Tag Archives: Invest 92L

Potential Tropical Development Over Northern Gulf of Mexico

The potential exists for the development of a tropical cyclone over the northern Gulf of Mexico this week.  A low pressure system was over Georgia on Monday afternoon.  The low was drifting slowly southward, but it was forecast to move more toward the south-southwest during the next two days.  Several numerical models were predicting that the low pressure system would strengthen into a tropical depression or a tropical storm after it moves over the northern Gulf of Mexico later this week.  The National Hurricane Center was indicating that the low pressure system, currently designated as Invest 92L, had a 30% probability of developing into a tropical cyclone during the next two days and an 80% probability of developing into a tropical cyclone during the next five days.

The low pressure system exhibited a surface circulation on Monday afternoon, but the wind speed was near 15 m.p.h. (25 km/h).  Bands of showers and thunderstorms formed during the daytime heating over land, but they weakened at night.  There was also a counterclockwise rotation in the lower and middle troposphere which may have been the remnants of a mesoscale convective vortex (MCV), which developed over the Middle Mississippi River Valley a few days ago.  The low was not generating upper level divergence on Monday afternoon.

If the low pressure system does move over the northern Gulf of Mexico on Tuesday or Wednesday, it will move into an environment more favorable for the development of a tropical depression.  The Sea Surface Temperature of the water in the northeastern Gulf of Mexico is near 30°C.  The low pressure system will move southeast of an upper level ridge over the southern U.S.  The ridge will produce northeasterly winds, but the winds will be relatively weak and the vertical wind shear will not be too strong.  More thunderstorms are likely to develop when the low pressure system moves over the warm water.  If those thunderstorms generate upper level divergence that pumps mass away, then the surface pressure will decrease and a tropical depression will form.

The upper level ridge is forecast to steer the low pressure system toward the west after it moves over the Gulf of Mexico later this week.  On its anticipated track the low pressure system will move slowly toward the coast of Louisiana and Texas.  The future intensity of the system will be determined by how far the system moves into the Gulf of Mexico.  If the low pressure system takes a track along or near the north coast of the Gulf of Mexico, then it will likely become a tropical depression or a weak tropical storm.  Even if the low only strengthens into a tropical depression, it could drop heavy rain and the potential for flooding exists along the northern Gulf Coast.  If the low pressure system moves farther out into the Gulf of Mexico and remains over warm water for a longer period, then it might intensify into a hurricane.  Residents along the Gulf Coast should monitor this system carefully.

Hurricane Gert Intensifies to Cat. 2 South of Nova Scotia

Hurricane Gert intensified to Category 2 on the Saffir-Simpson Scale as it sped over the Gulf Stream south of Nova Scotia on Wednesday afternoon.  At 5:00 p.m. EDT on Wednesday the center of Hurricane Gert was located at latitude 38.7°N and longitude 62.4°W which put it about 410 miles (665 km) south of Halifax, Nova Scotia.  Gert was moving toward the northeast at 31 m.p.h. (50 km/h).  The maximum sustained wind speed was 100 mp.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 970 mb.

Although Hurricane Gert is at a fairly high latitude, it has the classic structure of a Hurricane.  There is a fairly small eye at the center of circulation.  The eye is surround by a ring of strong thunderstorm and the strongest winds are occurring in this ring of thunderstorms.  There are additional bands of showers and thunderstorms revolving around the core of the hurricane.  The circulation is symmetrical and thunderstorms in the core are producing upper level divergence which is pumping away mass to the northeast of the hurricane.  Winds to hurricane force extend out about 40 miles (65 km) primarily to the east of the center of circulation.  Winds to tropical storm force extend out about 140 miles (225 km) from the center.

Hurricane Gert is moving over the Gulf Stream which means it is moving over water where the Sea Surface Temperature (SST) is near 28.5°C.  An upper level trough west of Gert is producing southwesterly winds which are blowing toward the top of the hurricane.  However, there is not much change of wind speed with height, which means that there is little vertical wind shear.  The combination of the warm water of the Gulf Stream and little vertical shear, allowed Hurricane Gert to strengthen on Wednesday.

Hurricane Gert could intensify during the next few hours, but it will soon move into a much less favorable environment.  Gert will soon move north of the Gulf Stream where the SSTs are much cooler.  The upper level trough is moving closer to Hurricane Gert and the winds are the upper level are forecast to get stronger.  When those winds increase, there will be much more vertical wind shear.  Colder water and more wind shear will cause Hurricane Gert to weaken on Thursday.  Gert could make a transition to an extratropical cyclone in colder environment of the North Atlantic.

Southwesterly winds in the upper level trough are steering Hurricane  Gert quickly toward the northeast and that general motion is expected to continue.  On its anticipated track, Hurricane Gert will move south of Labrador and Greenland.

Even as Hurricane Gert speeds away over the North Atlantic three new tropical waves over the tropical Atlantic have the potential to develop into tropical cyclones.  A tropical wave about 800 miles (1290 km) east of the Lesser Antilles designated as Invest 91L showed signs of organization on Wednesday.  A few more thunderstorms developed closed to the center of circulation.  A reconnaissance plane is scheduled to investigate this system on Thursday.  A little farther to the east another tropical wave designated Invest 92L was also showing evidence or more organization.  A third tropical wave just west of Africa also has the potential to develop during the next few days.

Invest 92L Becomes Potential Tropical Cyclone Two, Warnings Issued for Windward Islands

The National Hurricane Center (NHC) changed the designation of Invest 92L to Potential Tropical Cyclone 02 on Sunday evening.  NHC implemented a new policy for 2017 which allows it to issue tropical cyclone watches and warnings before it officially classifies a system as a tropical cyclone.  NHC issued Tropical Storm Warnings for some of the Windward Islands because of Potential Tropical Cyclone 02 on Sunday evening in accordance with the new policy.

At 11:00 p.m. EDT on Sunday the center of Potential Tropical Cyclone 02 was located at latitude 7.9°N and longitude 52.4°W which put it about 630 miles (1015 km) east-southeast of Trinidad.  It was moving toward the west-northwest at 23 m.p.h. (37 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.

Tropical Cyclone Warnings have been issued for Barbados, St. Vincent, the Grenadines, Grenada, Trinidad, and Tobago.

The circulation of Potential Tropical Cyclone 02 appeared to get better organized on Sunday evening.  Satellite imagery seemed to indicate that a more circular area of thunderstorms was forming around the center of circulation.  The system was already producing sustained winds to 40 m.p.h. (60 km/h) and if a center of circulation develops, it will be classified as a tropical storm.

Potential Tropical Cyclone 02 will move through an environment that will be somewhat favorable for intensification during the next 24 hours.  It will move over water where the Sea Surface Temperature is near 29°C.  An upper level trough over the eastern Caribbean Sea is generating southwesterly winds that are causing some vertical wind shear.  Potential Tropical Cyclone 02 has about 24 to 36 hours before the shear increases significantly.  After that time the system will weaken.

A subtropical high pressure system over the Atlantic is steering Potential Tropical Cyclone 02 toward the west-northwest.  A general west-northwesterly motion is expected to continue.  On its anticipated track Potential Tropical Cyclone 02 will reach the southern Windward Islands later on Monday.  It will bring gusty winds and locally heavy rain when it gets there.

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.