558
FXHW01 KWNH 040852
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
352 AM EST SUN JAN 4 2026
VALID 00Z MON 05 JAN 2026 - 00Z MON 12 JAN 2026
CLOSED ULL TO THE NORTHWEST OF HAWAII WILL TREK WEST OF THE
ISLANDS WITH FLOW SHIFTING QUICKLY OUT OF THE SOUTH LEADING TO A
MERIDIONAL PUSH OF DEEPER TROPICAL MOISTURE LEADING TO WIDESPREAD
PWAT ANOMALIES BETWEEN 2-3 STANDARD DEVIATIONS ABOVE NORMAL. THE
SETUP WILL LEAD TO A SHIFT IN THE FOCUS OF CONVECTION AND HEAVY
RAINFALL ACROSS THE ISLANDS TO THE CENTRAL AND WESTERN SIDE OF THE
ISLAND CHAIN WITH MORE EMPHASIS FOR THE WESTERN HALF OF THE
ISLANDS WITH IMPACTS STILL ONGOING FOR MAUI AND THE BIG ISLAND.
MODELS DIFFER ON THE MAGNITUDE OF RAINFALL, HOWEVER THE PROSPECTS
FOR SIGNIFICANT RAIN ARE MUCH HIGHER THAN THE PREVIOUS TRADE WIND
PATTERN DUE TO THE DEEPER MOISTURE LAYER PRESENCE AS NOTED VIA THE
SATURATED RH% BETWEEN THE BOUNDARY LAYER TO 500MB. SEVERAL INCHES
WILL BE PLAUSIBLE IN THE HARDEST HIT AREAS WITH THE GREATEST
POTENTIAL LIKELY TO BE THE SOUTHERN HALF OF THE BIG ISLAND AND THE
EASTERN SIDE OF MAUI.
ULL WILL CONTINUE TO CHURN THROUGH TUESDAY WITH AN EVENTUAL
BREAKDOWN IN THE DISTURBANCE EXPECTED MID-WEEK LEADING TO A SHIFT
BACK INTO A LIGHTER TRADE WIND PATTERN. MODELS DIVERGE ON THE
HANDLING OF THE NEXT MID-LEVEL TROUGH TO THE NORTHWEST OF HAWAII
WITH THE ECMWF LEANING TOWARDS A FRONTAL PASSAGE APPROACHING END
OF THE WEEK WITH THE GFS LEANING TOWARDS ANY FRONT BEING STRUNG
OUT TO THE NORTH WITH SOME REMNANT MOISTURE FROM THE PREVIOUS
DISTURBANCE GETTING PULLED POLEWARD WITH LINGERING SHOWERS ACROSS
THE ISLANDS THROUGH THE END OF THE WEEK. IN ANY CASE, RAIN CHANCES
WILL BE PRESENT THROUGH THE EXTENDED, HOWEVER THE COVERAGE IS THE
KEY DIFFERENCE BETWEEN THE SYNOPTIC SETUP. LEANING TOWARDS THE EC
SOLUTION WITH THE EC-AIFS ENSEMBLE RELATIVELY STEADY IN ITS
INTERPRETATION OF A FRONTAL APPROACH SIMILAR IN THE DETERMINISTIC
EC OUTPUT. WILL BE A PERIOD TO MONITOR FROM FRIDAY THROUGH THE END
OF THE FOLLOWING WEEKEND.
KLEEBAUER
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