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Tropical Storm Marco Strengthens, Hurricane Watch for New Orleans

Tropical Storm Marco strengthened on Saturday and a Hurricane Watch was issued for a portion of the central Gulf Coast.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Marco was located at latitude 21.9°N and longitude 68.1°W which put it about 50 miles (80 km) west of the western tip of Cuba.  Marco was moving toward the north-northwest at 13 m.p.h. (20 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 992 mb.

A Hurricane Watch was issued for the portion of the coast from Intracoastal City, Louisiana to the Mississippi/Alabama border including Lake Pontchartrain, Lake Maurepas and New Orleans.  A Tropical Storm Watch was in effect for the portion of the coast from the Mississippi/Alabama border to the Alabama/Florida border.  A Tropical Storm Warning was in effect for the Cuban province of Pinar del Rio.

Tropical Storm Marco exhibited much better organization on Saturday.  Weather radar on a reconnaissance plane and from Cuba as well as visible satellite images indicated that a small eye developed at the center of Marco.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Tropical Storm Marco.  Storms near the core were generating upper level divergence which was pumping away to the north of the tropical storm.  The circulation around Marco was small.  Winds to tropical storm force extended out 100 miles (160 km) to the east of the center of circulation.  Winds to tropical storm force only extended out 50 miles (80 km) on the western side of the tropical storm.

Tropical Storm Marco will move through an environment favorable for intensification during the nextt 24 hours.  Marco will move over water where the Sea Surface Temperature is near 30°C.  It will move east of an upper level trough over the Gulf of Mexico.  The trough will produce southwesterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear is not likely to be enough to prevent intensification.  Tropical Storm Marco is likely to intensify into a hurricane during the next 24 hours.  Since he circulation around Marco is small, the tropical storm could strengthen or weaken quickly if the environment changes.

The upper level trough and a subtropical high pressure system over the Atlantic Ocean will steer Tropical Storm Marco toward the north-northwest during the next 36 to 48 hours.  On its anticipated track Marco could approach southeastern Louisiana by Monday afternoon.  Marco could be a hurricane when it approaches the coast.

Elsewhere, Tropical Storm Laura dropped heavy rain over Puerto Rico and it prompted the issuance of a Tropical Storm Watch for the Florida Keys.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Laura was located at latitude 18.0°N and longitude 68.1°W which put it about 125 miles (200 km) east-southeast of Santo Domingo, Dominican Republic.  Laura was moving toward the west at 18 m.p.h. (30 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 1004 mb.

Tropical Storm Warnings were in effect for the U.S. Virgin Islands, Puerto Rico, Vieques and Culebra.  A Tropical Storm Warning was in effect for the northern coast of Hispaniola from Le Mole St. Nicholas, Haiti to Cabo Engano, Dominican Republic.  Tropical Storm Warnings were in effect for the Turks and Caicos, the Acklins, Long Key, Crooked Island, the Inaguas, and the Ragged Islands.  A Tropical Storm Warning was also in effect for the Cuban provinces of Las Tunas, Holguin, Santiago de Cuba, Guantanamo and Granma.

A Tropical Storm Watch was issued for the Florida Keys from Ocean Reef to Key West.  Tropical Storm Watches were in effect for the Central Bahamas and for Andros Island.

Tropical Storm Marco is forecast to move over HIspaniola and the mountains there are likely to disrupt the circulation.

TD 14 Strengthens into Tropical Storm Marco

Former Tropical Depression Fourteen strengthened into Tropical Storm Marco over the northwestern Caribbean Sea on Friday night.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Marco was located at latitude 18.7°N and longitude 84.9°W which puts it about 180 miles (290 km) southeast of Cozumel, Mexico.  Marco was moving toward the north-northwest at 13 m.p.h. (20 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 1003 mb.

A Hurricane Watch was in effect for the portion of the coast from Punta Herrero to Cancun, Mexico.  A Tropical Storm Warning was in effect for the portion of the coast from Punta Herrero to Dzilam, Mexico.

An Air Force Reserve Hurricane Hunter reconnaissance aircraft found winds to tropical storm force in former Tropical Depression Fourteen and the National Hurricane Center upgraded the system to Tropical Storm Marco.  More thunderstorms developed near the center of Marco.  Many of the thunderstorms were occurring in short bands northeast of the center of circulation.  The strongest winds were occurring in those bands.  Storms near the center were generating upper level divergence which was pumping mass away to the northeast of the tropical storm.  Winds to tropical storm force extended 80 miles (130 km) to the northeast of Marco.  The winds in the other parts of the tropical storm were blowing at less than tropical storm force.

Tropical Storm Marco will move through an environment favorable for intensification during the next 24 hours.  Marco will move over water where the Sea Surface Temperature is near 29°C.  It will move east of a large upper level trough over the Gulf of Mexico.  The trough will produce southwesterly winds which will blow toward the top of Tropical Storm Marco.  Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification.  Marco will intensify on Saturday and it could strengthen quickly because the circulation is small.  Tropical Storm Marco could also weaken quickly if the center moves over the Yucatan Peninsula.

Tropical Storm Marco will move around the western end of a subtropical high pressure system over the Atlantic Ocean.  The high and the upper level trough will interact to steer Marco toward the northwest during the next 24 to 36 hours.  On its anticipated track the center of Tropical Storm Marco could pass near the northeastern part of the Yucatan Peninsula on Saturday.

Elsewhere over the Atlantic Ocean, disorganized Tropical Storm Laura sped across the northern Leeward Islands on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Laura was located at latitude 17.0°N and longitude 84.9°W which put it about 195 miles (315 km) east-southeast of San Juan, Puerto Rico.  Laura was moving toward the west-northwest at 18 m.p.h. (30 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 1008 mb.

Tropical Storm Warnings were in effect Saba, St. Eustatius, St. Maarten, St. Martin, St. Barthelemy, the British Virgin Islands, the U.S. Virgin Islands, Puerto Rico, Vieques, Culebra, the north coast of HIspaniola from Le Mole St. Nicholas, Haiti to Cabo Engano, Dominican Republic, the Turks and Caicos, the Acklins, Crooked Island, Long Cay, the Inaguas, and the Ragged Islands.  A Tropical Storm Watch was in effect for the Central Bahamas.

Tropical Storm Laura Develops, Warnings for Puerto Rico and Leeward Islands

Tropical Storm Laura developed east of the northern Leeward Islands on Friday morning.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Laura was located at latitude 17.0°N and longitude 60.2°W which put it about 210 miles (335 km) east-southeast of the northern Leeward Islands.  Laura was moving toward the west at 18 m.p.h. (30 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 1007 mb.

Tropical Storm Warnings were in effect for Saba, St. Eustatius, St. Maarten, Antigua, Barbuda, St. Kitts, Nevis, Anguilla, St. Martin, St. Barthelemy, the British Virgin Islands, the U. S, Virgin Islands, Puerto Rico, Vieques, and Culebra.

Tropical Storm Watches were in effect for the portion of the north coast of Hispaniola from Le Mole St. Nicholas, Haiti to Cabron, Dominican Republic and for the Turks and Caicos, the Acklins, Crooked Island, Long Cay, the Inaguas, and the Ragged Islands.

A NOAA plane found winds to tropical storm force in former Tropical Depression Thirteen on Friday morning and the National Hurricane Center upgraded the system to Tropical Storm Laura.  Even though the plane found winds to tropical storm force, the circulation around Tropical Storm Laura was not well organized. There were several clusters of thunderstorms in the northern half of the circulation, but there were fewer thunderstorms in the southern half of Laura.  Winds to tropical storm force extended out about 150 miles (240 km) on the northern side of the tropical storm.  The winds in the southern half of the circulation were blowing at less than tropical storm force.

Tropical Storm Laura will move through an environment favorable for intensification during the next 24 hours.  Laura will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  The lack of organization of the circulation around Laura will limit how quickly the tropical storm can intensify.  Tropical Storm Laura is likely to get stronger during the next 24 hours.

Tropical Storm Laura will move south of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer Laura toward the west-northwest during the next several days.  On its anticipated track Tropical Storm Laura will move across the northern Leeward Islands later today.  Laura could reach Puerto Rico by Saturday.  Tropical Storm Laura will bring gusty winds and locally heavy rain to the islands when it passes over them.

Elsewhere, Tropical Depression Fourteen was getting more organized over the northwestern Caribbean Sea.  At 11:00 a.m. EDT on Friday the center of Tropical Depression Fourteen was located at latitude 16.6°N and longitude 84.1°W which put it about 325 miles (525 km) southeast of Cozumel, Mexico.  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. (75 km/h).  The minimum surface pressure was 1008 mb.

A Hurricane Watch was in effect for the portion of the coast from Punta Herrero to Cancun, Mexico.  A Tropical Storm Warning was in effect for the Bay Islands, Honduras and from Punta Herrero to Cancun, Mexico.  A Tropical Storm Watch was in effect for the portion of the coast from Cancun to Dzilam, Mexico.

Tropical Depression Fourteen Forms Over Western Caribbean

Tropical Depression Fourteen formed over the western Caribbean Sea on Thursday morning.  At 11:00 a.m. EDT on Thursday the center of Tropical Depression Fourteen was located at latitude 15.1°N and longitude 79.7°W which put it about 235 miles (375 km) east of Cabo Gracias a Dios.  The depression was moving toward the west at 21 m.p.h. (33 km/h).  The maximum sustained wind speed was 35 m.p.h. (55km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1007 mb.

A Tropical Storm Watch was issued for the portion of the coast of Honduras from the border with Nicaragua to Punta Castilla including the Bay Islands.

Satellite images on Thursday morning indicated that a center of circulation had developed within a tropical wave over the western Caribbean Sea and the National Hurricane Center designated the system as Tropical Depression Fourteen.  The circulation around Tropical Depression Fourteen was still organizing.  Bands of showers and thunderstorms were developing and they were beginning to revolve around the center of circulation.  Storms near the center started to generate upper level divergence which was pumping mass away from the depression.

Tropical Depression Fourteen will move through an environment favorable for intensification during the next 36 to 48 hours.  The depression will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and the will be little vertical wind shear.  Tropical Depression Fourteen will strengthen during the next day or two.

Tropical Depression Fourteen will move around the southwester part of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer the depression toward the west-northwest during the next 24 hours.  The depression will turn toward the northwest on Friday when it gets closer to the western end of the high.  On its anticipated track Tropical Depression Fourteen will pass near the coast of Honduras on Friday.  It will approach the Yucatan Peninsula on Saturday.  The depression could drop heavy rain over eastern Honduras and flash floods will be possible.

Elsewhere over the Atlantic Ocean,, Tropical Depression Thirteen was speeding toward the northern Leeward Islands.  At 11:00 a.m. EDT on Thursday the center of Tropical Depression Thirteen was located at latitude 16.0°N and longitude 52.0°W which put it about 750 miles (1205 km) east-southeast of the northern Leeward Islands.  The depression was moving toward the west-northwest at 21 m.p.h. (33km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1008 mb.

Tropical Storm Watches were in effect for Saba and St. Eustatius, St. Maarten, St. Kitts, Nevis, Antigua, Barbuda and Anguilla.

Tropical Depression Fifteen Forms Southeast of Cabo Verde Islands

Tropical Depression Fifteen formed southeast of the Cabo Verde Islands on Monday.  At 5:00 p.m. EDT on Monday the center of Tropical Depression Fifteen was located at latitude 13.2°N and longitude 20.2°W which put it about 320 miles (515 km) southeast of the Cabo Verde Islands.  The depression was moving toward the northwest at 8 m.p.h. (13 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. (75 km/h).  The minimum surface pressure was 1006 mb.

A large, well developed low pressure system embedded in the northern end of a tropical wave moved over the Atlantic Ocean west of North Africa on Monday.  Bands of showers and thunderstorms began to strengthen when the low moved over water and the National Hurricane Center designated the system as Tropical Depression Fifteen.  Bands of showers and thunderstorms were revolving around the center of the depression.  Storms closer to the center were generating upper level divergence which was pumping mass away from Tropical Depression Fifteen.  The circulation around the depression was quite large.  The diameter of the low level circulation was about 500 miles (800 km).

Tropical Depression Fifteen will move through an environment favorable for intensification during the next 24 to 48 hours.  The depression will move over water where the Sea Surface Temperature is near 28°C.  It will move under the western end of an upper level ridge centered over North Africa.  The upper level winds will be weak and there will be little vertical wind shear during the next day or two.  Tropical Depression Fifteen is likely to strengthen into Tropical Storm Nestor.

The ridge over North Africa will steer Tropical Depression Fifteen toward the northwest during the next several days.  On its anticipated track the center of the depression could reach the Cabo Verde Islands within 24 hours.  Since the depression is forecast to strengthen into a tropical storm watches and/or warnings could be issued.

Elsewhere over the Atlantic Ocean, Tropical Storm Melissa completed a transition to an extratropical cyclone on Monday.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Melissa was located at latitude 41.0°N and longitude 51.4°W which put it about 405 miles (650 km) south-southeast of Cape Race, Newfoundland.  Melissa was moving toward the east at 23 m.p.h. (37 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 1004 mb.

Subtropical Storm Melissa Develops off Northeast U.S. Coast

Subtropical Storm Melissa developed off the northeast coast of the U.S. on Friday.  At 11:00 a.m. EDT on Friday the center of Subtropical Storm Melissa was located at latitude 38.5°N and longitude 69.6°W which put it about 190 miles (300 km) south of Nantucket, Massachusetts.  Melissa was moving toward the south-southwest at 3 m.p.h. (5 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 995 mb.

More thunderstorms developed near the center of a large low pressure system off the northeast coast of the U.S. on Friday morning and the National Hurricane Center designated the system as Subtropical Storm Melissa.  Melissa initially began as an extratropical cyclone along a slow moving cold front off the east coast of the U.S earlier this week.  The cold front moved east of the surface low pressure system and the surface low stalled underneath an upper level trough.  More showers and thunderstorms began to develop in bands and the low pressure system started to look more subtropical.

The circulation around Melissa was characteristic of a subtropical storm.  There was a well defined center of circulation visible on satellite images.  However, many of the stronger thunderstorms were occurring in a band that wrapped around the northern portion of the circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.  The circulation was drawing cooler, drier air into the western and southern parts of the subtropical storm.  The wind field around Subtropical Storm Melissa was large and asymmetrical.  Winds to tropical storm force extended out 350 miles (565 km) from the center in the northeastern part of Melissa.  Tropical storm force winds only extended out 100 miles (160 km) to the southeast of the center of circulation.

The intensity of Subtropical Storm Melissa may not change much during the next 12 to 24 hours.  Melissa will remain under the middle of the upper level trough during the rest of Friday.  The winds are weak in the middle of the trough and there will not be much vertical wind shear.  Subtropical Storm Melissa will be over water where the Sea Surface Temperature is near 24°C.  So, there will not be a lot of energy in the upper ocean to support intensification.  The upper level trough will move eastward on Saturday and westerly winds will blow toward the top of Melissa.  The westerly winds will cause significant vertical wind shear, which will start to weaken Subtropical Storm Melissa.

Since the winds are weak in the middle of the upper level trough, Subtropical Storm Melissa is unlikely to move much during the rest of Friday.  Stronger westerly winds will steer Melissa to the east during the weekend.  On its anticipated track Subtropical Storm Melissa is forecast to move away from the U.S. during the weekend.  The large circulation around Melissa will generate large waves which will affect the south coast of New England and the Mid-Atlantic states.  Coastal flooding could occur in some locations.

NHC Upgrades Hurricane Michael to Cat. 5

The National Hurricane Center (NHC) upgraded Hurricane Michael to Category 5 on the Saffir-Simpson Scale after it completed and released its post storm analysis on Friday.  NHC does a post storm analysis of every tropical cyclone in its area of responsibility after the end of the hurricane season.  The maximum sustained wind speed at the time of landfall in northwest Florida of Hurricane Michael, which was given originally as 155 m.p.h. (250 km/h), was increased to 160 m.p.h. (260 km/h) after the post storm analysis.  Hurricane Michael becomes one of only four hurricanes to make landfall in the U.S. as a Category 5 hurricane.  The other Category 5 hurricanes to hit the U.S. were the Labor Day Hurricane which hit the Florida Keys in 1935, Hurricane Camille which hit Mississippi in 1969 and Hurricane Andrew which hit south Florida in 1992.

The National Hurricane Center prepares a Tropical Storm Report on every tropical cyclone in its area of responsibility and those reports are available on NHC’s web site.  J. L. Beven II, R. Berg and A. Hagen were the authors of the Tropical Cyclone Report on Hurricane Michael.  They explain in the Tropical Cyclone Report how they arrived at the intensity of Hurricane Michael at landfall.  They analyzed aircraft data including flight level winds and SMFR intensities.  They did an analysis of the Dopper wind velocities observed by the WSR-88D radar at Eglin Air Force Base.  They also considered available data on the surface winds and pressures and satellite derived estimates of the intensity of Hurricane Michael.  Based on analysis of all of that information, they concluded that the intensity of Hurricane Michael when it made landfall in northwest Florida was 160 m.p.h. (260 km/h).  Their full Tropical Cyclone Report on Hurricane Michael is available on NHC’s website at https://www.nhc.noaa.gov/data/tcr/AL142018_Michael.pdf.

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.