Hurricane Pali weakened quickly on Wednesday as it moved closer to the Equator and it is now classified as a tropical storm. At 10:00 p.m. EST on Wednesday the center of Tropical Storm Pali was located at latitude 2.7°N and longitude 172.2°W which put it about 330 miles (530 km) east-northeast of Howland Island. Pali was moving toward the south-southwest at 9 m.p.h. (17 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 993 mb.
As Hurricane Pali moved closer to the Equator, it moved into an area of strong vertical wind shear and weakened. A large area of thunderstorms east-northeast of Samoa could be consolidating into a new tropical cyclone. That area of thunderstorms is generating a lot of upper level divergence which is spreading across the Equator as strong upper level winds from the south. Those upper level winds created strong vertical wind shear over Pali as the hurricane moved south on Wednesday. The wind shear pushed the upper portion of Tropical Storm Pali toward the north and disrupted the vertical integrity of Pali’s circulation. The lack of vertical integrity resulted in a significant decrease in the surface wind speed on Wednesday.
The environment around Tropical Storm Pali will be unfavorable for intensification for the next several days. The vertical wind shear will continue and it could increase if a tropical cyclone develops east of Samoa. Tropical Storm Pali is expected to continue to weaken on Thursday. However, if the surface circulation remains intact for another 48 hours, the wind shear could decrease during the weekend. The Sea Surface Temperature is near 30°C and so there is sufficient energy to support intensification, if the upper level winds decrease. If there is still a surface circulation on Saturday, then it could begin to reorganize and get stronger. Alternatively, if the wind shear gets stronger, Tropical Storm Pali could dissipate over the weekend.
A subtropical ridge to the northwest of Pali is steering the tropical storm toward the south. As Pali weakens, the low level circulation will be steered more by winds closer to the surface. Those winds are blowing from the east and Tropical Storm Pali or its remnants are expected to move toward the west during the next few days.
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.
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.