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Subtropical Storm Alberto Moves Into the Gulf of Mexico

Subtropical Storm Alberto moved over the southeastern Gulf of Mexico on Saturday.  At 11:00 p.m. EDT on Saturday the center of Subtropical Storm Alberto was located at latitude 23.9°N and longitude 84.6°W which put it about 120 miles (195 km) west-southwest of the Dry Tortugas.  Alberto was moving toward the north-northeast 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 1001 mb.

Tropical Storm Warnings were in effect for the Dry Tortugas and the portions of the coast from Bonita Beach to Anclote River and from the Aucilla River to the border between Alabama and Mississippi.  A Tropical Storm Watch was in effect from the border between Alabama and Mississippi to the Mouth of the Pearl River.

The circulation of Subtropical Storm Alberto remained poorly organized on Saturday.  Several low level centers dissipated and new low level centers of circulation developed on the southwestern edge of an area of thunderstorms northeast of the center.  Even though the center of circulation reorganized several times, the pressure did decrease slowly during the day.  The strongest wind speeds were occurring in the area of thunderstorms northeast of the center of circulation.  The winds were weaker south and west of the center.

Subtropical Storm Alberto will move through an environment that will become more favorable for intensification during the next 48 hours.  Alberto will move over water where the Sea Surface Temperature is near 28°C.  An upper level trough over the western Gulf of Mexico was producing southwesterly winds which were blowing across the top of the circulation.  Those winds were causing significant vertical wind shear which was inhibiting the intensification of Subtropical Storm Alberto.  The shear was also preventing thunderstorms from persisting near the center of circulation, which was keeping Alberto from making a transition to a tropical storm.  An upper level ridge was forming over Florida.  The ridge was starting to enhance upper level divergence to the east of Subtropical Storm Alberto.

The upper level trough will gradually evolve into a closed upper level low.  The vertical wind shear will slowly decrease during the next several days.  When the shear decreases, it will allow Subtropical Storm Alberto to strengthen.  Less vertical wind shear will also let thunderstorms persist closer to the center of circulation.  If thunderstorms persist near the center, then Alberto could exhibit the structure of a tropical cyclone and it could be designated as a tropical storm.  Subtropical Storm Alberto could intensify into a hurricane over the northern Gulf of Mexico.

The reformations of the low level center of circulation increase the uncertainty of track forecasts.  The upper level trough is likely to steer Subtropical Storm Alberto toward the north on Sunday.  Alberto could turn more toward the north-northwest when the trough changes into an upper level low.  On its anticipated track Subtropical Storm Alberto could approach the coast of the northern Gulf of Mexico within 48 hours.  Alberto could be a strong tropical storm or a hurricane at that time.

Subtropical Storm Alberto will be capable of causing minor wind damage when it makes landfall.  Alberto will drop locally heavy rain north and east of the center of circulation.  Flood Watches have been issued for several states in the southeastern U.S.  The Gulf Coast is very susceptible to storm surge.  There will be increases in the water level along the eastern and northern Gulf Coast where the winds blow water toward the shore.

Subtropical Storm Alberto Forms Over Northwest Caribbean Sea

Subtropical Storm Alberto formed over the northwestern Caribbean Sea on Friday morning.  The National Hurricane Center (NHC) designated an area of low pressure as Subtropical Storm Alberto on Friday morning based on data from buoys and ship reports.  At 5:00 p.m. EDT on Friday the center of Subtropical Storm Alberto was located at latitude 19.4°N and longitude 86.3°W which put it about 85 miles (135 km) south-southeast of Cozumel, Mexico.  Alberto was moving toward the east at 2 m.p.h. (3 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1005 mb.

A Tropical Storm Watch has been issued for the portion of the U.S. coast from Indian Pass, Florida to Grand Isle, Louisiana including New Orleans.  The government of Mexico issued a Tropical Storm Watch for the portion of the coast from Tulum to Cabo Catoche.  The government of Cuba issued a Tropical Storm Watch for the province of Pinar del Rio.

The circulation around Subtropical Storm Alberto was asymmetrical.  The low level center of circulation was located just to east of the Yucatan Peninsula.  The strongest thunderstorms were occurring in a band located about 100 miles (160 km) east and north of the center.  Flow around 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 strong vertical wind shear which was the reason why the thunderstorms were occurring well to the east of the center of circulation.

Subtropical Storm Alberto will move through an environment marginally favorable for intensification during the next 24 to 36 hours.  Alberto will move over water where  the Sea Surface Temperature is near 28°C.  So, there is sufficient energy in the upper ocean to support intensification.  However, the upper level trough will continue to cause moderate to strong vertical wind shear during the next day or so.  The wind shear will inhibit intensification.  Some gradual strengthening is possible.  The winds are weaker near the axis of the upper level trough.  If Alberto moves under the axis of the trough when it reaches the northern Gulf of Mexico, then the wind shear will decrease.  Alberto could strengthen more quickly if that happens.  There is a chance that Alberto could reach hurricane intensity.  If more thunderstorms form closer to the center of circulation, then NHC could change the designation of Alberto to a tropical storm.

Subtropical Storm Alberto is moving around the western end of a large high pressure system over the Atlantic Ocean.  The high is steering Alberto slowly toward the north-northeast.  A general motion toward the north is forecast during the next day or so.  When Alberto gets farther north, the upper level trough could steer it more toward the north-northwest.  There is a chance that the steering currents could weaken when Alberto nears the Gulf Coast.  Thus, there is much more uncertainty about the track forecast after that time.

The greatest risk with Subtropical Storm Alberto will be locally heavy rain and the potential for flooding.  Most of the heavy rain is likely to fall north and east of the center.  Much less rain is likely to fall from the western side of Alberto.  The coast of the Gulf of Mexico is very susceptible to storm surges.  The water level will rise along the eastern and northern coasts of the Gulf of Mexico where the winds blow the water toward the shoreline.

Hurricane Nate Brings Gusty Winds and Surge to Mississippi Coast

Hurricane Nate brought gusty winds, heavy rain and a storm surge to the coast of Mississippi on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Hurricane Nate was located at latitude 29.9°N and longitude 89.1°W which put it about 35 miles (60 km) south-southwest of Biloxi, Mississippi.  Nate was moving toward the north at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 85 m.p.h. (140 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 983 mb.

A Hurricane Warning was in effect for the portion of the coast from the mouth of the Pearl River to the Alabama/Florida border.  Tropical Storm Warnings were in effect for the portion of the coast from Grand Isle, Louisiana to the mouth of the Pearl River, for New Orleans and Lake Pontchartrain and for the coast from the Alabama/Florida border to Indian Pass, Florida.

Some drier air wrapped into the western side of Hurricane Nate on Saturday afternoon.  In addition an upper level trough approaching Nate from the west produced southwesterly winds which caused vertical wind shear.  The drier air and shear caused the circulation of Hurricane Nate to become asymmetrical.  The stronger winds are occurring in the eastern half of the circulation.  The winds are weaker in the western side of the hurricane.  The bands of showers and thunderstorms are also occurring in the eastern half of Hurricane Nate.  Very little rain was falling on the western side of the hurricane.

The partial eyewall north of the center of Hurricane Nate was moving over the coast of Mississippi from Pascagoula to Gulfport.  Strong gusty winds and heavy rain were falling on that section of the coast.  Winds blowing water toward the coast were pushing a storm surge onto the coast.  A water level gauge at a NOAA laboratory in Pascagoula, Mississippi was reporting a storm surge of 6.75 feet (2.06 meters).  The highest surges were occurring in Mississippi, but there were also storm surges on the coast of Alabama and Florida.  Bands of showers and thunderstorms were dropping heavy rain over southeastern Mississippi, southwestern and central Alabama and northwestern Florida.  Brief tornadoes spun up in some of the thunderstorms on Saturday.

Hurricane Nate will move inland over southeastern Mississippi during the overnight hours.  Nate will weaken after it moves inland, but it will continue to bring gusty winds as it spins down.  There is a strong flow of moist air from the south and heavy rain will continue to fall east of the track of Hurricane Nate.  Places west of the track will experience weaker winds and will receive little rain.  Locations west of a line from New Orleans to Hattiesburg to Meridian,  Mississippi could see little minimal impacts from Nate.  Nate will cross over west central Alabama on Sunday morning.  It will continue to move toward the north-northeast and the remnants of Nate could reach eastern Tennessee on Sunday night.  Areas of heavy rain will fall over northwestern Florida, Alabama, northern Georgia, eastern Tennessee and western North Carolina.  Fresh water flooding could occur in some of those areas.  Tornadoes could develop in the rainbands again on Sunday afternoon.

Hurricane Nate Speeds Toward Gulf Coast

Strengthening Hurricane Nate sped toward the central Gulf Coast on Saturday.  At 11:00 a.m. EDT on Saturday the center of Hurricane Nate was located at latitude 26.6°N and longitude 88.4°W which put it about 265 miles (425 km) south of Biloxi, Mississippi.  Nate was moving toward the north-northwest at 26 m.p.h. (43 km/h).  The maximum sustained wind speed was 90 m.p.h. (150 km/h) and there were wind gusts to 105 m.p.h. (165 km/h).  The minimum surface pressure was 984 mb.

A Hurricane Warning was in effect for the portion of the coast from Grand Isle, Louisiana to the Alabama/Florida border including New Orleans and Lake Pontchartrain.  A Hurricane Watch was in effect for the portion of the coast from the Alabama/Florida border to the Okaloosa/Walton County line and from Grand Isle to Morgan City, Louisiana.  A Tropical Storm Warning was in effect for the portion of the coast from the Alabama/Florida border to Indian Pass, Florida and from Grand Isle to Morgan City.  A Tropical Storm Watch was in effect for the portion of the coast from Morgan City to Intracoastal City, Louisiana.

Hurricane Nate strengthened on Saturday as it moved over the warm water in the Gulf of Mexico.  An eye with a diameter of 30 miles (50 km) began to form at the center of circulation.  A ring of thunderstorms around the eye was generating strong upper level divergence which pumped mass away from Hurricane Nate.  The strongest winds were occurring in the eastern side of the circulation.  Winds to hurricane force extended out about 35 miles (55 km) east of the center of circulation.  Winds to tropical storm force extend out about 120 miles (195 km) east of the center, but they only extend out about 60 miles (95 km) to the west of the center.

The Hurricane Intensity Index (HII) for Hurricane Nate is 13.9.  The Hurricane Size Index (HSI) is 7.7 and the Hurricane Wind Intensity Size Index (HWISI) is 21.6.

Hurricane Nate will continue to intensify during the next 12 hours until it makes landfall.  Nate will move over water where the Sea Surface Temperature is near 29°C.  An upper low over the western Gulf of Mexico is producing southerly winds which are blowing toward the top of the circulation.  However, there are also southerly winds in the lower levels of the atmosphere and as a result, there is not much vertical wind shear.  Hurricane Nate is likely to intensify to a Category 2 hurricane on the Saffir-Simpson Scale before it makes landfall.  There is a chance Hurricane Nate could intensify to Category 3 before landfall, if it continues to intensify rapidly.

The upper low and an upper level ridge east of Florida are combining to steer Hurricane Nate quickly toward the north-northwest and that motion is expected to continue for the next few hours.  An upper level trough over the Central U.S. will approach Nate on Saturday night as the hurricane nears the coast.  The trough will turn Hurricane Nate more toward the north as it reaches the coast.  The trough should steer Nate quickly toward the north-northeast after it makes landfall.  On its anticipated track the center of Hurricane Nate will pass near the mouth of the Mississippi River on Saturday evening.  The center of Nate will likely make landfall on the coast of Mississippi or near Mobile on Saturday night.

Hurricane Nate will be capable of causing regional serious damage when it makes landfall.  Nate will produce strong winds, especially in locations east of the track of the hurricane.  Nate will also be capable of producing a storm surge of 10 to 12 feet (3 to 4 meters) along the coast.  The surge will be higher in bays, inlets and mouths of rivers that funnel the water into specific areas.  Nate will also be capable of dropping heavy rain as it moves inland.

Stronger Tropical Storm Nate Speeds Toward Gulf of Mexico, Hurricane Warning for New Orleans

A stronger Tropical Storm Nate sped toward the Gulf of Mexico on Friday afternoon and a Hurricane Warning was issued for the city of New Orleans.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Nate was located at latitude 20.3°N and longitude 85.7°W which put it about 80 miles (125 km) east of Cozumel, Mexico and about 710 miles (1145 km) south-southeast of New Orleans, Louisiana.  Nate was moving toward the north-northwest at 21 m.p.h. (33 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 993 mb.

A Hurricane Warning was in effect for the portion of the coast from Grand Isle, Louisiana to the Alabama/Florida border including New Orleans and Lake Pontchartrain.  A Hurricane Watch was in effect for the portion of the coast from the Alabama/Florida border to the Okaloosa/Walton County line in Florida.  A Tropical Storm Warning was in effect for the portion of the coast from Grand Isle to Morgan City, Louisiana and from the Alabama/Florida border to the Okaloosa/Walton County line.  A Tropical Storm Watch was in effect from Morgan City to Intracoastal City, Lousiana and from the Okaloosa/Walton County line to Indian Pass, Florida.  A Hurricane Watch and a Tropical Storm Warning are in effect for the portion of the coast from Punta Herrero to Rio Lagartos, Mexico.  A Tropical Storm Warning is in effect for Pinar del Rio province in Cuba.  A Tropical Storm Watch is in effect for Isle of Youth province in Cuba.

The inner core of Tropical Storm Nate tightened up on Friday afternoon.  A primary rainband wrapped about three quarters of the way around the center of circulation.  There was an opening to the northeast of the center.  The rainband could develop into an eyewall if it wraps completely around the center of circulation.  Additional bands of showers and thunderstorms formed outside the core of Tropical Storm Nate.  Winds to tropical storm force extended out about 125 miles (200 km) to the east of the center of circulation.  The winds were weaker in the western half of the circulation.  Thunderstorms near the core began to generate stronger upper level divergence which was pumping out mass and the surface pressure decreased on Friday afternoon.

Tropical Storm Nate will move through an environment favorable for intensification on Saturday.  Nate will move over water where the Sea Surface Temperature is near 30°C.  An upper level low over the western Gulf of Mexico is producing southerly winds which are blowing toward the top of the circulation but the vertical wind shear is not too strong.  Tropical Storm Nate will become a hurricane over the Gulf of Mexico.  If an eyewall and an eye form, then Nate could have a period of rapid intensification.

The upper low over the western Gulf of Mexico and a ridge east of Florida are combining to steer Tropical Storm Nate toward the north-northwest and that general motion is expected to continue on Saturday.  An upper level trough approaching from the west will turn Nate toward the northeast when it nears the U.S.  On its anticipated track Tropical Storm Nate will pass near the northeastern end of the Yucatan peninsula and move into the Gulf of Mexico on Friday night.  Nate will approach southeastern Louisiana and Central Gulf Coast on Saturday night.

Nate will be a hurricane when it nears the U.S.  It will be capable of producing serious regional wind damage and power outages.  Nate could cause a storm surge of 10-12 feet (3 to 4 meters) near where the center makes landfall.  Nate could also drop locally heavy rain and cause fresh water flooding when it moves inland in the southern U.S.