094
FXHW01 KWNH 190804
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
404 AM EDT THU MAR 19 2026
VALID 00Z FRI 20 MAR 2026 - 00Z FRI 27 MAR 2026
...PROLONGED WET PATTERN TO CONTINUE THROUGH THE UP COMING WEEKEND
ACROSS HAWAII...
A PAIR OF UPPER LEVEL RIDGES; ONE ANCHORED OVER NORTHEAST RUSSIA
AND THE ALEUTIANS, AND THE OTHER OVER THE WESTERN CONUS, HAVE
CAUSED SHORTWAVE TROUGHS TO ROUTINELY BECOME CUT-OFF FROM THE JET
STREAM NORTH OF HAWAII. THESE TROUGHS HAVE THEN TAPPED INTO RICH
TROPICAL PACIFIC MOISTURE AND DIRECTED THE MOISTURE RIGHT AT THE
ISLANDS. NAEFS SHOWS AN UNUSUALLY STRONG SUBTROPICAL JET, SPORTING
WINDS ABOVE THE 90TH CLIMATOLOGICAL PERCENTILE, PLACING THE NOSE
OF THE JET OVER HAWAII THROUGH THE END OF THE WEEK AND INTO THE
UPCOMING WEEKEND. NAEFS ALSO SHOWS IVT VALUES THROUGH SATURDAY THAT
ARE TOPPING THE 90TH CLIMATOLOGICAL PERCENTILE. THE HEIGHT OF THE
MOISTURE PLUME ARRIVES FRIDAY AND LINGERS INTO THE DAY ON
SATURDAY AS LOW PRESSURE DEEPENS TO THE NORTHWEST. PWATS WELL
ABOVE 1.75", OR ABOVE THE 99TH CLIMATOLOGICAL PERCENTILE, WILL
STREAM OVER THE ISLAND WITH HEAVY RAINFALL ONCE AGAIN OVERTAKING
THE WATTER-LOGGED HAWAIIAN ISLANDS. UPSLOPE FLOW AND HEALTHY
UPPER-LEVEL ASCENT WILL GENERATE EXCESSIVE RAINFALL RATES AND
RESULT IN WIDESPREAD HEAVY RAIN THROUGH THE WEEKEND. THE ECMWF
EFI ALSO SHOWS SOME >0.8 VALUES IN THE HEART OF THE ISLANDS,
SUGGESTING THAT THERE IS THE POTENTIAL FOR SIGNIFICANT RAINFALL
FOR MID-LATE MARCH. WITH SOILS SATURATED AND CREEKS/RIVERS HIGH
FROM RECENT HEAVY RAINS, ADDITIONAL RAINFALL THROUGH THIS WEEKEND
WILL SUPPORT THE RISK OF LIFE-THREATENING FLASH FLOODING AND
LANDSLIDES STATEWIDE DURING THIS PERIOD.
GUIDANCE SHOWS THE NEXT POTENTIAL WINDOW FOR DRIER CONDITIONS
BEGINS TO TAKE SHAPE SOMEWHERE BETWEEN LATE MONDAY AND TUESDAY OF
NEXT WEEK WHEN THE UPPER TROUGH TO THE NW FINALLY RACES NORTH AND
EAST INTO THE NORTHEAST PACIFIC. HOWEVER, EC-AIFS ENSEMBLES STILL
SHOW A FAIR AMOUNT OF SPREAD IN THE SPEED AND DEPTH TO WHICH THE
NORTHERN PACIFIC SHORTWAVE TROUGHS BECOME NORTH OF HAWAII. A
WEAKER/SLOWER AMPLIFICATION COULD PROLONG RAINFALL IMPACTS, WHILE
A MORE PROGRESSIVE SCENARIO WOULD SUPPORT A DRIER SETUP. DESPITE
THE LOW CONFIDENCE IN TIMING, THERE DOES APPEAR TO BE SOME
PROVERBIAL "LIGHT AT THE END OF THE TUNNEL" FOR THE HAWAIIAN
ISLANDS NEXT WEEK.
MULLINAX
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