Monthly Archives: July 2017

Tropical Storm Sonca Near Landfall in Vietnam.

Tropical Storm Sonca neared a landfall on the coast of Vietnam on Monday night.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Sonca was located at latitude 16.7°N and longitude 108.2°E which put it about 60 miles (95 km) east-northeast of Hue, Vietnam.  Sonca was moving toward the west at 13 m.p.h. (20 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 991 mb.

The circulation of Tropical Storm Sonca is fairly small.  Winds to tropical storm force only extend out about 60 miles (95 km) from the center of circulation.  A subtropical ridge north of Sonca is steering the tropical storm toward the west and that general motion is expected to continue for another 24 to 36 hours.  On its anticipated track the center of Tropical Storm Sonca will make landfall north of Hue, Vietnam in a few hours.

Tropical Storm Sonca will bring gusty winds, locally heavy rain and the potential for floods when it makes landfall.  Sonca will continue to move inland over central Vietnam, central Laos and northeastern Thailand.  Sonca could continue to produce locally heavy rain over those areas as it moves inland and weakens.

Elsewhere in the Western North Pacific the circulations of Typhoon Noru and Tropical Storm Kulap are interacting east-southeast of Japan.  At 11:00 p.m. EDT on Monday the center of Typhoon Noru was located at latitude 25.9°N and longitude 157.0°E which put it about 1330 miles (2150 km) east-southeast of Tokyo, Japan.  Noru was moving toward the east at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 95 m.p.h. (155 km/h) and there were gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 966 mb.

At 11:00 p.m. EDT the center of Tropical Storm Kulap was located at latitude 32.9°N and longitude 155.8°E which put it about 1095 miles (1765 km) east-southeast of Tokyo, Japan.  Kulap 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 1000 mb.

Typhoon Noru and Tropical Storm Kulap are close enough to each other to rotate cyclonically around a point between them in what is called the Fujiwhara effect.  Typhoon Noru is the much larger and stronger circulation and upper level outflow from Noru is causing vertical wind shear over Tropical Storm Kulap.  If the two tropical cyclones move closer to each other, it is possible that the circulation of Kulap could be absorbed by the larger, more powerful circulation of Typhoon Noru.

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 Storm Roke Close to Landfall Near Hong Kong

Tropical Storm Roke is close to making a landfall near Hong Kong.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Roke was located at latitude 22.4°N and longitude 114.1°E which put it about 35 miles (55 km) east of Hong Kong.  Roke 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 sutface pressure was 1002 mb.

Tropical Storm Roke will make landfall on the coast of China near Hong Kong during the next few hours.  Roke will bring gusty winds and locally heavy rainfall as it move inland over eastern China.  Flash flooding could occur in places that receive heavy rain.

Elsewhere, there are three more tropical storms over the Western North Pacific Ocean.  Tropical Storm 08W is the only other imminent threat to land.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm 08W was located at latitude 17.6°N and longitude 111.5°E which put it about 85 miles (135 km) southeast of Hainan Island.  It was moving toward the west at 4 m.p.h. (6 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 999 mb.

At 11:00 p.m. EDT on Saturday the center of Tropical Storm Noru was located at latitude 28.3°N and longitude 151.3°E which put it about 920 miles (1485 km) east-southeast of Tokyo, Japan.  Noru was moving toward 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 997 mb.

At 11:00 p.m. EDT the center of Tropical Storm Kulap was located at latitude 30.8°N and longitude 166.8°E which put it about 790 miles (1270 km) north of Wake Island.  Kulap was moving toward the west-northwest at 13 m.p.h. (20 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 1000 mb.

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.

Tropical Storm Noru Forms Southeast of Japan

Tropical Storm Noru formed southeast of Japan on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Noru was located at latitude 28.3°N and longitude 157.0°E which put it about 1145 miles (1850 km) east-southeast of Tokyo, Japan.  Noru was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 40 m.p.h. (64 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1003 mb.

Tropical Storm Noru had a complicated development.  Noru began as a cold front that became stationary southeast of Japan.  The front stalled over water where the Sea Surface Temperature (SST) was near 30°C.  Transfers of internal energy from the ocean to the atmosphere warmed the air and the temperature difference between the two sides of the front gradually diminished.  A surface low pressure system developed along the dissipating front.  An upper level low initially near the front caused strong vertical wind shear over the surface low.  The wind shear kept blowing the tops off thunderstorms that started to develop near the surface low.  Eventually, the upper low moved far enough to the northwest of the surface low for the vertical wind shear to decrease and thunderstorms were able to develop near the surface low.  The low gradually began to exhibit tropical characteristics and the Japan Meteorological Agency designated the system as Tropical Storm Noru.

The circulation of Tropical Storm Noru is still not well organized.  Although there is a definite center of circulation at the surface most of the showers and thunderstorms are forming in bands in the eastern half of the circulation.  There are few showers and thunderstorms in the western half of the circulation.  Thunderstorms on the eastern side of Noru are generating some upper level divergence which is pumping mass away to the east of the tropical storm.

Tropical Storm Noru is an environment that is somewhat favorable for intensification.  Noru is moving over water where the SST is near 30°C.  However, the upper low northwest of Noru and an upper level ridge near Noru are generating moderate vertical wind shear.  The wind shear may be part of the reason for the asymmetrical distribution of thunderstorms.  Tropical Storm Noru is likely to intensify but the vertical wind shear will slow the rate of intensification.

A subtropical ridge to the north of Noru is steering the tropical storm toward the northwest.  The northwesterly motion is expected to continue for another day or two.  The steering currents are expected to weaken in 36 to 48 hours an Noru could meander southeast of Japan during the weekend.

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.

Tropical Storm Don Forms East of Windward Islands

Tropical Storm Don formed east of the Windward Islands on Monday.  An Air Force Reserve Hurricane Hunter reconnaissance aircraft found a small, but well defined center of circulation in a cluster of thunderstorms formerly designated Invest 91L.  Based on information from the recon plane, the National Hurricane Center classified the system at Tropical Storm Don.  At 5:00 p.m. EDT on Monday the center of Tropical Storm Don was located at latitude 11.2°N and longitude 52.6°W which put it about 595 miles (955 km) east of Trinidad.  Don was moving toward the west at 17 m.p.h. (28 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 1009 mb.

A Tropical Storm Warning has been issue for Grenada.  Tropical Storm Watches are in effect for Barbados, St. Vincent, the Grenadines and St. Lucia.

The reconnaissance plane found a small, tight center of circulation near the surface.  A thin band of showers and thunderstorms wrapped partially around the western side of the center.  Other thin bands of showers and thunderstorms were occurring north and west of the center.  There were fewer showers and thunderstorms in the eastern half of Tropical Storm Don.  The circulation of Tropical Storm Don is small and winds to tropical storm force only extend out about 25 miles (40 km) from the center of circulation.  Thunderstorms in the band west of the center of circulation were generating some upper level divergence but it was not well developed.

Tropical Storm Don will move through an environment that will be somewhat favorable for intensification during the next several days.  Don will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge east of Don is generating easterly winds which are blowing over the top of the tropical storm.  Those easterly winds are generating some vertical wind shear and the shear may partly explain why there are fewer showers and thunderstorms in the eastern half of the circulation.  The shear will also inhibit intensification, but Tropical Storm Don could strengthen during the next 24 to 48 hours.

A strong subtropical high over the Atlantic Ocean is steering Tropical Storm Don toward the west and a generally westward motion is expected to continue during the next several days.  On its anticipated track the center of Tropical Storm Don could pass south of Barbados on Tuesday.  Tropical Storm Don could move over the southern Windward Islands on Tuesday night.  Tropical Storm Don could bring gusty winds and locally heavy rain to the southern Windward Islands.  Flash floods could occur in areas of steep terrain, if they receive locally heavy rainfall.

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.

Tropical Storm Talas Makes Landfall in Vietnam

Tropical Storm Talas made landfall on the coast of Vietnam on Sunday.  Talas was bringing gusty winds and heavy rainfall to parts of Vietnam, Laos and Thailand.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Talas was located at latitude18.6°N and longitude 105.5°E which put the center near Vinh, Vietnam.  Talas was moving toward the west at 17 m.p.h. (27 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 984 mb.

Tropical Storm Talas strengthened before it made landfall in Vietnam.  A primary band wrapped around the western and southern sides of the center of circulation.  Thunderstorms formed near the center of Talas as the tropical storm approached the coast of Vietnam.  The strongest winds in Tropical Storm Talas were occurring in thunderstorms over the South China Sea.  Tropical Storm Talas will weaken as it moves farther inland.

Tropical Storm Talas was bringing gusty winds and heavy rain to parts of Vietnam, Laos and Thailand.  Locally heavy rain could cause flooding, which will be the greatest risk as Tropical Storm Talas moves farther inland.