Invest 98L Forms in the Gulf – Heavy Rain Threat for Florida

A well-defined area of low pressure churned in the Northeast Gulf of Mexico on Sunday. While it is non-tropical in nature, the potential for it to become subtropical or even tropical over the next 24-36 hours prompted its designation of Invest 98L. The National Hurricane Center is giving the low a 20% chance of becoming our next tropical depression over the next 48 hours, and a 30% chance in the extended term.


The low has formed along a nearly stationary frontal boundary that has stalled out across northern Florida. This has provided a decent pool of moisture for the low. However, upper level winds are only marginally conducive to development. Sea surface temperatures on the other hand are favorable for development as most of the Gulf is running 1°-2°C above average.


Regardless of development, the low and the associated frontal boundary will bring copious amounts of rainfall to Florida through the middle of the week. Bands of rain and storms will pile up along the peninsula over the next few days, and rain will be heavy at times. There will likely be a widespread 2″-4″ across Central Florida, but there could be some spots that see locally higher amounts.



94L Still Likely to Organize But Time Running Out

Invest 94L was still churning in the open Atlantic waters, about 850 miles WSW of the Cabo Verde islands at 2pm Wednesday EDT. The low pressure system developed a closed surface circulation Wednesday morning, as evident from satellite imagery and a Wednesday morning ASCAT pass. The system was also developing an increasing amount of thunderstorm activity, though mainly on the west side of the low. The chances for development of 94L into our next tropical depression was lowered to 60% Wednesday afternoon from the National Hurricane Center.


Part of the reason the chance of development has been lowered is because time is running out for 94L to become better organized. While conditions right now are marginally conducive to development, they become less favorable over the next couple of days. As the low moves farther west-northwest, it will run into an area of moderate to strong wind shear.


In addition, there is quite a bit of dry air on the north and west side of the system, thanks mainly to the Saharan Air Layer. That dry air is likely already impeding development, and will continue to do so in the coming days.


Either way, the low will continue on a west-northwest trajectory in the next 3-5 days, eventually sliding a few hundred miles north of the Lesser Antilles by this weekend. At that point, many of the models completely open up the wave and see no further development from it. The GFS keeps a very week system through that timeframe.


Meantime, Colorado State researchers have updated their latest hurricane forecasts. The upward trend in the numbers continues with this update – they now predict 15 named storms, 8 hurricanes, and 3 major hurricanes (including the 3 named storms we have already had). That trend has been primarily because of the increased likelihood of no El Niño this summer and an increase in Atlantic SST in the MDR (Main Development Region), although the latter has slowed down in recent weeks.



Invest 90L Remains Disorganized: Development Still Expected By Weekend

As of Wednesday afternoon, Invest 90L in the Southwest Caribbean remained very disorganized and lacked much convection. However, a modest swirl was still evident on enhanced satellite imagery, and the odds of development are still rather high over the next 5 days. The National Hurricane Center has 2 day odds at 30%, but 5 day odds at 80%.


Regardless of development, 90L will be a slow and erratic mover. There is little steering current in the Southwest Caribbean over the next week, and so the models are split in every which direction of where 90L will meander. Below are several model forecasts through next Tuesday.


As for actual development, the European model has been the most aggressive. By the middle of next week, the operational run shows Tropical Storm Otto in the Southwest Caribbean, and several of its more prominent ensemble members show the same solution. They also show little in the way of movement in that timeframe. Here is the forecast from the ECMWF for one week from today.


Meanwhile, the GFS hasn’t showed as much development, and keeps 90L as a tropical depression, or even just a broad area of low pressure. Here is the GFS solution for the middle of next week.


Even though its late in the season, there are a couple factors working in favor of tropical development for Invest 90L. The wind shear over the Southwest Caribbean will remain quite light over the next week, and sea surface temperatures are above average (~1° above normal).



Regardless of development, the biggest threat for 90L looks to be heavy rain. While most of the models keep the heaviest rain offshore, a wobble or shift west in the track could mean very heavy rain for portions of Central America.


Nicole Becomes 3rd Named Storm in Atlantic to Last 10+ Days

Nicole continued to churn in the North Atlantic Friday afternoon after making a direct hit to Bermuda on Thursday as a Category 3 hurricane. The small island nation saw wind gusts measured at 120-130mph and torrential rain, but seemed to have escaped with little damage. As for Nicole’s current look, enhanced satellite imagery shows a sheared storm that may be beginning its extratropical transition. The storm lacks much convection, and almost all of the shower activity and cloud cover are on its north side. (Statement in article title H/T Phil Klotzbach)nicole-enhanced-satellite

As of 5pm, Nicole was still a hurricane with maximum sustained winds of 75mph. It was located 715 miles SSW of Cape Race Newfoundland and was moving ENE at 20mph. Minimum central pressure was 971mb. The storm is expected to become fully post-tropical by Saturday or Sunday.


Elsewhere across the Atlantic, things are pretty quiet. There are a couple tropical waves out there, but dry air and strong wind shear should prevent anything from getting going in the next 5-7 days.


While the Atlantic looks quiet, we will continue to watch the Gulf and Caribbean over the next couple of weeks. Several of the models have periodically hinted at development in these basins over the next 7-10 days. This would be a reasonable area of development climatologically-speaking, and something to look out for in the coming days. Below is the Euro model showing a broad area of low pressure in the NW Caribbean late next week.



Matthew Moving into the Bahamas, Headed for Florida

As of 5pm, Matthew had sustained winds of 120mph, with a minimum central of 963mb. The storm was located 400 miles SE of West Palm Beach, and about 205 miles SSE of Nassau, Bahamas. The motion was to the NW at 12mph.matthew-png-2

The forecast cone has continued its gradual westward shift. The new track now lines up right on the Atlantic coast of Florida, and a landfall anywhere from West Palm Beach to Jacksonville is possible. All areas along the east coast of Florida should prepare for the worst case scenario as many models show Matthew as a major hurricane while along the coast.


After its brush with Florida, Matthew will take a turn to the northeast and weaken some. However, the potential still exists for another landfall in coastal Georgia or South Carolina still as a hurricane. Residents in this area should also prepare accordingly. After this northeastward turn, the models have shifted the track of Matthew farther south than previously, thus removing the Mid-Atlantic and Northeast from the cone of uncertainty. Some models have even shown Matthew completing a loop and drifting back toward Florida early next week (albeit much weaker). The official forecast from the NHC now shows that loop as a distinct possibility.matthew

Tropical storm watches have now been extended westward along the Gulf Coast of Florida, with Watches upgraded to Warnings along the spine of the Peninsula. Preparations should be underway or completed for a major hurricane along the immediate east coast. For the west coast, impacts will be significantly less, though tropical storm force wind gusts will still be possible for some time Friday.






Matthew Begins Restrengthening While Headed Toward Bahamas

After hitting Haiti and Cuba Tuesday and Tuesday night, Matthew has re-emerged over warm water in a low shear environment. Its satellite presentation has shown signs of improvement Wednesday morning. In addition, NOAA and Air Force Hurricane Hunters flying through the storm have noted an increase in wind speed. Thus, the 11am advisory has maximum sustained winds at 120mph. The minimum central pressure is 962mb and the storm was moving to the NW at 12mph.matthew

As the storm continues through the Bahamas, it is likely to restrengthen a bit further in the low shear/warm SST environment. In addition, Matthew turned to the NW early Wednesday morning as it begins to round the perimeter of the Bermuda high. It will now likely continue on this northwesterly track through Friday. The official forecast track takes Matthew through the Bahamas as a dangerous category 4 hurricane, and then parallels the Florida east coastline late Thursday and Friday. By Saturday, the forecast gets a bit more murky. Models Tuesday night and Wednesday have begun to hint at a loop in the long term track of Matthew. Instead of an impact to the Mid-Atlantic and the Northeast, the storm would stay south of the Outer Banks and turn southeastward early next week as high pressure builds in from the north. While not all models have jumped on this, it looks increasingly likely that the Carolinas would be spared a direct hit. Nonetheless, they are still well within the cone of uncertainty and should stay alert.


As previously mentioned, the models are not all in agreement with Matthew’s forecast. Not only are there a couple models that remain well offshore of Florida, but there are several that do not make the aforementioned ‘loop’ in the extended term.


The next area to see the impacts from Major Hurricane Matthew will be the Bahamas. The track of Matthew takes it directly over many of the islands during the next 24-36 hours, including the capital city of Nassau. This would bring the worst winds through some of the more heavily populated islands, as well as a potentially devastating storm surge and very heavy rain. The storm surge could be 10′-15′ in spots, with 8″-12″ of rainfall likely and isolated amounts of 15″! While the center may not move over every island, the wind field is rather large. Hurricane force winds extend outward 45 miles from the center, and tropical storm force winds extend 175 miles from the center.


After impacts with the Bahamas, Matthew will track uncomfortably close to the east coast of Florida Thursday night and Friday. The 11am Advisory continues a gradual westward nudge in the track, with the center-line now well within 50 miles of the coastline. The concern for hurricane conditions on Friday along the immediate coast has certainly grown. The track is close enough to the coast that only a slight shift west or east will have a significant effect on impacts.


With the forecasted track this close to the coast, all kinds of watches and warnings have been issued. Tropical Storm Warnings are up for the Upper Keys through Miami-Dade County, and northward along the spine of the Peninsula. Meanwhile, Hurricane Warnings have been issued for Broward County north through Volusia, with Hurricane Watches just north of that through Jacksonville.


Winds will significantly vary along Florida’s east coast on Friday depending on just how close the center of the storm comes to a direct landfall. As of now, even with a storm just offshore, many of the coastal cities from the Treasure Coast through the Space Coast are in the path of hurricane wind gusts. A snapshot of wind gust speeds Friday morning shows the potential for hurricane force gusts. The model depicted below is from the GFS. While the strongest winds would be within a few miles of the coast, tropical storm force winds will cover a much larger area. Inland counties along the spine of the Peninsula have the potential to see tropical storm force winds for some time on Friday. Gusts 30-40mph could even be possible all the way back to the west coast.


Another potential impact from Matthew will be the rainfall. While the heaviest rains may very well line up just offshore, coastal areas of Florida could easily see 4″-7″ with isolated amounts of 10″+. That heavy rain may extend northward along the coasts of Georgia and South Carolina into Saturday. The image below from NOAA shows rainfall from Wednesday morning through Saturday morning.


In addition to the rainfall and wind potentials, another impact from Matthew will be the storm surge and wave heights. The map below shows wave heights offshore easily above 18′ Friday morning. If the high tide lines up with Matthews maximum storm surge, the water could reach 3′-5′ above ground from North Palm Beach to the Flagler/Volusia County line. However, if the storm moves a bit farther west and makes landfall somewhere in Florida, these water heights will likely increase significantly.




Tropical Storm Matthew Gains Strength in the Eastern Caribbean

Matthew continued its westward trek on Thursday away from the Lesser Antilles and into the Caribbean. As of 11am Thursday, the storm had maximum sustained winds of 70mph and a minimum central pressure down to 996mb. Matthew’s forward speed had slowed a bit since its first advisory on Wednesday, but it was still moving at 15mph. Tropical Storm Watches were up for the Netherland Antilles (Aruba, Bonaire, and Curacao).


The forecasted path of Matthew is rather certain for the next couple of days. Thanks to a large ridge to its north, the storm will continue moving to the west, albeit gradually slowing down at the same time. However, a digging trough across the east coast this weekend will sharply turn the storm to the north. While the models disagree on the timing of this turn, they all feature it at some point. The official forecast from the NHC has Matthew making a turn to the northwest on Saturday, and northward by Sunday. The intensity forecast from NHC has the storm strengthening to a hurricane by Friday, and peaking at Category 2 strength on Monday before landfall on the eastern edge of Cuba Tuesday.


Matthew is a rather large storm, with tropical storm force winds extending outward up to 205 miles from the center. Tropical rains continued to drench the islands of the Lesser Antilles on Thursday morning despite the storm being several hundred miles west of them. In fact, showers from the storm extended as far north as the northern Lesser Antilles all the way south to the northern coast of South America. However, enhanced satellite imagery still showed a sheared storm. Moderate to at times high wind southwesterly wind shear has continued to push the convection to the east of the center of circulation, exposing the low-level swirl.


While wind shear is currently high enough to keep Matthew from organizing too much, it is expected to drop in the next couple of days. Models still differ on just how much it will slacken, but even if it drops off marginally, this should allow for Matthew to strengthen this weekend. The maps below depict the GFS wind shear forecast from Thursday morning (top image) to Saturday (bottom image). The lower wind shear will likely stick around through the weekend, allowing for more strengthening of the storm.



In addition to lower wind shear, Matthew is moving into an area of extremely warm waters. Sea surface temperatures are in the mid 80s and even running a few degrees above the climatological averages.


While the warm waters and lower wind shear will certainly help Matthew strengthen, one environmental factor working against it is the amount of moisture in the atmosphere. Water vapor imagery shows an area of drier air just to the west of the current location of the storm. It’s not dry enough to choke off Matthew but it may ultimately limit the short-term strengthening of the storm (before this weekend).


Spaghetti plots show most of the models (statistical, dynamical, and consensus) depict a sharp turn to the north this weekend, though they differ significantly on the timing of that turn and the ultimate intensity of Matthew. It is possible that the storm will have ‘2’ periods of peak intensity – one before landfall or interaction with Cuba/Hispaniola and another after the storm emerges into the Atlantic near the Bahamas.


Two of the major models we look at for forecasting track and intensity of tropical storms are the GFS and ECMWF (Euro). While both models show a turn northward, the GFS shows it about a day earlier. The ECMWF is also a bit farther east. By the middle of next week, the differences are really highlighted with the GFS showing a storm nearing the East Coast of the US while the Euro is farther south and east with a strengthening storm in the Bahamas. It is interesting to note that the last hurricane to make US landfall north of Florida in October was Hazel in 1954 (Sandy was post-tropical). While it still is more than a week away from any potential US impact, it is worth noting that the forecasted track of Matthew does somewhat mirror that of Hazel.



Karl and Lisa to Become Post-Tropical; Watching the Caribbean Next Week

Karl passed east of Bermuda early Saturday morning as a strong tropical storm. However, the good news for the island nation was that it was on the weaker side of the system, and therefore didn’t see much in the way of wind. However, it did see heavy rain from time to time. As of Saturday evening, Karl was about 450 miles NE of Bermuda and continuing to move to the NE at 29mph. Maximum sustained winds were 65mph and minimum pressure was 992mb. Enhanced satellite imagery shows a large area of deep convection – however that convection is somewhat removed from the low level center.


Karl will continue accelerating to the northeast during the day on Sunday. The storm is expected to strengthen some by Sunday night before undergoing extratropical transition and being absorbed by a large upper level low. Before the transition, Karl may become the season’s 5th named hurricane. Nonetheless, it will remain out to sea and won’t affect land.


Farther east, Lisa was devoid of convection for several hours on Saturday and therefore was designated post-tropical. The remnants of the storm will continue moving northward over the next 24-48 hours before completely dissipating.


While Karl and Lisa are winding down, another area in the Atlantic is just heating up. Several hundred miles southwest of the Cabo Verde Islands is a disorganized tropical wave. The wave is too close to the equator right now (<10°N) to develop any spin of its own at this point.


The wave is moving very quickly (20-25mph) to the west and should gain more latitude in the coming days. As it does so, there’s a decent chance it becomes the next tropical depression or storm. In fact, many of the models and their ensemble members develop this wave into a tropical storm in the Caribbean later next week once it moves beyond the Lesser Antilles. The National Hurricane Center is giving the wave only a 10% chance of development by Monday evening, but a 70% chance of development by Thursday night.


Since the potential movement into the Caribbean is still 5-7 days out, there remains plenty of uncertainty for this wave’s future, including how close it gets to certain islands or even South America. However, if it does emerge unscathed in the Caribbean, this is a dangerous spot for it to be. Sea surface temperatures are running 1°-2°C above average and there shouldn’t be much dry air around. We’ll continue to monitor this potential in the coming days.


Karl Now a Depression; Lisa Still Disorganized

Karl became more disorganized early Wednesday morning, officially downgraded to a tropical depression for the 5am advisory. As of 5pm, the storm was located about 800 miles SSE of Bermuda, with maximum sustained winds of 35mph and minimum central pressure of 1007mb. It was moving to the NW at 12mph, but it is expected to turn more to the north and eventually the northeast over the coming days. The official track from the NHC has it sliding just SE of Bermuda over the weekend. However, it will be close enough that interests in the area should pay attention to future forecast updates.


It has been struggling for days with wind shear associated with an upper level low. That wind shear will slacken a bit over the coming days but will still remain somewhat hostile for strengthening. Nonetheless, with water temperatures above average the storm is still expected to intensify and is forecasted to become the season’s 5th hurricane just east of Bermuda this weekend.


Meanwhile, to the east of Karl is weak Tropical Storm Lisa. Lisa is about 600 miles WNW of the Cabo Verde Islands and is moving to the NW at 7mph. As of 5pm Wednesday, maximum sustained winds were 45mph and minimum central pressure was 1004mb. The storm has also been struggling with strong upper level winds and vertical wind shear of 15-20kts. That shear is expected to increase in the next day or so, and therefore the forecast is not promising for Lisa’s prospects. The track turns Lisa quickly to the north and the forecasted intensity never climbs above where it’s at right now. It’s no threat to land and should become a remnant low over the open Atlantic waters later this weekend.


Not Much Change with Julia and Karl

Julia remained a tropical depression on Sunday evening about 110 miles SSE of Myrtle Beach, with maximum sustained winds of 30mph. The storm continues to lack convection near the center and buoy reports have been unimpressive. However, the storm does have a decent low level swirl evident on satellite. In addition, wind shear, which has been hostile for the storm, is expected to drop Sunday night into Monday. This, combined with the proximity of the extremely warm Gulf Stream waters, may allow for a brief re-strengthening of Julia on Monday. By Monday night, conditions are expected to once again become unfavorable for Julia and should allow for it to weaken. The track forecast brings Julia (or its remnants) inland by Tuesday.


Meanwhile, Tropical Storm Karl continues to churn in the central Atlantic. Environmental conditions are expected to become slightly more conducive to strengthening over the coming days, and so the official intensity forecast is fairly conservative for the storm. By the middle of the week, it is expected to become the 5th hurricane of the season as it passes well north of the Greater Antilles islands. A trough approaching the East Coast around this time should allow for the storm to curve to the north and head toward Bermuda. Interests in this area should pay close attention.


The European model in particular brings a strong tropical storm or hurricane near Bermuda by next weekend.


East of Karl is Invest 96L. The NHC is giving this cluster of showers and storms a 50% chance of development by Tuesday evening, but a high (80%) chance for development by late week. Either way, the models have consistently been immediately curving whatever system may form to the north of where Karl is currently located and therefore no long term threat to land.