Tag Archives: Florida

NHC Initiates Advisories on Potential Tropical Cyclone Two

The National Hurricane Center (NHC) initiated advisories on Potential Tropical Cyclone Two on Wednesday morning.  NHC initiated the advisories in order to be able to issue watches for a portion of the coast of Louisiana.  At 11:00 a.m. EDT on Wednesday the center of Potential Tropical Cyclone Two was located at latitude 28.5°N and longitude 86.4°W which put it about 170 miles (270 km) east-southeast of the Mouth of the Mississippi River.  It was moving toward the west-southwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1011 mb.  A Tropical Storm Watch was issued for the portion of the coast from the Mouth of the Mississippi River to Morgan City, Louisiana.

The circulation around Potential Tropical Cyclone Two was not well organized.  There was a large, but relatively weak circulation near the surface.  There was not a well defined center of circulation near the surface.  There was a stronger counterclockwise circulation between about 10,000 feet (3000 meters) and 25,000 feet (7600 meters) above the surface, which was located above the southwestern part of the surface circulation.  Many of the stronger thunderstorms were occurring in bands on the northern and western sides of the circulation above the surface.  There were fewer thunderstorms in the eastern side of the larger, surface circulation.

Potential Tropical Cyclone Two will move through an environment very favorable for development and intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  The system will move through a region where the upper level winds are weak and there will be little vertical wind shear.  It is likely that a center of circulation will form at the surface underneath the counterclockwise circulation above the surface.  Potential Tropical Cyclone Two will strengthen slowly until the surface center is underneath the center higher in the atmosphere.  After the circulation becomes aligned vertically, the system could strengthen more rapidly.  Potential Tropical Cyclone Two is likely to become a hurricane within 48 to 60 hours.

Potential Tropical Cyclone Two will move south of a ridge over the southeastern U.S.  The ridge will steer Potential Tropical Cyclone Two toward the southwest.  It will move more toward the west on Thursday and then turn back more toward the northwest on Friday when it nears the western end of the ridge.  There will be significant uncertainty about the future track of the system until a well defined center of circulation forms at the surface.  On its anticipated track the center of Tropical Cyclone Two could approach the coast of Louisiana and northeast Texas on Friday.  Hurricane Watches and Warnings are likely to be issued for portions of the coast later this week.

Potential Tropical Cyclone Two presents a wide range of hazards.  It will bring hurricane force winds to portions of Louisiana and Texas and it will disrupt operations of offshore facilities in the northwestern Gulf of Mexico.  After the center of the system moves west of New Orleans, southerly winds will force water into the Mouth of the Mississippi River.  The level of the Mississippi River around New Orleans is already near flood stage and any additional rise in the water level could cause serious flooding around the city.  If Potential Tropical Cyclone Two strengthens into a hurricane, as expected, it will cause a significant storm near where the center makes landfall.  The system also has the potential to drop heavy rain and flooding could occur when it moves inland.

Potential Tropical Development Over Northern Gulf of Mexico

The potential exists for the development of a tropical cyclone over the northern Gulf of Mexico this week.  A low pressure system was over Georgia on Monday afternoon.  The low was drifting slowly southward, but it was forecast to move more toward the south-southwest during the next two days.  Several numerical models were predicting that the low pressure system would strengthen into a tropical depression or a tropical storm after it moves over the northern Gulf of Mexico later this week.  The National Hurricane Center was indicating that the low pressure system, currently designated as Invest 92L, had a 30% probability of developing into a tropical cyclone during the next two days and an 80% probability of developing into a tropical cyclone during the next five days.

The low pressure system exhibited a surface circulation on Monday afternoon, but the wind speed was near 15 m.p.h. (25 km/h).  Bands of showers and thunderstorms formed during the daytime heating over land, but they weakened at night.  There was also a counterclockwise rotation in the lower and middle troposphere which may have been the remnants of a mesoscale convective vortex (MCV), which developed over the Middle Mississippi River Valley a few days ago.  The low was not generating upper level divergence on Monday afternoon.

If the low pressure system does move over the northern Gulf of Mexico on Tuesday or Wednesday, it will move into an environment more favorable for the development of a tropical depression.  The Sea Surface Temperature of the water in the northeastern Gulf of Mexico is near 30°C.  The low pressure system will move southeast of an upper level ridge over the southern U.S.  The ridge will produce northeasterly winds, but the winds will be relatively weak and the vertical wind shear will not be too strong.  More thunderstorms are likely to develop when the low pressure system moves over the warm water.  If those thunderstorms generate upper level divergence that pumps mass away, then the surface pressure will decrease and a tropical depression will form.

The upper level ridge is forecast to steer the low pressure system toward the west after it moves over the Gulf of Mexico later this week.  On its anticipated track the low pressure system will move slowly toward the coast of Louisiana and Texas.  The future intensity of the system will be determined by how far the system moves into the Gulf of Mexico.  If the low pressure system takes a track along or near the north coast of the Gulf of Mexico, then it will likely become a tropical depression or a weak tropical storm.  Even if the low only strengthens into a tropical depression, it could drop heavy rain and the potential for flooding exists along the northern Gulf Coast.  If the low pressure system moves farther out into the Gulf of Mexico and remains over warm water for a longer period, then it might intensify into a hurricane.  Residents along the Gulf Coast should monitor this system carefully.

Hurricane Michael Makes Landfall in Northwest Florida

Powerful Hurricane Michael made landfall in Northwest Florida Wednesday afternoon.  The center of Hurricane Michael officially made landfall between Panama City and Mexico Beach, Florida.  At 2:00 p.m. EDT on Wednesday the center of Hurricane Michael was located at latitude 30.0°N and longitude 85.5°W which put it about 20 miles (30 km) southeast of Panama City, Florida.  Michael was moving toward the north-northeast at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 155 m.p.h. (250 km/h) and there were wind gusts to 180 m.p.h. (290 km/h).  The minimum surface pressure was 919 mb.

Hurricane Michael intensified rapidly right up to landfall on the Gulf Coast.  The minimum surface pressure decreased from 933 mb to 919 mb in the six hours prior to landfall.  With a maximum sustained wind speed of 155 m.p.h. (250 km/h) Hurricane Michael was at the top end of Category 4 on the Saffir-Simpson Scale.  Michael is the strongest hurricane on record to make landfall on that portion of the Gulf Coast and it was one of the most intense hurricanes to make landfall anywhere along the coast of the U.S. during the month of October.

Even though Hurricane Michael is moving inland, a Hurricane Warning remains in effect for the portion of the coast from the Alabama-Florida border to Suwanee River, Florida.  A Tropical Storm Warning is in effect from the Suwanee River to Chassahowitzka, Florida.  A Tropical Storm Warning is also in effect for the Atlantic Coast from Fernandina Beach, Florida to Duck, North Carolina including Albemarle and Pamlico Sounds.  A Tropical Storm Watch remains in effect from Chassahowitzka to Anna Maria Island, Florida.

Winds to hurricane force extended out about 45 miles (75 km) from the center of Hurricane Michael at the time of landfall.  Winds to tropical storm force extended out about 185 miles (290 km) from the center of circulation.  The Hurricane Intensity Index (HII) was 33.3.  The Hurricane Size Index (HSI) was 16.1 and the Hurricane Wind Intensity Size Index (HWISI) was 49.4.  Hurricane Michael will cause regional significant damage.

Tyndall Air Force Base reported a wind gust of 119 m.p.h. (191 km/h).  The Florida State University Panama City Campus reported a wind gust of 116 m.p.h. (187 km/h).   The Panama City Treatment Plant reported a wind gust of 94 m.p.h. (151 km/h).

The coast along the northeastern Gulf of Mexico is very vulnerable to storm surges.  The winds were pushing water toward the coast in the eastern half of the circulation of Hurricane Michael.  Some locations could have a storm surge of 10 to 15 feet (3 to 5 meters).  There have already been reports of damage due to storm surge.

An upper level trough will steer Hurricane Michael toward the northeast.  Michael will weaken as it moves inland, but it will carry hurricane force winds over northeastern Florida, extreme southeastern Alabama and southern Georgia.  The center of Hurricane Michael will pass between Dothan, Alabama and Tallahasse, Florida.  it will move toward Albany, Georgia and then pass south of Macon, Georgia.  Michael will move across South Carolina and North Carolina as a tropical storm before exiting the U.S. near Norfolk, Virginia.

Hurricane Michael will cause widespread power outages and numerous outages are already occurring in northwest Florida.  Michael will also produce locally heavy rain and flash floods could occur as it moves inland.  Wind and rain will disrupt efforts in South Carolina and North Carolina to recover from the effects of Hurricane Florence.

One of the most unusual aspects of Hurricane Michael was that it intensified rapidly right up until it made landfall in northwest Florida.  In the past most major hurricanes weakened while they approached the coast along the northern Gulf of Mexico.  Those hurricanes encountered drier air and more vertical wind shear and they weakened.  The Sea Surface Temperatures in the northern Gulf of Mexico is 2°C to 3°C warmer than normal and that may have contributed to the rapid intensification of Hurricane Michael before landfall.  Hurricane Camille in 1969 also intensified right up until it made landfall in Mississippi.  However, Camille occurred in August, while Hurricane Michael occurred in October.

Powerful Hurricane Michael Nearing North Florida

Powerful hurricane Michael was nearing north Florida on Wednesday morning.  Michael intensified rapidly to Category 4 on the Saffir-Simpson Scale during the overnight hours.  At 8:00 a.m. EDT on Wednesday the center of Hurricane Michael was located at latitude 29.0°N and longitude 86.3°W which put it about 90 miles south-southwest of Panama City, Florida.  Michael was moving toward the north at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 145 m.p.h. (230 km/h) and there were wind gusts to 170 m.p.h. (275 km/h).  The minimum surface pressure was 933 mb.

A Hurricane Warning was in effect for the portion of the coast from the Alabama-Florida border to Suwanee River, Florida.  Tropical Storm Warnings were in effect for the portions of the coast from the Alabama-Florida border to the Alabama-Mississippi border and from Suwanee River to Chassahowitzka, Florida.  A Tropical Storm Warning was in effect for the Atlantic Coast from Fernandina Beach, Florida to Surf City, North Carolina.  Tropical Storm Watches were in effect for the portions of the coast from the Alabama-Mississippi border to the Mouth of the Pearl River and from Chassahowitzka to Anna Maria Island, Florida.  A Tropical Storm Watch was also in effect from Surf City to Duck, North Carolina including Albemarle and Pamlico Sounds.

Hurricane Michael intensified rapidly during the past 12 hours.  An eye with a diameter of 20 miles (32 km) is surrounded by a ring of strong thunderstorms.  The strongest winds are occurring in that ring of storms.  Storms near the core of Hurricane Michael are generating strong upper level divergence which is pumping large quantities of mass away from the hurricane.  The removal of mass allowed the surface pressure to decrease rapidly to 933 mb.

Winds to hurricane force extend out about 45 m.p.h. (75 km/h) from the center of Hurricane Michael.  Winds to tropical storm force extend out about 185 miles (290 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Hurricane Michael is 29.9.  The Hurricane Size Index (HSI) is 16.1 and the Hurricane Wind Intensity Size Index (HWISI) is 46.0.  Hurricane Michael is capable of causing regional significant damage.

Hurricane Michael is stronger than any other hurricane to hit north Florida in the historical record.  Michael is similar in intensity to what Hurricane Charley was when Charley hit southwest Florida in 2004.  Hurricane Michael is bigger than Charley was in 2004.

An upper level trough over the Central U.S. and a subtropical high pressure system over the western Atlantic Ocean are combining to steer Hurricane Michael toward the north.  The trough will turn Michael toward the northeast when it reaches the coast.  On its anticipated track Hurricane Michael will make landfall near Panama City and Port St. Joe, Florida in about six hours.

Hurricane Michael will bring destructive winds to the coast of north Florida.  The strongest winds will be near the center and east of the center.  Those winds will push water toward the coast and a storm surge of 10 to 15 feet (3 to 5 meters) will occur east of where the center of Michael makes landfall.  The coast of the northeast Gulf of Mexico is very vulnerable to storm surges and significant damage will occur.

The center of Hurricane Michael will move between Dothan, Alabama and Tallahassee, Florida.  It will pass near Albany, Georgia and then move south of Macon, Georgia.  The center of Michael could move near Columbia, South Carolina and then it could exit the East Coast of the U.S. near Norfolk, Virginia.

Michael will bring hurricane force winds to northeast Florida, extreme southeast Alabama and southern Georgia.  There will be widespread power outages.  Winds to tropical storm force will occur in South Carolina and North Carolina.  Hurricane Michael will drop locally heavy rain when it moves inland.  The wind and rain will disrupt efforts to recover from the effects of Hurricane Florence in South Carolina and North Carolina.

Michael Strengthens to a Major Hurricane

Hurricane Michael strengthened into a major hurricane on Tuesday afternoon.  At 5:00 p.m. EDT on Tuesday the center of Hurricane Michael was located at latitude 26.0°N and longitude 86.4°W which put it about 290 miles (470 km) south of Panama City, Florida.  Michael was moving toward the north at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 140 m.p.h. (225 km/h).  The minimum surface pressure was 957 mb.

A Hurricane Warning is in effect for the portion of the coast from the Alabama-Florida border to the Suwanee River, Florida.  Tropical Storm Warnings are in effect for the portions of the coast from the Alabama-Florida border to the Alabama-Mississippi border, from Suwanee River to Chassahowitzka, Florida and from Fernandina Beach, Florida to South Santee River, South Carolina on the Atlantic Coast.  Tropical Storm Watches are in effect for the portions of the coast from the Alabama-Mississippi border to the Mouth of the Pearl River, from Chassahowitzka to Anna Maria Island, Florida and from South Santee, River South Carolina to Duck, North Carolina including Albemarle and Pamlico Sounds.

The inner core of Hurricane Michael tightened on Tuesday afternoon.  The diameter of the eye decreased from 30 miles (50 km) to 22 miles (35 km).  The ring of thunderstorms around the eye tightened around the smaller eye and the strongest winds were closer to the center of circulation.  Storms around the core of Michael were generating upper level divergence which was pumping mass away from the hurricane.  The removal of mass allowed the surface pressure to decrease from 965 mb to 957 mb during the past six hours.

Winds to hurricane force extend out about 45 miles (75 km) from the center of Hurricane Michael.  Winds to tropical storm force extend out about 170 miles (280 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Hurricane Michael is 22.1.  The Hurricane Size Index (HSI) is 14.6 and the Hurricane Wind Intensity Size Index (HWISI) is 36.7.  Hurricane Michael is capable of causing regional major damage.

Hurricane Michael will move through an environment favorable for intensification for another 12 to 18 hours.  Michael will move over water where the Sea Surface Temperature is near 29°C.  An upper level trough over the Central U.S. is producing westerly winds which are blowing toward the top of Hurricane Michael, but those winds are not causing enough vertical wind shear to prevent intensification.  Hurricane Michael could intensify to Category 4 on the Saffir-Simpson Scale before it makes landfall.

Hurricane Michael is moving between a subtropical high pressure system over the western Atlantic Ocean and the upper level trough over the Central U.S.  Those two weather systems are steering Michael toward the north and that general motion is expected to continue for another 12 hours.  On its anticipated track Hurricane Michael will make landfall near Panama City and Port St. Joe, Florida early on Wednesday afternoon.  The upper level trough will steer Michael more toward the northeast after it makes landfall.  The center of Michael is likely to move between Dothan, Alabama and Tallahassee, Florida and it could pass near Albany, Georgia.

Hurricane Michael will bring strong winds to northwest Florida, extreme southeast Alabama and southern Georgia.  There will be wind damage and widespread power outages could occur.  The coast of the northeastern Gulf of Mexico is very vulnerable to storm surges.  Hurricane Michael will produce a storm surge of 10 to 15 feet (3 to 5 meters) at some points along the coast.  Michael will drop locally heavy rain.  Although Hurricane Michael will weaken when it moves inland, it will bring gusty winds and heavy rain to South Carolina and North Carolina.  Hurricane Michael will hinder efforts in those states to recover from the effects of Hurricane Florence.

Michael Strengthens Into a Hurricane, Watches Issued for Gulf Coast

Former Tropical Storm Michael strengthened into a hurricane on Monday morning and Watches were issued for portions of the Gulf Coast.  At 11:00 a.m. EDT on Monday the center of Hurricane Michael was located at latitude 21.2°N and longitude 84.9°W which put it about 50 miles (80 km) south of the western end of Cuba.  Michael was moving toward the north at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 982 mb.

A Hurricane Watch was in effect for the portion of the coast from the Alabama-Florida border to Suwanee River, Florida.  Tropical Storm Watches were in effect for the portions of the coast from the Alabama-Florida border to the Alabama-Mississippi border and from Suwanee River to Anna Maria Island, Florida.  A Hurricane Warning was in effect for the Cuban province of Pinar del Rio.  Tropical Storm Warnings were in effect for the Cuban province of Isle of Youth and for the portion of the coast from Tulum to Cabo Catoche, Mexico.

Hurricane Michael continued to organize quickly.  A circular eye with a diameter of about 30 miles (50 km) was forming at the center of Michael.  A ring of strong thunderstorms was wrapping around the eye and the strongest winds were occurring in the ring of storms.  Several bands of showers and thunderstorms were wrapping around the core of Hurricane Michael.  Storms near the core were generating upper level divergence which was pumping mass away from the hurricane.

Winds to hurricane force extended out about 30 miles (50 km) primarily to the northeast of the center of Hurricane Michael.  Winds to tropical storm force extended out about 175 miles (280 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Hurricane Michael was 10.4.  The Hurricane Size Index (HSI) was 6.8 and the Hurricane Wind Intensity Size Index (HWISI) was 17.2.

Hurricane Michael will move into an environment that will become increasingly favorable for intensification.  Michael will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough over the Gulf of Mexico was producing westerly winds which were blowing toward the top of the circulation.  Those winds were causing some vertical wind shear.  However, the upper level trough will move westward away from Hurricane Michael and the wind shear will decrease.  Hurricane Michael will continue to strengthen when it moves over the Gulf of Mexico and it could intensify rapidly once the eye and eyewall are fully formed.  Hurricane Michael is likely to strengthen into a major hurricane.

Hurricane Michael will move around the western end of a subtropical high pressure system centered over the western Atlantic Ocean.  The high will steer Michael in a northerly direction during the next several days.  It will get bigger and stronger during the next 48 hours.  On its anticipated track Hurricane Michael will approach the northeast coast of the Gulf of Mexico on Wednesday.  It is likely to be a major hurricane at that time.  Hurricane Michael has the potential to cause a storm surge of 10 to 15 feet (3 to 5 meters) at the coast.  It will bring strong winds which could cause regional major damage and result in significant power outages.  Locally heavy rain could cause flooding in some locations.

Tropical Storm Michael Strengthens East of Yucatan

Tropical Storm Michael strengthened east of the Yucatan peninsula on Sunday.  At 8:00 p.m. EDT on Sunday the center of Tropical Storm Michael was located at latitude 19.9°N and longitude 85.4°W which put it about 105 miles (170 km) east-southeast of Cozumel, Mexico.  Michael was moving toward the north at 5 m.p.h. (8 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 997 mb.

A Tropical Storm Warning was in effect for the Cuban provinces of Pinar del Rio and the Isle of Youth.  A Tropical Storm Warning is also in effect for the portion of the coast from Tulum to Cabo Catoche, Mexico.

The circulation around Tropical Storm Michael is still organizing and the distribution of thunderstorms is asymmetrical.  Most of the thunderstorms are occurring in bands in the eastern half of the circulation.  A new center of circulation formed on Sunday afternoon near those thunderstorms.  Many of the rainbands in the western half of Tropical Storm Michael contain primarily showers and lower clouds.  One outer rainband in the southwestern periphery of the circulation does contain numerous thunderstorms.  The strongest winds are occurring in the rainbands on the eastern side of Tropical Storm Michael.  The winds are weaker on the western side of the circulation.  Storms on the eastern side of Michael are generating some upper level divergence which was pumping mass away from the tropical storm and was allowing the surface pressure to decrease.

An upper level trough over the Gulf of Mexico is producing westerly winds which are blowing across the top of Tropical Storm Michael.  Those winds are causing moderate vertical wind shear which was slowing the rate of intensification, but the shear is not strong enough to prevent Michael from strengthening.  The wind shear is probably the reason for the asymmetrical distribution of thunderstorms.  The upper level trough will move westward during the next few days and the upper level winds will weaken.  Michael will move over water where the Sea Surface Temperature is warmer than 30°C.  Tropical Storm Michael will strengthen slowly during the next 24 hours.  However, it will intensify more rapidly on Tuesday when the upper level winds weaken.  Michael will strengthen into a hurricane when it moves over the Gulf of Mexico and it could intensify into a major hurricane.

Tropical Storm Michael has been moving slowly while the circulation organizes and the center reforms.  Michael will move around the southwestern part of the subtropical high pressure system over the western North Atlantic Ocean.  The high will steer Michael in a northward direction during the next two or three days.  On its anticipated track the center of Tropical Storm Michael will pass between the western end of Cuba and the Yucatan peninsula on Monday.  Michael could approach northern Florida by Wednesday.  It will be a hurricane at that time and it could be a major hurricane.  Michael could produce strong winds, a significant storm surge and drop heavy rain when it reaches the coast.

Possible Tropical Development Near Yucatan Peninsula

A tropical cyclone could develop near the Yucatan peninsula during the next few days.  At 2:00 p.m. EDT on Friday the center of Invest 91L was located at latitude 16.0°N and longitude 84.3°W which put it about 400 miles (640 km) southeast of Cancun, Mexico.  It was moving toward the northwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1007 mb.

A broad area of low pressure is over the western Caribbean Sea, Central America and the adjacent waters of the Eastern North Pacific Ocean.  Several smaller, mesoscale centers of rotation appear to be revolving around the larger low pressure system.  One of the mesoscale centers is over the Eastern North Pacific Ocean just west of the coast of Central America.  One or two other mesoscale centers appear to be over the western Caribbean Sea near Honduras.  The low level circulation is not currently well organized.  It is broad and diffuse.  Thunderstorms are clustered around the mesoscale centers, but large scale rainbands have not formed.

Westerly winds in the upper levels are are blowing over the top of the system.  Those winds are creating moderate vertical wind shear which is inhibiting the development of the low pressure system.  The upper level winds are forecast to weaken during the next few days and the wind shear will diminish.  The Sea Surface Temperature of the water in the northwestern Caribbean Sea and Gulf of Mexico is near 30°C.  The broad low pressure system could slowly organize during the next two to three days.  The National Hurricane Center is indicating that there is a 70% probability of formation of a tropical cyclone near the Yucatan peninsula or over the southern Gulf of Mexico during the next five days.  A reconnaissance plane is scheduled to investigate the low pressure system on Sunday, if necessary.

The broad low is southwest of a subtropical high pressure system over the Atlantic Ocean.  The high is expected to steer the low toward the northwest during the weekend.  On its anticipated track the low will move over the northwestern Caribbean Sea during the next several days.  it could move into the Gulf of Mexico on Monday.

Elsewhere over the Atlantic Ocean, Tropical Storm Leslie continued to meander northeast of Bermuda.  At 11:00 a.m. EDT on Friday the center of Tropical Storm Leslie was located at latitude 36.2°N and longitude 58.4°W which put it about 455 miles (730 km) northeast of Bermuda.  Leslie was moving toward the north-northwest at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 986 mb.

Hurricane Florence Moves Closer to the Carolinas

Hurricane Florence moved closer to the Carolinas on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Hurricane Florence was located at latitude 32.0°N and longitude 73.7°W which put it about 280 miles (455 km) east-southeast of Wilmington, North Carolina.  Florence was moving toward the northwest at 17 m.p.h. (28 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 957 mb.

A Hurricane Warning was in effect for the portion of the coast from South Santee River, South Carolina to Duck, North Carolina including Pamlico and Albemarle Sounds.  A Hurricane Watch was in effect for the portion of the coast from Edisto Beach, South Carolina to South Santee River, South Carolina.  A Tropical Storm Warning is in effect for the portion of coast from Duck, North Carolina to the North Carolina-Virginia border.  A Tropical Storm Watch was in effect for the portion of the coast from the North Carolina-Virginia border to Cape Charles Light, Virginia and for Chesapeake Bay south of New Point Comfort.

The wind speed in Hurricane Florence decreased on Wednesday but the circulation increased in size.  It appeared that another eyewall replacement cycle could have started.  Satellite microwave images suggested that there could be two eyewalls and a reconnaissance plane reported a double wind maxima.  Both of those things could be evidence of concentric eyewalls.  In addition, counterclockwise flow around a small upper level low near Florida may have produced southerly winds that blew toward the south side of Hurricane Frances.  Those winds may have inhibited the upper level divergence to the south of Florence.  Since the hurricane was unable to pump out as much mass, the surface pressure increased and the wind speed decreased.

The circulation of Hurricane Florence increased in size on Wednesday.  Winds to hurricane force extended out about 80 miles (130 km) from the center of circulation.  Winds to tropical storm force extended out about 200 miles (320 km) from the center.  The Hurricane Intensity Index (HII) for Hurricane Florence was 19.2.  The Hurricane Size Index (HSI) was 25.5 and the Hurricane Wind Intensity Size Index (HWISI) was 44.7.  Those indices are very similar to the numbers for Hurricane Jeanne just before Jeanne made landfall in southeast Florida in 2004.

Hurricane Florence will move through an environment favorable for intensification on Thursday.  Florence will move over water where the Sea Surface Temperature is near 29°C.  Florence will move farther away from the upper low near Florida and the low should not inhibit divergence to the south of the hurricane as much.  In addition, Hurricane Florence will move over the warm water in the Gulf Stream about 6 to 12 hours before it reaches the coast.  It will be able to extract extra energy at that time.  If the inner core becomes more organized, then Hurricane Florence could intensify on Thursday.  If the inner core does not get better organized, then Florence will likely maintain its current intensity or weaken slowly.

Hurricane Florence will move near the western end of the subtropical high pressure system over the western Atlantic Ocean.  The high will steer Florence toward the northwest on Thursday.  On its anticipated track the center of Hurricane Florence will be near the coast of North Carolina on Thursday night.  A ridge over the eastern U.S. is likely to block the northward motion of Hurricane Florence when it reaches the coast.  The ridge will steer Florence slowly toward the west-southwest on Friday and Saturday.

Hurricane Florence will have the impact of a major hurricane regardless of the actual sustained wind speed.  The large circulation and slow rate of movement when Florence reaches the coast means that locations could experience strong winds for extended periods of time.  Wind damage and power outages could be extensive.  Some places in North Carolina had a rainy summer and strong winds could uproot trees.  Hurricane Florence will produce a dangerous storm surge along the coast.  The surge could exceed 10 feet (3 meters) in some locations east of where the center makes landfall.  The slow forward speed also means that Hurricane Florence could drop locally heavy rain and severe flooding could occur.

Elsewhere the rest of the Atlantic Ocean was also very active.  Tropical Storm Isaac was nearing the Lesser Antilles, Hurricane Helene was weakening south of the Azores and Subtropical Storm Joyce formed northwest of Helene.

At 11:00 p.m. EDT on Thursday the center of Tropical Storm Isaac was located at latitude 15.3°N and longitude 58.0°W which put it about 220 miles (355 km) east of Dominica.  Isaac was moving toward the west at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1006 mb.  Tropical Storm Warnings were in effect for Guadeloupe, Martinique and Dominica.  Tropical Storm Watches were in effect for Antigua, Montserrat, St, Kitts and Nevis, Saba and St. Eustatius, St. Martin and St. Maarten.

At 11:00 p.m. EDT on Thursday the center of Hurricane Helene was located at latitude 22.4°N and 36.9°W which put it about 1270 mile (2045 km) south-southwest of the Azores.  Helene was moving toward the north at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 983 mb.

At 11:00 p.m. EDT on Thursday the center of Subtropical Storm Joyce was located at latitude 15.3°N and longitude 46.6°W which put it about 910 miles (1465 km) west-southwest of the Azores.  Joyce was moving toward the southwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1006 mb.

Hurricane Warnings Issued for Carolinas for Hurricane Florence

Hurricane Warnings were issued for the Carolinas on Tuesday for the potential impacts of Hurricane Florence.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Florence was located at latitude 28.4°N and longitude 68.7°W which put it about 670 miles (1075 km) east-southeast of Cape Fear, North Carolina.  Florence was moving toward the west-northwest at 17 m.p.h. (28 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 946 mb.

A Hurricane Warning was in effect for the portion of the coast from South Santee River, South Carolina to Duck, North Carolina.  Hurricane Watches were in effect for the portions of the coast from Edisto Beach to South Santee River, South Carolina and from Duck, North Carolina to the North Carolina-Virginia border.  Tropical Storm Watches were in effect for the portions of the coast from Duck, North Carolina to Cape Charles Light, Virginia and for Chesapeake Bay south of New Point Comfort.

Hurricane Florence completed an eyewall replacement cycle and it continues to be a powerful hurricane.  There was a circular eye with a diameter of 30 miles (48 km) at the center of Florence.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  The eyewall replacement cycle resulted in a larger circulation.

Winds to hurricane force extended out about 60 miles (95 km) from the center of circulation of Hurricane Florence.  Winds to tropical storm force extended out about 175 miles (280 km) from the center.  The Hurricane Intensity Index (HII) for Hurricane Florence was 28.2.  The Hurricane Size Index (HSI) was 18.9 and the Hurricane Wind Intensity Size Index (HWISI) was 47.1.  Hurricane Florence is capable of causing extensive significant damage.

Hurricane Florence will move through an environment favorable for strong hurricanes during the next 24 to 36 hours.  Florence will move over water where the Sea Surface Temperature is near 29°C.  it will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Hurricane Florence is likely to maintain its intensity and it could strengthen.  If another eyewall replacement cycle occurs, then there could be fluctuations in intensity.

Hurricane Florence will move around the western end of a subtropical high pressure system over the western Atlantic Ocean.  The high will steer Florence toward the west-northwest during the next 24 to 36 hours.  On its anticipated track Hurricane Florence could approach the coast of the Carolinas later on Thursday.  The steering winds are forecast to weaken when Florence nears the coast and there is great uncertainty about the track when that occurs.  Hurricane Florence will bring strong winds to coastal North Carolina and eastern South Carolina.  Wind pushing water toward the shore will cause a significant storm surge.  A slow forward speed will mean that Hurricane Florence will drop a lot of rain and there is a risk of significant flooding of rivers and streams.

Elsewhere over the Atlantic Ocean, Tropical Storm Isaac was speeding toward the Lesser Antilles and Hurricane Helene was weakening far south of the Azores.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Isaac was located at latitude 14.5°N and longitude 52.3°W which put it about 580 miles (935 km) east of Martinique.  Isaac was moving toward the west at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 999 mb.  Tropical Storm Warnings were in effect for Dominica, Martinique and Guadeloupe.  Tropical Storm Watches were in effect for Antigua, Montserrat, St. Kitts and Nevis, and Saba and St. Eustatius.

At 11:00 p.m. EDT on Tuesday the center of Hurricane Helene was located at latitude 18.0°N and longitude 35.4°W which put it about 1479 miles (2370 km) south-southwest of the Azores.  Helene was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 973 mb.