Monthly Archives: August 2015

Typhoon Goni Moving Closer to Northern Luzon and Taiwan

Typhoon Goni moved steadily westward on Wednesday and it got closer to northern Luzon and Taiwan.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Goni was located at latitude 18.9°N and longitude 125.3°E which put it about 350 miles (565 km) southeast of Taipei, Taiwan.  Goni was moving toward the west at 12 m.p.h. (19 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 937 mb.

Typhoon Goni intensified on Wednesday and it is a very well organized tropical cyclone.  It has a large well formed eye.  The circulation is symmetrical although there are more thunderstorms in the south half of the typhoon.  Upper level divergence is well developed and it is pumping out mass in all directions.  Goni remains over warm Sea Surface Temperatures and the upper level winds are relatively light.  Some further intensification is possible during the next day or so.  Goni could run into stronger upper level winds in two or three days which would create more vertical wind shear and start to weaken the typhoon.

A subtropical ridge has been steering Goni toward the west and it is expected to do so again on Thursday.  However, Goni is nearing the western end of the ridge and it is forecast to turn to the north on Friday.  Goni appears to have moved more slowly during the past few hours, which may be an indication that it is reaching the western end of the ridge.  An upper level trough northwest of Goni is expected to turn Goni toward the northeast during the weekend and then accelerate it toward western Japan.

On its anticipated track, the center of Goni is expected to pass northeast of Luzon.  However, the circulation is large enough that some of northern Luzon could experience strong winds and heavy rain.  The center of Goni is forecast to pass east of Taiwan, but it could also bring strong winds heavy rain to some locations there as well.  The core of Goni could pass very near Ishigaki Jima and bring very strong winds and heavy rain to the islands in that area.

Tropical Storm Danny Heading West

Tropical Storm Danny has moved steadily westward during the past 24 hours.  At 11:00 a.m. EDT on Wednesday the center of Tropical Storm Danny was located at latitude 11.2°N and longitude 41.1°W which put it about 1385 miles (2235 km) east of the Lesser Antilles and about 2740 miles (4410 km) east-southeast of Miami, Florida.  Danny 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 60 m.p.h. (95 km/h).  The minimum surface pressure was 1000 mb.

The organization of the circulation of Danny has varied during the past day.  It has a visible tight core at the center, but earlier today there was no convection around the core.  Recent satellite images show new thunderstorms developing near the core.  The environment around Danny is complex and it contains both positive and negative factors.  Danny is currently over water where the Sea Surface Temperature (SST) is near 28°C.  However, there is slightly cooler water just to the north of the tropical storm.  Satellite imagery indicates that there could also be drier air north of the circulation and some of that drier air could be pulled into Danny.  The upper level winds are light and upper level divergence is occurring.  However, a surge in the low level trade winds is about 250 miles (400 km) east of Danny.   If the surge in the trade winds reaches the core of Danny, it could push the lower part of the circulation out ahead (to the west) of the upper part of the circulation.  In that case Danny would weaken.

The complexity of the environment around Tropical Storm Danny makes the intensity forecast challenging.  If the trade wind surge does not reach the core of Danny and it stays over warm SSTs, then gradual intensification is possible.  On the other hand, if Danny moves more northward over cooler SSTs and into drier air, or if the trade wind surge creates more vertical wind shear, then Danny could weaken.

A subtropical ridge to the north of Danny is steering Danny toward the west and a generally west or west-northwest motion is forecast for the next few days.  If Danny is a little stronger, it could move a little farther north, and if it is weaker, it could stay farther south.  On its anticipated track, Danny could approach the Lesser Antilles in four or five days.  Interests in those areas should monitor Danny for future developments.

Typhoon Atsani Reaches Equivalent of Cat. 5 Hurricane

Typhoon Atsani intensified over the past 24 hours and it is now the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  At 8:00 a.m. EDT on Wednesday the center of Typhoon Atsani was located at latitude 19.6°N and longitude 151.3°E which put it about 1340 miles (2160 km) southeast of Tokyo, Japan.  Atsani was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 185 m.p.h. (300 km/h).  The minimum surface pressure was 918 mb.

Atsani is in an environment that is very favorable for tropical cyclones.  The Sea Surface Temperature (SST) is near 28°C.  The upper level winds are very light and there is almost no vertical wind shear.  Upper level divergence is pumping out mass in all directions and Atsani has a very circular appearance with a large eye evident on satellite imagery.  There are more rainbands and thunderstorms in the southern half of the circulation which is probably the result of warmer, moister air in area.

Atsani could maintain its current intensity for another 24 hours or so, although an eyewall replacement cycle will cause weakening if one occurs.  In another day or two the typhoon will start to move over cooler SSTs.  In addition as Atsani moves northward, it will start to be affected by the upper level westerlies in the middle latitudes.  Those winds will increase wind shear and weaken Atsani further.

Atsani is moving around the western end of a subtropical ridge which is steering it toward the northwest.  That general motion is expected to continue for another couple of days.  When Atsani reaches the western end of the ridge it will start moving toward the north.  Eventually, the upper level westerly winds will accelerate Atsani off to the northeast.  On its anticipated track Atsani would pass north of the Marianas and northeast of Iwo To.  At the current time the center of Atsani is forecast to pass about 100 miles east of ChiChi Jima.  However, a slight deviation of the track toward the west could bring Atsani closer to Chichi JIma and Iwo To.

 

Tropical Depression 4 Forms over Eastern Atlantic

As the calendar reaches mid-August, the environment over the tropical Atlantic Ocean typically becomes more favorable for tropical cyclone formation.  The Sea Surface Temperature warms and vertical wind shear decreases.  Despite the ongoing El Nino in the tropical Pacific Ocean, we are seeing the typical pattern develop in the Atlantic for this time of year.  A low level circulation within an area of thunderstorms over the eastern Atlantic Ocean became better organized on Tuesday and the National Hurricane Center classified the system as Tropical Depression Four (TD4).  At 11:00 a.m. EDT on Tuesday the enter of Tropical Depression Four was located at latitude 10.6°N and longitude 36.5°W which put it about 1665 miles (2765 km) east of the Windward Islands.  TD4 was moving toward the west at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 35 m.p.. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1009 mb.

TD4 is currently in an environment that is favorable for intensification.  The upper level winds are light and the thunderstorms are generating upper level divergence in all directions.  It is currently over water where the Sea Surface Temperature is near 28°C.  As long as TD4 moves westward, it will stay over warmer water and intensification will be likely.  If TD4 were to move more toward the northwest, then it would move over slightly cooler water and less intensification would occur.  Since TD4 is forecast to move west, it is expected to become Tropical Storm Danny, and it could be a hurricane later this week.

A subtropical ridge north of TD4 is steering it toward the west and that steering motion is expected to continue for the next 24 to 48 hours.  Later this week an upper level trough passing north of the ridge is expected to weaken the ridge, which could cause TD4 to move northwesterly for a day or so.  After the upper level trough moves off to the east, the subtropical ridge is forecast to steer TD4 back more toward the west.  On its anticipated track TD4 is expected to be east of the Windward Islands this weekend.

Typhoon Goni Heading West

Typhoon Goni moved steadily westward away from the Mariana Islands on Monday.  At 11:00 p.m. EDT on Monday the center of Typhoon Goni was located at latitude 18.3°N and longitude 135.3°E which put it about 780 miles (1260 km) southeast of Okinawa.  Goni was moving toward the west at 19 m.p.h. (31 km/).  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.

Goni appeared to go through an eyewall replacement cycle on Monday which resulted in a reduction in the maximum wind speed.  As the tiny pinhole inner eye weakened, the stronger winds were located in the larger outer eyewall.  The reduction in wind speed could be temporary, if the outer eye begins to contract.  Goni remains in a favorable environment.  It is moving over warm Sea Surface Temperature and the vertical wind shear is very modest.  The circulation is producing upper level divergence in all directions.  Goni will remain in a favorable environment for another two or three days and it should remain strong during that time period.

A subtropical ridge is steering Goni toward the west-northwest and that steering pattern is expect to continue for another 48 to 72 hours.  Later this week an upper level trough could approach the typhoon from the northwest.  Southwesterly winds on the eastern side of the trough could turn Goni toward the north later this week. On its anticipated track Goni could be near Taiwan, the northern Philippines or Okinawa when it makes that turn.

Typhoon Atsani Getting Bigger and Stronger

Typhoon Atsani continued to grow bigger and stronger on Monday.  At 11:00 p.m. EDT on Monday the center of Typhoon Atsani was located at latitude 16.3°N and longitude 155.8°E which put it about 1700 miles (2740 km) southeast of Tokyo, Japan.  Atsani was moving west-northwest at 12 m.p.h. (19 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 937 mb.

Typhoon Atsani has a very well organized circulation.  It is very symmetrical with a well formed eye and eyewall and it has multiple rainbands spiraling around the center of circulation.  Upper level divergence is pumping out mass in all directions, which is allowing the surface pressure to decrease.  There is little vertical wind shear and Atsani is moving over warm Sea Surface Temperatures.  Further intensification is likely, although eyewall replacement cycles could cause fluctuations in intensity.

A subtropical ridge is steering Atsani toward the northwest and that general steering pattern is expected to continue for the next few days.  On its anticipated track Atsani will pass north of the Marianas and it could be east of Iwo To in three or four days.

Goni Intensifies Rapidly Into a Strong Typhoon

Goni intensified rapidly from a tropical storm into a strong typhoon on Sunday.  At 11:00 p.m. EDT on Sunday the center of Typhoon Goni was located at latitude 16.7°N and longitude 141.1°E which put it about 265 miles (425 km) west of Anatahan.  Goni was moving toward the west-northwest at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) which made Goni the equivalent of a major hurricane.  There were wind gusts to 160 m.p.h. (260 km/h) and the minimum surface pressure was 937 mb.

The circulation of Goni organized quickly on Sunday and it was able to intensify rapidly.  The primary rainband wrapped tightly around the center of circulation and a tiny pinhole eye formed in the center.  The band continued to wrap about the core of the circulation and it could be about to form a second, larger concentric eyewall.  The structure of Goni looks a lot like the circulation of Typhoon Soudelor did when it intensified rapidly.  Light easterly winds in the upper levels enhanced divergence to the west of Goni and pumped out mass allowing the pressure to fall rapidly.

Goni is moving over water where the Sea Surface Temperatures are warm.  The vertical wind shear is minimal and further intensification is possible.  If concentric eyewalls form, eyewall replacement cycles could produce fluctuations in intensity.

A subtropical ridge is steering Goni toward the west-northwest and that general steering pattern is expected to continue for another three or four days.  At that time Goni could be near the western end of the subtropical ridge.  An upper level trough in the mid-latitude westerlies could approach the typhoon from the northwest and turn it toward the north.

Tropical Storm Goni Brings Wind and Rain to the Marianas

Tropical Storm Goni brought wind and rain to the Northern Marianas on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Goni was located at latitude 15.1°N and longitude 144.4°E which put it about 60 miles (95 km) west of Tinian.  Goni was moving toward the northwest at 10 m.p.h. (16 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 Warning continues for Guam, Rota, Tinian, and Saipan and a Typhoon Watch continues for Saipan and Tinian.

The center of Tropical Storm Goni passed between Rota and Tinian on Saturday.  The tropical storm brought wind and rain to the northern Marianas.  The airport on Saipan reported a wind gust to 56 m.p.h. (90 km/h).  The stormy conditions could have setback the recovery from damage caused by Typhoon Soudelor.

The circulation around Goni continued to organize on Saturday.  A primary spiral band wrapped around the center of circulation and there have been indications that an eye may be forming in the center.  An upper level ridge east of Goni is causing some easterly winds over the circulation and is creating some vertical wind shear.  The shear is limiting thunderstorm activity on the eastern side of the circulation.  As Goni moves farther west, the wind shear will decrease.  It is moving over water where the Sea Surface Temperature is near 29°C.  The favorable environment will cause intensification and a period of rapid intensification is possible.

A subtropical ridge is steering Goni toward the west-northwest and that general steering pattern is expected to continue for the next few days.  Goni will move farther west of the Marianas on Sunday and conditions there should gradually improve.

Tropical Storm Goni Prompts Watches for Marianas

Tropical Storm Goni formed east of the Marianas on Friday and watches were issued for some of the islands because of the imminent threat it posed.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Goni was located at latitude 13.0°N and longitude 148.0°E which put it about 235 miles (370 km) southeast of Saipan.  Goni was moving toward the west-northwest at 10 m.p.h. (16 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 996 mb.  A Typhoon Watch has been issued for Saipan and Tinian.  A Tropical Storm Watch has been issued for Guam and Rota.

The circulation of Tropical Storm Goni is still organizing.  Most of the thunderstorms are developing in the western half of the circulation.  An upper level ridge is generating easterly winds which are blowing across Goni and those winds are inhibiting the development of convection in the eastern part of the tropical storm.  Goni is moving over water where the Sea Surface Temperatures (SSTs) are near 29°C.  The environment supports intensification and Goni could intensify more rapidly in a day or two when the circulation is more well organized.  Goni could reach typhoon intensity within 48 hours.

A subtropical ridge is steering Goni toward the west-northwest and that general motion is expected to continue during the next few days.  On its anticipated track, the center of Goni could be very near Saipan in about 24 hours.  Goni could be a strong tropical storm on the verge of becoming a typhoon at that time.  Saipan is still recovering from the effects of Typhoon Soudelor.  Strong winds and heavy rain could set back those recovery efforts.

 

Shear Weakens Hilda, Tropical Storm Watch Dropped

Strong vertical wind shear weakened Tropical Storm Hilda again on Wednesday and the Tropical Storm Watch for the Big Island of Hawaii was discontinued by the Central Pacific Hurricane Center.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Hilda was located at latitude 17.2°N and longitude 152.4°W which put it about 245 miles (395 km) southeast of Hilo, Hawaii.  Hilda was moving toward the west at 4 m.p.h. (6 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.

An upper level low north of the Hawaiian Islands is generating very strong southwesterly winds that are blowing right over the top of Tropical Storm Hilda.  Those winds are blowing thunderstorms away from the core of the circulation.  The western half and inner core of Hilda consists of bands of low clouds rotating counterclockwise around the exposed center of circulation.  Thunderstorms continue to form in some of the bands northeast of the center of circulation, but the strong upper level winds quickly blow the tops off of those storms.  Since the upper level low isn’t moving, strong vertical wind shear is expected to continue and Hilda should slowly spin down.  It is likely to weaken to tropical depression status on Thursday.

As the circulation gets shallower, Hilda will be steered by the winds in the lower atmosphere.  Those winds are blowing from the east and the will push the tropical storm or its remnants toward the west.  On its anticipated track Hilda would pass south of Hawaii as a tropical depression during the next several days.