Monthly Archives: September 2011

Tropical Storm Ophelia, Tropical Storm Philippe & Possible Caribbean Development

The remnants of Ophelia has been getting better organized over the past two days and the remnants of Ophelia has been entering in an environment that is more conducive and as of the 5PM Advisory yesterday, Ophelia has regenerated to Tropical Depression Ophelia. Satellite imagery along with reconnaissance did indicate that Ophelia had finally developed a closed surface circulation. The upper level winds that sheared ex-Ophelia to a remnant low has relaxed and along with some warm SST’s, the regeneration of Ophelia did seem imminent. As of the 11AM advisory today from the NHC, Ophelia was upgraded to Tropical Storm Ophelia. Although Ophelia has been been wobbling, a north-northwestern track is now forecast. As Ophelia continues to head north-northwest, later during the week a very large trough will be over the eastern CONUS and eventully in the western Atlantic. The trough will turn Ophelia north and possibly turn slightly north-northeast and hopefully enough to keep the storm away from Bermuda.
Intensity is difficult to forecast as there is still shearing west of the center but possibly just enough of a favorable environment to make hurricane status later in the forecast period.

Visible Satellite

Wind Shear


Models

 


 

Tropical Storm Philippe is being affected by western shear and the low level of circulation is exposed with all the convection east of the center. Although the forecast originally was for Philippe to head north then northeast, the forecast models have changed. At the moment, Philippe is heading west-northwest but as Philippe approaches the western periphery of a ridge, a turn to the northwest is forecast and should continue for the next few days. A very deep trough that picked up Ophelia will now have pulled up and this trough will be moving eastward and the subtropical ridge will be filling in this will now have Philippe heading on a westward track for several days and there is even a chance of a west-southwest track. Shear may eventually decouple the storm and can still be hang on as a tropical storm a second trough will be over the central US but probably will pull before it reaches Philippe but this should cause a weakness in the subtropical ridge and allow Philippe to turn north and then a sharp turn to the northeast. If Philippe degenerates to a remnant low, the remnants will not be head north but stay on a westward track.

Visible Satellite

12z GFS Model at 216 Hours

 


Elsewhere in the tropics, the MJO is still forecast to in the western Caribbean and the upward motion is still signaling some type of development in that area in nine or ten days. Although the MJO was supposed to be in the area of the western Caribbean some time ago, it was delayed and all indications are the MJO will be there this time.

12z GFS Model at 360 Hours

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Tropical Storm Ophelia – A Little Stronger??

Tropical Storm Ophelia overnight intensified slightly to 65 MPH. The intensity was basically due to a reporting NOAA Buoy 41041 that had peak (one minute) sustained winds of 54 knots and a gust of 68 knots. Whether this is indicative of a trend or not, it is still impressive how tenacious some the storms this season has been so far. Strong 25-35 knots of southwesterly shear along with some dry air that is wrapping around the outer core continues to keep the convection well east and northeast of the center of circulation. The center of circulation again is visible from satellite presentation due to the strong shear will be present for the next 36-48 hours.

Visible Satellite Image

 

Wind Shear

Assuming Ophelia can continue tropical storm status, most of the global models are in agreement of an upper level trough later in the forecast period that might weaken the ridge slightly which might allow the environment for Ophelia to a bit more conducive and allow some strengthening. For me, I am not convinced that strengthening will occur even with the weakening of the ridge, at least not in the short term.

Guidance is in good agreement for Ophelia to begin the turn west-northwest, probably tomorrow afternoon or sooner, and the turn to the northwest sometime late Sunday. Ophelia will be near the southwestern edge of the subtropical ridge and the turn to the north is forecast sometime early next week. Intensity is always difficult to determine, but I do not believe Ophelia will make hurricane status.

Steering Current

 

Ophelia Models

 


Elsewhere in the tropics, at the moment there is nothing to report about but there is the possibility of development later on in the Western Caribbean and the southern GOM. The MJO has continued to forecast that the strong upward motion and the environment in those areas will be conducive for some type of development sometime in the first week of October. The GFS and Euro models have been off and on for any development so we will just have to see…

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Tropical Storm Ophelia

Invest 98L has been upgraded to Tropical Storm Ophelia as of the 11PM advisory last night from the NHC. Due to strong westerly and southwesterly shear, Ophelia will struggle and any increase in intensity will be gradual. At the moment, the LLC is exposed and all the convection is to the east of the center due to the strong westerly shear. Ophelia is south of a subtropical high pressure ridge. For the next 36-48 hours Ophelia will be heading westward or just north of due west, after that the forecast is for a deep layer trough to dig down as it heads off the eastern coast of the US. Ophelia will be on the southwestern periphery of the ridge and the trough will turn west-northwest then northwest. Eventually, the trough will turn Ophelia north and then northeast.

Visible Satellite Image


 
Wind Shear


 
Steering Current

Before Ophelia gets close or near the northern Lesser Antilles, shear may relax a little and allow some strengthening. Once Ophelia begins to get close to 60°W longitude, shear is forecast to strengthen significantly and at that point, further intensity will be difficult, if not impossible. Once Ophelia begins the northern turn, the upper level winds may begin to ease and allow some more strengthening, but that is part of the long term forecast – so the dynamics may change.


 


 

12z GFS Model


 
00z Euro Model

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Invest 98L

The tropical wave tagged as Invest 98L about 1400 miles east of the Windward Islands has continued to develop and is much better organized than yesterday. Conditions are now much more favorable for the few days 98L may develop into a tropical depression possibly as soon as tomorrow. Most of the major players in the global models guidance are in agreement for Invest 98L to develop as a tropical storm as it continues to head westward and eventually into the eastern Caribbean. That said, both the European and the GFS models do want to weaken 98L possibly to just a tropical depression, mostly due to a ridge of high pressure that is forecast to strengthen along with increasing shear. This should cause 98L to accelerate it’s forward motion leaving the convection behind and eventually decoupling whatever is left of 98L back to just a tropical wave.

Dependent on what is left of 98L and also what the track guidance will be, regeneration may or may not occur. If 98L continues it’s westward track and can pass through the “graveyard” (an area near Hispaniola hostile for storms) somewhat intact, as it gets to 75°W longitude there is the slight chance, of regeneration, albeit very slim. More likely than not, 98L will not track westward but a more west-northwest and affecting the Leeward Islands and possibly Puerto Rico, although it would be more of a rain event than a wind event due to the shear.

 

 

 

Models

 

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Tropical Storm Maria Still Struggling

Tropical Storm Maria, a resilient storm with maximum sustained winds of 50 MPH (a decrease from yesterday of 60 MPH) continues to struggle despite all it going through. Again, the convection is to the east of the center of circulation and satellite presentation shows the “naked swirl”. Maria is again heading westward but at a turtles speed of about 1 or 2 MPH. Whether this is the beginning of the turn or not is to early to tell. Due to the westward movement, models tracks have been shifted slightly to the left of the original. An upper-level low to the northwest of the storm is creating 20-25 knots of westerly shear and not allowing Maria to better organized. The shear is forecast to decrease slightly in a few days which may allow some gradual strengthening but this is for a short window of time. A sharp increase of shear is forecast and along with some of the upwelling from where Hurricane Katia’s track was will keep Maria in an unfavorable environment and limit further intensification, if any.

IR Satellite Image

Wind Shear

The global models are in very good agreement as to what track Maria will take. A mid to upper level trough which is currently over the eastern US will slowly begin to turn Maria to the north in about 36-48 hours. Another trough, this one much deeper and stronger, later during the week will eventually turn Maria to the northeast along with an increase in the forward speed.

First Trough

Second Trough

Model Tracks

 


 

Elsewhere in the tropics, a few of the models (long term) are hinting that some tropical mischief may appear somewhere between 10 – 14 days most likely in the mid to western Caribbean or the Gulf of Mexico. The MJO does show upward motion (in green) in that area during those time frames. We will have to see if anything does develop.

Madden Julian Oscillation

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Tropical Storms Maria & Nate

Tropical Storm Maria is just barely hanging on enough to still be classified as a Tropical Storm. The center of circulation is well east of the convection and the entire storm is elongated. Maria started to make the more true WNW direction yesterday and now a NW direction. A few days ago, the forecast for the ridging of the subtropical high in the Atlantic was to strengthen and keep Maria a more WNW track. As of yesterday, it appeared that the ridging was not going to be as strong. Maria will soon be near the southwestern side of the ridge and due to an approaching trough to the southeast US coast, Maria will be heading NW and eventually a turn to the north is forecast. The track guidance confidence within the models seems to be very high and when that usually happens, 95 percent of the time it is correct.

At the moment, there an upper level low to the NNW of Maria and the flow from the ULL (SW shear) along with some flow from a high to the east of Maria. The combination of the two is inducing a hostile environment for further development for Maria. The ULL is slowly moving away to the northeast and the shear levels will be reduced allowing some strengthening within 24-48 hours and eventually enough for Maria to become a hurricane later on in the forecast . Although the track guidance is very clear, intensity will be a problem. Category one hurricane status seems to be foreseeable as long as Maria does develop but I don’t believe a category two storm is probable, but I don’t want to rule it out either.

Overall, the Leeward Islands and possibly Puerto Rico may have tropical force winds, but since all the winds are in the area with the convection which is east of the center, this most likely will not happen but those in that area should monitor just in case . The Bahamas this time seem to be spared but any westward movement could allow some higher winds to the the Bahamas and although it is highly unlikely, the Outer Banks of North Carolina.

 


 

Tropical Storm Nate which for days was somewhat adrift has finally been tracking almost due west toward Mexico. Tropical Storm Nate who was drifting for those days has had problems with both dry air intrusion and the depths of the ocean there is somewhat shallow, upwelling also seemed to keep Nate from strengthening. As Nate is heading away from the cooler waters, further strengthening should occur. Due to the bowl shape of Bay of Campeche, convergence may help Nate in strengthening for a short period of time before land interaction will stop further intensification.

Nate at the moment is in an environment of low shear and Nate may intensify enough to become a hurricane not to long before landfall. Once landfall begins, Nate will begin to lose it’s strength and identity as it heads into the mountains.

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Hurricane Katia, Tropical Storm Maria & Tropical Storm Nate

As Hurricane Katia traverse’s through cooler waters it appears that Katia is also having serious problems with dry air entrainment that is wrapping around from the southwest and into the inner eyewall along with moderate shearing. Katia is now a mid-category one storm and intensification is not indicated, in fact, the weakening process will continue for at least the next 24 hours. Due to the cooler SST’s any attempt to intensify with the shear decrease later in the forecast will be nullified by the SST’s. Once Katia begins the transformation to extra-tropical, Katia may slightly intensify, in 72- 96 hours during the transformation. Katia is heading NW at the moment but will be making the turn to the north within the next 24 hours and later turn to the NE while also accelerating and into the westerlies.

 


 

Tropical Depression Fourteen was upgraded to Tropical Storm Maria the 11am advisory from the NHC. As Hurricane Specialist Lixion Avila stated “…and yet another tropical storm in the Atlantic…” in the NHC Tropical Weather Outlook, it seems we are definitely in the peak of the hurricane season.
Tropical Storm Maria is heading just west of due west-northwest and the forward motion is currently at 23 MPH. If this continues, the Low-Level Circulation may out run the mid to upper levels of the convection. If so, Maria will have a very difficult time organizing and trying to intensify or at least it would be gradual. At the moment, the environment is not that conducive for further development as upper level winds in the 20-30 knot range may affect Maria but the overall pattern should allow for slow strengthening.

Although it is a little to early where Maria may head, the latest model runs with the exception of the BAMM (Shallow) tend to have Maria north of the Leeward Islands in several days. For what it’s worth, my own opinion is that the model are still a little biased to the north and although I believe the more turn to the WNW will happen, the more “western” track will happen before making the turn, thus this might be a much closer to the islands than forecast. As Katia leaves the scene, the sub-tropical ridge will want to build and keep Maria on that western track until finally heading on a more west-northwest track along the periphery of the southwestern edge of the ridge. A deep layered trough is forecasted by some of the models by 72 hours to be near the East coast of the US about the time Maria will be close or near the Leewards Islands. This trough should make Maria turn toward the NW and later to the north.

 


 

Invest 96L has been upgraded to Tropical Storm Nate as of the 5pm advisory from the NHC. Although Tropical Storm Nate had been “suggested” that it would develop to a at least a tropical depression, recon flew into the storm and found winds at flight level of 53 knots (un-flagged) or about 42 MPH at the surface, thus the storm was initiated as Tropical Storm Nate. As has been noted earlier, Nate has been drifting somewhat as the steering currents are quite weak. With the weak steering currents which may hang around for a few days, Nate will be in warm waters but there is vert dry air to the NW of Nate and this dry air (as been with many of the storms this year) may impact Nate later in the forecast period. Models at this time feel that Nate, in time, will be influenced by a developing ridge in the western Caribbean and making Nate turn to the west and into Mexico. Although this scenario may play out, if Nate moves further north, Nate will be north of the developing ridge and would then head toward the Gulf states or the Florida panhandle. It is just to early to say how this will play out with Nate.

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Hurricane Katia, Tropical Depression Fourteen, & Tropical Trouble in the Gulf – Invest 96L

Hurricane Katia, which last night had been upgraded to Category Four Storm has lost some of it’s intensity and decreased organization and in now down to a Category Two hurricane. Katia may be in the process again of going through an Eyewall Replacement Cycle but shear and dry air to from the northwest and west may have gotten into the outer core. Katia seems be reaching much cooler waters in the western Atlantic thus further intensification is not indicated. The good news is that Katia is forecast to be on a track that is optimum where the center of Katia will pass between and Bermuda as it makes a sharp turn to the northeast later in the forecast. There is a very good consensus within the models as far as the track is concerned.
No matter there Katia’s track will be, those along the east coast and Bermuda beware of rip tides and large swells!!


Invest 95L which continued to develop during the day has been upgraded to Tropical Depression Fourteen as of the 5PM advisory from the NHC. This no surprise as Tropical Depression Fourteen began to look very healthy and this is the peak of the hurricane season. Although the upper level winds are only marginal for TD 14 to develop, it is forecast to continue it’s development slowly. There is still a spread between the models as to the forecast track, but a WNW track should continue along with a decrease in it’s forward motion.


Invest 96L which was tagged late this afternoon is a system that was ready to start as that area has been near the monsoonal flow near the East Pacific. 96L is part of the energy left from the tail end of now remnants of Lee, now combining with the monsoonal flow. The MJO is in the upward motion in this area and 96L was forecasted to develop by some models. Most of the models at the moment want to take 96L into Mexico, which still may be the case but another possibility might be for it to be pulled up and head toward the Alabama/Florida Panhandle possibly as a tropical storm or low end category one hurricane.

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Hurricane Katia & Invest 95L (Pouch P24L)

Hurricane Katia regained hurricane status again yesterday then the Rapid Intensification leveled off. Katia is a category two hurricane but the environment will be in place for Katia to intensify again to a category three storm. During the early morning hours, Katia was struggling for a short period of time as an Eyewall Replacement Cycle (ERC) was allowing some dry air to enter the inner core of the storm. This has finished and Katia started to have a very large eye but is now contracting, and the upper levels of the environment became conducive for further intensification within the next 6-12 hours and as of the 5PM advisory today, Katia became a category three hurricane. Oceanic heat will not be a factor this time so intensification will be limited for 48-72 hours or so. After that forecast period, vertical shear will be on the increase along with cooler waters. No matter where the storm goes, there will be very dangerous swells and rip tides, along the US east coast and Bermuda, please be careful!!!
EDIT: Extremely Powerful Hurricane Katia has been upgraded to category Four storm, as of the 11PM advisory for the NHC.

Katia is moving NW around the southwestern periphery of a central Atlantic high pressure system(subtropical ridge) and also a very deep trough that is in the eastern US and the western Atlantic ocean. Although there are some differences in the models, there should be a decrease is the forward speed within the next 36-48 hours. The track guidance within most of the models is very good and a very sharp recurve is forecast that hopefully will take the center of Katia between Bermuda and the the US east coast.


Invest 95L is a strong and very well established tropical wave with excellent cyclonic turning. The environment for Invest 95L will be conducive for further development and a tropical depression may form within the next 24-48 hours, if not sooner. Since this system has really just got started and the time the models were initiated, track guidance will not be the best in the beginning runs. Furthermore, there is no LLC as of yet and it seems at least this year, many models have had a bias too much to the north. The GFS 18z run has 95L well east of Florida at 156 hours where as the Euro (ECMWF) has it just off the coast of Florida at 216 hours. Whether or not 95L develops and if so, will it be a low rider (heads due west into the western Caribbean) or is a storm that may affect the Windward/Leeward Islands, Bahamas, Florida – is just to early to forecast at this point.

GFS Model at 156 hours

ECMWF Model at 216 hours


Elsewhere in the tropics, Some models are hinting that there might be some development of a system in the Bay of Campeche in the Gulf of Mexico. The GFS run has backed out for now but the ECMWF is still hinting something will form. With the Monsoonal trough near the East Pacific and especially the MJO in a upward motion in that area in 8-10 days from now, development is not far fetched.

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Katia, A Temporary Downgrade to Tropical Storm

Hurricane Katia has been downgraded be to Tropical Storm status as Katia’s low level core is at least 3/4th exposed. Several factors have created this possible downgrade, but the major problem Katia is having southwesterly shear. This shear is mostly being caused by an upper level low to the northwest of Katia. This upper level low is forecast to eventually lift out which should allow a much better environment of upper level winds aloft. Katia is also having problems with dry air intrusion which is disrupting the circulation of the storm. This seems to have been the problem for a majority of the storms this year.

Although Katia has been downgraded, all indictions are that this is just temporary and Katia will regain hurricane status, possibly in 24-48 hours and should still be a major hurricane in a few days.

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