Tag Archives: Hawaii

Tropical Depression 2E Intensifies Into Tropical Storm Agatha

Tropical Depression 2E intensified into Tropical Storm Agatha on Saturday morning.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Agatha was located at latitude 15.6°N and longitude 118.9°W which put it about 775 miles (1245 km) southwest of the southern tip of Baja California.  Agatha was moving toward the west-northwest at 12 m.p.h. (19 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 upper level winds blowing over the top to Tropical Depression 2E weakened and the vertical wind shear decreased.  Less vertical wind shear allowed thunderstorms on the northwestern side of the circulation to wrap around the southern side of the center.  With the center of circulation embedded near the main area of thunderstorms the National Hurricane Center named the system Tropical Storm Agatha.  Agatha is a small system and tropical storm force winds only extend out about 45 miles (75 km) from the center.

Agatha has a limited period in which to intensify further.  It is currently moving over water where the Sea Surface Temperature (SST) is near 28°C.  However, Agatha is moving toward cooler SSTs where there will be less energy to drive the circulation.  In addition, there is much drier air north and west of the tropical storm.  Since there is little vertical wind shear, Agatha could intensify during the next 12 to 24 hours.  It will start to weaken when it moves over the cooler SSTs.

A ridge of high pressure north of Agatha is steering the tropical storm toward the east-northwest and that general motion is expected to continue for another day or two.  Agatha currently poses no threat to land.

Agatha was named on July 2.  This is the latest date for the naming of the first tropical storm over the Eastern North Pacific since Ava was named in 1969.

Tropical Depression 2E Forms Southwest of Baja California

After a prolonged period of relatively quiet weather over the Eastern North Pacific Ocean, a tropical depression formed southwest of Baja California.  At 11:00 p.m. EDT on Friday the center of Tropical Depression 2E (TD2E) was located at latitude 14.7°N and longitude 116.7°W which put it about 730 miles (1170 km) southwest of the southern tip of Baja California.  TD2E was moving toward the west-northwest at 9 m.p.h. (15 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 1007 mb.

A tropical wave over the Eastern North Pacific Ocean developed a well defined low level circulation and the National Hurricane Center classified the system as Tropical Depression 2E on Friday night.  Although the structure of the low level wind field is symmetrical, most of the thunderstorms are located northwest of the center of circulation.  An upper level ridge north of the depression is generating easterly winds over the top of the circulation.  The vertical wind shear is causing the asymmetrical distribution of the thunderstorms.

The environment around Tropical Depression 2E is marginal for intensification because there are both positive and negative factors.  TD2E is moving over water where the Sea Surface Temperature is near 29°C.  So, there is plenty of energy in the upper ocean to support intensification.  However, the air to the west of the tropical depression is very dry, which will limit the growth of thunderstorms and the formation of rain bands in that part of the system.  In addition moderate vertical wind shear will also inhibit intensification.  Tropical Depression 2E could intensify during the weekend and it has a chance to become the first named storm of the 2016 Eastern Pacific hurricane season.  However, the potential for intensification is limited.

The ridge to the north of TD2E is expected to continue to steer it toward the west-northwest during the next several days.  Tropical Depression 2E poses no threat to land during the next five days.

Possible Hurricane Formation Southwest of Mexico

Guidance from recent runs of the Global Forecasting System (GFS) model indicate that a tropical cyclone could form southwest of Mexico during the next few days.  A tropical wave will move into the Eastern North Pacific Ocean south of Mexico.  The wave will move over water where the Sea Surface Temperature is between 29°C and 30°C.  Vertical wind shear caused by an upper low near the west coast of Mexico will initially inhibit development of the wave.  The GFS model is forecasting that the tropical wave will move into a region where the upper level winds are light and there will not be much vertical wind shear.  If that scenario occurs then a tropical cyclone could develop during the weekend near latitude 10°N and longitude 105°W.

If a tropical cyclone forms, a ridge of high pressure to the north of the cyclone would likely steer it in a generally west-northwesterly direction which would move it away from Mexico.  The environment would be favorable for intensification.  Rapid intensification may be possible and the system could become a major hurricane next week.

The development of this tropical wave could also be a signal that the Eastern North Pacific is getting active.  Although it has been a bit of a slow start to the hurricane season in that basin, the formation of a hurricane during the next week or so would be consistent with the long term climatology for that region.

Pali Intensifies into Rare January Hurricane

Tropical Storm Pali intensified steadily on Monday and it has become a rare January hurricane over the Central Pacific Ocean.  At 10:00 p.m. EST on Monday the center of Hurricane Pali was located at latitude 8.1°N and longitude 171.9°W which put it about 1305 miles (2100 km) southwest of Honolulu, Hawaii.  Pali was moving toward the east-southeast at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 982 mb.

The structure of Hurricane Pali improved significantly on Monday.  A primary rainband wrapped all of the way around the center of circulation and became a well formed eyewall.  The eye has been clearly visible on satellite images from the past few hours.  Thunderstorms around the eye are generating upper level divergence in all directions which is pumping out mass.

Hurricane Pali is in an environment favorable for intensification.  An upper level ridge is generating light westerly winds over the top of Pali, but the vertical wind shear is modest.  Hurricane Pali is moving over water where the Sea Surface Temperatures (SSTs) are near 28°C.  Wind shear will be the primary factor that will determine intensify changes during the next 24 to 48 hours.  If the wind shear remains minimal, then Hurricane Pali will intensify further.  If the wind shear increases to the magnitude that existed during the weekend, then Pali will weaken.  The most likely scenario is for Pali to intensify during the next 12 to 24 hours, then maintain a steady state or slowly weaken during the middle of the week.  Rapid intensification could continue during the next few hours.

Hurricane Pali remains in an area where the steering currents are weak.  It could meander slowly toward the southeast or east for another day or two.  After that time a subtropical ridge could strengthen and start to steer Pali more toward the west.

Wind Shear Weakens Tropical Storm Pali

Upper level winds blowing from the east over the top of Pali weakened the tropical storm on Saturday.  At 10:00 p.m. EST on Saturday the center of Tropical Storm Pali was located at latitude 7.7°N and longitude 174.5°W which put it about 1450 miles (2335 km) southwest of Honolulu, Hawaii.  Pali was moving toward the west at 2 m.p.h. (3 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.

A narrow upper level ridge is generating easterly winds that are blowing over the top of Tropical Storm Pali.  The vertical wind shear produced by those winds caused the structure of Pali to become asymmetrical on Saturday.  Most of the stronger thunderstorms formed west of the center of circulation.  There are rainbands east of the center, but they are not as tall as the bands in the western half of the circulation.  Occasionally, when the wind shear lessens, new thunderstorms form closer to the center of circulation.  At times the wind shear also causes the circulation to tilt toward the west with height.  Tropical Storm Pali is over water where the Sea Surface Temperature is near 28°C.  So, there is sufficient energy in the upper ocean to support intensification, if the wind shear decreases.  However, if the wind shear stays at its current magnitude, slow weakening will continue.

Tropical Storm Pali is embedded in a larger trough of low pressure.  As a result the steering winds are relatively weak.  The easterly winds are slowly pushing Pali toward the west.  That general motion is expected to continue for another day or two.  On its anticipated track Tropical Storm Pali could meander over the Central Pacific well southwest of Hawaii for a few more days.

Tropical Storm Pali Forms Southwest of Hawaii

A surface circulation organized quickly on Thursday in an area of thunderstorms southwest of Hawaii and the Central Pacific Hurricane Center designated the system as Tropical Storm Pali.  At 4:00 p.m. EDT on Thursday the center of Tropical Storm Pali was located at latitude 4.7°N and longitude 171.2°W which put it about 1450 miles (2335 km) southwest of Honolulu, Hawaii.  Pali was moving toward the north-northwest at 7 m.p.h. (11 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.

Several well formed spiral bands developed within a large area of thunderstorms and the system exhibited sufficient organization to be classified as a tropical storm.  Two of the inner spiral bands appear to be wrapping around the center of circulation and the inner core of Tropical Storm Pali is organizing quickly.  A partial eyewall may be forming around the southern and western sides of the center of circulation.  Thunderstorms near the core of Pali are generating upper level divergence, which is pumping out mass.

The environment surrounding Tropical Storm Pali is favorable for further intensification.  It is moving over water where the Sea Surface Temperatures are near 29°C.  An upper level ridge east of Pali is generating southeasterly winds over the top of the tropical storm, but the vertical wind shear is not too strong.  Pali is likely to intensify further during the next 24 hours.  A period of rapid intensification may be possible, if the inner core consolidates around an eye.

A subtropical ridge east of Pali is steering the tropical storm toward the north-northwest and that general motion is expected to continue.  However, the winds steering the storm are not too strong, and it may not move much during the next several days.

Although the historical record of tropical storms over the Central Pacific is relatively short, it appears that Tropical Storm Pali may have reached tropical storm intensity at a lower latitude than any other tropical storm on record did in that region.

Olaf Becomes a Cat. 4 Hurricane

Hurricane Olaf intensified rapidly on Monday and it reached Category 4 on the Saffir-Simpson Scale.  At 11:00 p.m. EDT on Monday the center of Hurricane Olaf was located at latitude 10.1°N and longitude 139.5°W which put it about 1235 miles (1985 km) east-southeast of Hilo, Hawaii.  Olaf was moving toward the west at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 949 mb.

Olaf is a small but well organized hurricane.  The core is very symmetrical.  Hurricane Olaf has a clear eye with a diameter of about 12 miles (19 km/h) and the eye is surrounded by a ring of strong thunderstorms.  Several spiral rainbands are rotating around the inner core of the hurricane.  Upper level outflow channels to the northeast and southwest of Olaf are carrying mass away from the center of circulation, which is allowing the surface pressure to decrease.

Hurricane Olaf is moving just south of a band of stronger upper level westerly winds.  It is in an area of modest vertical wind shear.  The ocean beneath Hurricane Olaf has Sea Surface Temperatures  near 29°C.  The compact structure of Olaf allowed the hurricane to efficiently convert energy it extracted from the ocean to kinetic energy associated with higher wind speeds.  Olaf could remain in a favorable environment for another day or two, which may allow for further intensification.  However, if eyewall replacement cycles begin to occur, they will cause fluctuations in the intensity of Hurricane Olaf.

A subtropical ridge north of Olaf is steering the hurricane toward the west and that general steering motion is expected to continue for another day or two.  The western end of the subtropical ridge is expected to weaken later this week and that should allow Olaf to turn toward the north.  On its anticipated track, Olaf would turn toward the north before it reaches the Hawaiian Islands.

Olaf Becomes a Hurricane Between Baja and Hawaii

The core of the circulation of Olaf consolidated on Sunday and the National Hurricane Center upgraded it to a hurricane.  At 11:00 a.m. EDT on Sunday the center of Hurricane Olaf was located at latitude 9.5°N and longitude 133.2°W which put it about 1620 miles (2610 km) east-southeast of Hilo, Hawaii.  Olaf was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 989 mb.

The circulation of Hurricane Olaf consists of a small core of thunderstorms around the center of circulation and a primary rainband that spirals around the western and southern sides of the hurricane.  The core of thunderstorms is producing some upper level divergence, but upper level winds are inhibiting the outflow on the western side of the center.

Hurricane Olaf is moving over water where the Sea Surface Temperature is near 30°C and there is plenty of energy in the upper ocean to support intensification.  However, an upper level trough north of Olaf is producing westerly winds which are blowing over the top of the hurricane.  The upper level winds are blocking upper level outflow on the western side of Olaf and the vertical wind shear is inhibiting the intensification of Olaf.  If the wind shear decreases, then further intensification will be possible.

A subtropical ridge is steering Hurricane Olaf toward the west and that general motion is expected to continue for another day or two.  When Olaf reaches the western end of the ridge, it will start to turn more toward the north.

Tropical Storm Nora Moves Into the Central Pacific

Tropical Storm Nora moved west of longitude 140°W on Sunday which meant that it officially crossed from the Eastern North Pacific into the Central North Pacific Ocean.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Nora was located at latitude 13.5°N and longitude 143.8°W which put it about 860 miles (1385 km) east-southeast of Hilo, Hawaii.  Nora was moving toward the west-northwest at 9 m.p.h. (15 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 m.p.h.).  The minimum surface pressure was 993 mb.

Nora is a small tropical storm.  Wind to tropical storm force only extend out about 70 miles (110 km) from the center of circulation.  Most of the stronger thunderstorms are located northwest of the center of circulation and there is not much deep convection in the other parts of Nora.  Although Nora is over water where the Sea Surface Temperature is near 29°C, southerly winds in the upper levels appear to be causing vertical wind shear.  The wind shear is likely to increase as an upper level trough north of Hawaii gets closer to Nora.

Tropical Storm Nora is nearing the western end of a subtropical ridge which has been steering it toward the west.  If the vertical structure of Nora remains intact, the tropical storm should turn toward the north during the next day or two.  After that time the upper level trough north of Hawaii could sweep Nora toward the northeast.  An alternate and possibly more likely scenario, given the small size of Tropical Storm Nora, is that the vertical wind shear blows the upper portion of the circulation north of the surface circulation.  If that happens, then the surface circulation will be steered westward until it dissipates by the winds in the lower atmosphere.

Tropical Storm Nora Form Far East of Hawaii

Another Tropical Cyclone has formed over the Eastern North Pacific Ocean well east of Hawaii and the National Hurricane Center has upgraded Tropical Depression 18-E to Tropical Storm Nora.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Nora was located at latitude 11.3°N and longitude 135.1°W which put it about 1470 miles (2365 km) east-southeast of South Point Hawaii.  Nora was moving toward the west at 16 m.p.h. (26 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 1006 mb.

The circulation inside Tropical Storm Nora is still in the process of organizing.  There is one primary rainband that wraps around the western and southern side of the tropical storm.  More thunderstorms are forming near the center, but a clearly defined core of convection has not yet developed.  The storms close to the center of circulation are producing more upper level divergence which is pumping out mass.

Tropical Storm Nora is in an environment that favors intensification,   The Sea Surface Temperature is warmer than 29°C,  The upper level winds are light and there is not much upper level divergence.  Nora is expected to intensify gradually into a hurricane.  Once a tight, well organized inner core develops, it could intensify more quickly.

A subtropical ridge north of Nora is steering the tropical storm westward.  That general steering pattern is expected to continue for another day or two.  When Nora reaches the western end of the subtropical ridge, it is expected to turn toward the north.