Area forecast discussion National Weather Service tiyan GU 504 PM chst Thursday may 23 2013 Synopsis...radar and satellite indicate isolated showers within the marianas marine zones. Satellite imagery indicates the band of showers associated with the weak surface trough moved north of the marianas marine zones. && Discussion... reasoning follows continuity from the last 36 hours except the weak trough forecast to bring a slight chance of thunderstorms moved north of the marine zones. Models continue in general agreement with satellite imagery and continue to indicate trade- wind flow over the marianas forecast zones with a few embedded weak troughs the next several days. Since the first trough moved north of Saipan and no longer shows signs of thunder...and since the k-index and precipitable water on the morning satellite decreased to 26 and 1.77 respectively since last night...thunder has been removed from the forecast for tonight. The next distinguishable trough on the models appears to arrive at the marianas about Tuesday or Wednesday. Except for the slightly wetter conditions from the weak troughs...expect generally dry conditions for the marianas the next several days. && Eastern micronesia... synoptic configuration has not changed much during the past day or so. Trade-wind convergence zone remains focused between 2n and 8n. TUTT overlying all 3 forecast points is shearing any deep convection that develops to the north of 8n. Did extend scattered showers for Pohnpei tonight and for Kosrae through Friday night based on satellite trends and near term model solutions. Convection to the west of Majuro has stopped back building for now...but evening shift should monitor satellite imagery in the vicinity of Majuro just in case. Otherwise...do not expect weather setup over eastern micronesia to change very much during the next 5 days. Zone of trade-wind convergence should generally remain focused to the south of Majuro and Pohnpei. Trade-wind surge arriving by the weekend should dry things out a bit for the first part of next week. Did add a foot to combined seas for all 3 forecast points Sunday through Tuesday to account for increasing trade-wind waves and swell during this time frame. && Western micronesia... a weak circulation was centered southwest of Pohnpei near 4n155e. Most of the attendant convection was located to the east of the center. A convectively inactive TUTT was moving westward away from Yap and Koror. Forecast for western micronesia generally follows persistence. Backed Chuuk winds overnight from east to northeast to factor in the wind field on the west side of the circulation centered to the southeast. Added mostly cloudy skies and isolated showers to the Chuuk forecast for Friday and Friday night. Believe remnants of circulation will provide some moisture and instability during that time frame. Forecasts for Yap and Koror remain unchanged. Models still keep deep-layer ridging in control over these locations. Remnants of circulation should dissipate before making as far west as Yap and Koror. && Gum watches/warnings/advisories... GU...none. Marianas waters...none. && $$ Devita/McElroy