Tag Archives: WP27

Tropical Storm Ma-On Forms East of the Northern Marianas

Tropical Depression 27W intensified into Tropical Storm Ma-On east of the Northern Marianas on Thursday.  At 10:00 a.m. EDT on Thursday the center of Tropical Storm Ma-On was located at latitude 17.7°N and longitude 153.7°E which put it about 405 miles (655 km) south-southeast of Minami Tori Shima.  Ma-On 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 1003 mb.

More thunderstorms developed near the center of a system originally designated Tropical Depression 27W and the Japan Meteorological Agency named it Tropical Storm Ma-On on Thursday.  Although many of the thunderstorms are still developing east of the center of circulation, a few stronger thunderstorms are forming around the center.  The thunderstorms around the center are beginning to generate upper level divergence which is pumping out mass.  Some additional rainbands appear to be forming in the eastern half of the circulation.

Tropical Storm Ma-On is moving through an environment that is favorable for intensification.  Ma-On is moving over water where the Sea Surface Temperature is near 30°C.  Ma-On is moving under the western end of an upper level ridge.  The upper level winds in that part of the ridge are not too strong and the ridge may be enhancing upper level divergence.  Tropical Storm Ma-On could intensify during the next day or so.  When Ma-On gets farther west, it will approach an upper level trough moving off of Asia.  There are stronger southwesterly winds on the eastern side of the trough and the vertical wind shear will increase at that time.

Tropical Storm Ma-On is moving along the southwestern end of a subtropical high pressure system.  The subtropical high is expected to steer Ma-On in a general west-northwesterly direction during the next two or three days.  On its anticipated track Tropical Storm Ma-On could approach the northernmost Marianas in about 36 hours.  It could bring gusty winds and locally heavy rain.

In-Fa Weakens to a Tropical Storm on Its Way to Iwo To

In-Fa weakened below typhoon intensity on Tuesday as it moved toward Iwo To.  At 10:00 p.m. EST on Tuesday the center of Tropical Storm In-Fa was located at latitude 20.1°N and longitude 135.3°E which put it about 540 miles (870 km) southwest of Iwo To.  In-Fa was moving toward the northeast at 10 m.p.h. (16 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 994 mb.

A large upper level trough that extends south of Japan is producing strong southwesterly winds over the top of Tropical Storm In-Fa.  Those winds are causing strong vertical wind shear which is tilting the upper portion of the circulation of the tropical storm toward the northeast.  The stronger thunderstorms are all located northeast of the center of In-Fa.  It also appears drier air is wrapping around the southwestern part of the circulation.  The strong vertical wind shear will continue to weaken Tropical Storm In-Fa.  As it moves into a cooler environment In-Fa will gradually make a transition to an extratropical cyclone during the next 48 hours.

The upper level trough will continue to steer Tropical Storm In-Fa toward the northeast while it makes the transition to an extratropical cyclone.  On its anticipated track In-Fa could bring tropical storm force winds to Iwo To in 24 to 36 hours.

Typhoon In-Fa Turns Toward Iwo To

Typhoon In-fa turned northeast and started to move toward Iwo To late on Monday.  At 10:00 p.m. EST on Monday the center of Typhoon In-Fa was located at latitude 19.0°N and longitude 132.6°E which put it about 695 miles (1120 km) southwest of Iwo To.  In-Fa was moving toward the northeast at 13 m.p.h. (21 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 956 mb.

Although In-Fa may be beginning to respond to increased vertical wind shear, it remains a well organized typhoon.  There are signs that a cloud filled eye still exists at the core of In-Fa.  The eye is surround by a ring of strong thunderstorms.  The outer portion of In-Fa’s circulation is becoming more asymmetrical, which is probably the result of increased wind shear.  Most of the thunderstorms outside the core are north and east of the center of circulation.  There are few thunderstorms in the southwestern part of In-Fa.

Typhoon In-Fa is currently over water where the Sea Surface Temperature (SST) is near 28°C.  In-Fa will move over increasingly cooler SSTs as it moves northeast.  The strength of the upper level southwesterly winds will increase as In-Fa moves northeast.  The combination of cooler SSTs and more vertical wind shear will cause Typhoon In-Fa to weaken during the next several days.  It could weaken to a tropical storm by Wednesday.

An upper level trough is steering Typhoon In-Fa toward the northeast and that general motion is expected to continue during the next 48 hours.  In-Fa could start to move faster as the upper level winds increase.  In-Fa could be near Iwo To in about 48 hours.

Typhoon In-Fa Passes North of Yap

The center of Typhoon In-Fa passed north of Yap on Saturday.  At 10:00 p.m. EST on Saturday the center of Typhoon In-Fa was located at latitude 13.7°N and longitude 136.0°E which put it about 285 miles (465 km) north-northwest of Yap.  In-Fa was moving toward the west-northwest at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h).  The minimum surface pressure was 944 mb.

The structure of Typhoon In-Fa deteriorated slightly on Saturday, but it remains the equivalent of a major hurricane.  Fewer thunderstorms formed in the northwestern quadrant of the circulation and there are indications that a gap may have opened on the northwestern side of the eyewall.  It is possible that some drier air could have been pulled into that part of the circulation.  However, an eye may still exist at the center of circulation and there are multiple bands around the eastern and southern sides of the typhoon.

Typhoon In-Fa is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds over the top of the circulation are light and there is not much vertical wind shear over the core of the typhoon.  Typhoon In-Fa could maintain its intensity or weaken slowly on Sunday.  When it moves farther north, it will encounter stronger southwesterly winds which will increase the vertical wind shear.  When the wind shear increases, the rate of weakening will increase.

A subtropical ridge is steering Typhoon In-Fa toward the west-northwest and that general motion is expected to continue for another day or so.  In-Fa could reach the western end of the ridge and turn northward on Monday.  In 36 to 48 hours the southwesterly upper level winds will start to push the typhoon toward the northeast.  On its anticipated track Typhoon In-Fa could be near Iwo To in about four days.

In-Fa Intensifies Back Into a Typhoon and a Tropical Storm Warning Is Issued for Guam

In-Fa intensified rapidly back into a typhoon on Thursday and a Tropical Storm Warning was issued for Guam.  At 10:00 p.m. EDT on Thursday the center of Typhoon In-Fa was located at latitude 10.1°N and longitude 148.1°E which put it about 365 miles (590 km) southeast of Guam.  In-Fa 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 gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 954 mb.

After weakening slightly on Wednesday, In-Fa intensified rapidly back into a typhoon on Thursday.  Typhoon In-Fa has a compact tightly wound structure with a small inner core and a tiny pinhole eye.  The strongest winds are contained in the ring of thunderstorms around the pinhole eye.  Many of the strongest thunderstorms outside the eyewall are located southwest of the eye, but there are spiral bands in all quadrants of the storm.  The storms around the core of Typhoon In-Fa are generating upper level divergence in all directions.

Typhoon In-Fa is an environment favorable for intensification.  It is over water where the Sea Surface Temperature is near 29°C.  The upper level winds around In-Fa are light and there is not much vertical wind shear.  In-Fa is likely to intensify more during the next day or two.

A subtropical ridge north of In-Fa is steering the typhoon to the west-northwest and that general motion is expected to continue for another 48 hours.  On its anticipated track the center of In-Fa is likely to pass about 100 miles (160 km) to 150 miles (240 km) south of Guam in about 18 to 24 hours.  The center of Typhoon In-Fa is likely to pass about 200 miles (320 km) northeast of Yap in about 48 hours.

Tropical Storm In-Fa Near Fananu, Watch Issued for Guam

Tropical Storm In-Fa is near Fananu and it is bringing wind and rain to islands around Chuuk.  At 10:00 p.m. EST on Wednesday the center of Tropical Storm In-Fa was located near latitude 8.6°N and longitude 152.0°E which put it about 25 miles (40 km) southeast of Fananu and about 620 miles (1000 km) southeast of Guam.  In-Fa was moving toward the northwest at 15 m.p.h. (24 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 982 mb.

A Tropical Storm Watch has been issued for Guam.  A Typhoon Warning is in effect for Chuuk lagoon, Losap, Ulul and Fananu.

In-Fa was briefly a typhoon earlier on Wednesday when it had a small, but well formed eye.  However, the core of In-Fa weakened slightly and the eye filled with clouds.  A small, but circular, area of thunderstorms has intensified in the core of the tropical storm during the past few hours.  There are signs that In-Fa may be strengthening again.  The environment surrounding Tropical Storm In-Fa is favorable for intensification.  It is over water where the Sea Surface Temperature is near 29.5°C.  The upper level winds are light and the vertical wind shear is modest.  In-Fa could regain typhoon intensity on Thursday and a period of rapid intensification may be possible once the inner core reorganizes.

A subtropical ridge north of In-Fa is steering the tropical storm toward the northwest and that general motion is expected to continue for another two or three days.  On its anticipated track the center of In-Fa will pass near Fananu during the next few hours.  In-Fa could be south of Guam in about 48 hours.

Tropical Storm In-Fa Intensifying, Typhoon Watch for Fananu

Tropical Storm In-Fa intensified quickly on Tuesday and it caused watches and warnings to be issued for the area around Chuuk.  At 10:00 p.m. EST on Tuesday the center of Tropical Storm In-Fa was located at latitude 6.0°N and longitude 156.3°E which put it about 385 miles (620 km) east-southeast of Fananu and about 985 miles (1590 km) east-southeast of Guam.  In-Fa was moving toward the west-northwest 18 m.p.h. (29 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 983 mb.  A Typhoon Watch has been issued for Fananu.

The circulation of Tropical Storm In-Fa organized rapidly on Tuesday.  A tight core formed in the center of circulation and an eyelike feature appeared on satellite images.  A small ring of thunderstorms formed around the eye and a large primary rainband wrapped around the circulation.  The circulation became more symmetrical and upper level outflow began to create divergence in most directions.

Tropical Storm In-Fa remains in an environment favorable for intensification.  It is over water where the Sea Surface Temperature is near 30°C.   The upper level winds are light and the vertical wind shear is modest.  In-Fa is likely to continue to intensify and now that an inner core has developed, it could intensify rapidly.  In-Fa could become a typhoon on Wednesday and it could become the equivalent of a major hurricane later this week.

A subtropical ridge north of In-Fa is steering the tropical storm toward the west-northwest and that general motion is expected to continue for the rest of the week.  On its anticipated track In-Fa will approach Fananu in about 24 hours and it could be a typhoon at that time.  In-Fa could be approaching Guam in about three days as a typhoon.

Tropical Depression 27W Forms Southeast of Pohnpei

A center of circulation formed in an area of thunderstorms southeast of Pohnpei and the system was designated Tropical Depression 27W (TD 27W).  At 10:00 p.m. EST on Monday the center of Tropical Depression 27W was located at latitude 4.7°N and longitude 162.3°E which put it about 360 miles (585 km) east-southeast of Pohnpei.  TD 27W was moving to the west at 17 m.p.h. (27 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1001 mb.

The circulation of TD 27W is still organizing.  A clearly defined low level center of circulation formed near the northern edge of an area of thunderstorms.  However, most of the stronger thunderstorms are southwest of the center.  Those storms are generating upper level divergence that is expanding south and west of the center.

Tropical Depression 27W is in an environment that favors further intensification.  It is over water where the Sea Surface Temperature is near 30°C.  An upper level ridge north of TD 27W is producing light easterly winds over the top of the depression.  The vertical wind shear is modest, and it should only slow the rate of intensification.  Intensification could be slow initially as a stronger inner core forms around the center of circulation.  Once the core of the circulation consolidates, then intensification could occur more quickly.  TD 27W could become a tropical storm within 24 to 36 hours and it could be a typhoon in three or four days.

A subtropical ridge north of TD 27W is steering the depression toward the west.  A gradual turn toward the west-northwest is expected and that general motion is expected to continue for much of the week.  On its anticipated track TD 27W could be near Pohnpei in about 24 hours and it could bring tropical storm force winds and heavy rain.  The tropical cyclone could be approaching Guam by the end of the week and it could be a typhoon by that time.