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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 Depression Nine Causes Hurricane Watch for Part of Florida

Although Tropical Depression Nine did not strengthen on Tuesday afternoon, guidance from numerical models suggested it could be stronger when it eventually reaches the coast of Florida.  As a result, the National Hurricane Center at 5:00 p.m. EDT issued a Hurricane Watch for the portion of the Florida coast from Anclote River to Indian Pass.  A Tropical Storm Watch was issued for the portion of the coast from Indian Pass to the Walton County/Bay County line.

At 5:00 p.m. EDT on Tuesday the center of Tropical Depression Nine was located at latitude 24.4°N and longitude 87.3°W which put it about 345 miles (555 km) west of Key West, Florida.  It was moving toward the northwest at 5 m.p.h. (8 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. (70 km/h).  The minimum surface pressure was 1004 mb.

The circulation of Tropical Depression Nine is not currently well organized.  The surface center is located northwest of an apparent mid-level center.  Upper level divergence is not well developed.  The development of thunderstorms has been cyclical during the past several days.  Clusters of thunderstorms developed south and east of the center and then they weaken.  A few hours later more thunderstorms would develop, persist for a few hours and weaken again.  It appears that new thunderstorms are developing northeast and southwest of the surface center which would be a change from the previous pattern.

The vertical structure of Tropical Depression Nine has been out of sync.  As mentioned above, the surface center was northwest of the mid-level center.  Both the surface and mid-level centers have been located on the western edge of a larger upper level high.  Clockwise flow around the upper high has been creating vertical wind shear, which has prevented the development of a vertically coherent structure in the depression.  Despite the effect of the wind shear and the lack of a coherent vertical structure, the surface center has managed to persist and become a little more organized each day.

Tropical Depression Nine is moving through an environment that is currently marginal for intensification.  It is moving over water where the Sea Surface Temperature is near 31°C.  So, there is plenty of energy in the upper ocean.  The vertical wind shear mentioned previously is the primary factor inhibiting intensification.  However, as Tropical Depression Nine moves north, if is forecast to move into an area where the upper level winds are not as strong.  If that happens, then the depression will strengthen.  As the depression becomes more organized, the rate of intensification could increase and the depression could become a hurricane over the northeastern Gulf of Mexico.

An upper level ridge over the southeastern U.S. has been blocking the northward movement of Tropical Depression Nine.  An upper level trough approaching from the west is expected to weaken the ridge.  As the ridge weakens, The depression will be able to move north.  Eventually in a couple of days, the upper level trough is expected to steer the depression more toward the northeast.  On its anticipated track the depression could be approaching the northeastern Gulf Coast by Thursday afternoon.

The northeastern Gulf Coast is very susceptible to storm surges and a surge is the greatest risk.  Locally heavy rain could cause some flooding, and there could be some minor wind damage.

Tropical Depressions Form South of Key West & Southeast of Cape Hatteras

Two tropical depressions formed near the U.S. on Sunday.  Tropical Depression Nine formed south of Key West, Florida and Tropical Depression Eight formed southeast of Cape Hatteras, North Carolina.  Both depressions could have an impact on the U.S., but Tropical Depression Nine could pose a greater risk to the southeastern U.S.

At 5:00 p.m. EDT on Sunday the center of Tropical Depression Nine was located at latitude 23.7°N and longitude 81.7°W which put it about 60 miles (95 km) south of Key West, Florida.  It was moving toward the west at 9 m.p.h. (15 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. (70 km/h).  The minimum surface pressure was 1009 mb.

At 5:00 p.m. EDT on Sunday the center of Tropical Depression Eight was located at latitude 31.8°N and longitude 70.9°W which put it about 355 miles (570 km) southeast of Cape Hatteras, North Carolina.  It was moving toward the west at 9 m.p.h. (15 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. (70 km/h).  The minimum surface pressure was 1010 mb.

The circulation of Tropical Depression Nine is still organizing.  A NOAA plane found a distinct center of circulation, but most of the stronger thunderstorms are south and east of the center.  There is a broader counterclockwise rotation with numerous showers and thunderstorms indicated by the National Weather Service radar in Key West.  An upper level low east of Florida is contributing to easterly winds that are blowing across the northern side of the depression.  The vertical wind shear is inhibiting the development of thunderstorms north and west of the center.

The circulation of Tropical Depression Eight was more well organized earlier today.  Strong easterly winds from the same upper level low that is affecting Tropical Depression Nine are creating significant vertical wind shear.  Those winds and the shear they caused blew the upper portion of the depression’s circulation west of the low level center of circulation.  The low level circulation is presently exposed as seen on visible satellite imagery and by an Air Force Reserve Hurricane Hunter aircraft.

The intensity forecast for Tropical Depression Nine is challenging because it is moving through a complex environment.  The depression is moving over water where the Sea Surface Temperature is near 31°C.  So, there is plenty of energy in the upper ocean.  However, as mentioned above, an upper low is causing vertical wind shear which will inhibit intensification.  Tropical Depression Nine could move into a region where there is less shear when it moves over the Gulf of Mexico.  Tropical Depression Nine has a good chance to intensify into a tropical storm, but it is unclear if it could become a hurricane before it reaches the coast.

There is also significant uncertainty in the track forecast for Tropical Depression Nine.  A ridge over the southeastern U.S. is steering the depression toward the west and that general motion should continue for several more days.  The ridge is forecast to weaken during the middle of the week and that should allow Tropical Depression Nine to turn toward the north.  The timing of that turn and how sharp it will be are still uncertain.

The upper low is expected to continue to generate wind shear over Tropical Depression Eight.  If the upper levels winds remain as strong as they are now, the depression will slowly weaken.  If the upper level winds weaken, then Tropical Depression Eight could strengthen into a minimal tropical storm.  The upper level low is steering the depression west and that general motion is expected to continue in the short term.  The depression could stall just off the coast of North Carolina.

Tropical Depression Nine could intensify and bring wind and rain to the Gulf Coast later this week.  The Gulf Coast is also vulnerable to storm surges.  Given the uncertainty in both the track and intensity, interests along the coast should monitor official sources of information for updates on Tropical Depression Nine.  The primary effects of Tropical Depression Eight are likely to be higher than normal surf, rip currents and some beach erosion along the North Carolina coast.  People along the Mid-Atlantic coast should pay attention to the depression in case the forecast changes.

Tropical Storm Colin Forms Over Gulf of Mexico and Heads for Florida

A broad area of low pressure over the southern Gulf of Mexico became more organized on Sunday and a U.S. Air Force Reserve Hurricane Hunter reconnaissance aircraft found sustained winds of 40 m.p.h. (65 km/h).  As a result, the National Hurricane Center classified the system as Tropical Storm Colin.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Colin was located at latitude 23.6°N and longitude 87.8°W which put it about 450 miles (720 km) southwest of Tampa, Florida.  Colin was moving toward the north at 9 m.p.h. (15 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 Tropical Storm Warning has been issued for the portion of the coast from Indian Pass to Englewood, Florida.  A Tropical Storm Warning has also been issued for the East Coast from Sebastian Inlet, Florida to Altamaha Sound, Georgia.  A Tropical Storm Watch has been issued for the portion of the coast from Altamaha Sound, Georgia to South Santee River, South Carolina.

The circulation of Tropical Storm Colin is very asymmetrical.  The stronger winds and most of the thunderstorms are east of the center of circulation.  Some rotation in the middle levels in the primary band on the east side of Colin is apparent on satellite imagery.  Winds to tropical storm force are occurring up to 185 miles (295 km) from the center of circulation.  However, the winds are much weaker in the western half of the circulation.

The environment around Tropical Storm Colin is marginal for intensification.  Colin is moving over water where the Sea Surface Temperature is near 28°C to 29°C.  So, there is sufficient energy in the upper ocean to support intensification.  An upper level low near Texas and an upper level ridge east of Colin are combining to produce southwesterly winds that are blowing over the western half of the storm.  Those winds are causing strong vertical wind shear which is preventing the development of thunderstorms in that part of the storm.  Part of the upper level ridge is over the eastern half of the circulation.  The upper level winds are weaker there and there is less vertical wind shear, which is allowing strong thunderstorms to persist in that part of Colin.  The upper level ridge is also enhancing upper level divergence to the east of Tropical Storm Colin.  If a new center of circulation were to form closer to the upper level ridge, then more intensification would be possible.  Colin is likely to intensify somewhat on Monday.

The upper low and upper level ridge are also steering Tropical Storm Colin toward the north.  Those features are expected to turn Colin toward the northeast on Monday.  On its anticipated track Tropical Storm Colin will approach the coast of Florida between Tampa and Apalachicola on Monday evening.  However, if a new center of circulation develops farther east, Colin could make landfall farther south along the coast and earlier on Monday.

Heavy rainfall is the greatest risk with Tropical Storm Colin.  It is pulling very humid air from the Caribbean Sea northward over the eastern Gulf of Mexico.  Tropical Storm Colin could also generate a storm surge of 1-6 feet near where the center makes landfall.  The coast along the northeastern Gulf of Mexico is very susceptible to storm surges and water rises will occur in that area.  Wind damage is likely to be minimal, although power outages may occur.  Some tornadoes could be generated when Colin moves over land.  Locally heavy rain could also fall in portions of the Mid-Atlantic states as the circulation of Tropical Storm Colin interacts with a cold front.

Tropical Storm Colin was named on June 5, which is the earliest date on record on which the third Atlantic Tropical Storm has formed.  During the record setting year of 2005 Tropical Storm (later to become Hurricane) Cindy was named on July 5.

Disturbance Near Yucatan Could Develop Over Gulf of Mexico

A tropical disturbance over the northwestern Caribbean Sea near the Yucatan peninsula is moving northwest and it could develop into a tropical cyclone when it moves over the southern Gulf of Mexico.  The National Hurricane Center (NHC) has designated the disturbance as Invest 93L and NHC is putting the probability of development into a tropical cyclone during the next two days at 80%.  At 8:00 p.m. EDT the center of Invest 93L was located at latitude 18.5°N and longitude 87.5°W which put it about 170 miles (270 km) south of Cancun, Mexico.  Invest 93L was moving toward the northwest at 11 m.p.h. (17 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. (70 km/h).  The minimum surface pressure was 1005 mb.

Invest 93L consists of a broad area of low pressure at the surface.  Several bands of thunderstorms are occurring in the eastern and northern parts of the circulation.  There is no well defined center of circulation and there are fewer thunderstorms in the inner portion of the circulation.  The strongest winds are occurring in the bands of thunderstorms north and east of the center.  There is some upper level divergence to the east of Invest 93L.

The environment around Invest 93L is not totally favorable for development.  The Sea Surface Temperature in northwest Caribbean Sea is near 30°C, which means there is plenty of energy in the upper ocean.  However, an upper level low near Texas and an upper level ridge east of Invest 93L are combining to generate strong southwesterly winds that are blowing over the top of the disturbance.  Those winds are creating significant vertical wind shear which is inhibiting the development of Invest 93L.  The upper level ridge is enhancing the upper level divergence to the east of the disturbance which allowed the pressure to fall several millibars on Saturday.  The upper winds are lighter near the axis of the ridge which is why the stronger bands of thunderstorms are persisting in that area.

Invest 93L is forecast to move toward the Yucatan peninsula on Sunday.  If the broad area over low pressure moves over land that will prevent it from developing until it moves back over water.  Numerical models are guiding that the disturbance will develop into a tropical cyclone when the area of low pressure moves over the southern Gulf of Mexico.  The upper level ridge is forecast to extend over the southeastern Gulf and if that happens the wind shear could decrease enough to allow development to occur.  Invest 93L could become a tropical depression or a tropical storm over the Gulf of Mexico.

The southwesterly flow over the Gulf of Mexico is forecast to turn Invest 93L toward the northeast.  On its anticipated track the system could reach the west coast of Florida near Cedar Key late Monday or early Tuesday.  The primary risk is likely to be locally heavy rain.  However, the coast in that area is very susceptible to storm surge and there could be some rise in the water level.  The National Hurricane Center has tentatively tasked a reconnaissance plane to investigate Invest 93L on Sunday, if necessary.