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Tropical Depression Cindy Brings Stormy Weather to Southern U.S.

Tropical Depression Cindy brought stormy weather to parts of the southern U.S. on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Depression Cindy was located at latitude 33.1°N and 93.5°W which put it about 70 miles (115 km) southwest of Little Rock, Arkansas.  Cindy was moving toward the north-northeast at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 20 m.p.h. (30 km/h) and there were wind gusts to 30 m.p.h. (50 km/h).  The minimum surface pressure was 1000 mb.

Tropical Storm Cindy made landfall early on Thursday morning near the border between Texas and Louisiana.  Cindy moved steadily northward during the day and it was centered over southwestern Arkansas by Thursday night.  Broad counterclockwise rotation around Cindy transported warm and very humid air over the southern U.S.  Bands of showers and thunderstorms dropped locally heavy rain in some places.  Rivers and streams were above flood stage in several southern states.  Flash Flood Warnings and Flash Flood Watches were issued for portions of the southern U.S. and Ohio River Valley.  Several tornadoes formed in the bands of thunderstorms.  A tornado in Alabama caused property damage.  Southerly winds blowing toward the shore were still causing storm surges along the northern coast of the Gulf of Mexico.

Tropical Depression Cindy is forecast to move northeast toward the Ohio River Valley on Friday.  It will continue to produce locally heavy rain.  A slow moving cold front will approach the region from the west.  A band of stronger convergence could develop where the counterclockwise flow around Cindy interacts with the flow along the cold front.  Higher rainfall totals may occur where this interaction happens.  Wind shear created by the interacting weather systems could also create the potential for some tornadoes.  Tropical Depression Cindy could merge with the cold front during Friday night or Saturday.

Tropical Storm Cindy Nears Northwest Gulf Coast

Tropical Storm Cindy neared the northwestern coast of the Gulf of Mexico on Wednesday evening.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Cindy was located at latitude 28.6°N and longitude 93.4°W which put it about 95 miles (150 km) south-southeast of Port Arthur, Texas.  Cindy was moving toward the north-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 992 mb.

A Tropical Storm Warning is in effect for the portion of the coast from San Luis Pass, Texas to Grand Isle, Louisiana.

Tropical Cyclone Cindy exhibits a hybrid structure in which a broad surface low pressure system is interacting with an upper low centered near the Upper Texas coast.  There is a distinct center of low pressure at the surface.  A band of showers and thunderstorms is northwest of the surface center.  Drier air in the middle and upper levels wraps around the southern and eastern sides of the center and there are no thunderstorms in those quadrants of the core of Tropical Storm Cindy.  A broad flow of moisture is producing bands of showers and thunderstorms in the outer portions of the eastern and northern sides of the circulation.

Tropical Storm Cindy is moving around the western end of a subtropical high pressure system centered over the Atlantic Ocean.  The subtropical high is steering Cindy toward the north-northwest.  On its anticipated track Tropical Storm Cindy will make landfall near the border between Texas and Louisiana on Thursday.  Cindy will turn toward the north and then the tropical storm will move northeastward on Friday.

Some locations will experience prolonged periods of rainfall and fresh water flooding will be possible in those area.  There could also be a storm surge of 3 to 6 feet (1 to 3 meters) near where the center makes landfall.  A few tornadoes could be spun up as rainbands move over the coast.

Tropical Storm Cindy Strengthens Over the Central Gulf of Mexico

Tropical Storm Cindy strengthened on Tuesday night as is moved slowly over the Central Gulf of Mexico.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Cindy was located at latitude 26.4°N and longitude 91.0°W which put it about 305 miles (495 km) southeast of Galveston, Texas.  Cindy was moving toward the northwest at 7 m.p.h. (11 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. (110 km/h).  The minimum surface pressure was 997 mb.

A Tropical Storm Warning is in effect for the portion of the coast from San Luis Pass, Texas to the Alabama/Florida border including Metropolitan New Orleans and Lake Pontchartrain.

Although Tropical Storm Cindy does not look very impressive on infrared satellite imagery, data from reconnaissance aircraft and surface observations from buoys and ships indicate that it has strengthened during the past few hours.  Tropical Storm Cindy displays the structure of a highly sheared tropical storm.  There are no thunderstorms near the center of circulation.  Most of the showers and thunderstorms are in bands well to the east and north of the center of circulation.  The circulation of Tropical Storm Cindy is large and winds to tropical storm force extend out about 275 miles (445 km) northeast of the center.

A combination of an upper level low to the northwest of Cindy and an upper level ridge to the east of it have generated enough upper level divergence to cause the surface pressure to decrease.  The lower pressure at the center created a bigger pressure difference with the subtropical high over the Atlantic Ocean and the stronger pressure gradient force accelerated the wind speed.  So, even though the upper level low produced enough vertical wind shear to prevent a classical process of tropical intensification in Tropical Storm Cindy, the larger scale weather features combined to produce a stronger, larger tropical storm.

Tropical Storm Cindy could intensify a little more if the large scale environment pumps out more mass and the surface pressure decreases further.  The tropical storm could also intensify if the upper low moves farther away from Cindy and the wind shear decreases.  It is unlikely that Tropical Storm Cindy will intensify into a hurricane, but there is a slight possibility that could occur before it makes landfall.

The subtropical high over the Atlantic Ocean is steering Tropical Storm Cindy slowly toward the northwest and that general motion is expected to continue for another 12 to 24 hours.  Cindy could gradually turn toward the north as it approaches the coast and the tropical storm will turn toward the northeast after it moves inland.  On its anticipated track the center of Tropical Storm Cindy could approach the northwestern coast of the Gulf of Mexico on Wednesday night.

The large size of the circulation of Tropical Storm Cindy and its slow motion mean that locally heavy rain and flooding are the greater risks.  There is also the potential for rainbands to spin up tornadoes when they move onto the coast.  Southerly winds driving water toward the coast are already causing a storm surge along parts of the coast of Louisiana.  A storm surge of 3 to 6 feet (1 to 2 meters) may be possible where the strongest winds strike the coast.

Potential Tropical Cyclone Three Prompts Warnings and Watches for Louisiana and Texas

An area of low pressure designated Potential Tropical Cyclone Three moved into the Gulf of Mexico on Monday and the National Hurricane Center issued Tropical Storm Warnings and Watches for Louisiana and Texas.  At 11:00 p.m. EDT on Monday the center of Potential Tropical Cyclone Three was located at latitude 24.4°N and longitude 89.5°W which put it about 380 miles (610 km) south-southeast of Morgan City, Louisiana.  It was moving toward the north-northwest at 8 m.p.h. (13 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 1000 mb

A Tropical Storm Warning is in effect for the portion of the coast from Intracoastal City, Louisiana to the mouth of the Pearl River.  A Tropical Storm Watch has been issued for the portion of the coast from High Island, Texas to Intracoastal City, Louisiana.

The circulation of Potential Tropical Cyclone 03 is not very well organized.  The system does have a well defined low level center of circulation.  However, there are no thunderstorms near the low level center.  All of the strong showers and thunderstorms are occurring in bands well to the east of the center of circulation.  Some of those bands do contain winds to tropical storm force.  An upper level low over the northwestern Gulf of Mexico is producing strong southwesterly winds which are blowing over the top of the low level center.  The strong vertical wind shear created by those winds is preventing the development of storms closer to the low level center.

The environment around Potential Tropical Cyclone 03 will remain unfavorable for intensification on Tuesday.  The system will move move water where the Sea Surface Temperature is near 29°C.  So, there will be enough energy to support intensification.  However, the upper level low will continue to produce strong vertical wind shear over the low level center of circulation.  The upper low is forecast to move slowly toward the northwest.  It is possible that the strength of the upper level winds over the northwestern Gulf of Mexico could diminish in a day or two.  If the shear decreases, thunderstorms could form closer to the center and if the structure of the system takes on a more tropical appearance, it could be designated Tropical Storm Cindy.

Potential Tropical Cyclone 03 is moving around the western end of the subtropical high over the Atlantic Ocean.  The high is steering the system toward the north-northwest and that general motion is expected to continue.  On its anticipated track Potential Tropical Cyclone 03 is expected to approach the coast of Louisiana in about 48 hours.  The steering winds could weaken when the system gets closer to the coast and the uncertainty about the future track increases after about 48 hours.

Strong southerly flow on the eastern side of Potential Tropical Cyclone 03 will bring very humid air over the southeastern U.S.  The biggest risk is likely to be heavy rain and the potential for floods.  The system will also bring gusty winds and some storm surge to parts of the coast.

Invests 92L, 93L Monitored for Possible Development

Two weather systems designated as Invest 92L and Invest 93L are being monitored for possible development into tropical cyclones.  Invest 92L is a tropical wave that is speeding toward the Windward Islands.  At 2:00 p.m. EDT on Sunday the center of Invest 92L was located at latitude 7.3°N and longitude 49.4°W which put it about 800 miles (1290 km) east-southeast of the Windward Islands.  It was moving toward the west-northwest at 24 m.p.h. (39 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.

Invest 93L consists of a broad area of low pressure over the northwestern Caribbean Sea.  At 2:00 p.m. EDT on Sunday the surface center of Invest 93L was located at latitude 19.0°N and longitude 87.1°W which put it about 145 miles (230 km) south of Cancun, Mexico.  It was moving toward the north-northwest at 5 m.p.h. (8 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.

Invest 92L is a tropical wave and it has not yet develop a well defined surface center.  There is some evidence of cyclonic rotation on visible satellite imagery and there could be a center in the middle levels of the circulation.  Most of the stronger thunderstorms are located north and west of the center.  The are some bands of showers and thunderstorms south and west of the center.  There is some upper level divergence from the thunderstorms north and west of the center, but it is not well developed at the current time.

Invest 92L is in an environment that is moderately favorable to development of a tropical cyclone.  It is moving over water where the Sea Surface Temperature is near 28°C.  It is in a region of rapid easterly flow, but the wind speed is fairly similar at all levels.  So, there is not a lot of vertical wind shear.  The rapid easterly flow could be inhibiting the formation of a well defined center of circulation.  Invest 92L will be in a moderately favorable environment for about another 36 hours.  An upper level trough over the eastern Caribbean Sea will create increased vertical wind shear when Invest 92L reaches that location.  The National Hurricane Center is indicating that there is a 60% probability that Invest 92L will develop into a tropical cyclone during the next two days.

Invest 92L is being steered rapidly toward the west-northwest by a subtropical high north of it.  A fairly quick motion toward the west-northwest is expected to continue for the next few days.  On its anticipated track Invest 92L could be near the Windward Islands by late Monday.  Even it if does not develop into a tropical cyclone, the system will bring gusty winds and locally heavy rain to those islands.

The structure of Invest 93L is much more complicated.  There is a very broad but weak surface low pressure system over the Yucatan peninsula and the center of that low is being used as the center of the Invest.  However, there is a strong mid-level center of circulation near latitude 18.7°N and longitude 82.9°W which is about 115 miles (185 km) west-southwest of Grand Cayman.  Invest 93L is producing winds to near tropical storm force and those winds are occurring in thunderstorms associated with the mid-level circulation.  It is possible that downdrafts in those thunderstorms could transport enough momentum to the surface to generate a new surface center beneath the mid-level center.

Invest 93L is moving in an environment that will be favorable for the development of a tropical cyclone.  An upper level ridge is building between the trough over the eastern Caribbean Sea and another upper level trough over the northwestern Gulf of Mexico.  The trough over the northwestern Gulf is producing strong southwesterly winds which are causing vertical wind shear over the surface low over the Yucatan peninsula.  However, the upper level ridge is producing an area of slower winds over the mid-level center and there is less vertical wind shear there.  In fact, the upper level ridge is enhancing upper level divergence over the mid-level center.  If that continues, surfaces pressure will begin to decrease in that region.  The National Hurricane is indicating that there is a 70% probability of development of a tropical cyclone or a subtropical cyclone during the next two days.

Invest 93L is moving slowly north-northwestward around the western end of the subtropical high over the Atlantic Ocean.  A general north-northwesterly motion is expected to continue for another day or two, but there is some spread in the guidance from the numerical models.  If a cyclone forms from the surface low over the Yucatan peninsula, then the greatest risk would be to the western Gulf of Mexico.  If a new surface center forms farther east under the mid-level center, then there would be a greater risk for the central and eastern Gulf of Mexico.  Interests around the Gulf should monitor Invest 93L.

Tropical Storm Beatriz Brings Heavy Rain to Southern Mexico

Tropical Depression Two-E intensified into Tropical Storm Beatriz on Thursday and Beatriz brought heavy rain to parts of southern Mexico.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Beatriz was located at latitude 15.5°N and longitude 96.8°W which put it about 25 miles (40 km) southwest of Puerto Angel, Mexico.  Beatriz was moving toward the north-northeast at 5 m.p.h. (8 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 1004 mb.  A Tropical Storm Warning was in effect for the portion of the coast from Salina Cruz to Puerto Escondido.

Tropical Depression Two-E intensified into Tropical Storm Beatriz on Thursday even though its structure evolved into a more asymmetrical system.  Tropical Storm Beatriz appeared to consist of a larger low pressure system which was centered just off the coast of Mexico.  The weather radar from Puerto Angel confirmed that the center of circulation was still offshore.  There were several smaller (mesoscale) counterclockwise rotating circulations that were revolving around the center of the larger low.  At least one of the smaller circulations was already over southern Mexico.  Many of the thunderstorms were occurring in a broad band that wrapped around the eastern and northern portions of the larger low pressure system.  The strongest winds were occurring within this primary rainband.  There were far fewer thunderstorms in the western half of the circulation.  It seemed that after air descended from mountains in Mexico then the air was drawn into the western side of Tropical Storm Beatriz.  The warmer drier air was inhibiting the formation of thunderstorms in the western half of Beatriz.

Although Tropical Storm Beatriz is over water where the Sea Surface Temperature is near 30°C, other environmental factors are unfavorable for intensification.  The proximity to land and the apparent ingestion of drier air are both negative factors.  A narrow upper level ridge oriented from the south-southwest to the north-northeast and a upper level trough to the west of Beatriz are producing brisk southerly winds that are blowing toward the top of the circulation.  Those upper level winds are causing moderate vertical wind shear.  Therefore, Tropical Storm Beatriz is unlike to intensify further during the next several days.

The future track of Tropical Storm Beatriz is uncertain.  If the circulation of Beatriz remains intact then the upper level trough and upper level ridge are likely to steer it toward the north-northeast.  Tropical Storm Beatriz would dissipate over the mountains of Mexico if that scenario occurs.  If the upper level winds are strong enough, the vertical shear could detach the upper portion of the circulation from the low level circulation.  That scenario sometimes occurs when slow moving storms approach the south coast of Mexico.  If that happens, the upper half of the circulation could be transported across Mexico and move over the southern Gulf of Mexico.  Some models are suggesting that a new surface low could form over the southern Gulf in several days, but the wind shear would have to decrease in order for that to occur.  The lower level circulation could be left behind near the coast of Mexico where it would drift slowly near the coast.

Tropical Storm Beatriz is bringing heavy rains to parts of southern Mexico and the heavy rain will continue to fall on Friday.  Locally heavy rain in the more mountainous portions of Oaxaca could create the potential for dangerous flash floods.

Hurricane Matthew Causing Serious Flooding in the Carolinas

Hurricane Matthew produced heavy rainfall which led to serious flooding in South Carolina and North Carolina on Saturday.  The total rainfall in some locations exceeded 10 inches (25 cm) in numerous locations in those two states.  Heavy prolonged rain caused creeks and rivers to rapidly rise and flood.

The National Hurricane Center (NHC) still classified Hurricane Matthew as a hurricane in its 11:00 p.m. EDT advisory.  At 11:00 p.m. EDT on the center of Hurricane Matthew was located at latitude 34.1°N and longitude 76.5°W which put it about 35 miles (55 km) south of Cape Lookout, North Carolina.  Matthew was moving toward the east-northeast at 14 m.p.h. (22 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 Warning is in effect for the portion of the coast from Little River Inlet to Surf City, North Carolina.  A Hurricane Watch has been issued for the portion of the coast from Surf City to Duck, North Carolina including Pamlico and Albemarle Sounds.  A Tropical Storm Warning is in effect for the portion of the coast from Surf City to Duck, North Carolina including Pamlico and Albemarle Sounds.

According to NHC the center of Hurricane Matthew made an official landfall near Cape Romain southeast of McClellanville, South Carolina at 11:00 a.m. EDT on Saturday.  Since that time the center of Hurricane Matthew has moved back out over the Atlantic Ocean.  New bands of showers are forming closer to the center south of the coast of North Carolina.  The winds to hurricane force are occurring over a small area on the southwestern side of Hurricane Matthew.

Easterly winds blowing around the north side of Hurricane Matthew converged with northerly winds blowing along a cold front to generate a broad area of rising motion.  The rising motion and the existing rainbands of the hurricane combined to produce very heavy rain over South Carolina and the southeastern half of North Carolina.  The area of heavy rain spread into southeastern Virginia around Norfolk on Saturday night.  The prolonged heavy rainfall caused the water in creeks and rivers to rise very quickly.  Serious flooding was occurring in parts of South Carolina and North Carolina.  Numerous roads were closed because of flooding in those two states.

Along the coast of North Carolina southeasterly winds were blowing water toward the coast and Hurricane Matthew was still generating storm surges.  When Matthew moves east of the Outer Banks of North Carolina, the wind will change direction and it will blow from the northwest.  Those northwesterly winds will push water in Pamlico and Albemarle Sounds onto the western sides of the Outer Banks.  Storms surges caused by Hurricane Matthew caused varying amounts of damage from Florida to North Carolina.  The most destructive storm surges appear to have been near Jacksonville Beach, Florida, around the barrier islands of Georgia and South Carolina.  However, a full damage assessment has not been made of those locations at this time.

Even though the center of Hurricane Matthew stayed over the Atlantic Ocean most of the time, gusty winds caused power outages from Florida to North Carolina.  As the heavy rain saturated the ground, gusts of winds toppled trees which fell onto power lines.  More power outages are likely in eastern North Carolina and southeastern Virginia as more trees are uprooted.

Hurricane Matthew will slowly move out to sea on Sunday.  Matthew appears to be making a transition to an extratropical cyclone.  During that transition the wind field is likely to expand.  So, conditions should improve slowly over North Carolina and Virginia on Sunday.

Hurricane Matthew Bringing Wind and Heavy Rain to the Carolinas

Hurricane Matthew was bringing wind and heavy rain to South Carolina and North Carolina on Saturday morning after causing damage along the coasts of Florida and Georgia on Friday.  At 9:00 a.m. EDT on Saturday the center of Hurricane Matthew was located at latitude 32.6°N and longitude 79.7°W which put it about 30 miles (50 km) southeast of Charleston, South Carolina.  Matthew was moving toward the northeast at 12 m.p.h. (19 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 963 mb.

A Hurricane Warning is in effect for the portion of the coast from Altamaha Sound, Georgia to Surf City, North Carolina.  A Hurricane Watch is in effect for the portion of the coast from Surf City to Cape Lookout, North Carolina.  A Tropical Storm Warning is in effect for the portion of the coast from Surf City to Duck, North Carolina.

The center of Hurricane Matthew is moving just south of the coast of South Carolina.  The winds to hurricane force are occurring in a small area over the Atlantic ocean near the center of Matthew.  Wind gusts to near hurricane force were occurring occasionally at the coast.  Beaufort, South Carolina reported a wind gust to 71 m.p.h. (114 km/h).  Earlier on Saturday a pier at Foley Beach, South Carolina reported a wind gust to 76 m.p.h. (122 km/h).  Inland stations in South Carolina and North Carolina were reporting winds in the range of 20 to 50 m.p.h. (30 to 80 km) with occasional higher gusts.

The wind damage caused by Hurricane Matthew is likely to be minor in many locations.  The winds are strong enough to bring down trees and cause widespread power outages.  There are also some stronger thunderstorms in some of the rainbands that are capable of causing more severe local wind damage and could spin up brief tornadoes.  Hurricane Matthew is also producing heavy rain over South Carolina and North Carolina.  The relatively slow movement of Hurricane Matthew could produce prolonged periods of heavy rain and cause fresh water flooding.  In addition, southeasterly winds on the east side of Hurricane Matthew are pushing water toward the shore and are causing storm surges at the coast.

An upper level trough over the eastern U.S. is steering Hurricane Matthew toward the northeast and that general motion will continue to today.  On its anticipated track the center of Hurricane Matthew will move very near the coast of South Carolina and North Carolina.  Since about half of the circulation of Hurricane Matthew is over land, friction will cause the hurricane to weaken slowly.

Hurricane Matthew Brings Wind, Rain and Surge to Northeast Florida

Hurricane Matthew brought gusty winds, heavy rain and storm surges to northeast Florida as the center of the hurricane moved northward just east of Florida on Friday.  A weather station on the tip of Cape Canaveral reported a wind gust to 107 m.p.h. (170 km/h) when the western side of the eyewall moved over that location.  Wind gusts to 71 m.p.h. (115 km/h) were reported at Daytona Beach.  A wind gust to 86 m.p.h. (139 km/h) was reported by a C-MAN station in St. Augustine, Florida.  Some wind damage and numerous power outages were reported in conjunction with the strong winds.  Easterly winds pushing water toward the coast were generating storms surges along the coast.

At 5:00 p.m. EDT on Friday the center of Hurricane Matthew was located at latitude 30.2°N and longitude 80.7°W which put it about 40 miles (65 km) east of Jacksonville Beach, Florida and about 135 miles (215 km) south of Savannah, Georgia.  Matthew was moving toward the north at 12 m.p.h. (19 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 948 mb.  Hurricane Matthew was a Category 2 hurricane on the Saffir-Simpson Scale.

A Hurricane Warning is in effect for the portion of the coast from the Flagler/Volusia County line in Florida to Surf City, North Carolina.  A Tropical Storm Warning is in effect for the portion of the coast from Surf City to Duck, North Carolina including Pamlico and Albemarle Sounds.  A Tropical Storm Warning is also in effect for the portion of the coast from the Brevard/Volusia County lie to the Volusia/Flagler County line in Florida.

The eye and the core of Hurricane Matthew remained over the Atlantic Ocean as Matthew moved parallel to the east coast of Florida.  Occasionally, the western side of the eyewall would move over the coast and bring stronger winds to those areas.  The remnants of the smaller inner eyewall dissipated during the afternoon.  Once the eyewall cycle was completed the remaining outer eyewall began to contract.  Thunderstorms around the eye generated enough upper level divergence to pump out mass and limited the increase of the surface pressure.  As a result, a strong pressure gradient force is still producing winds of over 100 m.p.h. (160 km/h) in the north and northeastern parts of the eyewall.

Hurricane Matthew has been moving around the western end of a subtropical high pressure system which steered the hurricane toward the north on Friday.  An upper level trough over the Central U.S. will move east and southwesterly winds with the trough will start to steer Matthew toward the northeast later tonight.  It is not clear exactly when the turn will occur and the exact timing of the turn to the northeast is very important.  If Hurricane Matthew continues to move north, the northern eyewall which contains the strongest winds could reach Savannah and the coast of South Carolina in 6-10 hours.  If those winds reach the coast, then the damage will be more severe.  If Hurricane Matthew turns northeast before the northern eyewall reaches the coast, then the damage will be less.

Even though Hurricane Matthew weakened slightly to a Category 2 hurricane and is no longer officially a major hurricane, it is still capable of causing regional serious damage.  Matthew will cause wind damage and widespread power outages along the coasts of Georgia and South Carolina, even if the center of the eye does not officially make landfall.  If the center of the eye brings the northern eyewall over the coast, the winds will be much stronger and the damage will be greater.  In addition, easterly winds on the northern side of Hurricane Matthew will drive water toward the coast and create serious storm surges.  In places where the shape of the coast funnels water into smaller areas, the surges will be even more dangerous.

Hurricane Matthew Develops Concentric Eyewalls on Its Way Toward Florida

The structure of Hurricane Matthew changed on Thursday as it strengthened on its way toward Florida.  A second larger outer eyewall formed around the small tight inner eye and eyewall.   At 5:00 p.m. EDT on Thursday the center of Hurricane Matthew was located at latitude 26.2°N and longitude 78.6°W which put it about 25 miles (40 km) south-southeast of Freeport, Bahamas and about 100 miles (160 km) east-southeast of West Palm Beach, Florida.  Matthew was moving toward the northwest at 13 m.p.h. (20 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 938 mb.  Hurricane Matthew was a Category 4 hurricane on the Saffir-Simpson Scale.

A Hurricane Warning is in effect for the portion of the coast from Golden Beach, Florida to South Santee River, South Carolina including Lake Okeechobee.  A Tropical Storm Warning is in effect for the portion of the coast South Santee River, South Carolina to Surf City, North Carolina.  A Tropical Storm Warning is in effect for the portion of the coast from Anclote River, Florida to Suwanee River.  A Tropical Storm Warning is in effect for the portion of the coast from Chokoloskee to Golden Beach, Florida and for the Florida Keys from Seven Mile Bridge eastward including Florida Bay.  A Tropical Storm Watch has been issued for the portion of the coast from Chokoloskee, Florida to Anclote River.  A Hurricane Warning is in effect for the northwestern Bahamas including the Abacos, Andros Island, Berry Islands, Bimini, Eleuthera, Grand Bahama Island and New Providence.

Hurricane Matthew began to strengthen early on Thursday morning.  The minimum surface pressure decreased from 961 mb at 11:00 p.m. EDT on Wednesday night to 940 mb at 8:00 a.m. EDT on Thursday morning.  A decrease of 17 mb in nine hours is a very rapid pressure fall, but the maximum wind speed only increased from 115 m.p.h. ((185 km/h) to 125 m.p.h. (205 mk/h) during that time period.  The rapid decrease in pressure and the increase in the pressure gradient force around the center of Hurricane Matthew contributed to the reformation of a small circular eye at the center of the hurricane.  Once the new eyewall was established, the wind speed increased to 140 m.p.h. (225 km/h) within three hours.

The structure of the circulation of Hurricane Matthew continued to improve during the day on Thursday as the hurricane moved over the very warm water around the Bahamas.  A circular inner eye with a diameter of 18 miles (29 km) was surrounded by a ring of strong thunderstorms.  A rainband wrapped all the way around the original eye and eyewall and a second outer eyewall formed.  The outer eyewall has a diameter of 70 miles (105 km).  The strongest winds in Hurricane Matthew are occurring in the inner eyewall.  Hurricane Matthew has maintained a double eyewall structure in recent hours.

Matthew is moving through an environment that is favorable for hurricanes.  The Sea Surface Temperature is near 30°C.  There upper level winds are weak and there is not much vertical wind shear.  Hurricane Matthew is likely to maintain its current intensity as long as the inner eyewall remains intact.  If the inner eye starts to dissipate, then the strongest winds would be found in the outer eyewall, but those winds are not as strong as the winds in the inner eyewall.  So the intensity of Hurricane Matthew would decrease if that happened.  However, the wind field of a hurricane typically gets larger if the outer eyewall becomes the strongest part of the circulation.

Hurricane Matthew is moving around the western end of a subtropical high pressure system which is steering it toward the northwest and that general motion is expected to continue until the hurricane gets close to the coast of Florida.  When Hurricane Matthew gets close to the coast, it will be at the western end of the high and the hurricane will turn north.  It is still unclear if the turn will occur just before Matthew reaches the coast or whether it will occur after the center of Matthew moves on shore.  Eventually, when Hurricane Matthew moves farther north, an upper level trough approaching form the west will steer it toward the northeast, but the timing of that turn is still uncertain too.

The future track of Hurricane Matthew will be a critical factor in determining the damage it causes.  If Matthew turns north before it reaches the east coast of Florida, the the strongest winds would stay over the Atlantic Ocean.  The same holds true for the turn toward the northeast.  If the turn occurs before Hurricane Matthew reaches Georgia and South Carolina, then the strongest winds would stay offshore.  A much more destructive scenario would unfold if Hurricane Matthew reaches the coast of Florida and then turns north.  If Matthew grinds its way north along the coast, the strongest winds and highest storm surge would occur.  Matthew could move over cities like Daytona Beach and Jacksonville.  If the turn to the northeast is delayed, then Matthew would also move near Savannah, Georgia and Charleston, South Carolina.

The Hurricane Intensity Index (HII) for Hurricane Matthew is 28.2.  The Hurricane Size Index (HSI) is 18.4 and the Hurricane Wind Intensity Size Index (HWISI) is 46.6  The indices indicate that Hurricane Matthew is stronger than Hurricanes Frances and Jeanne were when they hit southeast coast of Florida in 2004.  Matthew is smaller than Frances and Jeanne were in 2004.  The HWISI for Matthew is similar to the ones for Frances and Jeanne, which would suggest that Matthew is capable of causing similar damage.  Hurricane Frances cause 11 billion dollars of damage in 2004.  Hurricane Jeanne caused about 8 billion dollars of damage.  So, Hurricane Matthew has the potential to be a very destructive hurricane, but the damage it does will be determined by its ultimate path.  Matthew will do much less damage if the core of the hurricane stays offshore.

Hurricane Matthew will bring gusty winds and heavy rain to the southeast coast of Florida on Thursday night.  It will do the same to the northeast coast of Florida on Friday.  Strong easterly winds on the northern side of the center of circulation will drive water toward the shore and create dangerous storm surges as Hurricane Matthew moves along the coast.  The heavy rain is likely to cause fresh water flooding in some locations.  Hurricane Matthew could have the greats impact on the coasts of Georgia and South Carolina on Friday night and Saturday.