Julia Weakens into a Depression; TD Twelve Moves Out of Cabo Verde Islands

Tropical Storm Julia weakened into a tropical depression early Thursday morning. The storm was in an upper level regime of strong westerly wind shear, pushing the majority of the convection to the east of the low level center. As of 11am, the storm’s center was located about 125 miles ESE of Charleston, South Carolina with maximum sustained winds of 35mph. The minimum central pressure was at an unimpressive 1010mb and was moving East at 8mph. However, it’s forward motion is expected to slow during the day on Thursday.

florida-visible-satellite

While the storm is still occasionally bringing showers to coastal South Carolina, the worst of the storm should stay well offshore. The strong wind shear will continue to push the worst convection and strongest winds to the east of the center and therefore, offshore (image below courtesy University of Wisconsin).

wind-shear

The official track forecast from the National Hurricane Center remains fairly complicated, though it is a bit farther east from the previous forecast. As Julia’s forward speed east slows, it’s expected to double back and head back toward the SE coastline. However, the high wind shear should keep it from re-strengthening much if at all. It’s expected to become a remnant low by this weekend, perhaps still bringing a few showers to coastal Carolinas over the next several days.

julia

Tropical Storm Ian continues to accelerate to the north in the Atlantic. The storm was located nearly 900 miles ENE of Bermuda, and moving NE at 24mph. Maximum sustained winds were 50mph and central pressure was at 998mb. The storm will accelerate and perhaps strengthen a bit over the next day before transitioning to extratropical on Friday.

ian

Meanwhile, in the Northeast Atlantic, Tropical Depression Twelve has emerged from the Cabo Verde Islands with an impressive low level circulation. However, moderate wind shear continues to plague the system and has thus pushed all the convection away from the center. While the wind shear should remain moderate to high over the next couple days, it should slacken by this weekend after which TD Twelve may become Tropical Storm Karl. While the forecast is far from certain, the official NHC forecast does call for Karl to form by Monday several hundred miles east of the Lesser Antilles.

td12

Besides wind shear, the other issue that Karl may deal with is dry air associated with the Saharan Air Layer. The map below (courtesy University of Wisconsin) shows dry air east and west of the depression which could impact its future.

saharan-air-layer

If the storm does survive the dry air and higher wind shear, the forecast path becomes rather interesting. Not all of the models or their ensemble members re-curve TD Twelve out to sea. The 00Z Thursday operational run of the European model brings the storm northeast of the Bahamas by next weekend. With plenty of time between now and then, lots can and will change with this storm. We’ll continue to watch it closely.

ecmwf-mslp-and-precip-rate

 

Tropical Storm Julia Drenches Coastal GA & SC

Tropical Storm Julia formed on Tuesday night after a quick day of organization on the Florida east coast. What makes it even more peculiar (in addition to its unexpectedly quick development) is that it technically was over land when being designed a tropical storm. According to Colorado State University hurricane researcher Phil Klotzbach, Julia is the first tropical storm on record to be named while over land in Florida. As of 11am, Julia had maximum sustained winds of 40mph and a minimum central pressure of 1011mb. It was moving to the N at 7mph, now over coastal Georgia.

julia1

Despite its tropical designation, Julia remains a disorganized storm, seeing the effects of some higher wind shear. Most of the stronger winds and heavier rain are displaced to the northeast of the center of circulation. While there were some wind gusts over coastal Florida on Tuesday in the tropical storm force range, most of the winds Wednesday have been much weaker.

floater-wind-speed-and-gusts

While winds aren’t a big threat with Julia, it will have some localized flooding rains associated with it. Radar Wednesday morning still showed the majority of the heavy rain just offshore. However, model forecasts along with the official WPC (Weather Prediction Center) forecast call for heavy rain (locally 7″+) along the Georgia/South Carolina coastline over the next couple days before Julia weakens into a remnant low later this week.

vipir florida-4km-rpm-precip-acc-without-plot

Meanwhile Tropical Storm Ian continues to churn in the central Atlantic. The storm has maximum sustained winds of 50mph, but it faces moderate wind shear in its northward path in the coming days. Warmer sea surface temperatures and interaction with an extratropical feature should still allow for some strengthening, though the storm will not affect land.

ian

Also in the Atlantic, we now have Tropical Depression 12 (formerly Invest 95L) over the Cabo Verde islands. The storm has shown enough organization to be designated a tropical depression, but still remains fairly unorganized overall. The forecast calls for it to strengthen some into a tropical storm over the coming days as it moves almost due west. However, there is a quite a bit of uncertainty in its forecast beyond day 5. Any interaction with land at this point is still too far out to forecast. Models also indicate another tropical wave moving off the African Coastline over the next week.

td12currents

td12

Meanwhile, in the Northwest Pacific, Super Typhoon Meranti eyes China for landfall. The storm reached peak intensity on Tuesday, with maximum sustained winds of 190mph and a minimum central pressure of 890mb, putting it amongst elite company of most powerful cyclones in recorded history. The storm travelled just south of Taiwan Tuesday night and was making its way close to a landfall in China Wednesday. While the storm has weakened some, it is still extremely dangerous with maximum sustained winds of 145mph.

meranti

While wind damage will certainly be extensive and storm surge may be an issue, the worst for China will likely be from devastating rainfall. Meranti drenched parts of Taiwan with more than 30″ of rain in 24 hours and it was still raining! The chart below shows many areas in the country above 20″ (chart via Phil Klotzbach).

china-rainfall

 

Hermine Strengthens, Prepares for Landfall in Florida

Tropical Storm Hermine only became a tropical storm at 2pm on Wednesday, and yet it is wasting no time strengthening. As of the 8pm Intermediate Advisory, Hermine has strengthened to 1001mb, with maximum sustained winds of 50mph. It’s forward speed has also picked up, moving to the NNE at 8mph.

Hermine Currents

Hermine has already dumped a ton of rain well to its northeast, thanks to some good low-level convergence over west-central Florida. Rainfall in and around Tampa Bay has set daily rainfall records, and the rain continues into the overnight hours. Some parts of Pinellas County have seen more than 10″ of rain since it began falling early Wednesday morning. The Sarasota-Bradenton International Airport set a new daily rainfall record for the entire month of August with more than 7″ of rain (and counting).

48 hr Rainfall Totals - Location1 Rainfall Totals2

The track for Hermine should take it to near Apalachicola Thursday evening and through the Tallahassee area. This will likely bring tropical storm conditions (or higher if the storm intensifies before landfall) to the Big Bend area.

Hermine Track1

Beyond that, there is quite a bit of uncertainty in the track of Hermine. It is expected to undergo extratropical transition this weekend but still bring heavy rain and gusty winds to the mid-Atlantic. How far north into New England the strong winds and heavy rain get still remains to be seen. At this point, it looks like it will make a sharp turn east just off the Jersey Shore and head out to sea, though not all models agree with this solution.

Hermine Track2

While the extended timeframe for Hermine remains a bit murky, the short-term forecast is fairly set in stone, at least for the track. Therefore, tropical storm warnings are up for the Big Bend of Florida, from Destin to the Anclote River. This same area has a hurricane watch in effect in case Hermine intensifies into one before landfall. Meanwhile, on the east coast, a tropical storm watch is up from Altamaha Sound in Georgia to Marineland, FL.

Tropical  Watches and Warnings 3

Rain will likely be heavy, at least on the eastern side of this system. Another hazard will be storm surge. The storm surge inundation map from the National Hurricane Center shows much of the coast under tropical storm warnings can expect storm surge greater than 3 feet. However, Apalachee Bay may see storm surge above 6 feet as a reasonable worst case scenario.

storm surge inundation wide view

Another issue with this storm will be the wind. The European model shows future wind gusts approaching hurricane force later Thursday night from Panama city down to Tampa.

Floater Wind Gusts

While Florida prepares for Hermine, Hawaii has a twin threat of storms in the coming days. First is Madeline, which was downgraded to a tropical storm early Wednesday afternoon. The storm is passing about 100 miles south of the Big Island, though parts of the island will likely still see tropical storm force winds and torrential rain. Surf will be very high the next couple days as well.

Madeline

The second possible storm for Hawaii in the next week will be Lester. Lester is currently a category 4 monster with winds of 130mph. The storm will move slightly north of the track Madeline took, and likely end up close to Oahu or Kauai this weekend.

Lester

Tropical Depressions 8 & 9 Look to Make Impact in US

Little has changed in the organization or forecasted tracks for tropical depressions eight and nine in the Atlantic and Gulf of Mexico. Both are still expected to make an impact to the mainland US in the next couple of days. Tropical Depression Eight continued to douse western Cuba with more than a foot of rain in spots. However, enhanced satellite imagery showed a fairly disorganized system, still suffering from the effects of moderate wind shear and the higher elevations of the island.

Florida Satellite-Radar Transition to Enhanced Satellite

As the system continues to move to the west, the effects from the mountains of Cuba will lessen, and the wind shear should drop a bit. While there is still quite a bit of dry air in the mid-levels of the atmosphere, the very warm waters of the Gulf should overcome that and allow for gradual strengthening. A mid-level trough should still pick up the system and turn it drastically to the northeast later Tuesday evening, moving it toward the Big Bend of Florida. Most models are in decent agreement for this track thought.

TD9 Models

The official track forecast from the National Hurricane Center has TD #9 becoming a tropical storm on Tuesday, with tropical storm watches likely for much of the Florida west coast by morning. The intensity forecast is still a bit uncertain for this storm, with the NHC forecast a bit on the conservative side. The storm is expected to approach the Florida coastline (near the Big Bend) and make landfall some time Thursday afternoon, though there are some models that are faster, and some that are slower than that.

TD9

With a track in this location, a strong tropical storm would cause significant coastal flooding for the Big Bend through the Tampa Bay area. In addition, wind gusts could be above 40mph, especially if the storm were to intensify just a bit more before landfall.

Tropical Potential Impacts - Wind

While still a few days away, the chances for tropical storm force winds across West Florida have been increasing. The map below shows the chance for tropical storm force winds in any spot.

Probability Tropical Storm Winds

Rainfall is also expected to be heavy for much of the west coast of Florida and northern portions of the state. The official forecast from the WPC (Weather Prediction Center) calls for a widespread 3″-6″, with isolated amounts to near 10″.

rainfall

Meanwhile, elsewhere in the Atlantic Tropical Depression Eight has shown signs of better organization. It is expected to become a tropical storm at some point on Tuesday and graze the Outer Banks Tuesday night. Tropical Storm Warnings are up for the Outer Banks and rainfall of 1″-3″ can be expected (isolated amounts up to 5″ possible).

TD-8

Also, in the Pacific, Hawaii is in the crosshairs of a couple tropical systems. Major Hurricanes Madeline and Lester are moving toward Hawaii from the east, and expected to come close to the Big Island over the next week. At this point, Madeline looks like the more threatening storm, expected to come within a few miles of the Big Island on Wednesday/Thursday. Winds will likely be gusty for the state, surf will be high and possibly damaging, and rainfall will be significant.

Madeline1

 

Tropical Depressions 8 and 9 Form; Gaston Now a Major Hurricane

Sunday was quite an active day for the Atlantic Hurricane season. Firstly, Gaston re-intensified, and as of Sunday evening was now the season’s first major hurricane. Maximum sustained winds were up to 115mph and a minimum central pressure of 962mb. The storm was moving slowly northwest, but should quickly turn to the northeast and head in the general direction of the Azores throughout the week.

Gaston Track

Meanwhile, Invest 91L near Bermuda wasted no time in becoming a tropical depression. The storm saw a burst of convection early Sunday and was designated Tropical Depression Eight. However, by later Sunday, most of the convection had waned and the storm was left with a fairly exposed circulation.

td8

Nonetheless, TD 8 is expected to moderately strengthen into a tropical storm over the next couple of days as it heads toward the Outer Banks. It may clip land before turning back out to sea around mid-week. Tropical Storm Watches may be issued for this area if it does strengthen.

TD 8 TRACK

Meanwhile, the most-talked about invest in the history of invests (99L) finally got its act together enough on Sunday to warrant an upgrade to Tropical Depression Nine. However, enhanced satellite imagery shows the system is still disorganized as of Sunday evening.

Floater IR Enhanced2

TD 9 will continue on a generally westward track for the next 24-48 hours. Beyond that, most models agree it will stall out before a deepening trough pushes it sharply northeastward. While the models agree on a turn, they disagree on the exact track and peak intensity.

Invest 92L Models

For now, the official forecast from the National Hurricane Center calls for TD 9 to become a tropical storm Monday night or Tuesday. It has a somewhat conservative peak intensity estimate of 50mph, and a landfall near the Big Bend area of Florida Thursday afternoon. However, the cone of uncertainty includes areas from just east of Mobile, AL to Naples, FL. Interests in any area in between should pay close attention to future updates to the forecast.

TD9

 

A Still Disorganized 99L Meanders Near the Bahamas

The ‘Invest 99L Watch’ continues on Friday, with little change to the structure of the disturbance. The tropical wave remains unorganized and lacking a center of circulation. An earlier Hurricane Hunter flight was cancelled because of the lack of organization. Nonetheless, there are signs of life in the invest as a plume of convection near the center, though small, has persisted for much of the day. The disturbance took a hit from the higher elevation of Hispaniola on Thursday, and has seemingly done the same from the mountains of Cuba on Friday.

Floater IR Enhanced2

Due to the lack of organization, the chances for development of this invest have dropped. NHC now puts the 48-hour/5-day odds at 30%/60%. The storm is still expected to move NW through the Florida Straits and into the Gulf. However, development, if any, is most likely to hold off until the disturbance is in the Gulf.

99L Spaghetti Plots

Besides its proximity to Hispaniola and Cuba affecting its formation, Invest 99L also suffered from higher-than-expected wind shear. Upper level winds were not conducive for development through Friday morning, but they were becoming more favorable in the afternoon. A look at the GFS model shows wind shear fairly favorable for development through the weekend.

99L Wind Shear

Even if the storm doesn’t develop tropically, it’s still expected to bring a plume of moisture with it toward Florida. The models have wavered a bit on rainfall totals, but it looks like their could be significant rain closer to the coast early next week from the Keys up the peninsula and into the panhandle.

99L GFS Rainfall

The Euro model has been insistent for several days that Invest 99L would form tropically and move into South Florida before emerging in the Gulf and strengthening there. At the same time, the GFS has been insistent on just an open wave moving toward Florida and the Gulf. So far the GFS has been correct and now the Euro has backed off on its initial call. It now calls for that same open wave in the Gulf.

99L GFS MSLP99L ECMWF

While these models have backed off on development, some of their ensemble members still depict a storm in the Gulf for early to mid week. And another model that’s fairly reliable for storm intensity, the HWRF, shows a well-developed hurricane in the NE Gulf mid-week (image courtesy FSU). Certainly, while Invest 99L has not developed and looks rather unimpressive on satellite, we can’t write it off yet and need to continue to monitor its potential.

FSU weather

Still Waiting on Invest 99L to Get More Organized

Not much has changed in the last 24 hours in regards to Invest 99L. It is still a rather disorganized mess of clouds, showers, and thunderstorms and lacks a closed circulation. The storm has been severely impacted by the higher elevation of Hispaniola and has not been able to get its act together. Enhanced satellite imagery is not very impressive.

Floater IR Enhanced2

In addition to being impacted by the higher elevations of the Dominican Republic and Haiti, Invest 99L has also been battered by moderate to strong wind shear. However, that wind shear will be slackening in the next couple of days, and will be more favorable for development by later Friday into Saturday.

GFS Wind Shear with Text

Another factor that has been working against the development of Invest 99L has been the dry air associated with the Saharan Air Layer in place over the Caribbean and Gulf of Mexico. However, the atmosphere is slowly moistening up ahead of the disturbance, which will be a better atmosphere for development in the next couple days.

Water Vapor Floater

With all of these environmental factors moving into the ‘more favorable for development’ column, and with a path over extremely warm water, the expectation is still that Invest 99L will develop. However, it is likely not going to occur until this weekend. The National Hurricane Center has backed off on 48 hour odds of development, now calling for a 40% chance. However, the 5-day odds are still high, at 70%.

Invest 90L Models

Models continue to differ widely on both track and intensity. As consistent as the ECMWF (Euro) has been in developing the disturbance, the GFS has been in the opposite corner. The American global forecast system model doesn’t develop Invest 99L at all and instead keeps a rather open wave moving over Florida early next week.

GFS MSL and Precip Rate

Meanwhile, the Euro has been rather consistent in bringing at least a tropical depression or storm somewhere between Miami and the Florida Straits on Sunday. However, it has diverged a bit run to run after that. The last few runs in a row do show a weaker system headed into the northeast Gulf, paralleling the west Florida coastline. A track this close to land would likely not allow for much further development of Invest 99L beyond tropical storm before an impact near the Big Bend Tuesday/Wednesday.

ECMWF MSLP and Precip Rate1

ECMWF MSLP and Precip Rate2

In addition to the track still being up in the air, the intensity is far from set in stone. Here’s a look at some of the afternoon model runs from today and their intensity forecasts. Note how most keep the disturbance near or below hurricane strength. Nonetheless, we’ll be sure to keep a close eye on Invest 99L as it tries to develop into the weekend.

Intensity Diagram

All Eyes on Invest 99L; Formation and Track Still in Question

The Atlantic has been heating up over the last couple of weeks. We had the weak Tropical Storm Fiona well south and east of Bermuda, and now we have Tropical Storm Gaston. Gaston, as of Wednesday afternoon, was nearing hurricane strength. It had maximum sustained winds of 70mph and a minimum central pressure of 999mb. The storm was moving NW at 16mph. While it is not expected to impact land, the storm is forecasted to be close enough to Bermuda next week that interests in the area should pay attention.

Gaston Track

While Gaston is likely to remain out to sea and not threaten any land, the same cannot be said with Invest 99L. In fact, the disturbance was already battering parts of the northern Lesser Antilles with heavy rain and gusty winds. However, as a whole, the storm remains rather disorganized. The enhanced satellite picture shows a batch of convection south of what appears to be a low-level center. The appearance may be a bit deceiving though, since an Air Force Recon flight didn’t find any closed circulation earlier Wednesday morning. Therefore, despite a maximum flight level wind of 63mph, the disturbance remains unclassified. National Hurricane Center still keeps the chances of development high though, with 48-hour/5-day odds at 60%/80%.

Hurricane Hunter With Satellite and Radar

One of the reasons for lack of development and organization thus far for 99L has been moderate northerly wind shear on the north side of the system. This is what has been pushing the convective plume to the south of an apparent center of circulation. In the coming days though, 99L should be moving into a more favorable upper level wind pattern. (Image courtesy University of Wisconsin)

Wind Shear

As Invest 99L moves to the NW, most of the models are fairly tightly clustered in the first few days. However, there are still some questions in that time frame. The first revolves around the fact that the disturbance has yet to develop a closed off circulation. Therefore, it’s a bit of a guessing game for the models to pinpoint where the actual storm center is. Also, the storm will move somewhat close to the higher elevation of Hispaniola which can wreak havoc on a developing system.

Invest 99L Spaghetti

Despite the potential interaction with land, Invest 99L will be moving into an area very conducive to development. In addition to the aforementioned lower wind shear, water temperatures are extremely warm from the Bahamas into the Gulf. SST’s generally are in the upper 80s, and are even running a couple of degrees above average.

 

 

With all these complicating factors in mind, it’s no wonder that the models are differing in their development of the disturbance. The GFS has been extremely inconsistent – the latest run keeps a weak, broad area of low pressure into the east coast of Florida early next week before curving out to sea. This scenario may bring additional moisture to the state but would likely do little else.

GFS MSL and Precip Rate1

Meanwhile, the ECMWF (Euro) is more aggressive with 99L. It begins to develop a tropical storm in the Bahamas before moving it over either Miami or the Keys later this weekend.

ECMWF MSLP and Precip Rate1

After that, the model has diverged from run to run. While it has fairly consistently been strengthening the storm once into the Gulf, the ultimate track (and therefore landfall) of any potential storm has been all over the place. Last night’s run brought a hurricane toward Texas (first image), while today’s run brings a storm up the west coast of Florida and into the Big Bend (second image). More model consistency is needed from run to run before any credence can be given to any particular model solution. However, the threat of a storm is there so it would be wise to go over your hurricane plan and check your hurricane supply kit. For what it’s worth, most of the other reliable hurricane models do develop a tropical system somewhere in the Bahamas, and fall more in line with the Euro. Check back here in the coming days for the latest forecast.

ECMWF MSLP and Precip Rate2

 

Tropical Storm Fiona Not Expected to Strengthen; Watching Other Tropical Waves

Tropical Storm Fiona was a fairly small storm on Friday situated in the middle of the Atlantic. The storm has maximum sustained winds of 45mph but those winds only extended outward about 45 miles from the center. Fiona is moving WNW at 10mph and has a minimum central pressure of 1006mb. The storm is expected to remain on a west-northwest track over the next several days with little change in intensity or gradual weakening. By mid-week next week, a weak tropical depression or remnant low should still be southeast of Bermuda.

Fiona

Fiona is located in fairly low wind shear right now, but as it moves westward it should encounter higher wind shear and thus, hostile conditions for any strengthening. The map below (courtesy the University of Wisconsin) shows moderate to high southwesterly wind shear just northwest of Fiona.

wind shear around Fiona

In addition to wind shear, Fiona will be encountering dry air. For now, dry air has yet to be pulled deep into the circulation. However, the low-level center of Fiona has, at times, been exposed from the bursts of deep convection and therefore is susceptible to dry air affecting it. In addition, the layer of dry air is fairly significant on the western flank of the storm which should gradually affect the storm more in the coming days.

Caribbean WV

While Fiona may ultimately fizzle out, there is another tropical wave in the Atlantic that bears watching. Invest 99L is located just southeast of Fiona, about 500 miles southwest of Cabo Verde. It is fairly disorganized right now but that should change in the coming days.

IR Enhanced

Invest 99L is south of much of the dry air associated with the Saharan Air Layer (SAL) and will be moving into a more favorable upper level wind pattern. Because of its south positioning, interests in the Lesser Antilles should pay close attention to the forecast in the coming days. The models are fairly consistent in bringing the tropical wave near the Islands by later next week.

Invest 99L Models

Some of the models used to predict tropical development do show development of the system next week. One of those models, the GFS model, is very aggressive and shows a large tropical storm or hurricane near the leeward islands late next week. However, not all models are on board with this solution.

GFS MSL and Precip Rate 99L

Obviously, since we’re still a week away from any land interaction for 99L, much can change in the forecast and likely will. Nonetheless, we’ll pay close attention to it. The current odds for development from the National Hurricane Center are 10%/50% for 2-day/5-day. There is also another tropical wave behind 99L that is expected to emerge from the African Coast into the Cape Verde islands at some time on Saturday. The NHC puts the odds of development over the next 5 days at 30%.

NHC 5 day probabilities

Watching a Trough in the Northeast Gulf

We continue to watch a trough of low pressure in the Northeast Gulf Saturday afternoon. Abundant moisture is supplying a train of heavy rain to coastal portions of Florida, especially near the Big Bend.Precipitable Water

The area of clouds and showers has a 20% chance to develop into a tropical depression over the next few days before it moves inland over the Southeast.

Tropical Development

Even if it doesn’t develop tropically, this trough of low pressure will continue to bring very heavy rain to portions of Florida. The heaviest rain will fall closer to the coast where Flood Watches are in effect through Tuesday. When all is said and done, a widespread 3″-6″ of rain is possible for most of the Panhandle and parts of the Peninsula. Meanwhile, closer to the coast and within the Flood Watch, more than a foot of rain will be possible.

p120i

While it looks like the heaviest rain will fall near the Big Bend, there still remains some uncertainty just how far south and inland the heavy rain will fall. Stay tuned for updates on any shift in the heavy rain path.