Monthly Archives: August 2017

Tropical Storm Hato Forms Southeast of Taiwan

Tropical Storm Hato formed southeast of Taiwan on Sunday.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Hato was located at latitude 19.6°N and longitude 126.1°E which put it about 390 miles (630 km) east-southeast of Taitung, Taiwan.  Hato was moving toward the west-northwest at 15 m.p.h. (22 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1001 mb.

A low level center of circulation developed near the western edge of a cluster of thunderstorms southeast of Taiwan and the Japan Meteorological Agency designated the system as Tropical Storm Hato.  The structure of Tropical Storm Hato is very asymmetrical.  Most of the showers and thunderstorms are forming in the western half of the circulation.  There are some very tall strong thunderstorms west of the center of circulation.  An upper level ridge north of Hato is producing easterly winds which  are blowing toward the top of the tropical storm.  Those winds are limiting upper level divergence toward the east and they are probably the reason for the asymmetrical distribution of thunderstorms.

Tropical Storm Hato will move through an environment that will be somewhat favorable for intensification.  Tropical Storm Hato is moving over water where the Sea Surface Temperature is near 31°C.  The upper level ridge is creating moderate vertical wind shear, which is inhibiting intensification.  Tropical Storm Hato is likely to intensify, but it will do so more slowly because of the vertical shear.  Hato does have a chance to strengthen into a typhoon.

Hato is being steered toward the west-northwest by a subtropical ridge north of the tropical storm.  A general west-northwesterly motion is expected to continue for several more days.  On its anticipated track Tropical Storm Hato could reach the islands in the Luzon Strait or southern Taiwan in less than 36 hours.  Hato could make landfall on the east coast of China in less than three days.  Tropical Storm Hato will bring gusty winds and locally heavy rain when it passes near southern Taiwan and the islands in the Luzon Strait.

Tropical Storm Harvey Weakens to a Tropical Wave

Tropical Storm Harvey weakened to a tropical wave on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Wave Harvey was located at latitude 14.3°N and longitude 71.8°W which put it about 765 miles (1230 km) east of Cape Gracias a Dios.  The wave was moving toward the west at 22 m.p.h. (35 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 1007 mb.

An upper level ridge east of Harvey produced northerly winds that blew toward the top of the former tropical storm.  A subtropical high over the Atlantic Ocean produced strong easterly winds in the lower levels of the atmosphere.  The combination of northerly winds in the upper levels and easterly winds in the lower levels produced strong vertical wind shear which disrupted the vertical structure of Harvey.  A reconnaissance plane was unable to locate a low level center of low pressure on Saturday evening and the National Hurricane Center reclassified the system as a tropical wave.

Tropical Wave Harvey will continue to move west across the Caribbean Sea during the next several days.  It will move over water where the Sea Surface Temperature is near 30°C.  So, there will be sufficient energy in the ocean to support a tropical cyclone. When the tropical wave moves under the core of the upper level ridge, the wind shear will decrease.  If the tropical wave moves into a more favorable environment and slows down, a new center of circulation could redevelop.  Models are not forecasting significant redevelopment of the tropical wave at the current time, but the National Hurricane Center will continue to monitor the wave for possible redevelopment.

Tropical Storm Kenneth Develops Southwest of Baja California

Tropical Storm Kenneth developed southwest of Baja California on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Kenneth was located at latitude 15.0°N and longitude 119.1°W which put it about 810 miles (1305 km) southwest of the southern tip of Baja California.  Kenneth was moving toward the west at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1005 mb.

A distinct center of circulation developed in a tropical wave southwest of Baja California on Friday.  Thunderstorms began to form near the center and the National Hurricane Center designated the system as Tropical Storm Kenneth, which was the 11th named tropical storm to form over the Eastern North Pacific during 2017.

A cluster of thunderstorms formed near the core of Tropical Storm Kenneth on Friday.  Even after thunderstorms formed near the core, the circulation of Tropical Storm Kenneth was asymmetrical.  Bands of showers and thunderstorms developed in the western half of the circulation.  The bands in the eastern half of the circulation consisted primarily of showers and low clouds.  Thunderstorms near the core of Kenneth were generating upper level divergence which was pumping mass away to the west of the tropical storm.

Tropical Storm Kenneth will move through an environment that will be favorable for intensification during the next several days.  Kenneth will move over water where the Sea Surface Temperature is near 28.5°C.  An upper level ridge to the north of Tropical Storm Kenneth is producing easterly winds which are blowing toward the top of the circulation.  Those winds are producing moderate vertical wind shear which is probably the cause of the asymmetrical circulation of the tropical storm.  Even though there is moderate vertical wind shear, Tropical Storm Kenneth is likely to intensify and it could become a hurricane in a couple of days.

Tropical Storm Kenneth is begin steered toward the west by a subtropical ridge to the north of the tropical storm.  The subtropical ridge will continue to steer Tropical Storm Kenneth toward the west-northwest for another day or two.  When Tropical Storm Kenneth reaches the western end of the subtropical ridge, it will turn more toward the north.

Tropical Storm Harvey Develops East of Barbados

A reconnaissance plane found that a center of circulation and winds to tropical storm force had developed in a tropical wave previously designated as Invest 91L and Potential Tropical Cyclone Nine.  Based on data collected by the recon plane the National Hurricane Center named the system Tropical Storm Harvey on Thursday afternoon.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Harvey was located at latitude 13.0°N and longitude 55.8°W which put it about 250 miles (400 km) east of Barbados.  Harvey was moving toward the west at 18 m.p.h. (30 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 1004 mb.

A Tropical Storm Warning is in effect for Martinique, Barbados, St. Vincent and the Grenadines, and St. Lucia.  A Tropical Storm Watch is in effect for Dominica.

The circulation of Tropical Storm Harvey became better organized on Thursday.  A low level center of circulation developed and bands of showers and thunderstorms began to revolve around the center.  Intermittent bursts of thunderstorms occurred near and to the west of the center of circulation.  The circulation of Tropical Storm Harvey is asymmetrical.  Most of the stronger thunderstorms are occurring in the western half of the circulation.  The bands in the eastern half of the circulation consist primarily of showers and low clouds.  Thunderstorms near the core of Harvey were generating some upper level divergence which was pumping mass away to the south and west of the tropical storm.

Tropical Storm Harvey will be moving through an environment that will be somewhat favorable for intensification.  Harvey will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge northeast of Puerto Rico is producing northeasterly winds which are blowing toward the top of Tropical Storm Harvey.  Those winds are producing moderate vertical wind shear which is probably the cause of the asymmetrical distribution of thunderstorms.  Tropical Storm Harvey is likely to get better organized on Friday and it could strengthen.  The intensity guidance is mixed.  Some guidance forecasts that Harvey will become a hurricane as it moves over the Caribbean Sea, while other guidance weaken the tropical storm back to a tropical wave.  So far, the guidance has underpredicted the strength of Tropical Storm Harvey and so strengthen would seem more likely.

Tropical Storm Harvey is being steered quickly toward the west by the subtropical high over the Atlantic Ocean.  A general westerly or west-northwesterly track is forecast for the next few days.  On its anticipate track Tropical Storm Harvey could reach Barbados in about 12 hours.  Harvey could also reach Martinique, St. Lucia, St. Vincent and the Grenadines on Friday.  Tropical Storm Harvey will bring gusty winds and locally heavy rain to those islands when it moves over them.

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.

Gert Intensifies to a Hurricane West of Bermuda

Gert intensified to a hurricane west of Bermuda on Monday.  Gert became the second Atlantic hurricane of 2017 and it is the second hurricane to form during the past six days.  Hurricane Franklin developed over the southern Gulf of Mexico last week.  At 11:00 p.m. EDT on Monday the center of Hurricane Gert was located at latitude 31.2°N and longitude 72.3°W which put it about 445 miles (720 km) west of Bermuda.  Gert was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 986 mb.

An eye appeared on satellite images of Hurricane Gert at various times on Monday and it looked more like a hurricane.  There was a somewhat elliptical eye at the center of Hurricane Gert on Monday night.  The ring of thunderstorms around the eye did not completely surround the eye.  There was a large break on the northwest side of the eye.  Additional bands of showers and thunderstorms were occurring in the southeastern half of Gert.  There were fewer showers and thunderstorms in the northwestern half of the hurricane.  Thunderstorms near the core of Gert were generating upper level divergence which was pumping out mass to the south of the hurricane.

Hurricane Gert will be an environment that will be favorable for intensification for another 24 to 48 hours.  Gert will move over water where the Sea Surface Temperature is near 28.5°C.  An upper level ridge centered northwest of Gert is producing northerly winds which are blowing toward the top of the circulation.  Those winds are producing some vertical wind shear and they may be responsible for the asymmetrical distribution of showers and thunderstorms.  However, the vertical wind shear should not be strong enough to prevent Hurricane Gert from intensifying further.  An upper level trough will approach Gert from the west, but before the trough reaches the hurricane, the wind shear will decrease and a period of rapid intensification could occur.

Hurricane Gert is moving around the western end of a subtropical high over the Atlantic Ocean.  The high is steering Gert slowly toward the north.  When the upper level trough approaches Gert, southwesterly winds will start to steer the hurricane toward the northeast.  On its anticipated track Hurricane Gert should pass northwest of Bermuda.

TD 8 Strengthens to Tropical Storm Gert

Tropical Depression Eight strengthened to Tropical Storm Gert on Sunday afternoon.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Gert was located at latitude 28.1°N and longitude 71.7°W which put it about 505 miles (810 km) west-southwest of Bermuda.  Gert was moving toward the north-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1011 mb.

The structure of Tropical Storm Gert improved on Sunday.  Numerous bands of showers and thunderstorms developed and began to rotate around the center of circulation.  The thunderstorms began to produce upper level divergence which was pumping out mass in all directions.  The circulation of Tropical Storm Gert became more circular and symmetrical.

Tropical Storm Gert will move through an environment that will be favorable for intensification during the next 24 hours.  Gert will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds over Tropical Storm Gert are weak and there is not much vertical wind shear.  There is an upper level ridge northwest of Tropical Storm Gert and the ridge is producing northeasterly winds west of Bermuda.  So, the vertical wind shear could increase when Gert moves farther north.  Tropical Storm Gert will continue to intensify during the next 24 hours.

Tropical Storm Gert is moving around the western end of the subtropical high pressure system over the Atlantic Ocean.  The high is steering Gert toward the north-northwest and a northerly motion is  expected to continue for another 24 hours.  When Gert moves west of Bermuda, it will start to encounter the westerly winds in the middle latitudes.  Those winds should turn Tropical Storm Gert toward the northeast in a day or so.  On its anticipated track Tropical Storm Gert is expected to move east of the U.S. and west of Bermuda.

Tropical Depression Eight Forms East of the Bahamas

Tropical Depression Eight formed east of the Bahamas on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Tropical Depression Eight was located at latitude 25.3°N and longitude 70.3°W which put it about 470 miles (755 km) east of Nassau, Bahamas.  It was moving toward the north-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1011 mb.

Data from satellites and NOAA buoy 41046 indicated that a low level center of circulation formed within former Invest 99L.  Based on those data the National Hurricane Center classified the system as Tropical Depression Eight.  Bands of showers and thunderstorms began to develop in Invest 99L on Saturday afternoon.  There were more bands in the eastern half of the circulation than there were in the western half.  Thunderstorms in the bands began to generate upper level divergence which was pumping away mass.  The circulation took on a more circular appearance and they system exhibited the characteristics of a tropical depression.

Tropical Depression Eight will move through an environment favorable for intensification during the next 36 to 48 hours.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper low that was inhibiting the development of Invest 99L dissipated on Saturday.  When the upper low dissipated, the upper level winds weakened.  Tropical Depression Eight will move through an area where there is little vertical wind shear.  It will likely strengthen into Tropical Storm Gert on Sunday.  It could eventually intensify into a hurricane.

Tropical Depression Eight is moving around the western end of the subtropical high over the Atlantic Ocean.  The high is steering the depression toward the north-northwest and it is forecast to move primarily toward the north during the next 24 to 48 hours.  Tropical Depression Eight will eventually reach the westerly winds in the middle latitudes and it will turn toward the northeast when that happens.  On its anticipated track Tropical Depression Eight will remain east of the Bahamas.

Banyan Rapidly Intensifies Into a Typhoon

Tropical Storm Banyan rapidly intensified into a typhoon on Saturday.  At 5:00 p.m. EDT on Saturday the center of Typhoon Banyan was located at latitude 20.8°N and longitude 164.3°E which put it about 165 miles (265 km) west-northwest of Wake Island.  Banyan was moving toward the north-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 976 mb.

Banyan intensified rapidly from a tropical storm into a typhoon in less than 36 hours.  Banyan is a small well organized typhoon.  There is a small circular eye at the center of circulation.  The eye is surrounded by a ring of strong thunderstorms.  The strongest winds are occurring in that ring of storms.  A primary band of thunderstorms wraps around the eastern and northern sides of the core of Typhoon Banyan.  Other bands of showers and storms are revolving around the core of the typhoon.  Banyan has a small circulation.  Winds to typhoon force only extend out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force only extend out about 100 miles (160 km) from the center.

Typhoon Banyan will continue to move through an environment that is favorable for intensification on Sunday.  Banyan will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds are weak and there is little vertical wind shear.  Typhoon Banyan will continue to intensify during the next 24 hours and it could become the equivalent of a major hurricane.

Banyan is moving around the western end of a subtropical ridge, which is steering the typhoon toward the north-northwest.  Banyan is forecast to continue to move toward the north-northwest for another day or two.  On its anticipated track Typhoon Banyan will move away from Wake Island and the weather should improve on Sunday.

Tropical Storm Jova Develops South of Baja California

A center of circulation developed within the remnants of former Hurricane Franklin on Friday and the National Hurricane Center designated the low pressure system as Tropical Storm Jova.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Jova was located at latitude 19.3°N and longitude 109.8°W which put it 250 miles (400 km) south of the southern tip of Baja California.  Jova was moving toward the west-northwest at 14 m.p.h. (22 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.

The surface center of former Hurricane Franklin was disrupted as it passed over the mountains in Mexico.  However, the middle and upper portions of the circulation crossed the mountains relatively intact.  When the upper parts of the former hurricane emerged over the Eastern North Pacific Ocean, it took nearly a day for the vertical transfer of kinetic energy to spin up a new surface circulation.  Eventually a new surface circulation developed and the National Hurricane Center (NHC) classified the system as Tropical Storm Jova.  Established protocol is that when NHC ceases issuing an advisories on a tropical cyclone, the system is given a new name if it redevelops in a different basin.

The circulation of Tropical Storm Jova is broad, but winds to tropical storm force are occurring primarily in the northeastern quadrant of the circulation.  Most of the thunderstorms are occurring in a band that wraps around the western and southern sides of the center of circulation.  There are fewer thunderstorms in the eastern and northern sides of Tropical Storm Jova,  There is a broad counterclockwise circulation and a distinct center, but the horizontal structure is not well organized.

Tropical Storm Jova will be moving through an environment favorable for intensification during the next 24 hours.  Jova will move over water where the Sea Surface Temperature is near 30°C.  An upper lever ridge over northern Mexico is producing easterly winds which are blowing toward the top of the tropical storm.  Those winds are generating vertical wind shear.  The shear is moderate and it will inhibit intensification.  Tropical Storm is likely to intensify during the next 24 hours, but the broad circulation and vertical wind shear will limit the intensification.  In a day or two Tropical Storm Jova will move over cooler Sea Surface Temperatures and it will start to weaken.

A ridge in the middle levels is steering Tropical Storm Jova toward the west-northwest.  The ridge is expected to steer Tropical Storm Jova toward the west during the next several days.  On its anticipated track Tropical Storm Jova will move farther west of Mexico.