336
FXHW01 KWNH 090849
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
449 AM EDT THU APR 9 2026
VALID 00Z FRI 10 APR 2026 - 00Z FRI 17 APR 2026
...PROLONGED HEAVY RAINFALL EVENT EXCEPTED ACROSS THE ISLANDS THIS
WEEK...
THE SYNOPTIC PATTERN WILL CONTINUE TO UNDERGO A SIGNIFICANT SHIFT
THROUGH THE END OF THE WEEK 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 THEN
LIFT NORTHWARD.
AS THIS OCCURS, INSTABILITY AND DEEP MOISTURE GETS DRAWN
NORTHWARDS FROM THE TROPICS WHICH RESULTS IN THE ATMOSPHERE
BECOMING INCREASINGLY SUPPORTIVE OF HEAVY RAINFALL AND FLOODING
AS THE PERIOD BEGINS.
BY LATER TODAY 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
COVERAGE OF ORGANIZED HEAVY RAINFALL, WITH THE GREATEST THREAT
FOCUSED INITIALLY OVER THE WESTERN ISLANDS FROM LATER TODAY INTO
FRIDAY, BEFORE SHIFTING TOWARD THE CENTRAL AND EASTERN ISLANDS
FRIDAY INTO SATURDAY.
ENSEMBLE GUIDANCE (GEFS, ECENS, AND CMC) CONTINUED 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. SOME MODEL UNCERTAINTY
REGARDING THE INTERACTION AND EVOLUTION OF THESE FEATURES REMAINS,
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 AND RESERVOIRS OF INSTABILITY WILL LIKELY
SUPPORT ADDITIONAL ROUNDS OF HEAVY RAINFALL, MAINTAINING AN
ELEVATED RISK OF FLASH FLOODING INTO THE MIDDLE OF NEXT WEEK.
BANN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page