Tag Archives: AL90

Low Pressure System Causes Floods in South Florida

A low pressure system designated as Invest 90L caused floods in parts of South Florida on Wednesday. At 8:00 p.m. EDT on Wednesday the center of Invest 90L was located at latitude 28.6°N and longitude 81.0°W which put it about 10 miles (15 km) northwest of Titusville, Florida. The low pressure system was moving toward the northeast at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1010 mb.

Even though the center of the low pressure system moved across Central Florida, it produced a band of thunderstorms well to the south of the center of circulation. The band of thunderstorms dropped persistent rain over parts of southwestern and southeastern Florida. Naples reported 3.94 inches (100.1 mm) of rain on Tuesday. There were reports of street flooding in Naples on Wednesday. Ft. Lauderdale reported 6.77 inches (172.0 mm) of rain on Wednesday. Miami reported 2,25 inches (57.2 mm) of rain on Wednesday. West Palm Beach reported 2.38 inches (60.4 mm) of rain on Wednesday. There were reports of urban flooding in Miami, Miami Beach and Hallandale in southeastern Florida.

Flood Warnings were in effect for Collier and Hendry Counties in southwestern Florida. Flood Warnings were also in effect for Broward and Miami-Dade Counties in southeastern Florida. A Flood Watch was in effect for South Florida.

The low pressure system will move through an environment marginally favorable for the formation of a tropical cyclone during the next 24 hours. The low pressure system will move over water where the Sea Surface Temperatures are near 29°C during the next few hours. An upper level trough over the eastern U.S. will produce westerly winds that will blow across the top of the low pressure system. Those winds will cause strong vertical wind shear. The vertical wind shear will inhibit development of a tropical cyclone, but the wind shear could start to decrease on Thursday. The U.S. National Hurricane Center is indicating that probability is 20% that the low pressure system develops into a tropical cyclone after it moves over the western Atlantic Ocean off the coast of the southeast U.S.

The upper level trough will steer the low pressure system toward the northeast during the next 24 hours. On its anticipated track the low pressure system will move over the western Atlantic Ocean on Thursday. A new center of circulation could develop along the line of thunderstorms in the southern part of the current circulation.

Low Pressure System To Drop Heavy Rain on Central, South Florida

A low pressure system designated as Invest 90L will drop heavy rain over parts of Central and South Florida during the next 24 hours. At 2:00 p.m. EDT on Tuesday the center of Invest 90L was located at latitude 26.9°N and longitude 93.9°W which put it about 75 miles (120 km) west-southwest of Sarasota, Florida. The low pressure system was moving toward the east-northeast at 13 m.p.h. (20 km/h). The maximum sustained wind speed was 25 m.p.h. (40 km/h) and there were wind gusts to 35 m.p.h. (55 km/h). The minimum surface pressure was 1009 mb.

A low pressure system developed over the eastern Gulf of Mexico on Tuesday. The low pressure system was designated as Invest 90L. It was approaching the west coast of Florida near Sarasota on Tuesday afternoon. The low pressure system was being steered toward the east-northeast. It will move across the Florida Peninsula during Tuesday night. The low pressure system will drop heavy rain over parts of Central and South Florida.

A Flood Watch was in effect for South Florida.

A well defined low level circulation was visible on satellite images. Thunderstorms were occurring in the eastern and northern parts of the low pressure system. Thunderstorms were also occurring in a band just east of the center of circulation. Bands north and west of the center of the low pressure system consisted primarily of showers and lower clouds.

The low pressure system will move through an environment unfavorable for the formation of a tropical cyclone during the next 24 hours. The low pressure system will move over water where the Sea Surface Temperatures are near 30°C during the next few hours. Then it will move over the Florida Peninsula. An upper level trough over the eastern U.S. will produce westerly winds that will blow across the top of the low pressure system. Those winds will cause strong vertical wind shear. The combination of movement over land and strong vertical wind shear is likely to prevent the development of a tropical cyclone during the next 24 hours.

The low pressure system could move into a more favorable environment when it moves over the western Atlantic Ocean on Friday. The upper level trough could move northeast of the low pressure system which would cause the vertical wind shear to decrease. The U.S. National Hurricane Center is indicating that probability is 20% that the low pressure system develops into a tropical cyclone after it moves over the western Atlantic Ocean northeast of Florida.

The upper level trough will steer the low pressure system toward the east-northeast during the next 24 hours. On its anticipated track the low pressure system will reach the west coast of Florida near Sarasota in a few hours. The center of the low pressure system is likely to pass south of Orlando and Daytona Beach. It will drop heavy rain over parts of Central and South Florida. Some thunderstorms could approach severe criteria.

Tropical Cyclone Development Unlikely

The National Hurricane Center indicated on Monday that a strong extratropical cyclone over the Atlantic Ocean south of Nova Scotia is unlikely to make a transition to a tropical cyclone. At 1:00 p.m. EST on Monday the center of the extratropical cyclone was located at latitude 37.8°N and longitude 63.8°W which put it about 460 miles (745 km) south of Halifax, Nova Scotia. The extratropical cyclone was moving toward the north-northeast at 10 m.p.h. (16 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 986 mb.

The National Hurricane Center (NHC) issued a special Tropical Weather Outlook on Monday morning for a strong extratropical cyclone over the Atlantic Ocean south of Nova Scotia. NHC indicated in the Tropical Weather Outlook that it was unlikely the extratropical cyclone would make a transition to a tropical cyclone or a subtropical cyclone. The extratropical cyclone was subsequently designated at Invest 90L.

A circular area of showers and thunderstorms developed at the center of a large, occluded extratropical cyclone south of Nova Scotia on Monday. A clear circular area was visible at the center of the area of showers and thunderstorms on satellite images. The clear area resembled the appearance of an eye in a tropical cyclone. The thunderstorms did not extend high into the troposphere because the center of the extratropical cyclone was over water where the Sea Surface Temperatures are near 20˚C. The circular area of showers and thunderstorms in the middle of the extratropical cyclone was surrounded by a large area of cold, dry air. Bands of low clouds and showers were occurring in the cold, dry air. The extratropical cyclone was producing a large area of winds to tropical storm force.

The extratropical cyclone will move through an area that is only marginally favorable for a transition to a subtropical cyclone or a tropical cyclone. The extratropical cyclone will move over over water where the Sea Surface Temperatures are colder than 20˚C. It will move under the eastern part of an upper level low south of Nova Scotia. The upper level low will produce southerly winds that will blow toward the top of the extatropical cyclone. However, the upper level low is almost stacked vertically with the surface low pressure systems. So, the winds at different levels of the atmosphere are similar and there will be little vertical wind shear. Cold, dry air will continue to surrounded the circular area of thunderstorms at the center of the extratropical cyclone. Cold Sea Surface Temperatures and cold, dry air around the area of thunderstorms will inhibit a transition to a subtropical cyclone. There is a slight chance the extratropical cyclone could make a transition to a subtropical cyclone during the next 24 hours before it moves over even colder water.

The upper level low will steer the extratropical cyclone toward the north during the next 24 hours. On its anticipated track the extratropical cyclone could reach Nova Scotia on Tuesday. It will bring gusty winds and locally heavy rain to Nova Scotia.

Disturbance Drops Rain on Southeast U.S.

A disturbance designated as Invest 90L dropped rain over the southeast U.S. on Monday morning. At 8:00 a.m. EDT on Monday the center of the disturbance was located near latitude 32.7°N and longitude 86.7°W which put it about 30 miles (50 km) north-northwest of Montgomery, Alabama. The disturbance was moving toward the north-northeast at 23 m.p.h. (37 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1011 mb.

A disturbance that formed over the Gulf of Mexico during the weekend moved quickly toward the north-northeast and it was located over the southeast U.S. on Monday morning. The center of the disturbance made landfall on the northern Gulf Coast on Sunday night near Pensacola, Florida. The disturbance was dropping locally heavy rain over parts of Alabama and western Georgia on Monday morning. The disturbance will move quickly toward the north-northeast and it will merge with a cold front over the southeastern U.S. Locally heavy rain will spread over eastern Tennessee, western South Carolina, western North Carolina, eastern Kentucky, western Virginia and West Virginia. Heavy rain could cause flash floods in some locations.

Disturbance Moves Toward Gulf Coast

A disturbance generated by a cluster of thunderstorms moved toward the Gulf Coast on Sunday afternoon. At 2:00 p.m. EDT on Sunday the center of the disturbance was located near latitude 27.0°N and longitude 88.0°W which put it about 240 miles (390 km) south of Mobile, Alabama. The disturbance was moving toward the north-northeast at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1015 mb.

A disturbance generated by a cluster of thunderstorms over the central Gulf of Mexico was designated as Invest 90L on Sunday afternoon. Visible satellite images showed that a distinct center of circulation had formed in a disturbance over the north central Gulf of Mexico on Sunday afternoon. A swirl of lower clouds was clearly visible on the images. Some thunderstorms were beginning to develop in bands northwest of the center of circulation. Otherwise, there were mainly low clouds and showers in the other bands near the center. Thunderstorms were also occurring in a band on the northeastern periphery of the disturbance.

The disturbance will move through an environment that will be marginally favorable for the development of a tropical cyclone during the next 18 hours. The disturbance will move over water where the Sea Surface Temperatures are near 29˚C. The southern end of an upper level trough over the central U.S. will produce southwesterly winds that will blow toward the top of the disturbance. Those winds will cause some vertical wind shear and the wind shear will inhibit the development of a tropical cyclone. The disturbance is currently forecast not to develop into a tropical cyclone, but some development could occur if more thunderstorms form near the center of circulation. The National Hurricane Center in its 2:00 p.m. EDT Tropical Weather Outlook indicated the probability was 10% that the disturbance would develop into a tropical cyclone.

The upper level trough over the central U.S. will steer the disturbance toward the north-northeast. On its anticipated track the cluster of storms will move toward the central Gulf Coast. Bands of thunderstorms could drop locally heavy rain over northwest Florida and south Alabama during the next 48 hours. Heavy rain could cause flash floods in some locations. Some thunderstorms could approach severe criteria.

Possible Development near Southeast U.S.

A low pressure system could develop near the coast of the Southeast U.S. during the next 48 hours. At 8:00 a.m. EDT on Friday the center of a developing low pressure system currently designated as Invest 90L was located at latitude 31.3°N and longitude 79.3°W which put it about 150 miles (240 km) east of Brunswick, Georgia. It was moving toward the east-southeast at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 25 m.p.h. (40 km/h) and there were wind gusts to 35 m.p.h. (55 km/h). The minimum surface pressure was 1017 mb.

Early morning visible satellite images appeared to show that a low pressure system was forming along a nearly stationary front off the coast of the southeast U.S. More thunderstorms were forming in the developing low pressure system and some rotation was evident in satellite loops. Thunderstorms appeared to be organizing into bands. The southern end of an upper level trough over the eastern U.S. was producing westerly that were blowing across the top of the developing low pressure system. Those winds were causing moderated vertical wind shear. The upper level winds were also inhibiting the development of thunderstorms on the western side of the developing low pressure system.

The low pressure system will move through an environment somewhat favorable for the formation of a tropical cyclone during the next 48 hours. It will move over water where the Sea Surface Temperatures are near 28°C. The upper level trough will move northeast of the low pressure system on Saturday and the upper level winds will weaken. An upper level low east of the Bahamas could enhance upper level divergence to the southeast of the developing low pressure system. The National Hurricane Center is indicating the probability is 30% that a tropical cyclone forms during the next 48 hours. A reconnaissance plane has been tentatively tasked to investigate the system on Saturday afternoon, if necessary.

Tropical Storm Watch Issued for Bermuda

A Tropical Storm Watch was issued for Bermuda on Thursday. At 8:00 p.m. EDT on Thursday the center of a nontropical low pressure system designated as Invest 90L was located at latitude 34.9°N and longitude 55.0°W which put it about 635 miles (1010 km) east-northeast of Bermuda. Invest 90L was moving toward the north-northwest at 13 m.p.h. (20 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 1004 mb.

A non-tropical low pressure system east-northeast of Bermuda prompted the Bermuda Weather Service to issue a Tropical Storm Watch. The low pressure system exhibited a non-tropical structure on Thursday night. There were bands of showers and thunderstorms revolving around the center of the low pressure system. However, there were not any thunderstorms near the center of the low. The strongest winds were occurring in the outer part of the circulation around the low. The low pressure system may have also had a cold core in the upper levels.

The surface portion of the low pressure system was rotating counterclockwise around an upper level low. The upper level low was forecast to steer the surface low toward the west on Friday. If the surface low moves westward, it will move over warmer Sea Surface Temperatures. The low pressure system could extract more energy from the Atlantic Ocean and thunderstorms could form near the center of circulation. The structure of the low pressure system could make a transition to a subtropical or a tropical storm. The National Hurricane Center indicated that the probability was 80% that a subtropical or a tropical storm could form during the next 48 hours.

Disturbance South of Florida Keys

A disturbance south of the Florida Keys is currently designated at Invest 90L.  The disturbance could develop into a tropical or subtropical cyclone during the next few days.  At 8:00 p.m. EDT on Thursday the center of Invest 90L was located at latitude 23.9°N and longitude 81.2°W which put it about 55 miles (85 km) south of Marathon, Florida.  It was moving toward the east-northeast 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. (75 km/h).  The minimum surface pressure was 1013 mb.

A small trough in the middle troposphere moved over a stationary front south of the Florida Keys on Thursday.  Satellite images and radar loops detected rotation in the middle troposphere.  There was a broad counterclockwise rotation south of the Keys and radar loops also revealed several small counterclockwise rotations within the broader mid-level circulation.  However, there did not appear to be a distinct center of circulation with lower pressure at the surface.

Invest 90L is forecast to move toward the northeast during the next several days.  It will move into an environment more favorable for development into a tropical or subtropical cyclone.  Invest 90L will move over water where the Sea Surface Temperature is near 27°C.  There will be an upper level trough over the eastern Gulf of Mexico, but a small upper level ridge will develop east of Florida.  The combination of the upper level trough and the upper ridge will produce a region of upper level divergence east of Florida.  The upper level divergence will pump mass away and the surface pressure will decrease in that area.  A surface low pressure system is likely to form on Friday or Saturday.  The National Hurricane Center is indicating that there is an 80% probability of the formation of a tropical or subtropical cyclone.  A reconnaissance plane is tentatively scheduled to investigate the system on Friday afternoon, if necessary.

Low Pressure Developing East of the Leeward Islands

A low pressure system was developing east of the Leeward Islands on Sunday night.  The low pressure system was centered about 550 miles (890 km) east of the Leeward Islands.  The structure of the low pressure system was still organizing.  Thunderstorms were forming in bands southeast of the low level center of circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.

The low level center appeared to be located east of a small upper level low.  The upper low was causing southerly winds which were creating vertical wind shear over the western half of the surface center.  Some upper level divergence appeared to be occurring over the eastern half of the low level circulation.  The upper level divergence could be contributing to the development of the thunderstorms in that region.

The low pressure system will move through an environment somewhat favorable for development during the next several days.  The low will move over water where the Sea Surface Temperature is near 28°C.  It will move into a region where the upper level winds will not be too strong and there will not be too much vertical wind shear.  The National Hurricane Center is indicating that there is a 50% probability that a tropical or subtropical cyclone forms during the next five days.

The upper level low will steer the developing low pressure system toward the northwest on Monday.  A much large upper level trough off the east coast of the U.S. will steer the low pressure system more toward the north on Tuesday and Wednesday.  On its anticipated track the low pressure system will pass northeast of the Leeward Islands early next week.

Cyclone Likely to Form Over Gulf of Mexico

A cyclone is likely to form over the Gulf of Mexico during the upcoming weekend.  A broad area of low pressure at the surface is currently centered over the Yucatan Peninsula.  The area of low pressure is currently designated as Invest 90L.  The circulation around the low pressure system is not well organized at the current time.  The center of the surface low is over the Yucatan Peninsula.  Showers and lower clouds are occurring near the center of the low.  Stronger thunderstorms are occurring on the eastern side of the low over the northwestern Caribbean Sea.  Sustained winds of 20 m.p.h. to 30 m.p.h. (30 km/h to 50 km/h) were blowing across the northwestern Caribbean Sea.  The winds were weaker over land near the center of circulation.

An upper level trough over the Gulf of Mexico was producing strong westerly winds which were blowing over the top of the surface low.  Those winds were causing strong vertical wind shear and the wind shear was one of the reasons why the stronger thunderstorms were occurring east of the center of circulation.  Sinking motion in the western portion of the upper level trough was bringing drier air to the surface and the drier air was inhibiting the formation of thunderstorms in the western side of the surface low.

The National Hurricane Center (NHC) indicated in a Special Tropical Weather Outlook at 2:00 p.m. EDT on Thursday that there is a 70% probability of the formation of a subtropical or tropical depression during the next 48 hours.  NHC has tentatively tasked a reconnaissance aircraft to investigate the low pressure system on Friday afternoon if necessary.

The wind speeds are slower near the axis of the upper level trough.  If the surface low pressure system moves under the axis of the upper level trough, then there would be less vertical wind shear and a cyclone could form.  If thunderstorms develop near the center of circulation after the center moves over the northwestern Caribbean Sea or southeastern Gulf of Mexico, then NHC would likely designate the system as a tropical depression.  If the thunderstorms develop farther away from the center of circulation and the circulation does not exhibit a tropical appearance, then NHC could classify the system as a subtropical depression.  NHC would issue advisories on the cyclone even if it is designated a subtropical depression.

There is a strong high pressure system over the Atlantic Ocean and the high is likely to steer the surface low toward the north.  The Sea Surface Temperature of the water in the southeastern Gulf of Mexico is near 27°C.  So, there is enough energy to support the formation of a tropical cyclone.  Most of the stronger thunderstorms are likely to continue to form in the eastern side of the circulation because of the vertical wind shear and drier air to the northwest of the surface low.  The low pressure system could slowly organize into a tropical storm during the weekend.

Heavy rain and the potential for flooding are the greatest risks with this low pressure system.  There will be some storm surge along the eastern and northern coasts of the Gulf of Mexico as counterclockwise rotation around the low blows water toward the shore.