Monthly Archives: July 2015

Guillermo Intensifies Into a Hurricane

Guillermo intensified rapidly during the past 24 hours and it is now a hurricane.  At 5:00 p.m. EDT on Friday the center of Hurricane Guillermo was located at latitude 12.7°N and longitude 134.8°W which put it about 1430 miles (2300 km) east of Hilo, Hawaii.  Guillermo was moving toward the west-northwest at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 970 mb.

Guillermo moved through a very favorable environment of warm Sea Surface Temperatures and little vertical wind shear which allowed it to intensify rapidly from a tropical storm into a hurricane.  An eye was visible earlier today on satellite images, but it is either obscured or has filled with clouds on the most recent images.  The hurricane is moving over water where the Sea Surface Temperature (SST) is near 29°C.  The upper level winds are light, but the rapid movement toward the west-northwest may be generating some vertical wind shear.  If Guillermo moves more slowly, it has about another 24 hours before it starts to move over cooler SSTs.  Once Guillermo gets west of longitude 140°W, it will gradually move over cooler SSTs.  As it moves farther north, it will also get closer to stronger upper level winds blowing from the west.  The combination of cooler SSTs and more vertical wind shear are likely to weaken Guillermo as it approaches Hawaii.

A subtropical ridge north of Guillermo is steering the hurricane toward the west-northwest and that steering is likely to continue for several more days,  In a few days a trough approaching from the west will turn Guillermo toward the northwest.  On its anticipated track Guillermo could approach Hawaii in about five days.  The higher probability is that a weaker Guillermo will move north of Hawaii, but the guidance from numerical models has been changing today.

Tropical Storm Guillermo Forms East- Southeast of Hawaii

An area of low pressure organized on Wednesday well east-southeast of Hawaii and it has been classified as Tropical Storm Guillermo.  At 5:00 a.m. EDT on Thursday the center of Tropical Storm Guillermo was located at latitude 8.5°N and longitude 126.3°W which put it about 2070 miles (3340 km) east-southeast of Hilo, Hawaii and about 1475 miles (2370 km) southwest of the southern tip of Baja California.  Guillermo was moving toward the northwest 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 1003 mb.

Guillermo formed at an unusually low latitude over the eastern North Pacific.  It is over an area where the Sea Surface Temperatures (SSTs) are near 29°C.  The upper level winds are light over the circulation and there is not much vertical wind shear.  Guillermo will be moving through an environment favorable for intensification during the next two or three days and a period of rapid intensification will be possible when it nears hurricane intensity.  Guillermo will move over cooler SSTs when it gets closer to Hawaii and the wind shear may also increase.

A subtropical ridge north of Guillermo is steering the tropical storm toward the northwest and the ridge is expected to continue to steer the tropical storm toward the west-northwest during the next 48 to 72 hours.  Later in the weekend an upper level trough approaching from the west could turn Guillermo more toward the northwest.

Tropical Cyclone 02B Forms Near Bangladesh

An area of low pressure over the extreme northern portion of the Bay of Bengal developed enough characteristics of a tropical cyclone to be designated Tropical Cyclone 02B.  At 5:00 a.m. EDT on Wednesday the center of Tropical Cyclone 02B was located at latitude 21.3°N and longitude 91.4°E which put it about 80 miles south-southwest of Chittagong, Bangladesh.  It was moving toward the north-northeast at 4 m.p.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 1001 mb.

The circulation around Tropical Cyclone 02B slowly organized during the past several days and it now has the structure of a tropical cyclone.  There are several spiral bands of thunderstorms, although most of the thunderstorms are south of the center due to the proximity to land.  The tropical cyclone is over very warm water where the Sea Surface Temperature is near 31°C, and it has enough energy to intensify.  However, a large upper level ridge over Asia is generating moderate northeasterly winds over the circulation which is producing moderate vertical wind shear.  Proximity to land will also be an inhibiting factor.  Some modest intensification is possible before the center moves over land.

Tropical cyclone 02B is moving around the western end of a subtropical ridge which is steering it northward toward the coast of Bangladesh.  That general steering pattern is expected to continue for another 24 hours.  Then the easterly winds associated with the upper level ridge over Asia are expected to turn Tropical Cyclone 02B toward the west.  On its anticipated track Tropical Cyclone 02B could make landfall over Bangladesh in approximately 24 hours.  Given the bathymetry of the northern Bay of Bengal and the shape of the coast of Bangladesh some storm surge is possible.  Locally heavy rainfall could contribute to flooding as the tropical cyclone moves inland.

Typhoon Halola Nearing Ryukyu Islands

Typhoon Halola turned northwestward on Friday and it is nearing the Ryukyu Islands.  At 5:00 p.m. EDT on Friday the center of Typhoon Halola was located at latitude 25.8°N and longitude 130.2°E which put it about 185 miles (300 km) east-southeast of Okinawa and about 50 miles (80 km) west-southwest of Minamidiato Island.  Halola was moving toward the northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. 145 km/h).  The minimum surface pressure was 974 mb.

Halala weakened on Friday, but it was still a typhoon at the time of this post.  It has a well defined low level circulation, but there are fewer thunderstorms in northwestern portion of Halola.  It appears as if some drier air is moving into the northwestern side of the typhoon.  Upper level winds from the northeast are creating some vertical wind shear, but Halola has well developed upper level divergence to the south of the center.  Halola will move over water where the Sea Surface Temperature (SST) is near 28°C as it passes just north of Okinawa and it could stay at typhoon intensity for another 12 to 24 hours.  After that time it will move over cooler SSTs and the upper level winds will increase.  Halola is likely to weaken to a tropical storm over the weekend.

Typhoon Halola is moving around the western end of a subtropical ridge, which is why it has turned toward the northwest.  It will turn northward on Saturday and then turn northeastward in about 36 hours as strong upper level winds from the southwest begin to push it in that direction.  On its anticipated track the center of Typhoon Halola could pass between Okinawa and Amami in to 18 hours.  It is likely to bring wind and heavy rain to some of the Ryukyu Islands.  The center of Halola could be near or just west of Kyushu in about 36 hours.

Tropical Storm Felicia Forms Southwest of Baja California

A center of circulation finally developed in an area of thunderstorms southwest of Baja California and the system has been designated as Tropical Storm Felicia.  At 11:00 a.m. EDT on Thursday the center of Tropical Storm Felicia was located at latitude 19.1°N and longitude 114.9°W which put it about 415 miles (670 km) southwest of the southern tip of Baja California.  The maximum sustained wind speed was 40 m.p.h. (60 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1004 mb.

Felicia is not a particularly well organized tropical storm.  Most of the thunderstorms are forming in the southern half of the circulation and it does not have many spiral bands.  Recent satellite images seem to indicate that upper level divergence is beginning to occur.  Felicia is over water where the Sea Surface Temperature (SST) is near 27°C and the upper level winds do not appear to be too strong.  The potential for some intensification will exist for about another 24 hours.  In a day or so, Felicia will start to move over cooler SSTs and it will likely weaken by the weekend.

A subtropical ridge is steering Felicia toward the northwest and that general steering pattern is expected to continue as long as the vertical integrity of the circulation remains intact.  When Felicia moves over cooler SSTs, the height of the circulation will decrease and the storm will be steered by winds in the lower levels.  Those winds are expected to turn Felicia more toward the west in a day or two.  Felicia poses no threat to land at this time.

Typhoon Halola Heading Toward Okinawa

Typhoon Halola moved steadily toward the west-northwest on Wednesday and it moved to within 550 miles of Okinawa.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Halola was located at latitude 24.4°N and longitude 135.4°E which put it about 525 miles (850 km) east-southeast of Okinawa.  Halola was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 956 mb.

The organization of Typhoon Halola improved on Wednesday.  There is an inner eye and a primary rainband may be wrapping around the center as well.  The circulation is more symmetrical and more thunderstorms formed on the western side of the typhoon.  There is well developed upper level divergence over the southeastern half of Halola.  Upper level winds from the northeast are inhibiting some of the upper level divergence over the northwestern part of Halola.  Since the typhoon is still over warm Sea Surface Temperatures (SSTs), it has the potential to intensify further during the next several days.  If the primary rainband wraps entirely around the circulation and creates concentric eyewalls, then an eyewall replacement cycle could cause fluctuations in intensity.

A subtropical ridge is steering Halola toward the west-northwest and that general motion is expected to continue for another two days.  After about 48 hours Halola will reach the western end of the ridge and turn toward the north.  Halola could threaten southwestern Japan or South Korea over the weekend.  On its anticipated track Halola will approach Okinawa in about 48 hours.  It could be a significant typhoon at that time and bring strong winds and heavy rain to the islands around Okinawa.

Halola Becomes a Typhoon South of Japan

A tropical cyclone named Halola intensified a few hundred miles south of Japan on Tuesday and it reached typhoon intensity.  At 5:00 p.m. EDT on Tuesday the center of Typhoon Halola was located at latitude 23.1°N and longitude 140.2°E which put it about 840 miles (1360 km) east-southeast of Okinawa.  Halola was moving toward the west at 11 m.p.h.  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (170 km).  The minimum surface pressure was 967 mb.

Typhoon Halola is moving over water where the Sea Surface Temperature (SST) is near 28°C.  The circulation is relatively well organized and an eye has been visible intermittently on satellite imagery.  There are many more thunderstorms in the eastern half of the circulation and there have been breaks in the western side of the eyewall at times.  It could be that there is some drier air to the northwest of the center.  Halola is currently moving through a region where the upper level winds are relatively light and there has not been much vertical wind shear today.  The lack of wind shear has allowed upper level outflow to become well developed to the east and south of the center of circulation.  Halola has the potential to intensify further during the next 48 hours while it is a region of modest vertical wind shear.

A subtropical ridge is steering Halola toward the west and a general west-northwestward movement is expected to continue during the next several days.  In two or three days Halola will reach the western end of the subtropical ridge and it will turn toward the north.  Guidance from numerical models varies on the strength of the subtropical ridge and the timing of the northward turn.  It is possible that Halola could threaten southwestern Japan later this week.

Typhoon Nangka Making Landfall in Japan

Typhoon Nangka has reached the coast of Japan and it is making landfall.  At 11:00 a.m. EDT on Thursday the center of Typhoon Nangka was located at latitude 33.4°N and longitude 134.3°E which put it about 20 miles (35 km) southeast of Kochi, Japan.  Nangka was moving toward the north at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 974 mb.

Nangka will bring strong winds and locally heavy rain to parts of Shikoku and Honshu during the next 24 hours.  It will weaken to tropical storm intensity as it moves across those islands.  Nangka is likely to emerge over the Sea of Japan on Friday.  It will be over cooler Sea Surface Temperatures at that time.  In addition, stronger westerly winds in the upper levels will create strong vertical wind shear.  Nangka will weaken further as those westerly winds turn it toward the east.

Dolores Becomes a Major Hurricane

Hurricane Dolores intensified rapidly on Tuesday night and it has reached Major Hurricane status.  At 11:00 a.m. EDT on Wednesday the center of Hurricane Dolores was located at latitude 18.4°N and longitude 110.2°W which put it about 310 miles (500 km) south of Cabo San Lucas, Mexico.  The maximum sustained wind speed was 130 m.p.h. (215 km/h) which made Dolores a Category 3 hurricane on the Saffir-Simpson Scale.  There were wind gusts to 160 m.p.h. (260 km/h) and the minimum surface pressure was 946 mb.

Dolores is currently over water where the Sea Surface Temperature (SST) is around 29°C.  It is generating well developed upper level outflow which is pumping out mass and there is not much vertical wind shear.  Dolores could strengthen some more during the next 24 hours, although eyewall replacement cycles could produce fluctuations in intensity.  When Dolores moves north of latitude 20°N, it will move over cooler SSTs and it should start to weaken.  Given its size and intensity, it could take several days for the circulation around Dolores to spin down.

A ridge in the middle levels is steering Dolores toward the west-northwest.  That general steering pattern is expected to continue during the next few days and Dolores poses no current threat to land.

Typhoon Nangka Moving Toward Japan

Typhoon Nangka has moved steadily northward toward Japan during the past several days.  At 5:00 p.m. EDT on Tuesday the center of Typhoon Nangka was located at latitude 26.0°N and longitude 136.4°E which put it about 580 miles (935 km) south of Kobe, Japan.  Nangka was moving toward the north at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 956 mb.

Typhoon Nangka went through several eyewall replacement cycles in recent days which produced fluctuations in its intensity.  It currently has a circular, slightly ragged eye.  The circulation is still fairly symmetrical although the thunderstorms appear to be taller and stronger in the eastern half of the circulation.  There is strong upper level divergence to the east of the circulation.  Nangka remains over water where the Sea Surface Temperature (SST) is near 28°C.  There is little vertical wind shear and the typhoon has the potential for some intensification during the next 24 hours.

A subtropical ridge located east of Nangka is steering it toward the north and that general steering pattern is expected to continue during the next two days.  On its anticipated track Nangka could approach the island of Shikoku in about 48 hours.  The typhoon will move over cooler SSTs when it nears Japan, which will weaken it somewhat.  However, Nagka is a large powerful typhoon.  It has a Hurricane Intensity Index of 17.8 and a Hurricane Size Index of 26.7, which gives it a Hurricane Wind Intensity Size Index of 44.5.  At its current size and intensity Nanga is capable of producing widespread serious damage.