develops to my satisfaction.

Behind 94L

If that wasn’t enough, another area of low pressure likely associated with a tropical wave is located near 10N/23W. Satellite imagery (below) showed the impressive deep convection to the south and west of the suspected low level center based on QuikSCAT, just like with 94L on Sunday. This area, like 94L, is under 5 knots of shear, over warm SSTs and embedded within the moisture field of the ITCZ. It is my thinking that if this area continues to organize as it is, will likely become Invest 95L and who knows, beat 94L to TD 3. The area will be monitored as it moves slowly towards the west.

MSG Infrared Image from 5:00 pm EDT

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Trouble A’ Brewing In the Tropics

By: Weather456, 12:15 PM GMT on July 13, 2008

An area of disturbed weather is located in the central Atlantic with a 1009 mb low attached near 10N/34N has the potential to develop into the season third depression. It was dubbed 94L by the Navy as an area of interest this morning. Latest RGB and infrared satellite animations showed a decent lower level spin with most of the deep convection to the southwest of the wave/low axis due to easterly shear. QuikSCAT also showed strong west winds (rain contaminated) in the southwestern quadrant of this system. These are good signatures of development, as we see with the precursors of typhoons in the Western Pacific. Any signs of development would be consolidation of that convection near the wave/low axis and this should occur as environmental conditions improve over the next couple of days.

The confusion exists where the NAVY has the area centered near 36.4W, which is what I am seeing on satellite imagery and the NHC has a tropical wave and low position near 33W. My thinking is they will either adjust it on the next surface map at 11am or this area of disturbed weather is separate from the wave.

The global models agree on formation but are inconsistent with the track. The GFS has the system moving off towards the northwest once it develops, while other models are diffuse. What the GFS is hinting is that Bertha will create a weakness near 50W-65W which would cause this area to travel northwestward however, my thinking is west-northwest because the GFS has Bertha a stronger feature than it is now, and thus that weakness should not be as strong as the model is hinting. After which, we both agree that a westward motion will resume once the storm passes 60W.

It’s rather too early to speculate if Bertha will affect the islands and wherever else beyond. But based on the information the islands should continue to monitor Invest 94L. It is pretty far south and not developed yet, so even a direct northwest motion could placed it too close to comfort near the Leewards.

Infrared Image of Tropical Invest 94L

Tropical Storm Bertha

Bertha has weakened to tropical status and this is supported by the signature seen on visible imagery where most of convection is rather ragged and sloppy and displaced towards the southeast. Bertha’s really caused her own weakening by sitting over waters for hour pun’ hours, upwelling cool waters. If she doesn’t move, she will continue to degrade until she is picked up by the next trough so Bermuda should still watch her.

Bertha (Right) and South Carolina Disturbance (Left)


An old frontal boundary has move off the East Coast and we all know July is famous for these developments; the last was Tropical Storm Beryl in 2006. The area will be monitored for development as conditions seem favorable. Anything forming in my opinion will either diverge into Georgia, South Carolina or North Carolina or out to sea. My thinking is northeastward into North Carolina. QuikSCAT morning pass is currently processing the area.

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Hurricane Bertha and the Central Atlantic Disturbance

By: Weather456, 1:29 PM GMT on July 12, 2008

Good Saturday morning to all!

A tropical storm watch remains in effect for the island of Bermuda has Hurricane Bertha inches ever so closely to the island. Satellite images showed Bertha has a very large eye but a nice symmetrical cloud canopy. She appears to be moving at a rather sluggish pace towards the north-northwest, almost looks stationary on the last few satellite frames. Satellite imagery and QuikSCAT showed a typical re-curvature situation with a frontal trough to its northwest and southwesterly flow ahead of this trough. This southwesterly flow will lift Bertha towards the north and northeast over the next couple of days. Thus process normally takes 24-48 hours to occur but due to the nature of this frontal system, Bertha will be us at least up to Wednesday – a very long lasting storm indeed. As Bertha lifts and the ridge rebuilds, that would set the stage for another disturbance I am watching in the Central Atlantic.

Hurricane Bertha with surface observations overlaid

A tropical disturbance located near 40W-30W is being monitored for tropical development. The area can be pin-pointed now to 9N/35W where a surface low is located. This morning's visible and RGB imagery of the central tropical Atlantic showed define spinning along this feature but strongest in the lower atmosphere at this moment with little to moderate convection. This appears to be the area the models are hinting on. There is another area of greater surface vorticity just near 30W-28W that also maybe entwined in this situation. There is a lot of westerlies equatorward this area, very low vertical wind shear and high moisture, so the area if ripped for cyclogenesis and along with the model support, development seems fair. This one is far more south than Bertha when it was near 35W and is more likely to threaten the Northwern Leewards. This is something I am watching very closely. Vertical wind shear is/and will be very low for a large portion of the Atlantic.

Infrared image of the tropical Atlantic at 7:30am EDT. The area of interest is the centered feature

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Hurricane Bertha and 3 other areas

By: Weather456, 10:43 AM GMT on July 11, 2008

The hare is now a turtle

Hurricane Bertha has gone from the speeding hare to the dawdling turtle. She is now moving slowly towards the northwest near 6 knots. She has slowed down in response to the effects of a mid-latitude frontal trough just to its northwest. Satellite imagery showed Bertha remains an impressive hurricane with outré and inner banding and two eye walls, which is quite good to look at from the boring normal hurricane that has all the features we are accustom to in symmetrical order. Bertha will basically remain over warm waters with low ocean heat potential and low shear over the next 2-3 days, so she should maintain hurricane status. Thereafter, vertical wind shear will increase over Bertha prior and during re-curvature by the trough.

Bermuda’s battle ground

Bermuda is right in the middle between Bertha and the frontal trough. This has brought in the whole idea of timing into play. Bertha could affect Bermuda if that trough does not approach at the right time, or Bertha can re-curve out to see without affecting Bermuda. My idea is that, she will approach the island but then re-curve just to its east, with the outer bands affecting the island.


The models want to develop a cut off low off the SE Coast around this weekend into next week. Anything forming may be baroclinic in nature but can become subtropical over the Gulf Stream. Anything forming will also meander northward so it can travel out to sea or move into Georgia or the Carolinas.

The other area is an area of disturbed weather in the Southwest Caribbean that is associated with broad area of low pressure. The models are showing development in the Eastern Pacific from some of the energy of this feature. Meanwhile, the Atlantic side will continue to monitor the area. Satellite imagery showed an intense burst of convection associated with this feature.

Last but not least, another impressive wave has exited or exiting the coast of Africa that has the potential to develop into a tropical depression. Convection has waned with the wave, typical of waves moving off but there is decent mid-level turning and thus should be watched as it travels westward into favorable conditions, where the global models are hinting development. It rather too early to speculate impacts in the Windwards/Leewards but it will not be another Bertha, in terms of track.

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Tropical Update

By: Weather456, 10:40 AM GMT on July 10, 2008

Hurricane Bertha

This morning’s satellite images of Hurricane Bertha showed an impressive and expanding hurricane with expansive outflow jets despite a clouded eye. The hurricane continues to push off towards the northwest at a decreasing rate due to the presence of high pressure ridge to its north with a recent jog towards the west around 1945 UTC. This northwestward motion is expected over the next day or two. Hurricane Bertha or what will be left of it basically has a good amount of time with us. She is expected to re-curve under the influence of a mid-latitude trough in 4-5 days time around 35-40N. Sea surface temperatures are warm enough to support tropical cyclone as far north as 35N but vertical wind shear may increase over Bertha causing her to weaken just before and during re-curvature and extratropical transition. Bertha will most likely be with us tomorrow, which would be 11 days active, the longest lasting hurricane since Hurricane Helene of 2006. If she surpasses 12 days, she would be the longest lasting storm since Hurricane Irene of 2005 and if she surpasses 14 days, she would be the longest lasting storm since Hurricane Ivan in 2004.

Early morning visible image of Hurricane Bertha


I am watching an area of disturbed weather in the southwest Caribbean that appears to be associated with the ITCZ extending from the Eastern Pacific. The area will be monitored as conditions appear conducive for development and the GFS is hinting a weak area of low pressure to move towards the northwest, along Nicaragua then west into Honduras/Belize.

The models are persistently developing an area of low pressure in the Eastern Atlantic this weekend. First it was the GFS, then CMC and now the UKMET and ECMWF are onboard. I don’t see any active convective cells that may pose as candidates but conditions are expected to be favorable to support development so the situation will be monitored.

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Hurricane Bertha & The Tropics

By: Weather456, 9:06 PM GMT on July 09, 2008

I apologize for my absence over the past couple of days, but my blog is back and up.

The first hurricane and first major hurricane of the 2008 Atlantic Hurricane Season formed on Monday in the open Central Atlantic. Just as the storm quickly intensified on Monday, the following day it quickly weakened due to increase in vertical wind shear. Now, the storm is blossoming, impressive on satellite and microwave imagery. She is now up to 105 mph with a central pressure of 970 millibars as she traverses the warm waters*. Hurricane Bertha 2008 is the earliest Cape Verde-type hurricane I can found, beating the old record of Hurricane Bertha in 1996. Can you say déjàvu? Bertha even beat Hurricane Emily of the record breaking hurricane season 2005.

Where will Bertha go?

Bertha will continue slowly towards the northwest and north-northwest due to a bridging high to its north. As this high weakens as the next frontal trough exit the US east coast in 3 days, Bertha will traverse more towards the north and northeast. On this track Bertha should gradually strengthen then over the next day or two and then weaken over the baroclinic environment of the extra tropics. Don’t be surprise if Bertha becomes a cat 3 that far north. Alex did in 2004.


There are two areas of interest; a broad area of low pressure in the Southwest Caribbean and a tropical wave in the Eastern Atlantic. Both will be under marginal and favorable conditions over the next day and the SW Caribbean disturbance shows promise but no model support with the latter having more model support. More updates on these two areas as times goes on. Anything forming in both situations will travel west northwestward.

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Blog Updates - Tropics

By: Weather456, 10:38 AM GMT on July 08, 2008

Due to some unforeseen circumstances, I cannot update my blog in the day like before on week days. So starting from tonight, my updates will be posted 7 pm nightly.

Other than Bertha, there is another tropical wave along West Africa that I am watching for the potential for development. Updates later.

Tropical Storm Bertha & The Tropics

By: Weather456, 3:42 PM GMT on July 06, 2008

Tropical Storm Bertha

Tropical Storm Bertha is located near 17.4N/45.1W moving off towards the west near 18 mph with sustain winds of 50 mph and a minimum central pressure of 1000 mb. Recent visible imagery showed Bertha producing deep convection in and around the center of circulation as she transitions from 24C-25C to 26C plus waters. I expect Bertha to intensify some today and on Monday based on these warm sea surface temperatures and low vertical wind shear. I expect this intensification to be rather slow due to dry air ahead of the system. Satellite imagery is still showing sparse low clouds 1000-2000 km ahead of Bertha, which is an indication of the environment she is moving into to.

I am quite impressed that she manages to producing regular bursts of convection while moving over 25C waters and dry air. Tropical Storm Debby (2006) also originated from a strong tropical wave but never took flight due to dry air. This year is different as the waves are wetter and stronger and more able to stand up to the environment in the Eastern Sub-tropics.

Where will Bertha go?

Bertha will continue off towards the west, then west northwest over the next 3-4 days on the southern periphery of a deep layer ridge. After which, a mid-latitude trough is expected to exit the East Coast and create a weakness and reduce ridging Bertha’s forward speed. This where the fun begins. The trough is expected to quickly dissipate and pull over Eastern Canada, at which time Bertha is south of Bermuda still. What happens when the trough is gone and the ridge builds back? Is there another trough? Those questions are why Bertha re-curvature is a 50/50 chance. We will have better ideas when the storm approaches 60W.

Elsewhere in the tropics

I am watching one other area, which is a tropical wave just to the southeast of Bertha that has the potential to be declared our next invest. Currently, there is little change in organization but conditions are favorable for development. Anything forming will follow a trend similar to Bertha but much further south.

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Tropical Update

By: Weather456, 12:12 PM GMT on July 04, 2008

Good Friday morning to everyone and Happy 4th of July to those in the United States.

QuikSCAT Image of Bertha

Recently upgraded Tropical Storm Bertha continues to push off towards the west-northwest near 14 mph with maximum sustain winds near 45 mph and minimum central pressure down to 1002 millibars. The storm is located at 14.2N/28.3W. Recent visible animations of the Central Tropical Atlantic showed Bertha is producing decent burst of deep convection near her center of circulation despite the stable environment she is embedded and moving into to. The visible animations also showed a surge of northeasterlies just to Bertha’s northwest, which would have an effect her forecast path, which is discussed below. Bertha is currently moving over sea surface temperatures of 25C, which is below the 27C needed, and that is why most of Bertha’s circulation comprises scattered low-level clouds. Intensification should be slow over the next 48 hours until Bertha reaches progressively warmer waters near 40W. After which, intensification will speed up a bit and she could become a strong tropical storm.

Bertha will continue off towards the west-northwest track over the next 3 days but then re-curves her further west that previously stated. As I mentioned above, a surge of northeasterlies are just ahead of Bertha, which indicated that the high has shifted and changed in strength, which would imply a more westward movement by Bertha, and this is reflected in the latest NHC forecast track which doesn’t show re-curvature until Tuesday/Wednesday.

Bertha brought squally weather to the Southern Cape Verdes, but wind reports indicated none of the tropical depression or storm forced winds reached the islands.

Bertha is the most eastern forming tropical cyclone in July.

This week, 12 years ago, we had another Bertha out there in the Eastern/Central Atlantic. I would enter a lottery right about now. =)

Visible Image of Bertha

The other area of interest is a tropical wave in the Eastern/Central Caribbean which continues off towards the west. Recent visible animations showed there is an exposed surface circulation associated with this wave near 15N/73W. This feature continues to undergo significant wind shearing and this development seems unlikely at this point. But the fact that this feature has a surface circulation, it bears watching incase wind shear slackens and shows signs of development, especially in the event it enters the Gulf of Mexico. This wave should be near Jamaica in 24 hours. Regardless of development, the wave will generate some showers for Puerto Rico and Hispaniola as it moves westward.

No other areas of interest else where. The 00Z GFS is forecasting the formation of a low pressure area in the SW Gulf of Mexico (Bay of Campeche) on Monday; I would not discount this since we have a series of tropical waves to pose as candidates. The GFS is also showing development of another tropical wave in the Central Atlantic by Monday, not impossible, look at Bertha, so this one will be monitored as it will be further south and re-curvature of this one seems unlikely at this point.

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Tropical Depression 2 & 93L

By: Weather456, 10:47 AM GMT on July 03, 2008

Tropical Depression 2 formed a few hours ago in the Eastern Atlantic at 12.6N/22.7W moving off towards the west-northwest near 9 mph. Maximum sustain winds are near 35 mph and central pressure is down to 1008 mb. Recent visible images (below) showed a well organize depression with a small dense cold cover near the center of circulation surrounded by low level banding features. The system is moving over 27-28C waters, 5-10 knots of vertical shear and embedded within a broad moisture field, which should continue to allow increase organization and tropical depression 2 could become a tropical storm later today or on Friday.

The intensity and track forecast isn’t all that different from the last update. The depression will continue to move off towards the west-northwest for the time being (over the next 3 days) under the influence of a deep layer ridging to its north. Afterwards the storm should encounter a weakness within this ridge and turn more towards the northwest. On this track, 92L should encounter a region of sub-27C waters and a more stable environment (indicated by the stratocumulus clouds ahead of the system) and thus fluctuations in intensity are expected, but a general intensifying trend is expected.

Visible Image of Tropical Depression 2

The other area of disturbed weather is a tropical wave located within the Eastern Caribbean. Currently, satellite animations showed the wave has begun to interact with the southwesterly flow ahead of the tropical upper tropospheric trough (TUTT) and little development is expected of this area in the next 48 hrs. Despite development, local showers for the Northeast Caribbean islands can be expected. The area will be monitored for changes as it moves off towards the west-northwest, and should not be totally discarded until the fat lady sings.

GOES-12 Infrared Image of Tropical Invest 93L

Elsewhere, no other areas of concern.

Organizing 92L

By: Weather456, 10:41 AM GMT on July 02, 2008

Tropical Invest 92L wants to become 2008’s second depression. The tropical disturbance is located near 10.8N/16.5W at 2am EDT moving off towards the west near 15 knots. A recent QuikSCAT pass of the system showed a well-define circulation with associated winds of 25 knots or greater, with atmospheric pressure now down to 1009 millibars. However, recent satellite animations showed convection has waned with this system but overall organization has improve considerably over the past 24 hrs since it exited Africa with excellent outflow and banding features present. The system is moving over 27-28C waters, 5-10 knots of vertical shear and embedded within a broad moisture field, which should continue to allow increase organization and 92L could become a depression later tonight or on Thursday.

The 00Z global models are in consensus that 92L will develop and track off towards the west-northwest in 3 days, then turn more towards the northwest with time. One this track, 92L should encounter a region of sub-27C waters and thus fluctuation in intensity is expected. However, this occurs near 30W-40W and seems to be the only inhibitor for the time being. I expect a moderate to strong tropical storm from this disturbance based given information. As for the track, the global models begin to diverge a bit after 6 days, with the CMC further west and the GFS further east. This is due to the two different timings and strength of a mid-upper level circulation/trough that is expected to be in the Central Atlantic to influence the subtropical ridge. The GFS just stalls the system in the Central Subtropics in 7-8 days. However, track is unimportant right now, until 92L develops and the models have a better handle.

There are no other areas of concern or interest out in the tropics.

Infrared image of Tropical Invest 92L

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Tropical Invest 92L

By: Weather456, 10:58 AM GMT on July 01, 2008

The strong tropical wave mentioned yesterday has now exited the coast of Africa and wasted no time in being recognized by the National Hurricane Center (NHC) as Invest 92L. The disturbance is located near 10.8N/16.5W, moving off towards the west near 15-20 mph. This morning’s infrared images showed a fairly organize system with a series of convective bands in and around the center and the eastern quadrants. Visible imagery along with a partial QuikSCAT pass showed there is an associated somewhat broad surface circulation with this system based on the west winds observed south of the center and the NHC 06Z surface analysis chart confirmed a 1011 mb low along the wave. This actually places it in stage 1 of development (suspect area) and should be monitored for increase in convection and organization beyond the diurnal cycle. There is an upper anticyclone over the system and the resultant outflow is creating some easterly shear over the system’s convective bands, which is a favorable situation for development. Along with warm sea surface temperatures and increase organization, the formation of a tropical depression in 24 hrs seems good.

Where will 92L go?

It all depends on the strength of the system despite what models may say. The models basically take the system west-northwest in the initial weak stages, then northwest into the tropical Atlantic as a fairly strong tropical cyclone. However, the CIMSS steering product showed a two-path steering flow. If the system stays weak, a more westward movement is expected and if it develops as the models say it will move towards the northwest. Now, knowing that, I believe this would intensify, and so I’m going to go on the model sides, and this is very good news for the islands. One thing I noted is that the future path takes it across some waters below 27C in the central Atlantic and thus some fluctuation in strength is expected.

MSG-2 2km visible image of 92L Invest

There is a frontal boundary sitting off the coast of the Eastern United States that I will watch incase something tries to manifest considering marginal-favorable upper winds.

Otherwise, there are no other areas of interest.

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The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Weather456's Tropical Weather Blog

About Weather456

With a Bachelors Degree in Environmental Sciences (2009), began tracking tropical storms in 2002 and is now a private forecaster.