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Hurricane Maria Moves Away from Puerto Rico

Hurricane Maria moved away from Puerto Rico on Wednesday night after causing significant wind damage and serious flash floods.  At 11:00 p.m. EDT on Wednesday the center of Hurricane Maria was located at latitude 19.2°N and longitude 67.9°W which put it about 55 miles (85 km) northeast of Punta Cana, Dominican Republic.  Maria was moving toward the northwest at 9 m.p.h. (15 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 959 mb.

Hurricane Warnings are in effect for the Turks and Caicos, the Southeastern Bahamas, and the portion of the coast from Cabo Engano to Puerto Plata, Dominican Republic.  A Hurricane Watch is in effect for the portion of the coast from Cabo Engano to Isla Saona, Dominican Republic.  Tropical Storm Warnings are in effect for the portions of the coast from Puerto Plata to the northern border with Haiti and from Cabo Engano to Punta Palenque, Dominican Republic.

Hurricane Maria made landfall on the southeast coast of Puerto Rico near Yabucoa on Wednesday morning.  Maria was a Category 4 hurricane on the Saffir-Simpson Scale at the time of landfall.  Hurricane Maria moved northwest across Puerto Rico and the center emerged over the Atlantic Ocean near Arecibo on Thursday afternoon.

Hurricane Maria weakened as the core of the hurricane moved across Puerto Rico.  The mountains on Puerto Rico disrupted the circulation in the lower levels of Maria, but the middle and upper portions of the circulation remained intact.  Hurricane Maria was in the middle of an eyewall replacement cycle when it made landfall in Puerto Rico.  The timing of landfall may have caused Maria to weaken more than it would have if there had not been an eyewall replacement cycle.  The inner eyewall which contained the strongest winds dissipated at Hurricane Maria moved across Puerto Rico.  The strongest winds are occurring in the remaining outer eyewall.  The eyewall replacement cycle contributed to an increase in the size of the circulation of Hurricane Maria.  Wind to hurricane force extend out about 60 miles (95 km) from the center of circulation.  Wind to tropical storm force extend out about 160 miles (260 km) from the center.

Hurricane Maria will move through an environment favorable for intensification on Thursday.  Maria will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is not much vertical wind shear.  It could take another 12 to 24 hours for the lower portions of the circulation to reorganize.   The reorganization could limit the rate of intensification.  In addition the center will pass near the Dominican Republic.  Some of the southern part of the circulation will be over land and that could also limit intensification until Maria moves farther away from Hispaniola.

Hurricane Maria is moving around the southwestern portion of the subtropical high over the Atlantic Ocean.  That high has been steering Maria toward the northwest.  Many of the numerical models are forecasting that the high will weaken and Maria will turn toward the north on Thursday.  If the high remains stronger than the models are forecasting, then Hurricane Maria will move farther toward the west.  Hurricane Maria seems to have moved near the left side of the guidance from the numerical models in recent days.  On its forecast track the center of Hurricane Maria will move north of the Dominican Republic on Thursday.  Hurricane Maria could be near the Turks and Caicos on Friday.

Hurricane Maria is still capable of producing extensive significant damage.  Maria will drop heavy rain on parts of the Dominican Republic and there could be flash floods in some places where there is steeper terrain.

Elsewhere, Tropical Storm Jose move slowly east-northeast southeast of Massachusetts.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Jose was located at latitude 39.5°N and longitude 68.2°W which put it about 150 miles (245 km) southeast of Nantucket.  Jose was moving toward the east-northeast at 6 m.p.h. (9 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were ind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 982 mb.  A Tropical Storm Warning was in effect for the portion of the coast from Woods Hole to Sagamore Beach including Block Island, Martha’s Vineyard, Nantucket and Cape Cod.

Category 5 Hurricane Maria Bearing Down on Puerto Rico

Category 5 Hurricane Maria was bearing down on Puerto Rico on Tuesday night.  The eye was very near St. Croix.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Maria was located at latitude 17.3°N and longitude 64.7°W which put it about 30 miles (45 km) south-southeast of St. Croix and about 120 miles (190 km) southeast of San Juan, Puerto Rico.  Maria was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 175 m.p.h. (280 km/h) and there were wind gusts to 215 m.p.h. (345 m/h).  The minimum surface pressure was 909 mb.

Hurricane Warnings were in effect for Puerto Rico, Culebra, Vieques, the U.S. Virgin Islands, the British Virgin Islands, and for the portion of the coast from Cabo Engano to Puerto Plata, Dominican Republic.  Hurricane Watches were in effect for the Turks and Caicos, the Southeastern Bahamas, Saba, St. Maarten, St. Martin, St. Eustatius, St. Barthelemy, and the portion of the coast from Isla Saona to Cabo Engano, Dominican Republic.  Tropical Storm Warnings were in effect for Saba, St. Eustatius, St. Maarten, the portion of the coast from Puerto Plata,, Dominican Republic to the northern border with Haiti and for the portion of the coast from Cabo Engano to Punta Palenque, Dominican Republic,

Hurricane Maria is a very well organized powerful hurricane.  It has a small inner eye and a second outer eyewall extends most of the way around the inner eyewall.  The strongest winds are occurring in the inner eyewall.  Additional spiral bands are revolving around the core of the circulation.  The concentric eyewalls have caused the circulation of Hurricane Maria to increase in size.  Winds to hurricane force now extend out about 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extend out about 160 miles (260 km) from the center.

The Hurricane Intensity Index (HII) for Hurricane Maria is 40.4.  The Hurricane Size Index (HSI) is 19.2 and the Hurricane Wind Intensity Size Index (HWISI) is 59.6.  Those indices indicate that Hurricane Maria is capable of causing regional catastrophic damage.

Hurricane Maria will continue to move through an environment favorable for powerful hurricanes until it reaches Puerto Rico.  Maria will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  If the outer eyewall completely encircles the inner eyewall, then an eyewall replacement cycle could cause some weakening.  Hurricane Maria will weaken more if the center moves directly over Puerto Rico.  The amount of weakening will depend on the stage of the eyewall replacement cycle at the time of landfall.

Hurricane Maria is being steered toward the west-northwest by the subtropical high pressure system over the Atlantic Ocean.  The western end of the high is forecast to weaken during the next several days.  The weakening of the high will allow Hurricane Maria to move more toward the north.  The core of Hurricane Maria will pass near or over St. Croix during the next few hours.  On its anticipated track Hurricane Maria will reach Puerto Rico on Wednesday morning.

Hurricane Maria is a very dangerous hurricane.  It is capable of causing catastrophic damage.  Maria will also drop very heavy rain over Puerto Rico and there is the potential for significant flash flooding.  Maria could also cause a storm surge of up to 12 feet (4 meters) along the coast.

Elsewhere, Hurricane Jose weakened to a tropical storm east of the U.S.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Jose was located at latitude 37.9°N and longitude 70.8°W which put it about 230 miles (375 km) south of Nantucket.  Jose was moving toward the northeast at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 973 mb.

A Tropical Storm Warning was in effect for the portion of the coast from Woods Hole to Sagamore Beach, Massachusetts including Block Island, Martha’s Vineyard, Nantucket and Cape Cod.  A Tropical Storm Watch was in effect for the portion of Long Island from Fire Island Inlet to Port Jefferson.

Hurricane Maria Strengthens to Cat. 5 Near Leeward Islands

Hurricane Maria quickly strengthened to a Category 5 hurricane on the Saffir-Simpson Scale on Monday.  At 8:00 p.m. EDT on Monday the center of Hurricane Maria was located at latitude 15.3°N and longitude 61.1°W which put it about 15 miles (25 km) east-southeast of Dominica.  Maria was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 190 m.p.h. (305 km/h).  The minimum surface pressure was 925 mb.

Hurricane Warnings were in effect for Puerto Rico, Culebra, Vieques, Dominica, Guadeloupe, St. Kitts, Nevis, Martinique, Montserrat, the U.S. Virgin Islands and the British Virgin Islands.  Hurricane Watches were in effect for Saba, St. Eustatius, St. Maarten, Anguilla, St. Martin, St. Barthelemy and the portion of the coast from Isla Saona to Puerto Plata, Dominican Republic.  Tropical Storm Warnings were in effect for Anguilla, St. Lucia, Antigua, Barbuda, Saba, St. Eustatius and St. Maarten.  Tropical Storm Watches were in effect for St. Vincent, the Grenadines and the portion of the coast from Puerto Plata to the Haiti/Dominican Republic border.

Hurricane Maria has a tight compact circulation.  There is a small eye with a diameter of 10 miles (16 km) at the center of circulation.  The eye is surround by a ring of strong thunderstorms and the strongest winds are occurring in that ring of storms.  Additional bands of showers and thunderstorms are revolving around the core of Maria.  The overall circulation of Hurricane Maria is small.  Winds to hurricane force only extend out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force only extend out about 125 miles (200 km) from the center.

The Hurricane Intensity Index (HII) for Hurricane Maria is 35.0.  The Hurricane Size Index (HSI) is 9.1 and the Hurricane Wind Intensity Size Index (HWISI) is 44.1.

Hurricane Maria will continue to move through an environment very favorable for strong hurricanes.  Maria will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  Hurricane Maria could strengthen further.  Since the eye of Hurricane Maria is so small, it would be easy for a rainband to wrap around the eye.  If that happens, then an eyewall replacement cycle could begin and the cycle could result in a temporary weakening of the hurricane.

Hurricane Maria is being steered to the west-northwest by the subtropical high pressure system over the Atlantic Ocean.  That high is forecast to weaken and Maria is likely to move more toward the northwest during the next several days.  On its anticipate track the center of Hurricane Maria will pass very close to Dominica and Guadeloupe on Monday night.  Maria could pass near Montserrat, St. Kitts and Nevis on Tuesday.  It could be near the U.S. Virgin Islands on Tuesday night and Hurricane Maria will approach Puerto Rico on Wednesday.

Hurricane Maria is a small but very dangerous hurricane.  The winds in the core of Hurricane Maria are capable of causing extensive damage.  In addition, heavy rain falling over steep terrain will likely produce flash floods.  Hurricane Maria will affect some of the same islands that were severely damaged by Hurricane Irma.  Maria will significantly hamper efforts in some places to recover from the effects of Hurricane Irma.

Elsewhere over the Atlantic Ocean, Hurricane Jose has begun the transition to an extratropical cyclone as it moves northward off the east coast of the U.S.  At 5:00 p.m. EDT on Monday the center of Hurricane Jose was located at latitude 34.8°N and longitude 71.1°W which put it about 445 miles (720 km) south of Nantucket, Massachusetts.  Jose was moving toward the north at 10 m.p.h. (16 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 977 mb.

A Tropical Storm Warning was in effect for the portion of the coast from Watch Hill, Rhode Island to Hull, Massachusetts including Block Island, Martha’s Vineyard and Nantucket.  Tropical Storm Watches were in effect for the portion of the coast of Long Island from Fire Island Inlet to Port Jefferson and from New Haven, Connecticut to Watch Hill, Rhode Island.

The structure of Hurricane Jose began to change on Monday from the more circular shape of a purely tropical hurricane to an asymmetrical shape seen more commonly in extratropical cyclones.  Drier air wrapped around the western and southern sides of the circulation.  Most of the strong thunderstorms and heavy rain were occurring in the northern half of Jose.  Winds to hurricane force extended out about 60 miles (95 km) north of the center, but there were few if any winds to hurricane force south of the center.  The circulation of Hurricane Jose is much larger than the circulation of Hurricane Maria.  Winds to tropical storm force extend out about 320 miles (515 km) from the center of Jose.

The Hurricane Intensity Index for Hurricane Jose was 10.4.  The Hurricane Size Index for Jose was 15.6 and the Hurricane Wind Intensity Size Index was 26.0.

Hurricane Jose will move into an environment that is unfavorable for hurricanes on Tuesday.  Jose will stay over warm Sea Surface Temperatures until it moves north of the Gulf Stream.  Once Jose moves north of latitude 38°N, it will start to move over cooler water.  An upper level trough over the eastern U.S. is producing southerly winds which are causing moderate vertical wind shear over Jose.  Cooler water and moderate shear would normally cause a hurricane to weaken.  However, as Hurricane Jose makes the transition to an extratropical cyclone, it will start to be powered by the temperature difference between warm and cold air.  The transition to an extratropical cyclone can sometimes produce a stronger storm when it occurs.

Hurricane Jose is moving around the western end of the subtropical high.  Another surface high pressure system is forecast to move north of Jose when the hurricane approaches the northeastern U.S.  The second high will block the northward motion and it will force Hurricane Jose to move toward the east.  Some models are forecasting that Jose could make a clockwise loop southeast of Cape Cod.  Hurricane Jose could bring gusty winds and high waves to sections of the coast in the northeastern U.S. during the next few days.

Maria Becomes a Hurricane, Jose Prompts Watches for Northeast U.S.

A reconnaissance plane found that Tropical Storm Maria had intensified into a hurricane as it moved toward the Leeward Islands on Sunday afternoon.  At the same time Hurricane Jose moved farther north and Tropical Storm Watches were issued for the coast of the northeastern U.S.  At 5:00 p.m. EDT on Sunday the center of Hurricane Maria was located at latitude 13.8°N and longitude 57.5°W which put it about 275 miles (445 km) east-southeast of Dominica.  Maria was moving toward the west-northwest at 15 m.p.h. (24 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. (150 km/h).  The minimum surface pressure was 982 mb.

Hurricane Warnings were in effect for Guadeloupe, Dominica, St. Kitts, Nevis and Montserrat.  Hurricane Watches were in effect for the U.S. Virgin Islands, the British Islands, Saba, St. Eustatius, St. Maarten, St. Martin, St. Barthelemy, and Anguilla.  Tropical Storm Warnings were in effect for Martinique, St. Lucia, Antigua, Barbuda, Saba, and St. Eustatius.  Tropical Storm Watches were in effect for Barbados, St. Vincent and the Grenadines.

A reconnaissance plane found sustained winds to hurricane force when it investigated Hurricane Maria on Sunday afternoon.  The plane reported a circular eye with a diameter of 32 miles (52 km) at the center of circulation.  The eye was surrounded by an almost complete ring of thunderstorms.  The ring was broken south of the center.  The strongest winds wind occurring in that ring of thunderstorms.  Additional bands of showers and thunderstorms were developing in the eastern half of the circulation.  There were fewer showers and thunderstorms in the western half of Maria.  Hurricane Maria was generating upper level divergence which was pumping away mass and allowing the surface pressure to decrease.

Hurricane Maria will move through an environment that will be favorable for intensification.  Maria will move over water where the Sea Surface Temperature is near 29°C.  An upper level low over Caribbean Sea is causing southern winds which are blowing near the eastern side of Hurricane Maria.  Those winds do not appear to be causing significant vertical wind shear.  Hurricane Maria is likely to continue to intensify as it moves toward the Leeward Islands.  Maria could intensify rapidly once a fully closed eye develops.

Hurricane Maria is being steered toward the west-northwest by the subtropical high pressure system over the Atlantic Ocean and that general motion is expected to continue for several more days.  On its anticipated track Hurricane Maria could reach the Leeward Islands by later on Monday.  Maria could be near Puerto Rico by Wednesday.  Hurricane Maria will affect some of the same islands damaged by Hurricane Irma a few days ago.  Strong winds and heavy rain will significantly impact recovery efforts in those areas.

A reconnaissance plane also found that Hurricane Jose was stronger on Sunday afternoon.  At 5:00 p.m. EDT on Sunday the center of Hurricane Jose was located at latitude 31.5°N and longitude 71.8°W which put it about 335 miles (535 km) southeast of Cape Hatteras, North Carolina.  Jose was moving toward the north at 9 m.p.h. (15 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. (170 km/h).  The minimum surface pressure was 967 mb.

Tropical Storm Watches have been issued for the portions of the coast from Fenwick Island, Delaware to Sandy Hook, New Jersey and from East Rockaway Inlet, New York to Plymouth, Massachusetts including Long Island Sound, Block Island, Martha’s Vineyard and Nantucket.

Hurricane Jose strengthened on Sunday as it moved over water where the Sea Surface Temperature was near 29°C.  An eye appeared at times on visible satellite imagery.  The circulation of Hurricane Jose increased in size which often happens when hurricanes move north out of the tropics.  Winds to hurricane force extended out about 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extended out about 290 miles (470 km) from the center.

Hurricane Jose will move through an environment which will be marginal for further intensification.  Jose will move over water which is warm enough to support intensification.  However, an upper level trough over the eastern U.S. is producing southerly winds which are blowing toward the top of the circulation.  Those winds are producing strong vertical wind shear and they could weaken Jose during the next several days.  Jose will be moving over warm water until it gets north of the Gulf Stream.  If the upper level winds slow, then Jose could get stronger.

Hurricane Jose is being steered northward by the subtropical high over the Atlantic Ocean and the trough over the eastern U.S.  On its anticipated track the center of Jose is forecast to move toward the northeastern U.S. and turn toward the east before it reaches the coast.  If Jose follows the forecast track, then the core of the hurricane would remain offshore.  However, the circulation of Jose is large enough that even if the center stays offshore, there could still be tropical storm force winds along the coast.

Tropical Storm Maria Spins Up Quickly, Watches Issued for Leeward Islands

Tropical Storm Maria spun up quickly on Saturday and Watches were issued for the Northern Leeward Islands.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Maria was located at latitude 12.3°N and longitude 52.6°W which put it about 620 miles (1000 km) east-southeast of the Lesser Antilles.  Maria 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 1002 mb.

A Hurricane Watch was in effect for Antigua, Barbuda, St. Kitts, Nevis and Montserrat.  A Tropical Storm Watch was in effect for St. Lucia, Martinique, Guadeloupe, Dominca, Barbados, St. Vincent and the Grenadines.

The circulation of Tropical Storm Maria organized quickly on Saturday.  A primary rainband wrapped most of the way around the center of circulation.  Thunderstorms in the core of the circulation generated upper level divergence which pumped mass away from the tropical storm.  Numerous additional bands of showers and thunderstorms developed outside the core of the circulation.

Tropical Storm Maria will move through and environment that will be favorable for intensification.  Maria will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  Tropical Storm Maria could intensify rapidly during the next day or two.  Maria is likely to become a hurricane on Sunday.  Maria could strengthen into a major hurricane early next week.

The subtropical ridge over the Atlantic Ocean has been steering Tropical Storm Maria quickly toward the west.  The ridge is forecast to weaken slightly during the next several days and Tropical Storm Maria will move more toward the west-northwest.  Maria could reach the northern Leeward Islands within 48 hours.  Maria could be near Puerto Rico in about three days.  Maria will move over some of the same places that were seriously damaged by Hurricane Irma.  Maria could severely impact recovery efforts in that region.

Elsewhere over the tropical Atlantic Hurricane Jose moved slowly toward the north southeast of the U.S. and Tropical Storm Lee formed over the eastern Atlantic Ocean.  At 5:00 p.m. EDT on Saturday the center of Hurricane Jose was located at latitude 28.9°N and longitude 71.9°W which put it about 485 miles (780 km) south-southeast of Cape Hatteras, North Carolina.  Jose was moving toward the north at 6 m.p.h. (10 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 973 mb.

At 5:00 p.m. EDT on Saturday the center of Tropical Storm Lee was located at latitude 12.6°N and longitude 34.2°W which put it about 720 miles (1160 km) west-southwest of the Cabo Verde Islands.  Lee was moving toward the west at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1007 mb.

Hurricane Jose Turns Back Toward U.S.

Hurricane Jose completed the long slow clockwise loop it made this week over the Atlantic Ocean and it turned back toward the U.S.  At 5:00 p.m. EDT on Friday the center of Hurricane Jose was located at latitude 27.1°N and longitude 70.3°W which put it about 640 miles (1025 km) southeast of Cape Hatteras, North Carolina.  Jose was moving toward the northwest at 10 m.p.h. (16 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 983 mb.

An eye appeared to be forming at the center of Hurricane Jose as the primary rainband wrapped around the eastern and northern portions of the developing eye.  The strongest winds were occurring in that rainband.  Additional bands of showers and thunderstorms were revolving around the eastern half of the circulation.  There were fewer showers and thunderstorms in the western half of the circulation.

Hurricane Jose is moving over the part of the Atlantic Ocean that the hurricane traversed several days ago.  So, Jose is moving over cooler water that it mixed to the surface when it moved over the area the first time.  Hurricane Jose will soon move northwest of its previous track and it will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds will be weak and there will be little vertical wind shear.  Hurricane Jose will strengthen during the weekend and it could intensify rapidly once the eye and eyewall are fully formed.

After a few days of weak steering currents the large subtropical high pressure system over the Atlantic Ocean has started to steer Hurricane Jose toward the northwest.  A general northwesterly motion is forecast to continue for another 24 to 36 hours.  At that time Jose will reach the western end of the high and it will turn more toward the north.  On its anticipated track Hurricane Jose could be near the Outer Banks of North Carolina in two or three days.  It is still too early to know if the center of Hurricane Jose will move into the U.S.

Post Tropical Storm Hermine Edges Toward Long Island

The low pressure system that was Tropical Storm Hermine began to move back toward the west on Monday and the motion brought it closer to Long Island.  At 8:00 p.m. EDT on Monday the center of Post Tropical Storm Hermine was located at latitude 39.3°N and longitude 70.3°W which put it about 135 miles south of Nantucket Island.  Hermine was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 997 mb.

A Tropical Storm Warning remains in effect for the portion of the coast from Fire Island Inlet to Port Jefferson Harbor on Long Island and from New Haven, Connecticut to Sagamore Beach, Massachusetts including Block Island, Martha’s Vineyeard and Nantucket Island.  Most of the stronger winds are occurring over water, but a weather station at Nantucket, Massachusetts reported a sustained wind speed of 44 m.p.h. (71 km/h) and a wind gust ot 56 m.p.h. (90 km/h) on Monday.

Post Tropical Storm Hermine has not had the structure of a tropical cyclone for several days.  There are no thunderstorms near the center of circulation.  The taller clouds are all occurring west of the center.  The circulation pulled in drier air which has circulated into the core of the circulation.  An upper level low south of Hermine has generated southeasterly winds which are blowing across the top of the circulation.  The vertical wind shear combined with the drier air to prevent the development of new thunderstorms near the center of circulation.

The environment around Post Tropical Storm Hermine could become a little less hostile on Tuesday.  It will be moving over water where the Sea Surface Temperature (SST) is near 25.5°C.  As Hermine moves west the vertical wind shear will decrease.  However, the cyclone is surrounded by dry air.  If the surface low moves west, the complex environment could allow the system to maintain its intensity for another day or so.  If the surface low moves farther north, it will move over cooler SSTs and the wind speeds will decrease.

The upper low to the south of Post Tropical Storm Hermine and a ridge north of Hermine are combining to steer it toward the west-northwest.  That general motion is expected to continue for a few more hours.  As Post Tropical Storm Hermine interacts with the upper low, it could make a slow cyclonic loop.  On its expected track Hermine could move closer to Long Island on Tuesday.

Post Tropical Storm Hermine will continue to produce modest water rises along the coast.  In addition persistent wind and wave action will generate more beach erosion.

Post Tropical Storm Hermine Creates Coastal Flood Risk for Northeast U.S.

Although the structure of Tropical Storm Hermine changed significantly on Saturday and the National Hurricane Center designated it as Post Tropical, it still is creating a risk for coastal flooding for the northeastern U.S.  The size of the circulation of Hermine and its proximity to the U.S. is allowing its winds to push water toward portions of the coast.  The largest immediate risk is for the coasts of Virginia, Delaware and New Jersey.  When Hermine moves north, the greater risk will shift to New York, Rhode Island and Massachusetts.

At 11:00 p.m. EDT on Saturday the center of Post Tropical Storm Hermine was located at latitude 36.5°N and longitude 72.1°W which put it about 205 miles (330 km) southeast of Ocean City, Maryland.  Hermine was moving toward the east-northeast at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 998 mb.

A Tropical Storm Warning is in effect for the portion of the coast from Ocracoke Inlet, North Carolina to Watch Hill, Rhode Island including the Chesapeake Bay from Drum Point southward, Delaware Bay, New York City and Long Island.  A Tropical Storm Watch is in effect from Watch Hill, Rhode Island to Sagamore Beach, Massachusetts including Block Island, Martha’s Vineyard and Nantucket.

The circulation of Hermine changed from a tropical cyclone with a tight inner core to structure where area with the maximum wind speed is farther from the center.  In addition all of the thunderstorms near the center dissipated and most of the remaining thunderstorms are well northeast of the center of circulation.  The loss of tropical characteristics are the reason why the National Hurricane Center designated Hermine as Post Tropical.

Future changes of Hermine could continue to be complex.  Dry air has permeated the inner 100 miles (160 km) of the circulation which is devoid of any thunderstorms.  An upper level trough over the northeastern U.S. is forecast to move over the top of Hermine and cut off.  The would create a vertical structure which is the opposite of what is normally found in a tropical cyclone.  However, Hermine is moving over water where the Sea Surface Temperature (SST) is near 30°C.  A combination of cold air aloft in the upper low and warm SSTs could create enough instability to generate the development of new thunderstorms closer to the core of the circulation.  it is possible that Hermine could make a transition back to a more tropical cyclone like structure during the next several days.

The upper level trough is currently steering Hermine toward the east-northeast.  When the trough approaches Hermine, it will steer the storm more toward then north.  However, when the trough moves over the top of Hermine, the steering currents will be weak and Hermine could stall south of Long Island.  It is possible that the counterclockwise rotation in the upper trough could cause the storm to loop once or twice.  If Hermine makes a slow counterclockwise loop, it could move back closer to the coast of New Jersey on Monday.

The wind field in Hermine expanded during the structural changes.  Winds to tropical storm force extend out about 200 miles (320 km).  That makes Hermine about half as big as Hurricane Sandy was in 2012.

Hurricane Hermine Making Landfall in North Florida

After intensifying into a hurricane on Thursday, Hurricane Hermine is making landfall near St. Marks, Florida.  At midnight EDT the center of Hurricane Hermine was located at latitude 29.8°N and longitude 84.2°W which put it about 20 miles (30 km) south of St. Marks, Florida.  Hermine was moving toward the north-northeast at 14 m.p.h. (22 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 984 mb.

A Hurricane Warning is in effect from Suwannee River to Mexico Beach, Florida.  A Hurricane Watch is in effect from Anclote River to Suwannee River and from Mexico Beach to the Walton County/Bay County line.  A Tropical Storm Warning is in effect from Englewood to Suwannee River and from Mexico Beach to the Walton County/Bay County line.  A Tropical Storm Warning is also in effect from the Flagler County/Volusia County line to Duck, North Carolina including Pamlico and Albemarle Sounds.  A Tropical Storm Watch is in effect from Duck, North Carolina to Sandy Hook, New Jersey including the Chesapeake Bay from Smith Point southward and southern Delaware Bay.

The circulation of Hurricane Hermine organized quickly on Thursday.  It developed an eye with a mostly complete eyewall.  Spiral rainbands developed with strong winds in the eastern half of the circulation.  Upper level divergence to the east of Hermine pumped out mass and allowed the surface pressure to decrease.  The circulation is still asymmetrical with most of the stronger winds east of the center, but it looks a lot more typical of hurricanes that move toward the northern coast of the Gulf of Mexico.

Hurricane Hermine will weaken after it makes landfall.  It could interact with a cold front moving into the southeastern U.S.  It is possible that Hermine could develop a hybrid structure that is part tropical and part extratropical.  Hermine could have winds to tropical storm force as it passes over the Mid-Atlantic coast.  The stronger winds are likely to be out over the Atlantic Ocean and winds should be weaker farther inland.

An upper level trough is steering Hurricane Hermine toward the north-northeast and a general northeasterly motion is expected to continue for another 36 hours.  Later in the weekend a surface high pressure system could move north of Hermine and stall its progress.  Hermine could be stationary for a time.  On its anticipated track center of Hermine is likely to pass east of Tallahassee, Florida.  The center could pass north of Savannah, Georgia before coming near Charleston, South Carolina.  Hermine is likely to move near Cape Hatteras, North Carolina and out into the Atlantic Ocean.

Hurricane Hermine is capable of causing regional minor wind damage.  It is likely to cause widespread power outages.  The coast of the northeastern Gulf of Mexico is susceptible to storm surges and high water will effect that area overnight.  Locally heavy rainfall will create the potential for flooding.  When rainbands move ashore, wind shear could spin up tornadoes.  As Hermine moves near the Mid-Atlantic coast, easterly winds could cause water rises.

The Hurricane Intensity Index (HII) for Hurricane Hermine is 11.5.  The Hurricane Size Index (HSI) is 14.0.  The Hurricane Wind Intensity SIze Index (HWISI) is 25.5.  These indices are very similar to the ones for Hurricane Isaac before it hit the coast of Louisiana n 2012.  The HII for Isaac was 11.5.  Its HSI was 16.7 and its HWISI was 28.2.  This means that Hurricane Hermine is as strong and just smaller than Hurricane Isaac was just before it made landfall.  Hurricane Isaac did hit a more populated and more built up region.  Hurricane Isaac did 970 million dollars worth of insured damage.  It caused 407 million dollars to be paid out for flood insurance.  It is estimated that Hurricane Isaac caused 2.35 billion dollars worth of damage in the U.S.