SYNOPTIC DISCUSSION

TUESDAY 29th APRIL 2025 PM SHIFT.

TONIGHT INTO TOMORROW:

The prevailing southeasterly wind flow across the region remains influenced by a high-pressure system that has intensified to the east of New Zealand and is now progressing eastward. This situation is conducive to favourable weather conditions characterised by partly cloudy skies and minimal precipitation observed across the islands this afternoon into the evening, as supported by total precipitable water animations. The aforementioned system sustains a weak convergence zone in conjunction with a northern trough of low pressure, as indicated by the latest satellite imagery. Consequently, dry, cool, and pleasant weather is anticipated for tonight, with a possibility of a few showers in other areas of the forecast region. Furthermore, similar weather patterns are expected to persist into tomorrow morning, apart from a few isolated showers in the late afternoon into the evening in some areas of the nation as the high-pressure system continues its slow eastward movement.

THURSDAY THROUGH MONDAY:

The prevailing high-pressure system located to the east of New Zealand is expected to maintain the disorganised South Pacific Convergence Zone (SPCZ) north of Samoa as it continues its eastward movement by Thursday. Additionally, an upper trough is anticipated to form from the western side of Samoa, progressing over the region by late Thursday and settling to the east of the group by the same time. This upper-level system is likely to facilitate the convective development and enhancement of the surface system, potentially resulting in minimal shower activities from Thursday through Saturday. Furthermore, another high-pressure ridge is projected to develop from the south of Fiji and extend over the Tongan area, which is expected to push the surface system northward on Friday, accompanied by strengthening southeasterly winds lasting at least until Sunday. Moreover, the surface may experience light to moderate significant convective activity from late Sunday through the conclusion of the forecast period, as upper-level divergence is likely to prevail.

MARINE OUTLOOK:

According to the latest marine observations indicating wave and swell heights have slowly reduced below 2.5 meters in the southern seas of Samoa. This is due to the previously intensified high-pressure system to the east of New Zealand, which generated high southerly swells over the southern seas in the past few days has now slowly moved away and further eastward. Therefore, this validates the cancellation of the Marine Advisory for the southern marine waters of the nation.

ADVISORIES/WARNINGS:

CANCELLED: MARINE ADVISORY – SOUTHERN MARINE WATERS

Weather On-Duty Team:

G. Niko, A. Sofeni & L.C. Baker.