834
FXHW01 KWNH 040705
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
305 AM EDT SAT APR 4 2026
VALID 00Z SUN 05 APR 2026 - 00Z SUN 12 APR 2026
..HEAVY RAIN POTENTIAL INCREASES MID-TO-LATE WEEK
A RELATIVELY TRANQUIL SYNOPTIC PATTERN WILL PERSIST THROUGH THE
WEEKEND AS SURFACE RIDGING TO THE NORTH MAINTAINS A DRY AIRMASS
AND BELOW-AVERAGE PRECIPITABLE WATER (PW) VALUES ACROSS THE ISLAND
CHAIN. HOWEVER, THE PATTERN IS FORECAST TO UNDERGO A SIGNIFICANT
SHIFT EARLY NEXT WEEK AS AN UPPER-LEVEL TROUGH MOVES EAST OF THE
DATELINE AND AN UPPER LOW DEVELOPS WELL NORTHWEST OF THE STATE.
SHORTWAVE ENERGY FORECAST TO DIVE SOUTH OF THE LOW WILL AMPLIFY
THE TROUGH, PUSHING A FRONTAL BOUNDARY TOWARD THE ISLANDS FROM THE
WEST. WHILE THE FRONT ITSELF IS EXPECTED TO REMAIN WEST OF THE
REGION, LOW-LEVEL WINDS WILL VEER SOUTHERLY BY TUESDAY, DRAWING A
DEEP PLUME OF MOISTURE NORTHWARD OVER THE STATE.
CONFIDENCE IS INCREASING IN A MORE UNSETTLED AND POTENTIALLY
IMPACTFUL WEATHER REGIME FOR THE MID-TO-LATE WEEK PERIOD. ANOTHER
SHORTWAVE IS EXPECTED TO FURTHER AMPLIFY THE UPPER TROUGH WEST OF
THE ISLANDS, WITH LOW PRESSURE STRENGTHENING ALONG THE BOUNDARY
AS SECOND UPPER LOW CLOSES OFF NORTHWEST-TO-NORTH OF THE STATE
WEDNESDAY AND THURSDAY. THIS EVOLUTION WILL LIKELY FURTHER ENHANCE
THE SOUTHERLY FLOW, DRIVING PW ANOMALIES WELL ABOVE NORMAL AND
INCREASING THE THREAT FOR ORGANIZED HEAVY RAINFALL AND FLOODING.
WHILE MODEL DIVERGENCE EXISTS REGARDING THE EXACT PLACEMENT OF THE LOW
AND DEEPEST MOISTURE AXIS, BOTH GFS AND ECMWF ENSEMBLES INDICATE
NOTEWORTHY PROBABILITIES OF 24-HOUR RAINFALL TOTALS EXCEEDING AN
INCH DURING THE THURSDAY-FRIDAY TIMEFRAME. THE GROWING MODEL
CONSENSUS FAVORS A CLOSED LOW LINGERING NORTH OF THE ISLANDS
THROUGH THE END OF THE PERIOD, KEEPING A MOISTURE-LADEN BOUNDARY
OVER THE STATE AND MAINTAINING AN ELEVATED FLOOD THREAT INTO NEXT
WEEKEND.
PEREIRA
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