636
FXHW01 KWNH 080715
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
315 AM EDT WED APR 8 2026
VALID 00Z THU 09 APR 2026 - 00Z THU 16 APR 2026
...PROLONGED HEAVY RAINFALL EVENT EXCEPTED ACROSS THE ISLANDS THIS
WEEK...
THE SYNOPTIC PATTERN WILL CONTINUE TO UNDERGO A SIGNIFICANT SHIFT
THROUGH MIDWEEK AS A CLOSED UPPER-LEVEL LOW DIGS SOUTHEASTWARD
TOWARD THE ISLAND CHAIN, DISRUPTING THE TYPICAL TRADE WIND REGIME.
IN RESPONSE, SURFACE LOW PRESSURE IS EXPECTED TO ORGANIZE ALONG A
BOUNDARY STALLED WEST OF THE STATE AND LIFT NORTHWARD.
AS THIS OCCURS, LOW-LEVEL WINDS WILL VEER SOUTHERLY, DRAWING
ADDITIONAL DEEP TROPICAL MOISTURE ACROSS THE ISLANDS. THIS
INCREASINGLY MOIST AND UNSTABLE ENVIRONMENT WILL SUPPORT A GROWING
THREAT OF HEAVY RAINFALL AND FLOODING AS THE PERIOD BEGINS.
BY THURSDAY INTO FRIDAY, THE SURFACE LOW IS FORECAST TO DEEPEN
NORTHWEST OF THE ISLANDS, RESULTING IN STRONG AND GUSTY SOUTHERLY
WINDS ACROSS THE REGION. AT THE SAME TIME, A TRAILING COLD FRONT
WILL GRADUALLY PUSH EASTWARD. THIS PATTERN WILL FAVOR WIDESPREAD,
ORGANIZED HEAVY RAINFALL, WITH THE GREATEST THREAT FOCUSED
INITIALLY OVER THE WESTERN ISLANDS THURSDAY INTO FRIDAY, BEFORE
SHIFTING TOWARD THE CENTRAL AND EASTERN ISLANDS FRIDAY INTO
SATURDAY.
ENSEMBLE GUIDANCE (GEFS, ECENS, AND CMC) CONTINUE TO INDICATE A
STRONG SIGNAL FOR HEAVY RAINFALL, WITH 72-HOUR QPF PROBABILITIES
ENDING 00Z SUNDAY SUPPORTING WIDESPREAD TOTALS EXCEEDING 3 INCHES
ACROSS THE WESTERN PORTION OF THE STATE.
BY FRIDAY, THE INITIAL UPPER-LEVEL LOW IS EXPECTED TO INTERACT
WITH A SECOND SYSTEM TO THE NORTH. THERE REMAINS SOME MODEL
UNCERTAINTY REGARDING THE INTERACTION AND EVOLUTION OF THESE
FEATURES, WITH SOME MODELS SHOWING A VERTICALLY STACKED LOW
REMAINING NORTH OF THE ISLANDS INTO EARLY NEXT WEEK, WHILE OTHERS
ARE MORE PROGRESSIVE.
REGARDLESS OF THE PRECISE EVOLUTION, THE GENERAL MODEL CONSENSUS
SHOWS SOUTHWESTERLY FLOW ALOFT REMAINING ESTABLISHED ACROSS THE
ISLANDS. EMBEDDED SHORTWAVE ENERGY AND CONTINUED ACCESS TO DEEP
TROPICAL MOISTURE WILL LIKELY SUPPORT ADDITIONAL ROUNDS OF HEAVY
RAINFALL, MAINTAINING AN ELEVATED RISK OF FLASH FLOODING INTO THE
MIDDLE OF NEXT WEEK.
PEREIRA
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