Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

Tropical Storm Hermine Strengthens, Hurricane Warning Issued

Tropical Storm Hermine strengthened on Wednesday evening and a Hurricane Warning was issued for a portion of the northern Florida coast.  A Hurricane Warning was in effect for the portion of the coast from Suwannee River to Mexico Beach, Florida.  A Hurricane Watch and a Tropical Storm Warning was in effect for the portions of the coast from Anclote River to Suwannee River and from Mexico Beach to Destin, Florida.  The Tropical Storm Watch was extended farther up the Mid-Atlantic coast.  The Tropical Storm Watch was in effect for the portion of the coast from Marineland, Florida to South Santee River, South Carolina.

At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Hermine was located at latitude 25.8°N and longitude 87.0°W which put it about 295 miles (475 km) south-southwest of Apalachicola, Florida.  Hermine was moving toward the north-northeast at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 998 mb.

The circulation of Tropical Storm Hermine became better organized on Wednesday, but it is still not really well organized.  A tighter center of circulation developed.  However, the wind field is still asymmetrical.  The stronger winds are mainly east of the center and the winds are weaker in the western half of the circulation.  An area of strong thunderstorms developed near the center and another cluster of thunderstorms persisted southwest of the center.  There are not many thunderstorms northwest of the center.  There are some spiral rainbands, but they are fragmented.

Tropical Storm Hermine is in an environment that is favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 30°C.  The upper level flow pattern is enhancing the divergence of mass to the northeast of Hermine.  The enhanced upper level divergence pumped out enough mass to allow the surface pressure to decrease by a few millibars on Wednesday evening.  Tropical Storm Hermine is expected to continue to intensify on Thursday and it should become a hurricane before it makes landfall on Thursday night.

The upper level ridge that was blocking a northward motion of Hermine has weakened.  So, the tropical storm has begun to more toward the north-northeast.  An upper level trough is expected to steer Hermine a little faster toward the northeast on Thursday.  On its anticipated track Hermine could make landfall somewhere between Apalachicola and Tarpon Springs, Florida on Thursday night.  After it moves across northeast Florida, Hermine could move near the coast of Carolinas on Friday.

Hermine is likely to be a hurricane when it makes landfall on Thursday night.  The core of the circulation which will contain the highest winds is likely to be fairly small and Hermine is likely to cause localized minor wind damage.  There will undoubtedly be power outages.  The coastline around the northeastern Gulf of Mexico is vulnerable to storm surges and Hermine will also produce a storm surge which could range up to 7 to 8 feet (2 to 2.5 meters) near where the center crosses the coast.  The storm surge will be less farther away from where the center makes landfall.  In addition Hermine will generate locally heavy rain which could cause fresh water flooding.  Directional wind shear associated with rainbands moving inland could spin up tornadoes in the eastern half of Hermine.

Large Hurricane Gaston Prompts Tropical Storm Watch for Azores

Large Hurricane Gaston starting moving more quickly toward the northeast on Wednesday and it prompted a Tropical Storm Watch for some of the Azores.  The Tropical Storm Watch includes Flores, Corvo, Faial, Pico Gracsiosa, Sao Jorge and Terceira in the Azores.

At 8:00 p.m. EDT on Wednesday the center of Hurricane Gaston was located at latitude 35.6°N and longitude 46.5°W which put it about 1000 miles (1610 km) west of Faial in the Azores.  Gaston was  moving toward the northeast at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 969 mb.

Hurricane Gaston has a large circular eye with a diameter of 35 miles (55 km).  The eye is surrounded by a nearly complete eyewall, although the eyewall is thinner in the southwestern quadrant.  Winds to hurricane force extend out about 45 miles (70 km) from the center.  Hurricane Gaston has characteristics of an annular hurricane and the surrounding rainbands are mainly comprised of showers and shallow clouds.  The upper level divergence is inhibited over the southwestern past of the circulation, but divergence is still occurring north and east of the center.

Hurricane Gaston will be moving through an environment that will become increasingly unfavorable.  It is currently over water where the Sea Surface Temperature (SST) is near 27.5°C, but it will be moving over cooler SST during the next few days.  An upper level trough is producing southwesterly winds which are causing vertical wind shear.  The strength of the upper level winds is expected to increase.  The combination of cooler SSTs and more wind shear will weaken Gaston during the next few days.

Hurricane Gaston is being steering toward the northeast by the westerly flow in the middle latitudes.  That general motion is expected to continue.  On its anticipated track Hurricane Gaston could reach the western Azores within 48 hours.  It is expected to weaken below hurricane intensity by that time.  Because of its large size, Gaston could bring wind and rain to many of the Azores.

Tropical Depression Nine Causes Hurricane Watch for Part of Florida

Although Tropical Depression Nine did not strengthen on Tuesday afternoon, guidance from numerical models suggested it could be stronger when it eventually reaches the coast of Florida.  As a result, the National Hurricane Center at 5:00 p.m. EDT issued a Hurricane Watch for the portion of the Florida coast from Anclote River to Indian Pass.  A Tropical Storm Watch was issued for the portion of the coast from Indian Pass to the Walton County/Bay County line.

At 5:00 p.m. EDT on Tuesday the center of Tropical Depression Nine was located at latitude 24.4°N and longitude 87.3°W which put it about 345 miles (555 km) west of Key West, Florida.  It was moving toward the northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1004 mb.

The circulation of Tropical Depression Nine is not currently well organized.  The surface center is located northwest of an apparent mid-level center.  Upper level divergence is not well developed.  The development of thunderstorms has been cyclical during the past several days.  Clusters of thunderstorms developed south and east of the center and then they weaken.  A few hours later more thunderstorms would develop, persist for a few hours and weaken again.  It appears that new thunderstorms are developing northeast and southwest of the surface center which would be a change from the previous pattern.

The vertical structure of Tropical Depression Nine has been out of sync.  As mentioned above, the surface center was northwest of the mid-level center.  Both the surface and mid-level centers have been located on the western edge of a larger upper level high.  Clockwise flow around the upper high has been creating vertical wind shear, which has prevented the development of a vertically coherent structure in the depression.  Despite the effect of the wind shear and the lack of a coherent vertical structure, the surface center has managed to persist and become a little more organized each day.

Tropical Depression Nine is moving through an environment that is currently marginal for intensification.  It is moving over water where the Sea Surface Temperature is near 31°C.  So, there is plenty of energy in the upper ocean.  The vertical wind shear mentioned previously is the primary factor inhibiting intensification.  However, as Tropical Depression Nine moves north, if is forecast to move into an area where the upper level winds are not as strong.  If that happens, then the depression will strengthen.  As the depression becomes more organized, the rate of intensification could increase and the depression could become a hurricane over the northeastern Gulf of Mexico.

An upper level ridge over the southeastern U.S. has been blocking the northward movement of Tropical Depression Nine.  An upper level trough approaching from the west is expected to weaken the ridge.  As the ridge weakens, The depression will be able to move north.  Eventually in a couple of days, the upper level trough is expected to steer the depression more toward the northeast.  On its anticipated track the depression could be approaching the northeastern Gulf Coast by Thursday afternoon.

The northeastern Gulf Coast is very susceptible to storm surges and a surge is the greatest risk.  Locally heavy rain could cause some flooding, and there could be some minor wind damage.

Tropical Depression Eight Prompts Tropical Storm Warning for North Carolina

The approach of Tropical Depression Eight and the potential for intensification prompted the National Hurricane Center to issue a Tropical Storm Warning for the portion of the coast from Cape Lookout to Oregon Inlet, North Carolina including Pamlico Sound.

At 5:00 p.m. EDT on Monday the center of Tropical Depression Eight was located at latitude 33.6°N and longitude 74.0°W which put it about 140 miles (225 km) southeast of Cape Hatteras, North Carolina.  It was moving toward the northwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1011 mb.

Vertical wind shear disrupted the circulation of Tropical Depression Eight earlier today, but more thunderstorms developed northwest of the center of circulation during the afternoon.  The circulation is still not well organized, but there are indications on radar that it could be developing a tighter center.  An upper level low centered near Savannah, Georgia is producing southerly winds which are causing the moderate vertical wind shear over the depression.  The upper level winds are blocking upper level divergence to the south of Tropical Depression Eight, but there are some sign that upper level divergence could be occurring to the northeast.

Tropical Depression Eight could move into an area marginally more favorable for intensification.  As it gets farther from the upper level low, the winds aloft will decrease.  The depression is moving near the Gulf Stream and the Sea Surface Temperatures are near 29.5°C.  If thunderstorms persist near the center of circulation and a more coherent vertical structure develops, the the depression could strengthen into a tropical storm.

The upper low is steering Tropical Depression toward the northwest and that general motion is expected to continue for another day or so.  When the depression reaches latitude 35°N, westerly winds will begin to steer it off toward the northeast.  On its anticipated track Tropical Depression Eight could be very near Cape Hatteras in 24 to 36 hours.

Although Tropical Depression Eight will bring some stronger winds, locally heavy rain, rip currents, higher waves and beach erosion are greater risks.

Tropical Depressions Form South of Key West & Southeast of Cape Hatteras

Two tropical depressions formed near the U.S. on Sunday.  Tropical Depression Nine formed south of Key West, Florida and Tropical Depression Eight formed southeast of Cape Hatteras, North Carolina.  Both depressions could have an impact on the U.S., but Tropical Depression Nine could pose a greater risk to the southeastern U.S.

At 5:00 p.m. EDT on Sunday the center of Tropical Depression Nine was located at latitude 23.7°N and longitude 81.7°W which put it about 60 miles (95 km) south of Key West, Florida.  It was moving toward the west at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1009 mb.

At 5:00 p.m. EDT on Sunday the center of Tropical Depression Eight was located at latitude 31.8°N and longitude 70.9°W which put it about 355 miles (570 km) southeast of Cape Hatteras, North Carolina.  It was moving toward the west at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1010 mb.

The circulation of Tropical Depression Nine is still organizing.  A NOAA plane found a distinct center of circulation, but most of the stronger thunderstorms are south and east of the center.  There is a broader counterclockwise rotation with numerous showers and thunderstorms indicated by the National Weather Service radar in Key West.  An upper level low east of Florida is contributing to easterly winds that are blowing across the northern side of the depression.  The vertical wind shear is inhibiting the development of thunderstorms north and west of the center.

The circulation of Tropical Depression Eight was more well organized earlier today.  Strong easterly winds from the same upper level low that is affecting Tropical Depression Nine are creating significant vertical wind shear.  Those winds and the shear they caused blew the upper portion of the depression’s circulation west of the low level center of circulation.  The low level circulation is presently exposed as seen on visible satellite imagery and by an Air Force Reserve Hurricane Hunter aircraft.

The intensity forecast for Tropical Depression Nine is challenging because it is moving through a complex environment.  The depression is moving over water where the Sea Surface Temperature is near 31°C.  So, there is plenty of energy in the upper ocean.  However, as mentioned above, an upper low is causing vertical wind shear which will inhibit intensification.  Tropical Depression Nine could move into a region where there is less shear when it moves over the Gulf of Mexico.  Tropical Depression Nine has a good chance to intensify into a tropical storm, but it is unclear if it could become a hurricane before it reaches the coast.

There is also significant uncertainty in the track forecast for Tropical Depression Nine.  A ridge over the southeastern U.S. is steering the depression toward the west and that general motion should continue for several more days.  The ridge is forecast to weaken during the middle of the week and that should allow Tropical Depression Nine to turn toward the north.  The timing of that turn and how sharp it will be are still uncertain.

The upper low is expected to continue to generate wind shear over Tropical Depression Eight.  If the upper levels winds remain as strong as they are now, the depression will slowly weaken.  If the upper level winds weaken, then Tropical Depression Eight could strengthen into a minimal tropical storm.  The upper level low is steering the depression west and that general motion is expected to continue in the short term.  The depression could stall just off the coast of North Carolina.

Tropical Depression Nine could intensify and bring wind and rain to the Gulf Coast later this week.  The Gulf Coast is also vulnerable to storm surges.  Given the uncertainty in both the track and intensity, interests along the coast should monitor official sources of information for updates on Tropical Depression Nine.  The primary effects of Tropical Depression Eight are likely to be higher than normal surf, rip currents and some beach erosion along the North Carolina coast.  People along the Mid-Atlantic coast should pay attention to the depression in case the forecast changes.

Gaston Regains Hurricane Intensity East of Bermuda

Gaston intensified back into a hurricane east if Bermuda on Saturday.  At 11:00 p.m. EDT on Saturday the center of Hurricane Gaston was located at latitude 29.6°N and longitude 54.2°W which put it about 655 miles (1055) km east-southeast of Bermuda.  Gaston was moving toward the northwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 85 m.p.h. (140 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 980 mb.

The circulation of Hurricane Gaston is as well organized as it has ever been.  Gaston has a well formed circular eye surrounded by a ring of thunderstorms.  Multiple spiral rainbands are rotating around the circulation.  Upper level outflow channels to the southwest and east are enhancing upper level divergence and allowing the surface pressure to decrease.

Hurricane Gaston has moved into an environment that is favorable for further intensification.  If it moving over water where the Sea Surface Temperature is near 29°C.  An upper level low northeast of Puerto Rico and an upper level low southeast of Gaston are partially responsible for the two upper level outflow channels.  The upper level winds are weaker in between the two upper level lows and the vertical shear is less than it has been in recent days.  Gaston is likely to intensify further and it could become the first Major Hurricane of the 2016 Atlantic hurricane season.

The steering currents between the two upper lows are weaker and Hurricane Gaston has been moving more slowly toward the northwest.  Gaston is expected to move slowly northward for another day or two.  An upper level trough is likely to begin to steer the hurricane toward the east in 48 to 72 hours.  On its anticipated track Hurricane Gaston should pass well to the east of Bermuda.

Tropical Storm Gaston Forms Southwest of the Cape Verde Islands

A center of circulation quickly organized within a tropical wave on Monday night and the National Hurricane Center designated the system as Tropical Storm Gaston.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Gaston was located at latitude 12.6°N and longitude 30.7°W which put it about 450 miles (725 km) west-southwest of the Cape Verde Islands.  Gaston was moving toward the west-northwest at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1005 mb.

The circulation consolidated rapidly around the center of Tropical Storm Gaston on Monday.  Several spiral bands of thunderstorms formed close to the center and additional bands formed farther from the center.  The thunderstorms near the center began to generate upper level divergence, which pumped mass away from the center.

Tropical Storm Gaston is moving through an environment that is favorable for intensification.  It is over water where the Sea Surface Temperature is near 28°C.  The upper level winds are light and there is little vertical wind shear.  Gaston is likely continue to intensify steadily during the next several days and it is expected to become a hurricane.  Once a tightly organized core consolidates completely, Gaston could undergo a period of more rapid intensification.

A subtropical ridge is steering Tropical Storm Gaston toward the west-northwest and that general motion is expected to continue for a day or so.  The ridge is expected to weaken northwest of Gaston, and the tropical storm is expected to turn more toward the north during the middle of the week.  Gaston could be moving out into the Central Atlantic Ocean by the end of the week.

Tropical Depression Six Intensifies Into Tropical Storm Fiona

Tropical Depression Six intensified on Wednesday and the National Hurricane Center named it Tropical Storm Fiona.  At 5:00 p.m. EDT on Wednesday the center of Tropical Storm Fiona was located at latitude 15.1°N and longitude 37.8°W which put it about 1545 miles (2490 km) east of the Leeward Islands.  Fiona was moving toward the northwest at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1006 mb.

Tropical Storm Fiona has a small circulation and winds to tropical storm force only extend out about 25 miles (40 km) from the center circulation.  Most of the thunderstorms are occurring close to the center of circulation.  Those thunderstorms are generating some upper level divergence, but it does not extend very far from the core of Tropical Storm Fiona.  There are bands of lower clouds and showers rotating around the core of Fiona.

Tropical Storm Fiona is moving through an environment that is mostly favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 27°C.  An upper level ridge north of Fiona is generating northeasterly winds which are blowing across the top of the tropical storm.  Those winds are causing some vertical wind shear, but it should only inhibit, but not stop, intensification.  There is drier air northwest of Fiona and that is the main negative factor in the environment.  If the drier air gets pulled into the core of Tropical Storm Fiona, it will reduce the supply of energy and weaken Fiona.  Since the core of Fiona is so small, the tropical storm could intensify or weaken very quickly as the environmental conditions change.

The subtropical high that extends from Africa across the Atlantic Ocean is splitting into an eastern ridge and a western ridge.  Tropical Storm Fiona is moving toward the weakness where the split is occurring.  This is producing a motion toward the northwest and that general motion is expected to continue during the next several days.  On its anticipated track Tropical Storm Fiona could be northeast of the Leeward Islands in a few days.

Tropical Depression Six Forms Over Eastern Atlantic

A center of circulation developed within a tropical wave designated as Invest 98L on Tuesday and the National Hurricane Center classified the system as Tropical Depression Six.  At 11:00 p.m. EDT on Tuesday the center of Tropical Depression Six was located at latitude 12.6°N and longitude 34.1°W which put it about 1800 miles (2900 km) east of the Leeward Islands.  The depression was moving toward the northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1008 mb.

The circulation of Tropical Depression Six is still organizing.  A center of circulation exists near the surface and thunderstorms are developing near the center.  Several partial spiral bands are beginning to form.  The thunderstorms near the center are generating a small region of upper level divergence, but the divergence is occurring mainly to the southwest of the depression.

Tropical Depression Six is moving through an environment that favors intensification.  It is moving over water where the Sea Surface Temperature is near 27°C.  An upper level ridge to the north is causing northeasterly winds to blow across the top of the depression.  There is some vertical wind shear, but the shear will only slow the rate of intensification.  The shear is not strong enough to prevent intensification and Tropical Depression Six is expected to become a tropical storm during the next day or two.

The subtropical ridge over Africa and the Atlantic Ocean is splitting into two parts and Tropical Depression Six is moving toward the northwest into the split that is developing.  The depression is expected to continue to move toward the northwest in the short term.  The longer term motion will depend on how strong Tropical Depression Six becomes.  If it intensifies more and develops a taller circulation, then the depression will be steered by the winds higher in the atmosphere.  The winds at those levels are more likely to carry it into the central Atlantic Ocean.  However, if vertical wind shear weakens the depression and the circulation is shallower, then the winds in the lower levels of the atmosphere could carry the depression farther to the west.  In either case Tropical Depression Six is no immediate threat to any land area.

Tropical Storm Earl Strengthens Near Veracruz

Tropical Storm Earl regained strength on Friday after the center moved over the southern Bay of Campeche near Veracruz, Mexico.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Earl was located at latitude 18.8°N and longitude 95.0°W which put it about 85 miles (135 km) east-southeast of Veracruz, Mexico.  Earl was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 70 m.p.h. (115 km/h).  The minimum surface pressure was 1001 mb.

Because Tropical Storm Earl re-intensified and the radius of tropical storm force winds expanded to the north, the government of Mexico extended Tropical Storm Warnings farther north along the coast.  A Tropical Storm Warning is in effect for the portion of the coast from Puerto Dos Bocas to Tecolutla, Mexico.

Most of the circulation of Tropical Storm Earl remained intact while it moved over land from Belize to the Bay of Campeche.  As a result, the surface part of the circulation on the northern side of Earl began to redevelop quickly as the center approached the water in the Bay of Campeche.  A primary rainband wrapped most of the way around the center of circulation and other rainbands reformed over the Bay of Campeche.  There have been hints on an incipient eye forming at the center of circulation on recent visible satellite images.  Earl is a very well organized tropical storm.

The Sea Surface Temperature is near 30°C in the southern Bay of Campeche.  The upper level winds are weak and there is little vertical wind shear.  Upper level divergence is well formed in Tropical Storm Earl and it is pumping out mass.  The environment is favorable for further intensification.  However, the center of circulation is close to the coast and approximately 40% of the circulation is over land.  So, the proximity to land is the main factor inhibiting further strengthening.  Tropical Storm Earl does have a few hours to intensify and it could get stronger.

A subtropical ridge north of Earl is steering the tropical storm toward the west and that general motion is expected to continue.  On its anticipated track the center of Tropical Storm Earl will be very near Veracruz, Mexico in 10-12 hours.

The winds in Tropical Storm Earl are strong enough to create a storm surge of several feet (1-2 m) near where the center makes landfall and north of that location.  The primary risks from Tropical Storm Earl will be very heavy rainfall and flash flooding.