Monthly Archives: September 2016

Typhoon Malakas Moves Toward Taiwan and the Ryukyu Islands

Typhoon Malakas moved toward Taiwan and the southernmost Ryukyu Islands on Thursday.  At 8:00 p.m. EDT on Thursday the center of Typhoon Malakas was located at latitude 20.1°N and longitude 124.7°W which put it about 285 miles (460 km) south of Ishigaki, Japan.  Malakas was moving toward the northwest at 15 m.p.h. (24 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. (205 km/h).  The minimum surface pressure was 956 mb.

The structure of Typhoon Malakas is well organized.  A small eye has been evident intermittently on satellite imagery.  More of the thunderstorms are forming south of the center of circulation, although there are spiral bands of thunderstorms in all quadrants of the circulation.  The thunderstorms in the core of Typhoon Malakas are generating upper level divergence which is pumping out mass in all directions.  The circulation of Typhoon Malakas has been in a rough equilibrium during the past 24 hours and the intensity has remained relatively steady.

Typhoon Malakas is moving through an environment that is favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 30°C.  Although there is an upper level trough over China and an upper level low to the northeast of Malakas, the upper level winds around the typhoon are relatively light.  There is not much vertical wind shear.  Typhoon Malakas could strengthen further during the next 24 hours.

Typhoon Malakas is moving around the western end of a subtropical ridge.  Malakas turned more toward the northwest on Thursday.  It is expected to move more toward the north on Friday as is reaches the western end of the ridge.  When Malakas moves farther north, the upper level trough over China will steer the typhoon quickly toward the northeast toward the southern end of Kyushu.  On its anticipated track Typhoon Malakas will be near northeastern Taiwan and the southernmost Ryukyu Islands in about 24 hours.

Typhoon Malakas is smaller than Typhoon Meranti was, but Typhoon Malakas is capable of causing significant wind damage.  It will also bring heavy rain.  Since areas on Taiwan received heavy rain when Typhoon Meranti moved past them, it will take less additional rain to create the potential for flash flooding.

Tropical Storm Julia Edges Farther from the Southeast U.S.

Tropical Storm Julia moved slowly eastward on Thursday which took it farther from the Southeastern coast of the U.S.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Julia was located at latitude 32.1°N and longitude 77.1°W which put it about 150 miles (245 km) south-southeast of Wilmington, North Carolina.  Julia was moving toward the east at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1007 mb.

The circulation of Tropical Storm Julia is not well organized.  All of the stronger thunderstorms are well to the east of the center of circulation.  The broad low level circulation is elongated from the west-southwest of the east-northeast.  There are no thunderstorms close to the center of circulation.

Tropical Storm Julia is in an environment that is unfavorable for intensification.  It is moving over water where the Sea Surface Temperature is near 29°C.  So, there is sufficient energy in the upper ocean to support intensification.  However, upper level westerly winds are causing strong vertical wind shear.  The upper level winds have at least temporarily blown the upper part of the circulation east of the lower third of the circulation.  As long as the upper level winds are as strong as they are now, Tropical Storm Julia will slowly weaken.  If the upper level winds slow down, then more thunderstorms could develop near the center and Julia could get a little stronger.  With the current strong vertical wind shear Tropical Storm Julia should slowly weaken during the next few hours.

The vertical structure of Tropical Storm Julia maintained enough integrity that the westerly winds pushed the thunderstorms toward the east and they dragged the low level center with them.  However, it now appears that the vertical parts of the circulation have separated.  The low level circulation is being steered slowly back toward the southwest by a surface high pressure system to the north of Julia.  Tropical Storm Julia could move erratically during the next several days.  As long as no thunderstorms form near the center, it will drift slowly toward the southwest.  Any time thunderstorms form near the center of circulation, the taller storm will be pushed toward the east.

Strong Typhoon Meranti Nears Landfall in China

Strong Typhoon Meranti is near a landfall on the east coast of China close to Xiamen.  At 11:00 a.m. EDT on Wednesday the center of Typhoon Meranti was located at latitude 23.9°N and longitude 118.4°E which put it about 40 miles (65 km) south-southeast of Xiamen, China.  Meranti was moving toward the northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 175 m.p.h. (280 km/h).  The minimum surface pressure was 931 mb.

Meranti has weakened during the past 24 hours, but it remains a strong typhoon.  The Hurricane Intensity Index (HII) for Typhoon Meranti is 29.9.  The Hurricane Size Index (HSI) is 24.5 and the Hurricane Wind Intensity Size Index is 54.4.  These indices suggest that Typhoon Meranti is capable of causing widespread significant damage when it makes landfall.  As a comparison, the HII for Hurricane Ivan just before it made landfall on the Gulf Coast in 2004 was 22.1, the HSI was 34.1 and the HWISI was 56.2.  Thus, Typhoon Meranti is stronger than Hurricane Ivan was, but Meranti is also smaller than Ivan was in 2004.  The HWISI for Typhoon Meranti is close to what it was for Hurricane Ivan.

The center and inner eyewall of Typhoon Meranti moved just south of the southern end of Taiwan.  Since the eyewall stayed over water, it remained intact.  However, the outer concentric eyewall and much of the northern half of the circulation did move across Taiwan.  Flow over the mountains on Taiwan did weaken the northern half of the circulation, while the center and southern half of the circulation remained intact.  Since the core of the circulation stayed over the water, Typhoon Meranti stayed stronger than it would have if the inner eye had moved over Taiwan.

Most of the stronger thunderstorms and heavier rain are near the center of circulation and south of the center.  There are rainbands in other parts of Typhoon Meranti and some of those rainbands are already bringing heavy rain to parts of eastern China.

Typhoon Meranti is moving around the western end of a subtropical ridge which is steering it toward the northwest.  Meranti is expected to turn more toward the north as it move inland over China.  On its anticipated track Typhoon Meranti is expected to move northwest over Fujian province and then turn north toward Nanchang.

Typhoon Meranti is capable of causing significant wind damage over eastern China.  In addtion strong winds will create a significant storm surge along the coast near Xiamen.  Heavy rain will spread inland over Fujian province and the rain could create the potential for flooding over parts of eastern China.

Tropical Storm Julia Forms over Northeast Florida

Although tropical storms normally form over an ocean, Tropical Storm Julia formed over northeast Florida on Tuesday.  The National Hurricane Center (NHC) had tracked a tropical disturbance from Africa across the Atlantic Ocean to Florida.  NHC had designated the system as Invest 93L for tracking purposes.  Although the disturbance moved over the Florida peninsula on Monday, a distinct center of circulation developed at the surface on Tuesday while the disturbance moved north over the northeastern part of Florida.  An area of stronger thunderstorms formed over the Atlantic Ocean east of the center of circulation on Tuesday afternoon and persisted into Tuesday evening.  Because the system had a distinct surface center, persistent thunderstorms and winds to tropical storm force, the National Hurricane Center named it Tropical Storm Julia at 11:00 p.m. EDT on Tuesday and initiated advisories on the Julia.

At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Julia was located at latitude 30.3°N and longitude 81.6°W which put it about 5 miles (10 km) west of Jacksonville, Florida.  Julia was moving toward the north-northwest at 9 m.p.h. (15 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 issued for the portion of the coast from Ponte Vedra Beach, Florida to Altamaha Sound, Georgia.

The circulation of Tropical Storm Julia is very asymmetrical.  Most of the thunderstorms and rain are north and east of the of circulation.  There are few storms or rain west and south of the center.  One primary rainband extends part of the way around the southeastern portion of the circulation.  The thunderstorms to the east of the center are generating upper level divergence which is pumping out mass to the northeast of the circulation.

Since the center of Tropical Storm Julia is over land, intensification would normally be unlikely.  However, about half of the circulation is over water where the Sea Surface Temperature is near 28.5°C.  In addition, the atmospheric environment is favorable for strengthening.  The upper level winds are not too strong and the vertical wind shear is moderate.  It is possible that the wind speeds could increase in the thunderstorms in the part of the circulation that is over the Atlantic Ocean on Wednesday.

The steering currents around Tropical Storm Julia are quite complicated.  There is an upper low over the Gulf of Mexico, a ridge over the western Atlantic Ocean and an upper level trough moving toward the Great Lakes and East Coast of the U.S.  The upper low and ridge over the western Atlantic combined to steer Julia mainly toward the north-northwest on Tuesday.  At times the asymmetric circulation and the upper level divergence to the east of the circulation caused the center to move east as well.  It is likely that this motion will continue on Wednesday.  The center of Julia could move very close to the coast of Georgia.  If the center remains inland, then Tropical Storm Julia will start to weaken slowly.  If the center moves over the water, then it could intensify and persist longer.

The primary risk posed by Tropical Storm Julia will be locally heavy rain and the potential for flash flooding.  Winds and waves along the coast will cause rip currents and some beach erosion.  Water rises of several feet (one meter) will be possible.

Extremely Powerful Typhoon Meranti Nearing Southern Taiwan

The center of extremely powerful Typhoon Meranti moved closer to the southern end of Taiwan during the past few hours.  At 5:00 p.m. EDT on Tuesday the center of Typhoon Meranti was located at latitude 21.1°N and longitude 121.3°E which put it about 65 miles (105 km) south-southeast of Hengchun, Taiwan.  Meranti was moving toward the west-northwest at 11 m.p.h. (18 km/h).  The maximum sustained wind speed was 190 m.p.h. (305 km/h) and there were wind gusts to 230 m.p.h. (370 km/h).  The minimum surface pressure was 887 mb.

Typhoon Meranti is large and powerful.  The Hurricane Intensity Index (HII) is 46.1.  The Hurricane Size Index (HSI) is 27.9 and the Hurricane Wind Intensity Size Index (HWISI) is 74.0.  As a source of comparison, when Hurriane Katrina was at its peak intensity as a Category 5 hurricane over the Gulf of Mexico in 2005, its HII was 38.6, its HSI was 33.7, and its HWISI was 72.3.  Typhoon Meranti is stronger than Hurricane Katrina was, but Meranti is a little smaller than Katrina was in 2005.  The indices suggest that Typhoon Meranti is capable of causing widespread catastrophic damage.

The circulation of Typhoon Meranti is symmetrical and very well organized.  It possess a tight core consisting of a small inner eye surrounded by a ring of very tall thunderstorms.  A second, larger outer eyewall completely surrounds the inner eye.  The strongest winds are occurring in the inner eyewall near the center of circulation.  Winds to typhoon force are also occurring in the outer eyewall and extend out at least 80 miles (130 km) from the center of circulation.  Additional bands of strong thunderstorms are rotating around the outer eyewall.  Typhoon Meranti is generating strong upper level divergence which is pumping out large quantities of mass and is allowing the surface pressure to be so low.

Typhoon Meranti is probably at its peak intensity.  It is still moving over water where the Sea Surface Temperature is near 31°C.  However, the northwestern edge of the outer eyewall appears to be moving over the southern end of Taiwan.  As more of the circulation moves over Taiwan, there will be some disruption of the airflow.  The center of Typhoon Meranti could move very close to the southern tip of Taiwan.  If the center of Meranti moves over southern Taiwan, then the typhoon will weaken more quickly.  It currently appears that the center of Typhoon Meranti could move just south of the southern tip of Taiwan, and on that track the typhoon would not weaken as quickly.  When Typhoon Meranti moves west of Taiwan, it will move over slightly cooler SSTs before it reaches China.  Meranti will weaken more before it reaches China, but it will still be a significant typhoon when it makes landfall there.

The center of Typhoon Meranti is wobbling a little as the inner eye rotates around inside the outer eyewall.  If one averages the wobbles, then then core of Meranti is moving on a general west-northwesterly track.  On its anticipated track, the center of Typhoon Meranti will pass very near the southern end of Taiwan during the next few hours.  It could turn slightly toward the northwest as it moves west of Taiwan.  Typhoon Meranti could make a landfall on the coast of China between Xiamen and Shantou in about 24 hours.

Typhoon Meranti is an extremely dangerous storm.  It is capable of causing widespread catastrophic wind damage.  In addition, its intensity and size will produce very heavy rainfall, especially on the eastern slopes of the mountains on Taiwan.  Flash flooding is likely.  Typhoon Meranti will also produce heavy rain over eastern China and additional flooding is likely in that region.  Typhoon Meranti will also cause a significant storm surge in low lying coastal areas.

Typhoon Meranti Becomes Equivalent of Cat. 5 Hurricane and Threatens Taiwan

Typhoon Meranti rapidly intensified into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale as it moved on a course that threatens Taiwan.  At 11:00 a.m. EDT on Monday the center of Typhoon Meranti was located at latitude 19.2°N and longitude 127.6°E which put it about 495 miles (800 km) southeast of Taiwan.  Meranti was moving toward the west-northwest at 14 m.p.h. (23 km/h).  The maximum sustained wind speed was 180 m.p.h. (290 km/h) and there were wind gusts to 220 m.p.h. (355 km/h).  The minimum surface pressure.

Meranti is a large dangerous typhoon.  The Hurricane Intensity Index (HII) is 42.2.  The Hurricane Size Index (HSI) is 25.5 and the Hurricane Wind Intensity Size Index (HWISI) is 67.7.  Those indices suggest that Typhoon Meranti is capable of causing widespread catastrophic damage.

The structure of Typhoon Meranti is very well organized.  A well formed circular eye is surrounded by a ring of very tall thunderstorms.  Additional strong spiral bands of thunderstorms are rotating around the core of the circulation.  Typhoon Meranti is generating strong upper level divergence which is pumping out mass in all directions.

Typhoon Meranti is moving through an environment that will allow it to maintain much of its intensity until it reaches Taiwan.  It is moving over water where the Sea Surface Temperature is near 31°C.  The upper level winds are weak and there is not much vertical wind shear.  If a rainband wraps around the existing eye, then an eyewall replacement cycle could temporarily weaken Typhoon Meranti.

A subtropical ridge is steering Typhoon Meranti toward the west-northwest and that general motion is expected to continue for several more days.  On its anticipated track Typhoon Meranti will be very near the southern tip of Taiwan in about 36 hours.  After it moves past Taiwan it is forecast to move into eastern China.

Meranti is an extremely dangerous typhoon.  It is capable of causing widespread catastrophic wind damage.  In addition it will produce very heavy rain and flooding is a serious concern.

Tropical Storm Ian Forms in the Middle of the Atlantic

Tropical Storm Ian formed on Monday in the middle of the Atlantic Ocean.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Ian was located at latitude 21.8°N and longitude 50.4°W which put it about 1140 miles (1840 km) southeast of Bermuda.  Ian was moving toward the northwest at 13 m.p.h. (21 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. (95 km/h).  The minimum surface pressure was 1007 mb.

The circulation of Tropical Storm Ian is not well organized.  A large upper low west of Ian is generating strong southwesterly winds which are blowing across the top of the tropical storm.  There is a large cyclonic circulation in the lower levels, but there are no thunderstorms near the center of circulation.  The thunderstorms are forming northeast of the center in a rainband that is well removed from the core of the storm.

Tropical Storm Ian will through a hostile environment during the next several days.  Although Ian will move over water where the Sea Surface Temperature is near 29°C, the upper level trough will continue to cause strong vertical wind shear.  Ian is not likely to strengthen in the short term.  Eventually, later this week Ian will move farther from the upper level trough and it could strengthen somewhat at that time, if the low level circulation persists.

Tropical Storm Ian is moving around the western end of a subtropical ridge which is steering it toward the northwest and that general motion is expected to continue for another day or two.  When Ian moves farther north, it will turn toward the northeast and the tropical storm will begin to move faster.

Typhoon Meranti Strengthens Quickly Into the Equivalent of a Major Hurricane

Typhoon Meranti intensified rapidly on Sunday into the equivalent of a major hurricane.  At 11:00 p.m. EDT on Sunday the center of Typhoon Meranti was located at latitude 18.1°N and longitude 129.7°E which put it about 650 miles (1050 km) east-southeast of Taiwan.  Meranti was moving toward the west-northwest at 17 m.p.h. (27 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 948 mb.

Typhoon Meranti intensified very rapidly on Sunday.  A small, well formed eye developed at the center of Meranti.  A ring of strong thunderstorms surrounds the eye and additional bands of thunderstorms are spiraling around the core of the circulation.  The circulation is very symmetrical.  Thunderstorms in the core of Typhoon Meranti are generating strong upper level divergence which is pumping out large amounts of mass in all directions.  Meranti is a very well organized typhoon.

Typhoon Meranti is moving through a very favorable environment. It is moving over water where the Sea Surface Temperature is near 31°C.  The upper level winds are weak and there is little vertical wind shear.  Meranti will continue to intensify and it could become a Super Typhoon.  If an eyewall replacement cycle occurs, there could be fluctuations in the intensity of Meranti.

A subtropical ridge is steering Typhoon Meranti toward the west-northwest and that general motion is expected to continue for another couple of days.  On its anticipated track Typhoon Meranti will be near northern Luzon, Taiwan and the southern Ryukyu Islands in about 48 hours.  Meranti will be a dangerous typhoon at that time.  It will be capable of significant wind damage.  It will also cause very heavy rain and create the potential for significant flooding.

Tropical Storm Orlene Develops Rapidly West of Mexico

Tropical Storm Orlene developed rapidly southwest of Baja California on Sunday.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Orlene was located at latitude 16.6°N and longitude 118.3°W which put it about 700 miles (1125 km) southwest of the southern tip of Baja California.  Orlene was moving toward the northwest at 9 m.p.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 1001 mb.

Tropical Storm Orlene organized quickly on Sunday.  A primary rainband wrapped around the center of circulation and an eye appears to be forming.  Additional spiral bands are rotating around the core of Orlene.  Thunderstorms in the core of Tropical Storm Orlene are generating upper level divergence which is pumping out mass in all directions.  The circulation of Orlene is symmetrical and well formed.

Tropical Storm Orlene is moving through a very favorable environment.  It 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.  Tropical Storm Orlene will continue to intensify on Monday and it could intensify rapidly for another 24 hours.

Tropical Storm Orlene is moving northwest toward a weakness in the subtropical high and that general motion is expected to continue for another day or two.  Eventually, the subtropical ridge is expected to strengthen and turn Tropical Storm Orlene toward the west.

Tropical Storm Meranti Forms West of Guam

A center of circulation developed within an area of thunderstorms west of Guam on Saturday and the system was designated as Tropical Storm Meranti.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Meranti was located at latitude 16.0°N and longitude 135.8°E which put it about 1070 miles (1725 km) east-southeast of Taiwan.  Meranti was moving toward the west at 13 m.p.h. (20 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 991 mb.

The circulation of Tropical Storm Meranti is still organizing and the distribution of thunderstorms is asymmetrical.  Most of the thunderstorms are occurring east of the center of circulation.  There is a cluster of the thunderstorms just to the east of the center.  There are also two well formed rainbands east of the core of Tropical Storm Meranti.  Additional spiral bands are located in all parts of the tropical storm.  The thunderstorms near the center are generating upper level divergence which is pumping out mass in all directions.

Tropical Storm Meranti is moving through an environment which is favorable for further intensification.  It is moving over water where the Sea Surface Temperature is near 31°C.  An upper level ridge located to the northwest of Meranti is producing northeasterly winds which are blowing across the western portion of the tropical storm.  The upper level winds are weaker over the eastern half of the circulation and the vertical wind shear is only slowing the intensification.  Although there may be some drier air in the western half of the circulation, Tropical Storm Meranti could intensify into a typhoon on Sunday.  Meranti could become a strong typhoon in two or three days.

A subtropical ridge north of Tropical Storm Meranti is steering it toward the west.  The subtropical ridge is forecast to steer Meranti in a general west-northwesterly direction during the next two or three days.  On its anticipated track Tropical Storm Meranti is expected to approach the area of northern Luzon, Taiwan and the southern Ryukyu Islands in about three days.  It could be a strong typhoon at that time.