Category Archives: Eastern and Central Pacific

TCs between Mexico and Hawaii

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.

Tropical Depression Eleven-E Forms West of Mexico

Tropical Depression Eleven-E formed west of Mexico on Friday.  At 11:00 a.m. EDT on Friday the center of Tropical Depression Eleven-E was located at latitude 17.7°N and longitude 109.2°W which put it about 335 miles (535 km) west-southwest of Manzanillo, Mexico.  The depression was moving toward the west-northwest at 15 m.p.h. (24 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 1009 mb.

The circulation of Tropical Depression Eleven-E is not particularly well organized.  The depression does have a distinct center of circulation which can be seen on visible satellite images.  Most of the showers and thunderstorms are occurring in the western half of the circulation.  The rainbands east of the center of circulation are thin and consist mainly of lighter showers.  The thunderstorms west of the center of circulation are generating only a little upper level divergence which is carrying mass to the west of the depression.

Tropical Depression Eleven-E is in an environment that is only marginally favorable for intensification.  The depression is moving over water where the Sea Surface Temperature is near 28.5°C.  So, there is sufficient energy in the upper ocean to support intensification.  However, an upper level ridge centered over northern Mexico is producing strong northeasterly winds which are blowing across the top of the depression.  Those winds are causing significant vertical wind shear.  The shear is probably the reason for the asymmetrical pattern with all of the thunderstorms in the western half of the circulation.  The shear is forecast to continue and if it does, there will be little or no intensification.  If the shear is less, then some intensification could occur.

Tropical Depression Eleven-E is being steered to the west-northwest by the ridge to its north.  A general west-northwesterly motion is forecast to continue for the next several days.  If the vertical wind shear increases and the depression weakens to a low level system, then winds closer to the surface would steer it more toward the west.  On its anticipated track the depression is expected to move away from Mexico.

Tropical Storms Hilary and Irwin Interact As They Weaken

Tropical Storms Hilary and Irwin started to interact on Thursday as both storms began to weaken.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Hilary was located at latitude 18.3°N and longitude 117.3°W which put it about 575 miles (925 km) west-southwest of the southern tip of Baja California.  Hilary was moving toward the west-northwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were gust to 85 m.p.h. (140 m.p.h.).  The minimum surface pressure was 992 mb.

At 11:00 p.m. EDT on Thursday the center of Tropical Storm Irwin was located at latitude 14.9°N and longitude 124.6°W which put it about 1105 miles (1780 km) west-southwest of the southern tip of Baja California.  Irwin was moving toward the west at 2 m.p.h. (3 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 1000 mb.

Hilary weakened below hurricane intensity on Thursday.  It appeared that the circulation drew in drier more stable air around the northwestern side of the circulation.  The drier air reduced the formation of showers and thunderstorms and the core of the circulation weakened.  At the same time upper level divergence from Tropical Storm Hilary increased the vertical wind shear over Tropical Storm Irwin.  Irwin was over water where the Sea Surface Temperature is near 28.5°C and it was able to extract enough energy from the ocean to maintain most of its intensity.

Tropical Storms Hilary and Irwin will move over water where the Sea Surface Temperature is near 28°C on Friday.  However, the combination of drier, more stable air and vertical wind shear is likely to keep both of the storms from strengthening.  Hilary and Irwin will move over cooler water during the weekend and both tropical storms are likely to weaken when that occurs.

Tropical Storm Hilary is being steering toward the west-northwest by a subtropical high pressure system to the north of the tropical storm.  Hilary is forecast to continue moving toward the west-northwest.  Tropical Storm Hilary is larger than Irwin.  Winds to tropical storm force extend out about 110 miles (180 km) in Tropical Storm Hilary.  Winds to tropical storm force extend out about 70 miles (110 km) in Tropical Storm Irwin.

The centers of the two tropical storms are only about 540 miles (870 km) apart.  When Tropical Storm Hilary passes north of Irwin, Tropical Storm Irwin is forecast to start to revolve around the larger Tropical Storm Hilary.  Irwin is expected to turn toward the north after Tropical Storm Hilary passes by.  Some models are forecasting the that the centers of the two tropical storms will approach each other and the larger Tropical Storm Hilary will eventually absorb Tropical Storm Irwin.

Hurricanes Hilary and Irwin Churn Over Eastern Pacific

Hurricanes Hilary and Irwin continued to churn over the Eastern North Pacific Ocean on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Hilary was located at latitude 16.0°N and longitude 109.8°W which put it about 475 miles (765 km) south of the southern tip of Baja California.  Hilary was moving toward the west-northwest at 12 m.p.h.  The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 973 mb.

At 11:00 p.m. EDT on Tuesday the center of Hurricane Irwin was located at latitude 16.1°N and longitude 120.9°W which put it about 855 miles (1375 km) west-southwest of the southern tip of Baja California.  Irwin was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 105 m.p.h. (165 km/h).  The minimum surface pressure was 980 mb.

Hilary is the larger and stronger of the two hurricanes.  Hurricane Hilary has a small circular eye surrounded by a ring of strong thunderstorms.  A rainband spirals around the western and southern sides of the core of the circulation.  Thunderstorms in the core are generating strong upper level divergence which is pumping out mass in all directions.  Winds to tropical storm force extend out about 90 miles (145 km) from the center.

Hurricane Irwin has a smaller circulation.  Irwin has a small eye.  Most of the thunderstorms are occurring in the northwestern quadrant of the circulation.  Winds to tropical storm force extend out only about 70 miles (110 km) from the center of circulation.

Hurricane Hilary is moving through a more favorable environment.  Hilary is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear near Hilary.  Hurricane Irwin is moving over water where the Sea Surface Temperature is near 28°C.  An upper level low northwest of Irwin appears to be producing westerly winds which are undercutting the upper level divergence generated by thunderstorms near the core of the hurricane.  Some drier air also seems to wrapping around the eastern side of the circulation.

Hurricane Hilary is moving faster than Hurricane Irwin and Hilary is getting closer to Irwin.  The two hurricanes are expected to interact later this week.  Since Hilary is bigger and stronger than Irwin, Hilary is forecast to become the dominant circulation.  Hurricane Hilary is expected to continue to move in west-northwesterly direction.  When Hilary gets closer to Hurricane Irwin, Irwin is forecast to begin to revolve around Hilary in an interaction called the Fujiwhara effect.  On their anticipated tracks Hurricanes Hilary and Irwin are expected to remain south of the southern tip of Baja California.

Tropical Storm Irwin Forms, Greg Gets Larger, Hilary Strengthens

Tropical Depression Ten-E intensified into Tropical Storm Irwin, the circulation of Tropical Storm Greg increased in size and Tropical Storm Hilary strengthened on Sunday.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Irwin was located at latitude 14.9°N and longitude 116.6°W which put it about 705 miles (1135 km) southwest of the southern tip of Baja California.  Irwin was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1003 mb.

At 5:00 p.m. EDT on Sunday the center of Tropical Storm Greg was located at latitude 14.4°N and longitude 130.1°W which put it about 1445 miles (2325 km) west-southwest of the southern tip of Baja California.  Greg was moving toward the west at 14 m.p.h. (22 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 1001 mb.

At 5:00 p.m. EDT on Sunday the center of Tropical Storm Hilary was located at latitude 14.9°N and longitude 102.9°W which put it about 410 miles (660 km) south-southeast of Manzanillo, Mexico.  Hilary was moving toward the west-northwest at 9 m.p.h. (15 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 was 999 mb.

A primary rainband wrapped around the western and southern sides of the center of circulation of Tropical Depression Ten-E and the National Hurricane Center upgraded the system to Tropical Storm Irwin.  Several other bands of showers and thunderstorms were developing over the southern half of the circulation.  There were fewer showers and thunderstorms in the northern half of the circulation.  Thunderstorms near the center of circulation were generating some upper level divergence.

Tropical Storm Irwin will move through an environment that will be somewhat favorable for intensification.  Irwin will move over water where the Sea Surface Temperature (SST) is near 28°C.  An upper level ridge northwest of Irwin are generating northeastern winds which are blowing toward the top of the circulation.  Those winds are generating moderate vertical wind shear and the shear may be the cause of the asymmetric distribution of showers and thunderstorms.  Tropical Storm Irwin could intensify during the next 24 to 48 hours.

The circulation of Tropical Storm Greg grew in size on Sunday.  However, Tropical Storm Greg will move into a less favorable environment during the next several days.  Tropical Storm Greg is over water where the SST is near 28°C, but it will move over cooler water in a day or two.  Greg could intensify in the short term, but it will weaken by midweek.

Tropical Storm Hilary is moving through a very favorable environment.  Hilary is moving over water where the SST is near 30°C.  The upper level winds are weak and there is little vertical wind shear.  Tropical Storm Hilary could be beginning a period of rapid intensification.  Hilary is forecast to become a hurricane on Monday and it could be a major hurricane later this week.

A subtropical ridge is steering all three tropical storms in a general west-northwesterly direction.  Tropical Storms Greg, Hilary and Irwin are likely to continue to move a little to the north of due west during the next three days.  On its anticipated track Tropical Storm Hilary is expected to remain west of the west coast of Mexico.

Tropical Storm Hilary Develops South of Acapulco

More thunderstorms formed near the center of Tropical Depression Nine-E and the National Hurricane Center upgraded the system to Tropical Storm Hilary.  At 11:00 p.m EDT on Saturday the center of Tropical Storm Hilary was located at latitude 11.5°N and longitude 100.2°W which put it about 375 miles (600 km) south of Acapulco, Mexico.  Hilary 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 1005 mb.

The circulation of Tropical Depression Nine-E was not well organized during the past several days as the depression moved over the Eastern North Pacific Ocean.  Thunderstorms began to form close to the center of circulation late on Saturday.  The formation of a core of thunderstorms was evidence of a more organized circulation and the depression was upgraded to Tropical Storm Hilary.  Some bands of showers and thunderstorms also began to develop outside the core of the tropical storm.  The circulation is still somewhat asymmetrical.  More showers and thunderstorms were forming in the northern half of the circulation.  The thunderstorms near the center were starting to generate upper level divergence which is pumping out mass.

Tropical Storm Hilary will be moving through an environment that is favorable for intensification.  Hilary will move over water where the Sea Surface Temperature is near 30°C.  The tropical storm will move through an area where the upper level winds are weak and there will not be a lot of vertical wind shear.  Tropical Storm Hilary should strengthen and it could intensify rapidly if the core of the circulation develops an eye.  Tropical Storm Hilary is likely to become a hurricane and it strengthen into a major hurricane early next week.

Tropical Storm Hilary is moving south of a subtropical ridge which is steering the tropical storm toward the west-northwest.  A general west-northwesterly motion is expected to continue for several more days.  On its anticipated track Tropical Storm Hilary will pass west of the west coast of Mexico.

Tropical Storms Fernanda and Greg Continue West Across the Pacific

Tropical Storms Fernanda and Greg continued to move west across the Pacific Ocean on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Fernanda was located at latitude 18.4°N and longitude 141.4°W which put it about 900 miles (1445 km) east of Hilo, Hawaii.  Fernanda was moving toward the west at 12 m.p.h. (19 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 1000 mb.

At 11:00 p.m. EDT on Thursday the center of Tropical Storm Greg was located at latitude 14.3°N and longitude 117.4°W which put it about 770 miles (1240 km) southwest of the southern tip of Baja California.  Greg was moving toward the west at 10 m.p.h. (16 km/h).  The maximum 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 1003 mb.

Tropical Storm Fernanda is moving through an environment that is unfavorable for intensification.  Fernanda is moving over water where the Sea Surface Temperature (SST) is near 26°C.  An upper level trough northeast of Hawaii is producing southwesterly winds which are causing strong vertical wind shear over Fernanda.  Tropical Storm Fernanda has a strong low level circulation but the vertical wind shear will blow the tops off any new thunderstorms that form.  The shear is likely to cause Fernanda to continue to weaken and the low level circulation is likely to gradually spin down.

Tropical Storm Greg did not intensify much on Thursday but recent satellite images seem to indicate that Greg may be getting more organized.  A primary band of showers and thunderstorms has wrapped about two thirds of the way around the eastern and northern sides of the center of circulation.  Upper level outflow from Tropical Storm Fernanda, which is farther west and an upper level low northwest of Greg were generating strong southerly winds which were blowing toward the top of the tropical storm.  Those winds were causing strong vertical wind shear over Tropical Storm Greg.  The upper low appears to be moving farther away from Greg.  Tropical Storm Greg is moving over water where the SST is near 28°C.  If the vertical shear diminishes and the circulation organizes, then there is sufficient energy in the upper ocean to allow Greg to intensify into a hurricane.

A subtropical ridge north of Greg is steering the tropical storm toward the west.  A general westerly motion is expected to continue during the next several days.  Tropical Storm Greg could take a path similar to the track of Tropical Storm Fernanda.

Active East Pacific With Fernanda, Greg and TD 8E

The tropical Eastern North Pacific Ocean continued to be very active on Tuesday with Hurricane Fernanda, Tropical Storm Greg and Tropical Depression Eight-E.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Fernanda was located at latitude 16.5°N and longitude 134.4°W which put it about 1375 miles east of Hilo, Hawaii.  Fernanda was moving toward the northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 976 mb.

At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Greg was located at latitude 14.6°N and longitude 110.1°W which put it about 490 miles (785 km) southwest of Manzanillo, Mexico.  Greg was moving toward the west at 10 m.p.h. (16 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 1003 mb.

At 11:00 p.m. EDT on Tuesday the center of Tropical Depression Eight-E was located at latitude 14.8°N and longitude 119.9°W which put it about 860 miles (1385 km) southwest of the southern tip of Baja California.  It was moving toward the west 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 1007 mb.

Although Hurricane Fernanda is the strongest of the three tropical cyclones over the Eastern North Pacific Ocean, it is slowly weakening as it moves over cooler Sea Surface Temperatures  (SSTs).  Hurricane Fernanda is over water where the SSTs are near 26.5°C and it will move over cooler water as it moves west toward Hawaii.

Tropical Storm Greg strengthened on Tuesday as it moved over water where the SSTs are near 29°C.  A primary rainband wrapped around the western side of the center of circulation.  Additional showers and thunderstorms formed closer to the center.  Greg is also expected to move west as it moves south of a subtropical ridge.

The future of Tropical Depression Eight-E is less certain.  Upper level divergence from Hurricane Fernanda is creating strong vertical wind shear over the stop of the depression.  The strong wind shear is causing the circulation of the depression to be poorly organized.  There are few showers and thunderstorms in the northern portion of the circulation because of the strong shear.  The stronger upper level winds could shear the top of the circulation away from the lower level circulation of the depression.  It is also possible that Tropical Storm Greg could catch up to the depression and absorb the remnants of the depression into its circulation.

Hurricane Fernanda Slowly Weakens As It Moves West

Hurricane Fernanda weakened slowly as it moved farther west over the Eastern North Pacific Ocean on Sunday.  At 11:00 p.m. EDT on Sunday the center of Hurricane Fernanda was located at latitude 13.0°N and longitude 129.2°W which put it about 1440 miles (2315 km) west-southwest of the southern tip of Baja California.  Fernanda was moving toward the west-northwest at 12 m.p.h. (19 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. (220 km/h).  The minimum surface pressure was 960 mb.

Hurricane Fernanda completed at least one eyewall replacement cycle in which an outer eyewall formed around the original eyewall.  Eventually, the inner eyewall dissipated and a larger eye formed inside the outer eyewall.  The eyewall replacement cycle weakened Hurricane Fernanda when the stronger, inner eyewall dissipated.  Although Hurricane Fernanda is weaker, it is still a powerful hurricane.  There is a circular eye at the center of circulation.  A ring of strong thunderstorms still surrounds the eye and the strongest winds are occurring in that ring of storms.  Additional bands of showers and thunderstorms are revolving around the core of the circulation.  Thunderstorms in the core of Hurricane Fernanda are generating strong upper level divergence which are pumping out mass in all directions.

Hurricane Fernanda is moving over water where the Sea Surface Temperature (SST) is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  Fernanda will gradually move over cooler SSTs.  When Fernanda moves over the cooler SSTs, it will extract less energy from the ocean and the hurricane will continue to weaken.  The weakening could occur very gradually because the wind shear is limited.

Hurricane Fernanda is moving south of a subtropical high pressure system which is steering the hurricane toward the west-northwest.  The subtropical high is expected to steer Fernanda toward the west-northwest during the next several days.

Hurricane Fernanda Intensifies Rapidly to Category 4

Hurricane Fernanda intensified rapidly to Category 4 on the Saffir-Simpson Scale on Friday.  At 5:00 p.m. EDT on Friday the center of Hurricane Fernanda was located at latitude 10.7°N and longitude 119.7°W which put it about 1060 miles (1710 km) southwest of the southern tip of Baja California.  Fernanda was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 960 mb.

A clear circular eye formed at the center of Hurricane Fernanda.  The eye is surrounded by a ring of very strong thunderstorms and the strongest winds are occurring in the eyewall.  Additional bands of showers and thunderstorms formed outside the core of Fernanda.  There are more bands in the eastern half of the hurricane, but the overall circulation is fairly symmetrical.  The thunderstorms in the core of Fernanda are generating strong upper level divergence which is pumping mass away from the hurricane.

Fernanda is a small hurricane.  Winds to hurricane force only extend out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force only extend out about 70 miles (110 km) from the center.  The Hurricane Intensity Index (HII) is 25.1.  The Hurricane Size Index (HSI) is 9.0 and the Hurricane Wind Intensity Size Index (HWISI) is 34.1.  The indices indicate that Hurricane Fernanda is somewhat similar in size and strength to Hurricane Charley in 2004 when Charley was approaching the southwest coast of Florida.

Hurricane Fernanda will remain in an environment very favorable for intensification for another 24 to 48 hours.  It will move over water where the Sea Surface Temperature (SST) is near 28.5°C.  The upper level winds are weak and there is little vertical wind shear.  Hurricane Fernanda has a chance to intensify into a Category 5 hurricane on the Saffir-Simpson Scale before it moves into a less favorable environment.  When a hurricane becomes as intense as Hurricane Fernanda is, an outer rainband can wrap around the eye and an eyewall replacement cycle can occur.  If an eyewall replacement cycle occurs in Hurricane Fernanda, then fluctuations in intensity may also happen.  Eventually Fernanda will move over cooler SSTs and the hurricane will start to weaken.

Hurricane Fernanda is moving south of a subtropical ridge and the ridge is steering the hurricane a little south of due west.  A general westward motion is forecast to continue during the next few days.  On its anticipated track Hurricane Fernanda will continue to move farther away from Mexico.  Fernanda could approach Hawaii by the end of next week.