Scientific Forecaster Discussion

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AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE TIYAN GU
655 PM CHST FRI APR 18 2014

.MARIANAS SYNOPSIS...
JTWC LOW SUSPECT AREA 98W IS CENTERED SOUTH-SOUTHEAST OF GUAM NEAR 
10N146E. 98W SHOWS AN EXPOSED LOW-LEVEL CIRCULATION CENTER AND LOOKS 
RATHER ANEMIC. A SURFACE TROUGH EXTENDS NORTHEASTWARD FROM 98W TO 
NEAR 14N150E. SHOWERS HAVE BEEN DEVELOPING IN THE VICINITY OF THE 
SURFACE TROUGH BUT COVERAGE HAS BEEN LIMITED. A DIFFUSE SHEAR LINE 
RUNS FROM NORTHEAST TO SOUTHWEST OVER PAGAN...BUT THIS FEATURE HAS 
BEEN BACKING UP TOWARD THE NORTHWEST AWAY FROM THE FORECAST ZONES. 
RADAR AND SATELLITE HAVE BEEN SHOWING SHOWERS APPROACHING FROM THE 
SOUTHEAST...THEN FALLING APART BEFORE THEY REACH THE GUAM MARINE 
ZONES. A FEW THUNDERSTORMS HAVE BEEN FIRING NEAR 98W. WATER VAPOR 
LOOP AND GFS40 200MB WIND FIELDS SHOW A TUTT PASSING OVER SAIPAN 
FROM EAST- NORTHEAST TO WEST-SOUTHWEST. A RELATED ZONE OF STRONG 
UPPER- LEVEL CONVERGENCE EXTENDS NORTHWARD FROM THE FORECAST 
ZONES...WHILE UPPER-LEVEL DIVERGENCE IS FOUND FROM SOUTH OF GUAM TO 
NEAR 10N.

&&

.DISCUSSION...
LATEST FORECAST PACKAGE BACKS OFF CONSIDERABLY ON SHORT TERM POPS. 
MODEL AND SATELLITE TRENDS SUGGEST HOSTILE UPPER-LEVEL ENVIRONMENT 
WILL REMAIN IN PLACE FOR THE NEXT COUPLE OF DAYS. GFS 40 TIME-HEIGHT 
CROSS SECTION SHOWS PRONOUNCED MID-LEVEL DRYING OVERHEAD THROUGH 06Z 
SUNDAY. DID KEEP IN SLIGHT CHANCE THUNDER THROUGH SUNDAY DUE TO THE 
PROXIMITY OF THE TUTT. DRY TRADES ARE STILL ON SCHEDULE TO ASSERT 
THEMSELVES FROM MONDAY THROUGH DAY 7.

&&

.MARINE...
MADE SEVERAL ADJUSTMENTS TO THE MARINE SWELL GRIDS BUT OVERALL STORY 
REMAINS THE SAME. LATEST ALTIMETRY AND BUOY READINGS INITIALIZE 
COMBINED SEAS BETWEEN 6 AND 7 FEET. CDIP BUOY DIRECTIONAL SPECTRUM 
SHOWS NORTH SWELL PREDOMINANT AT BOTH THE RITIDIAN AND TANAPAG 
BUOYS. CONSEQUENTLY ADDED A FOOT TO NORTH SWELL AND SUBTRACTED A 
FOOT FROM THE EAST SWELL TONIGHT AND SATURDAY. STILL EXPECT SURF ON 
NORTH FACING REEFS TO SUBSIDE BELOW MODERATE RIP CURRENT RISK LEVELS 
BY SUNDAY AND SURF ALONG EAST FACING REEFS TO GRADUALLY BUILD BUT 
REMAIN AT MODERATE RIP CURRENT RISK LEVELS DURING THE NEXT FEW DAYS.

&&

UPDATED TO ADD MICRONESIA DISCUSSION

.EASTERN MICRONESIA...
RELATIVELY DRY WEATHER WILL BE SEEN OVER EASTERN MICRONESIA AS 
TRADES CONTINUE TO PUSH IN THE NEXT FEW DAYS. CONVECTION ASSOCIATED 
WITH A DISTURBANCE EMBEDDED WITHIN THE NEAR-EQUATORIAL TROUGH SHOULD 
STAY MAINLY SOUTH OF KOSRAE BUT ISOLATED THUNDERSTORMS ARE STILL 
POSSIBLE THRU SATURDAY NIGHT AS BEING SEEN EARLIER THIS AFTERNOON. 
POHNPEI SHOULD BE FAR ENOUGH NORTH OF THE CONVECTION SO THAT FAIR 
CONDITIONS WILL PREVAIL FOR THE NEXT FEW DAYS. TRADE WINDS WILL 
USHER IN PARTLY CLOUDY SKIES FOR MAJURO SATURDAY AND SATURDAY NIGHT. 
IN THE LONGER TERM...CHANCE FOR SHOWERS MIGHT INCREASE NEAR MID-WEEK 
AS THE NEAR-EQUATORIAL TROUGH AND EMBEDDED CIRCULATION COULD LIFT A 
BIT FURTHER NORTH.

&&

.WESTERN MICRONESIA...
THE CIRCULATION SOUTHEAST OF GUAM AT 10N146E IS GETTING SHEARED WITH 
CONVERGENCE ALOFT AS OPPOSED TO THE DIVERGENCE ALOFT THAT IT NEEDS 
TO DEVELOP. THIS MAKES THE EARLIER FORECASTS FOR YAP AND KOROR TO BE 
SOMEWHAT IN QUESTION...SO MADE ADJUSTMENTS ACCORDINGLY. SATELLITE 
SHOWS THE CIRCULATION IS EXPOSED...AND CELLS OF CONVECTION BETWEEN 
8N AND 12N FROM 145E TO 139E ARE MOVING TOWARD YAP. A CLUSTER OF 
THUNDERSTORMS IS CENTERED AT 9N148E WITH OTHER STORMS NEARBY. THIS 
CLUSTER OF THUNDERSTORMS MIGHT MOVE WESTWARD ACROSS YAP ALONG WITH 
THE CIRCULATION DURING THIS WEEKEND. CONVERGING WINDS SOUTH OF THE 
NEAR-EQUATORIAL TROUGH WERE TRIGGERING NARROW BANDS OF CONVECTION 
AND THUNDERSTORMS SOUTH OF KOROR THIS AFTERNOON FROM 7N130E TO 
5N144E. THIS CONVECTION IS EXPECTED TO STAY THERE AT LEAST THRU 
SATURDAY EVENING. FUTURE SHIFTS WILL NEED TO AMEND THE KOROR 
FORECAST ACCORDINGLY IF THIS CONVECTION BEGINS TO SHIFT NORTHWARD 
CLOSER TO KOROR. NO MAJOR CHANGES TO THE CHUUK FORECAST. CONDITIONS 
WILL CONTINUE TO IMPROVE THERE AS THE CIRCULATION CURRENTLY 
SOUTHEAST OF GUAM MOVES WEST. ANOTHER DISTURBANCE FROM THE EAST 
COULD BRING MORE SHOWERS MONDAY OR TUESDAY.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

MCELROY/DEVITA