Monthly Archives: July 2017

Tropical Storm Emily Makes Landfall on West Coast of Florida

Tropical Storm Emily made landfall on the west coast of Florida at Anna Maria Island late Monday morning.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Emily was located at latitude 27.5°N and longitude 82.7°W which put it about 10 miles (15 km) northwest of Bradenton, Florida.  Emily was moving toward the east at 9 m.p.h. (15 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 1005 mb.  A Tropical Storm Warning was in effect for the portion of the coast from Anclote River to Bonita Beach, Florida.

Thunderstorms developed near the center of the non-tropical low pressure system over the eastern Gulf of Mexico.  Latent energy released higher in the atmosphere by condensation in those storms created a warm core and the low pressure system made a transition to Tropical Storm Emily.  Thunderstorms near the core of Emily were generating a small area of upper level divergence.  Thunderstorms near the core, a warm core and upper level divergence are part of the typical structure of a tropical cyclone, which is why the National Hurricane Center classified the system as Tropical Storm Emily.  Emily has a well developed circulation, but most of the bands of showers and thunderstorms are in the eastern half of the tropical storm.  Drier air northwest of Emily and vertical wind shear are the probable causes of the asymmetrical distribution of precipitation.

Tropical Storm Emily is bringing gusty winds and heavy rain to parts of Central Florida.  A surface weather station in Sarasota (KSRQ) reported a sustained wind of 39 m.p.h. (63 km/h) and a wind gust of 49 m.p.h. (80 km/h).  The Skyway Bridge over Tampa Bay was closed due to strong winds.

Tropical Storm Emily is likely to weaken as it moves eastward across Central Florida.  When Emily moves over the Atlantic Ocean, it will move over water where the Sea Surface Temperature is near 29°C.  Emily could strengthen back into a tropical storm at that time.

Emily is being steered toward the east by a high pressure system north of the tropical storm.  An upper level trough over the Midwestern U.S. is forecast to move southeastward.  When Emily reaches the Atlantic Ocean southwesterly winds ahead of the trough will turn the tropical storm toward the northeast.

Noru Rapidly Intensifies Into a Super Typhoon

Typhoon Noru rapidly intensified into a Super Typhoon on Sunday.  At 11:00 p.m. EDT on Sunday the center of Typhoon Noru was located at latitude 22.9°N and longitude 140.3°E which put it about 150 miles (240 km) south-southwest of Iwo To.  Noru was moving toward the west at 5 m.p.h.  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h).  The minimum surface pressure was 922 mb.

The circulation of Typhoon Noru is very well organized.  There is a circular eye with a diameter of 20 miles (32 km) in the center of Noru.  The eye is surrounded by a wide ring of strong thunderstorms.  The strongest winds are occurring in this ring.  Bands of showers and thunderstorms are revolving around the core of Typhoon Noru.  Winds to typhoon force extend out about 45 miles (75 km) in all directions.  Winds to tropical storm force extend out about 150 miles (240 km) from the center.

The Hurricane Intensity Index (HII) for Typhoon Noru is 31.6.  The Hurricane Size Index (HSI) is 18.5 and the Hurricane Wind Intensity Size Index (HWISI) is 50.1.

Typhoon Noru is in a very favorable environment.  Noru is moving over water where the Sea Surface Temperature is near 30.5°C.  The upper level winds are weak and there is little vertical wind shear.  Typhoon Noru could maintain its intensity or weaken slowly over the next few days.

Typhoon Noru is moving around the western end of a subtropical ridge which is steering the typhoon slowly toward the west.  Noru is expected to start moving toward the north when it reaches the western end of the ridge.  On its anticipated track Typhoon Noru will remain south of Japan for much of the week.

Non-Tropical Low Forms Over Northeast Gulf of Mexico

A non-tropical low pressure system formed over the northeastern Gulf of Mexico on Sunday.  The low pressure system is currently designated as Invest 98L.  At 2:00 p.m. EDT on Sunday the center of Invest 98L was located at latitude 28.4°N and longitude 85.5°W which put it about 100 miles (160 km) south-southwest of Apalachicola, Florida.  It was moving toward the east at 8 m.p.h. (13 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 1009 mb.

The low pressure system formed along a frontal boundary that stalled over the northeastern Gulf of Mexico.  It is not usual for low pressure systems to form along stationary fronts.  A source of positive vorticity to provide counterclockwise rotation and upper level divergence to pump away mass and allow the surface pressure to decrease will generate a surface low.  The low pressure system does not have a warm core in the middle and upper levels and it is still associated with a frontal system.  So, it is classified as a non-tropical low pressure system.

The low pressure system will be moving through an environment that will be only marginally favorable for a transition to a tropical or subtropical cyclone.  The Sea Surface Temperature in the northeastern Gulf of Mexico is near 30°C.  So, there is plenty of energy to support the formation of a tropical cyclone.  However, an upper level ridge over the central U.S. and a trough over the northeastern U.S. are combining to produce northerly winds of 40 m.p.h. (65 km/h) over the northeastern Gulf of Mexico.  Those winds are generating significant vertical wind shear.  The shear has limited the development of thunderstorms in the northern half of the low and it may be tilting the vertical structure of the low toward the south.  The strong upper level winds will also inhibit divergence on the northern side of the low and they could make it difficult for a warm core to develop in the middle and upper levels.  The air north of the frontal boundary is drier continental air, which is another a negative factor for transition to a tropical cyclone.  Based on all of the environmental factors the National Hurricane Center is indicating that there is a 30% chance the low could make a transition to a tropical or subtropical cyclone.

The low pressure system is moving a little to the south of due east.  A strong surface high pressure system over the eastern U.S. is now pushing the front toward the south as a cold front.  The low is moving slowly eastward along the front.  Combination of the southward motion of the front and eastward motion of the low produces a forecast motion of a little south of due east.  On its anticipated track the low pressure system could reach the west coast of Florida in 24 to 36 hours.  So, the low has about a day, if it is going to transition to a tropical cyclone over the Gulf of Mexico.

Typhoon Nesat Causes Heavy Rain, Floods in Taiwan

Typhoon Nesat caused heavy rain and floods in parts of Taiwan when it moved over the island.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Nesat was located at latitude 26.2°N and longitude 118.9°E which put it near Fuzhou, China.  Nesat was moving toward the northwest at 13 m.p.h. (21 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 977 mb.

The core of Typhoon Nesat moved over northern Taiwan earlier today and the center passed close to Taipei.  The typhoon brought strong winds and heavy rain to parts of northern and eastern Taiwan.  The rainfall was heavy enough in some locations to cause flash flooding.  Nesat weakened to a tropical storm when the center passed over Taiwan.

Tropical Storm Nesat moved quickly across the Taiwan Strait and it made another landfall on the east coast of China near Fuzhou.  Nesat produced gusty winds and locally heavy rain near the coast.  Heavy rain will continue to fall over eastern China as Tropical Storm Nesat moves farther inland and the rain could result in flooding in some locations.

Parts of Taiwan could receive additional heavy rain on Sunday when Tropical Storm Haitang approaches the southern part of the island.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Haitang was located at latitude 20.8°N and longitude 119.7°E which put it about 370 miles (595 km) south-southwest of Taipei, Taiwan.  Haitang was moving toward the east-northeast at at 14 m.p.h. (22 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 997 mb.

The distribution of rain in Tropical Storm Haitang is very asymmetrical.  Almost all of the showers and thunderstorms are located south of the center of circulation.  However, there is a fairly large area of heavy rain in the southern half of the circulation of Haitang.  Tropical Storm Haitang is currently moving toward the east-northeast, but it is forecast to turn toward the north in a trough of low pressure left behind in the wake of Tropical Storm Nesat.  On its anticipated track Haitang, could make landfall in southwestern Taiwan near Kaohsiung in about 12 hours.  When the heavy rain in Haitang reaches Taiwan, it could exacerbate the flooding caused by Nesat.

Elsewhere over the Western North Pacific the center of Tropical Storm Noru passed just east of Iwo To.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Noru was located at latitude 23.5°N and longitude 141.4°E which put it about 80 miles (130 km) south-southeast of Iwo To.  Noru was moving toward the south-southwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 978 mb.

Tropical Storm Noru brought periods of heavy rain and gusty winds to Iwo To when the core of tropical storm moved east of the island.  Tropical Storm Noru is forecast to turn toward the west on Sunday.  The outer bands on the northern side of Noru will continue to cause gusty winds and periods of heavier rain on Iwo To as the tropical storm passes south of the island.

Strengthening Typhoon Nesat Nearing Taiwan

Strengthening Typhoon Nesat moved nearer to Taiwan on Friday.   At 5:00 p.m. EDT on Friday the center of Typhoon Nesat was located at latitude 22.0°N and longitude 123.3°E which put it about 275 miles (440 km) south-southeast of Taipei, Taiwan.  Nesat was moving toward the west-northwest at 10 m.p.h. (16 km/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/h).  The minimum surface pressure was 973 mb.

Typhoon Nesat has a very well organized circulation.  A ring of thunderstorms almost completely surrounds the eye.  There is a small gap in the ring on the northeastern rim of the eye.  Numerous additional bands of showers and thunderstorms are occurring in the southern half of the circulation.  There are fewer bands of showers and thunderstorms in the northern part of the circulation.  Thunderstorms in the core of Typhoon Nesat are producing upper level divergence which is pumping out mass.  Winds to typhoon force extend out about 40 miles (65 km) from the center of circulation.  Winds to tropical storm force extend out about 145 miles (230 km) from the center.

Typhoon Nesat will be moving through an environment favorable for intensification until it reaches Taiwan.  Nesat will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge centered west of Japan is producing east-northeasterly winds which are blowing toward the top of the circulation.  Those winds are causing some vertical wind shear, but they are not strong enough to keep Typhoon Nesat from strengthening.  Typhoon Nesat is likely to intensify for another 12-18 hours until it reaches Taiwan.  When it Nesat reaches Taiwan, the mountains will disrupt the circulation.

Typhoon Nesat is being steered toward the west-northwest by a subtropical ridge to its north.  A general west-northwesterly or northwesterly motion is expected to continue until Nesat makes landfall in Taiwan.  On its anticipated track Typhoon Nesat will make landfall on the east coast of Taiwan in 12 to 18 hours.  Neast will bring strong winds and heavy rain to Taiwan.  The heavy rain is likely to cause flash floods in the mountains.

Typhoon Noru Approaches Iwo To From Northeast

Typhoon Noru approached Iwo To from the northeast on Friday.  At 5:00 p.m. EDT on Friday the center of Typhoon Noru was located at latitude 27.6°N and longitude 143.0°E which put it about 220 miles (355 km) north-northeast of Iwo To.  Noru was moving toward the southwest at 11 m.p.h. (17 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. (150 km/h).  The minimum surface pressure was 975 mb.

Typhoon Noru retains a well organized circulation.  An eyewall wraps about three quarters of the way around the eye.  There is a break in the ring of thunderstorms on the northeastern rim of the eye.  Bands of showers and thunderstorms are occurring north and east of the center of circulation.  There are fewer showers and thunderstorms south and west of the center of the typhoon.  Thunderstorms near the center are generating some upper level divergence.  The circulation of Typhoon Noru is fairly large.  Winds to tropical storm force extend out about 200 miles (320 km) from the center of circulation.

Typhoon Noru will be moving through an environment that is marginally favorable for intensification.  Noru will move over water where the Sea Surface Temperature (SST) is near 29°C.  An upper level ridge centered west of Japan is producing northeasterly winds which are blowing toward the top of the circulation.  Those northeasterly winds are creating moderate vertical wind shear, which is limiting the upper level divergence to the north of the typhoon.  The wind shear is not strong enough to weaken Typhoon Noru, but it is strong enough to inhibit intensification.  Typhoon Noru may undergo small changes in intensity during the next several days, but it could maintain its status as a typhoon.

The ridge west of Japan is also steering typhoon Noru toward the southwest and that general motion is expected to continue for another day or so.  In 24 to 48 hours Noru is forecast to reach and area where the steering winds are weak and it could stall near Iwo To.  On its anticipated path Typhoon Noru could bring an extended period of strong gusty winds and heavy rain to Iwo To.

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.

Tropical Storm Nesat Forms Southeast of Taiwan

Tropical Storm Newsat formed southeast of Taiwan on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Nesat was located at latitude 18.0°N and longitude 127.5°E which put it about 620 miles (1000 km) southeast of Taipei, Taiwan.  Nesat was moving toward the north at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 988 mb.

A well organized surface circulation formed in an area of thunderstorms southeast of Taiwan on Wednesday.  A strong cluster of thunderstorms formed south of the center of circulation.  Additional bands of showers and thunderstorms developed in the western and southern portions of Tropical Storm Nesat.  There were few thunderstorms in the eastern half of the circulation.  More thunderstorms appeared to be forming near the core of the circulation in recent hours.  The thunderstorms in the core were generating upper level divergence which was pumping out mass.

Tropical Storm Nesat will be moving through an area that is favorable for intensification.  Nesat will move over water where the Sea Surface Temperature is near 31°C.  Tropical Storm Nesat is beneath the northeastern part of an upper level ridge.  The ridge is producing northeasterly winds which are blowing toward the top of the circulation.  Those winds are causing some vertical wind shear and the shear could be the reason for the asymmetrical distribution of thunderstorms.  Tropical Storm Nesat could move under the axis of the upper level ridge where the winds are weaker.  In that case the shear would be less and Nesat could intensify more quickly.  Tropical Storm Nesat is likely to intensify into a typhoon during the next 24 hours.

Tropical Storm Nesat is moving around a weak area in a subtropical ridge, which is allowing the tropical storm to move toward the north.  The ridge is forecast to strengthen and when that happens it will steer Nesat more toward the west.  On its anticipated track Tropical Storm Nesat could approach Taiwan in about three days.  Nesat could be a strong typhoon when it nears Taiwan.

Elsewhere in the Western North Pacific Typhoon Noru has turned back toward the west.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Noru was located at latitude 30.6°N and longitude 151.2°E which put it about 770 miles (1240 km) east-northeast of Iwo To.  Noru was moving toward the west at 19 m.p.h. (31 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. (150 km/h).  The minimum surface pressure was 978 mb.

A subtropical ridge north of Typhoon Noru is steering the typhoon toward the west.  A general westerly motion is forecast to continue for several more days.  Noru could reach an area of weaker steering winds in a few days and its motion may slow.  On its anticipated track Typhoon Noru could approach Iwo To in three or four days.

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 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.