Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 240855
Area Forecast Discussion
National Weather Service Tiyan GU
655 PM ChST Fri Feb 24 2017
Northeast winds, partly cloudy skies and isolated showers prevail
across the local area this afternoon.
Models keep the weather relatively dry through the forecast. Deep
layer moisture will remain low through at least the first half of
the coming week with models showing 700 mb RH below 50 percent
through Monday night. This should keep shower coverage at isolated
Trade-wind convergence will generate an increase in clouds Tuesday
onwards. A circulation is predicted to pass south of Guam the second
half of the coming week increasing the low-level convergence and
producing mostly cloudy skies Wednesday through Friday. Some models
hint at the possibility of scattered showers Thursday and Friday but
confidence in this is low so will keep showers isolated for now.
Observations from the Ritidian, Tanapag and Ipan buoys indicate
combined sea heights between 6 and 8 feet. A north and a east swell
prevail over the local area.
Ritidian buoy data show the north swell between 4 and 5 feet. A few
of the swell heights from Ritidian and Tanapag buoys were at 5.6 feet
at 13 seconds. Surf calculations indicate that surf of this height
and period should reach 9 feet, which is hazardous. The models have
been undercutting the sea and swell heights for a while so just added
a few feet to the seas and swell forecast. At this time hazardous
surf is expected through Saturday afternoon. Swell should decrease
enough to allow surf to decrease below hazardous level Saturday night.
Sea heights should remain below small craft advisory levels.
A convergence zone associated with a fresh trade-wind surge is seen
between 3N and 6N from southeast of Pohnpei at 160E to the Date Line.
Convection near this zone will continue to impact Kosrae tonight.
Much drier trades north of this zone will promote fair weather near
Chuuk and Pohnpei thru Sunday night, Majuro thru Saturday. By late
Saturday afternoon, these drier trades should also dominate Kosrae.
Latest visible and ASCAT satellite imagery reveals a broad trade-
wind disturbance east of the Date Line near 172W. This system could
be the next shower maker for the region from east to west starting
Large trade-wind swell and wind waves will maintain hazardous surf on
Kosrae into next week. Seas near Chuuk, Pohnpei and Majuro will be
hazardous for small craft thru Sunday night. Combining with lunar
high tides at Majuro thru Sunday night, coastal inundation up to one
foot is also possible along northeast and east facing shores.
A trade-wind disturbance approaching Yap this evening is being
enhanced by divergent flow aloft. As a result, pockets of deep
convection has been flaring up near this disturbance over the waters
just south of Yap. Expect this convection to eventually spread
northward over Yap later this evening. As this disturbance steadily
moves westward tonight, similar conditions will also reach Koror late
tonight. After the passage of this disturbance by Sunday evening, a
period of fair trade weather is anticipated for both places thru
Tuesday. In the long run, model guidance is establishing a near-
equatorial trough south of Koror and Yap near midweek next week.
Increasing converging winds north of this potential feature might
heighten the chance of showers over both locations.
Building trade-wind swell along with a modest north swell will cause
higher seas and surf across the Republic of Palau and western Yap
State thru Saturday night. At this point, both seas and surf should
stay just below hazardous levels.
GU...High Surf Advisory until 5 PM CHST Saturday for GUZ001>004.