807
FXHW01 KWNH 180801
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EST SAT FEB 18 2023
VALID 00Z SUN FEB 19 2023 - 00Z SUN FEB 26 2023
...HEAVY RAINFALL/FLOODING THREAT DECREASING OVERALL THOUGH RAIN
CHANCES REMAIN IN A LONGER TERM WET PATTERN...
EXPECT A WEAK UPPER LOW SOUTH OF THE STATE AS OF SATURDAY TO SHIFT
SOUTH-SOUTHEASTWARD AND EVENTUALLY SHEAR OUT EARLY NEXT WEEK. THE
DEEP-LAYER SOUTHEASTERLY FLOW BETWEEN THE UPPER LOW AND RIDGE OFF
TO THE NORTHEAST WILL CONTINUE TO BRING UP ABUNDANT MOISTURE INTO
THE ISLANDS, WITH A HEAVY RAINFALL/FLOODING THREAT CONTINUING OVER
SOUTHEASTWARD-FACING TERRAIN OF THE BIG ISLAND INTO EARLY SUNDAY.
MODEL GUIDANCE AGREES THAT RAIN TOTALS WILL DECREASE SIGNIFICANTLY
BY MONDAY.
FROM MONDAY THROUGH NEXT SATURDAY, MODELS AND ENSEMBLES MAINTAIN A
DECENT SIGNAL FOR SHORTWAVE ENERGY TO THE NORTHWEST TO FORM
ANOTHER TROUGH/UPPER LOW WHICH WILL SLOWLY SHIFT SOUTHWARD.
SIMILAR TO THE PATTERN OF THE PREVIOUS WEAK, THE PLACEMENT OF THIS
UPPER-LOW COMBINED WITH THE PERSISTENT UPPER RIDGE NORTHEAST OF
THE STATE WILL MAINTAIN SOUTHEASTERLY FLOW AND A
SOUTHEAST-NORTHWEST ORIENTED AXIS OF ENHANCED MOISTURE IN THE
REGION, INITIALLY TO THE SOUTHWEST OF THE ISLANDS. THE GFS IS AN
OUTLIER IN SHIFTING THIS MOISTURE BAND BACK OVER THE ISLANDS
FOLLOWING A BRIEF REPRIEVE ON MONDAY, AS OPPOSED TO THE AXIS
REMAINING TO THE SOUTHWEST IN THE OTHER GUIDANCE. OVERALL, THE
MODEL CONSENSUS SUPPORTS A DECREASE IN HEAVY RAIN CHANCES NEXT
WEEK, BUT WITH ENOUGH MOISTURE STILL PRESENT IN THE NEAR VICINITY
TO CONTINUE A PERIODIC RAINFALL THREAT OVER SOME LOCATIONS
(ESPECIALLY THE WESTERN ISLANDS AND THE BIG ISLAND).
PUTNAM
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