Tropical Storm Henri Forms East of Bermuda

An instrument on a satellite indicated that there could be surface winds to tropical storm force in an area of thunderstorms east of the center of Tropical Depression Eight and the National Hurricane Center designated the system as Tropical Storm Henri.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Henri was located latitude 31.3°N and longitude 60.7°W which put it about 250 miles (405 km) east-southeast of Bermuda.  Henri was moving toward the north at 5 m.p.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 1008 mb.

Henri is not a very well organized tropical storm.  An upper level low centered north of Bermuda is causing brisk southwesterly winds over the top of Henri.  The vertical wind shear is blowing the tops off of thunderstorms that start to form near the center of circulation.  As a result of the wind shear, the stronger thunderstorms are all located well to the east of the center of the tropical storm.  Henri is over warm Sea Surface Temperatures (SSTs) which are above normal in that part of the western Atlantic Ocean.  So, there is plenty of energy to support intensification.  However, as long as the upper level low creates significant vertical wind shear, intensification will be minimal.  It is possible that as Henri moves toward the north that the wind shear could decrease.  In that case Henri could intensify during the next day or two before it moves over cooler SSTs.

An upper level trough over the eastern U.S. should steer Henri toward the north during the next several day.  On its anticipated track, Henri could pass near Newfoundland during the weekend.  Henri could be in the process of transitioning from a tropical storm to an extratropical cyclone at that time, but it could still bring strong winds and rain to parts of extreme eastern Canada.

Linda Rapidly Intensifies Into a Major Hurricane

Hurricane Linda rapidly intensified on Tuesday and it now has a wind speed that qualifies it as a Category 3 Hurricane on the Saffir-Simpson Scale.  This makes Linda the fifth major hurricane in the Eastern North Pacific in 2015.  At 11:00 a.m. EDT on Tuesday the center of Hurricane Linda was located at latitude 21.3°N and longitude 113.9°W which put it about 280 miles (450 km) west-southwest of the southern tip of Baja California.  Linda was moving toward the north-northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 140 m.p.h. (225 km/h).  The minimum surface pressure was 956 mb.

Upper level winds over Linda decreased and the reduction in vertical wind shear allowed it to intensify rapidly during the past 12 hours.  A visible eye and symmetrical eyewall are evidence of a well organized inner core.  Thunderstorms near the center of circulation are generating upper level divergence in all directions which is pumping out mass and causing the pressure to decrease.  Linda could intensify for a few more hours, but it will start to move over much cooler Sea Surface Temperatures (SSTs) later today.  It will be unable to extract enough energy from the cooler water to maintain its intensity and Linda will start to weaken.  As Linda moves farther north, it will also start to encounter stronger upper level winds around the southern portion of an upper level trough near the west coast of the U.S.  Increased vertical wind shear in addition to cooler SSTs will speed up the rate at which Linda weakens.  Since Linda has a large circulation, it could take longer for it to spin down.

An upper level ridge over Mexico is steering Linda toward the north-northwest and that general motion is expected to continue as long as it maintains tall thunderstorms.  When Linda weakens to a tropical storm over cooler water, the circulation will not extend as high in the atmosphere.  After that time Linda will be steered more toward the west by winds lower in the atmosphere.  On its anticipated track Linda will move parallel to the coast of Baja California for several days before turning away from the coast later this week.

Tropical Storm Etau Develops and Heads Toward Japan

A center of circulation developed within a large area of thunderstorms a few hundred miles south of Japan and the system has been designated Tropical Storm Etau.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Etau was located at latitude 25.3°N and longitude 138.5°E which put it about 720 miles (1160 km) south-southeast of Osaka, Japan.  Etau was moving toward the north at 11 m.p.h. (18 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 998 mb.

Although Tropical Storm Etau does have a low level center of circulation, most of the stronger thunderstorms are located north-northwest of the center.  Etau is moving over water where the Sea Surface Temperatures are warm enough to support intensification.  However, a large upper level trough west of Japan is producing southwesterly winds over the top of the tropical storm.  The circulation appears to be tilting toward the north with height because  of vertical wind shear.  Tilted tropical cyclones are unable to efficiently convert energy to wind speed and intensify.  Etau could intensify a little during the next 24 hours, but then it will run into much stronger upper level winds associated with the upper level trough.  Stronger vertical wind shear will cause Etau to begin to weaken before it reaches Japan.

A subtropical ridge east of Etau is steering it toward the north-northwest and that general motion is expected to continue for the next several days.  On its anticipated track Etau will approach the coast of Japan near Honshu and Shikoku.  Landfall somewhere between Nagoya and Kochi could occur in about 36 hours.  Etau’s biggest impact will be to increase rainfall as it moves inland.

Tropical Storm Linda Forms South of Baja California

A spiral band continued to wrap more tightly around the center of circulation inside a large low pressure system west of Mexico on Sunday and the National Hurricane Center designated the system as Tropical Storm Linda.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Linda was located at latitude 14.1°N and longitude 109.0°W which put it about 610 miles (980 km) south of the southern tip of Baja California.  Linda was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1000 mb.

The circulation in Tropical Storm Linda is well organized.  There is one main spiral rainband and multiple outer rainbands.  Outside of the core of the circulation there are fewer thunderstorms east of the center, which could mean that some drier air is being pulled into that part of the storm.  Thunderstorms in the core are generating upper level divergence.  Linda is over water where the Sea Surface Temperatures (SSTs) are above 29°C.  An upper level trough near the west coast of the U.S. and an upper level ridge over northern Mexico are combining to create an outflow channel to the northeast, which is enhancing the flow of mass away from the tropical storm.  There is little vertical wind shear over the top of Linda and the environment is favorable for further intensification.  A period of rapid intensification is possible and Linda is likely to become a hurricane.  Eventually, when it moves farther north, Linda will move into an area of cooler SSTs and more vertical wind shear, which will cause it to weaken.

Linda appears to be moving a little more toward the west-northwest this afternoon.  The upper level ridge over northern Mexico is expected to steer it in a generally northwesterly direction during the next few days.  On its anticipated track, Linda would move west of Baja California during the middle of next week.

Tropical Storm Grace Forms Southwest of Cape Verde

Enough organization developed in the center of an area of low pressure that moved off the coast of Africa several days ago for the National Hurricane Center to classify it as Tropical Storm Grace.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Grace was located at latitude 12.6°N and longitude 26.4°W which put it about 285 miles (460 km) southwest of the Cape Verde Islands.  Grace was moving toward the west 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 1007 mb.

The area of low pressure that became Tropical Storm Grace had a large area of thunderstorms when it moved off the coast of West Africa.  A few thunderstorms developed closer to the center of circulation and there are signs that a couple of spiral bands could be forming near the core of Grace.  The strongest thunderstorms are occurring in the southwestern quadrant of the circulation.  Some of the thunderstorms appear to be getting taller, but the core of the circulation is still organizing.

Tropical Storm Grace is moving over water where the Sea Surface Temperature is near 29°C.  Although there are stronger upper level westerly winds north of the tropical storm, the vertical wind shear over Tropical Storm Grace is relatively modest.  It has a day or two for the core of the circulation to organize and to intensify.  When Grace moves farther west it could move into a region where there is drier air.  An upper level trough could produce more vertical wind shear when the tropical storm gets closer to the Caribbean Sea.

A subtropical ridge is steering Grace toward the west and that steering pattern is expected to continue for the next few days.  If Grace gets stronger and the convection taller, it would take a track a little farther to the north.  If it remains weaker and shallower, lower level winds will steer it more to the west.  On its anticipated track, Grace could approach the Lesser Antilles in five or six days.

Tropical Storm Kevin Forms Southwest of Baja California

Vertical wind shear decreased enough on Thursday to allow more thunderstorms to develop near the center of Tropical Depression 14E and the National Hurricane Center upgraded it to Tropical Storm Kevin.  At 11:00 a.m. EDT on Thursday the center of Tropical Storm Kevin was located at latitude 17.9°N and longitude 115.6°W which put it about 505 miles (815 km) southwest of the southern tip of Baja California.  Kevin was moving toward the north at 6 m.p.h. (9 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1000 mb.

Tropical Storm Kevin is a small tropical cyclone.  Winds to tropical storm force only extend out about 70 miles (115 km) from the center of circulation.  There is one short spiral band wrapping around the northwest side of the center and another short band wrapping around the southwest side of the center.  There are not many thunderstorms in the eastern half of the circulation.  Kevin is over water where the Sea Surface Temperature (SST) is near 29°C.  However, a large, high amplitude upper level trough along the west coast of the U.S. is generating moderate southwesterly winds over the top of Kevin.  The vertical wind shear inhibited the development of Kevin, but the shear seems to have lessened today and the circulation in the tropical storm has consolidated around the center.  Thunderstorms near the center of Kevin are generating upper level divergence over a small area.

As Kevin moves farther north it will move over cooler SSTs.   When it gets north of latitude 22°N, Kevin will move over SSTs cooler than 26°C.  If the vertical wind shear remains moderate, Kevin could intensify further during the next 24 to 48 hours.  After about two days, the tropical storm will move over cooler SSTs and into an area with more vertical wind shear.  At that point Kevin is likely to start to spin down.

A ridge over Mexico is steering Kevin toward the north and that general motion is expected to continue for another day or two.  When Kevin moves over cooler SSTs, the thunderstorms will not be as tall and it will be steered by the winds lower in the atmosphere.  Those winds could push Kevin more toward the west during the weekend.

Hurricane Fred Bringing Wind and Rain to Cape Verde Islands

Hurricane Fred brought strong winds and heavy rain to many places in the Cape Verde Islands on Monday.  At 5:00 p.m. EDT on Monday the center of Hurricane Fred was located at latitude 17.2°N and longitude 24.6°W which put it about 20 miles (30 km) east of Santo Antao in the Cape Verde Islands.  Fred was moving toward the northwest at 12 m.p.h. (19km/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 989 mb.  A Hurricane Warning was in effect for the Cape Verde Islands.  It is unusual for a tropical cyclone of with sustained winds to hurricane force to move through the Cape Verde Islands.

Hurricane Fred has probably already gotten as strong as it is going to get.  It is moving over water where the Sea Surface Temperature (SST) is around 27°C.  However, an upper level trough located northwest of Fred is generating southwesterly winds that are blowing across the top of the hurricane.  The resulting vertical wind shear is beginning to affect the circulation in Fred and the eyewall is not as intact as it was earlier today.  As Fred moves farther north, the SSTs will decrease and the vertical wind shear will increase.  Those negative environmental factors should caused a steady weakening of Fred.

Hurricane Fred is moving toward a weaker portion of the subtropical ridge.  The ridge is expected to strengthen this week.  In addition, as the hurricane gets weaker, its circulation will become shallower.  That will mean it will be steered by winds lower in the atmosphere.  Those winds are likely to turn Fred toward the west in a day or two.

Fred will continue to bring wind and heavy rain to the Cape Verde Islands on Monday night, but conditions should start to improve on Tuesday when the hurricane moves farther west and weakens.

Rapidly Intensifying Tropical Storm Fred Threatens Cape Verde Islands

An area of low pressure organized quickly after it moved off the coast of West Africa and the National Hurricane Center designated it as Tropical Storm Fred.  At 2:00 p.m. EDT on Sunday the center of Tropical Storm Fred was located at latitude 14.1°N and longitude 20.7°W which put it about 195 miles (315 km) east-southeast of Praia in the Cape Verde Islands.  Fred was moving toward the northwest at 16 m.p.h. (26 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 1000 mb.  A Hurricane Warning has been issued for the Cape Verde Islands.

Tropical Storm Fred was a well organized low pressure system when it moved over the eastern Atlantic Ocean from West Africa.  The input of energy from the ocean enhanced the existing thunderstorms and the low pressure system quickly reached the intensity necessary to be classified as a tropical storm.  The circulation continued to organize further on Sunday.  A primary rainband has wrapped almost entirely around the center of circulation.  A small eye and an eyewall may be forming and other spiral bands of thunderstorms are developing.  The thunderstorms are generating upper level divergence which is pumping out mass.  Fred is moving over water where the Sea Surface Temperatures (SSTs) are near 27°C to 28°C.  The winds in the upper levels are relatively light and there is not much vertical wind shear.  The favorable environmental conditions are allowing Fred to intensify rapidly and it could become a hurricane tonight.  As Fred moves farther toward the northwest, it will start to move over cooler SSTs and into a region where there is more vertical wind shear.  As a result, Fred is likely to weaken back to tropical storm intensity later this week.

There is a weaker area in the subtropical ridge over the Atlantic Ocean and Fred is moving northwest toward that area.  The ridge is expected to strengthen during the week and as it strengthens it will cause Fred to move more toward the west.  On its anticipated track Fred will reach the Cape Verde Islands in about 12 hours.  It could bring strong winds and heavy rain when it move across those islands.

Trio of Cat. 4 Hurricanes Churn Across the Pacific

A trio of powerful Category 4 hurricanes on the Saffir-Simpson Scale churned across the Central and Eastern North Pacific on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Hurricane Ignacio was located at latitude 17.0°N and longitude 147.6°W which put it about 525 miles (845 km) east-southeast of Hilo, Hawaii.  Ignacio was moving toward the northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there wind gusts to 170 m.p.h. (275 km/h).  The minimum surface pressure was 951 mb.

At 11:00 p.m. EDT on Saturday the center of Hurricane Jimena was located at latitude 13.3°N and longitude 127.5°W which put it about 1330 miles (2140 km) west-southwest of the southern tip of Baja California.  Jimena was moving toward the west-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there were wind gusts to 170 m.p.h. (275 km/h).  The minimum surface pressure was 945 mb.

At 11:00 p.m. EDT on Saturday the center of Hurricane Kilo was located at latitude 18.4°N and longitude 176.2°W which put it about 680 miles (1095 km) south of Midway Island.  Kilo was moving toward the west-northwest at 9 m.p.h.  The maximum sustained wind speed was 135 m.p.h. (215 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 948 mb.

Ignacio is the only one of the three powerful hurricane to pose an imminent threat to land.  On its anticipated track Ignacio could be northeast of the Big Island of Hawaii in about 48 hours.  Tropical Storm Watches have been issued for Hawaii County and Maui County including the islands of Maui, Molokai, Lanai and Kahoolawe.  An upper level trough passing north of Hawaii will cause westerly winds and increasing vertical wind shear over Ignacio as it moves closer to Hawaii.  Ignacio should weaken but it could still be a hurricane when it makes its closest approach to Hawaii.  Given the size of the circulation around Ignacio, Tropical Storm Watches were issued for some of the islands.

Jimena may be the most well organized of the three hurricanes.  It has concentric eyewalls and a very symmetrical structure.  Eyewall replacement cycles will cause fluctuations in the intensity of Jimena.  However, it is in a very favorable environment and it could reach Category 5 intensity at some point.  Fortunately, Jimena is about 1500 miles (2420 km) east of Ignacio and it is a long way from any land area.

After days when strong vertical wind shear kept Kilo a weak disorganized tropical depression, it intensified very rapidly during the past 48 hours.  Kilo is over warm Sea Surface Temperatures  and it could intensify a little more.  Kilo is not currently a threat to any land.

Tropical Storm Erika Bringing Heavy Rain to Hispaniola

Tropical Storm Erika is moving across Hispaniola and it is bringing heavy rain to parts of that island.  At 5:00 p.m. EDT the center of Tropical Storm Erika was located at latitude 17.9°N and longitude 71.2°W which put it about 95 miles (155 km) west-southwest of Santo Domingo, Dominican Republic and about 745 miles (1200 km) southeast of Miami, Florida.  Erika was moving toward the west at 21 m.p.h. (33 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 1009 mb.  Tropical Storm Warnings have been issued for the southeastern Bahamas, the Turks and Caicos, for the Dominican Republic, Haiti, for the Central Bahamas including Cat Island, the Exumas, Long Island, Rum Cay and San Salvador.  Tropical Storm Watches have been issued for the northwestern Bahamas including the Abacos, Andros Island, Berry Island, Bimini, Eleuthera, Grand Bahama Island and New Providence, the Cuban provinces of Ciego de Avila, Camaguey, Las Tunas, Holguin and Guantanamo.

The circulation around Tropical Storm Erika is even less well organized today.  At times a small cyclonic rotation appeared on visible satellite images, while at other times Erika looked a lot like a very strong tropical wave.  Vertical wind shear caused by an upper level trough over the western Caribbean Sea has prevented thunderstorms from forming near the core of the circulation.  The lower part of the circulation will be significantly disrupted by the mountains of Hispaniola, but the middle portion may make it across the island.  If the middle level circulation is disrupted as well, then Erika will degenerate into a disorganized area of thunderstorms.  If the middle level circulation is still intact when it emerges west of Hispaniola, then it is possible that momentum could be transferred to the surface and a new low level center spun up.  Erika would most likely be a tropical depression at most at that time.  The water north of Cuba is very warm and if Erika still exists, it could intensify somewhat as it moves toward Florida.

The winds in the lower levels continued to push Erika toward the west-northwest on Friday and that general motion is likely continue for the next 12 to 12 hours.  Erika is getting closer to the western end of the subtropical high and it could turn more toward the north during the weekend.  On its anticipated track Erika or its remnants could be approaching the Florida Keys on Sunday afternoon.  At this time it is almost impossible to know how strong it will be at that time.  If Erika does start to reorganize when it gets west of Hispaniola, watches and/or warnings could be issued for parts of Florida.