952
FXHW01 KWNH 060707
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
207 AM EST FRI MAR 6 2026
VALID 00Z SAT 07 MAR 2026 - 00Z SAT 14 MAR 2026
..FLASH FLOOD RISK WILL INCREASE NEXT WEEK
A SIGNIFICANT REGIME SHIFT IS EXPECTED ACROSS THE HAWAIIAN ISLANDS
DURING THE FORECAST PERIOD. THE CURRENT DRY AND STABLE PATTERN,
DOMINATED BY MODERATE TO BREEZY EAST-SOUTHEAST FLOW, WILL PERSIST
THROUGH THE WEEKEND. HOWEVER, A TRANSITION TO A HIGHLY-UNSTELLED
AND POTENTIALLY HAZARDOUS WEATHER PATTERN IS FORECAST TO BEGIN
MONDAY NIGHT, AS THE LEADING EDGE OF A 130-140KT 250MB JET STREAK
WILL MIGRATE DOWN THE WESTERN PERIPHERY OF AN UPPER TROUGH,
CAUSING THE TROUGH TO BECOME MORE NEGATIVELY TILTED AS IT DRAWS
CLOSER TO THE WESTERN ISLANDS. A MULTI-DAY FLASH FLOOD RISK IS
BECOMING INCREASINGLY LIKELY OVER AT LEAST PART OF THE ISLANDS BY
TUESDAY THROUGH THE REST OF NEXT WEEK.
STRONG LEFT EXIT REGION UPPER FORCING (UPPER DIVERGENCE AND
DIFLUENCE) WILL OVERSPREAD THE ISLANDS AS A RESULT, BOLSTERED BY
THE CURVED UPPER JET STRUCTURE IN THE BASE OF THE NEGATIVELY
TILTED TROUGH. THERE'S FAIRLY GOOD CONSENSUS WITH THE GLOBAL
GUIDANCE IN DEPICTING A BROAD AREA OF LOW PRESSURE NORTHWEST OF
THE ISLANDS BY EARLY NEXT WEEK, ANCHORED BY THE VIGOROUS SHORTWAVE
DIVING SOUTH WITHIN THE AFOREMENTIONED LEFT-EXIT REGION OF THE
POWERFUL PACIFIC JET. AT LOW-LEVELS, WINDS WILL VEER MORE SOUTHERLY
AND INCREASE WITHIN THIS BROAD UPPER LEVEL EXIT REGION, GIVEN THE
SOUTH-NORTH AGEOSTROPHIC RESPONSE. THIS WILL DRAW TROPICAL MOISTURE
NORTHWARD ACROSS THE ISLANDS, WITH PWATS EXPECTED TO EXCEED 1.75"
NEXT WEEK PER THE GUIDANCE (STARTING TUE ACROSS THE WESTERN
ISLANDS). DEEPENING WARM CLOUD LAYERS WILL ENHANCE RAINFALL
EFFICIENCY BY EARLY NEXT WEEK, WHICH ALONG WITH A TALL/SKINNY CAPE
PROFILE WILL RESULT IN A RAPID INCREASE IN COVERAGE AND INTENSITY
OF THE RAIN MONDAY NIGHT INTO TUESDAY.
HURLEY
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