708  
FXHW01 KWNH 111231  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
730 AM EST SUN FEB 11 2018  
 
VALID 00Z MON FEB 12 2018 - 00Z MON FEB 19 2018  
 
ONE UPPER LOW WILL CONTINUE TO SPIN JUST EAST OF THE HAWAI`IAN  
ISLAND CHAIN WITH SOME SCATTERED SHOWERS SWINGING SOUTHWESTWARD  
BACK TOWARD OAHU AND MOLOKA`I. THIS IS IN RESPONSE TO A WEAK AREA  
OF LOW PRESSURE, 1009 MB, BEING ANALYZED JUST TO THE NORTHEAST OF  
THE STATE. MODELS GRADUALLY SHEAR OUT THE SYSTEM WHILE A TRANSIENT  
SHORTWAVE RIDGE SETTLES IN THROUGH EARLY MONDAY. THE FOCUS THEN  
SHIFTS TO A STRONG UPPER TROUGH LURKING UPSTREAM WITH AN UPPER LOW  
LIKELY PEELING OFF FROM THE MID-LATITUDE FEATURE. HOWEVER, THE BIG  
SHIFT IN THE GUIDANCE FROM YESTERDAY HAS PERSISTED WHICH FAVORS AN  
EASTWARD DRIFTING UPPER LOW TRACKING NORTH OF KAUAI AND NI`IHAU. A  
SMALL FRACTION OF THE 00Z GEFS, ECMWF, CMC ENSEMBLE MEMBERS SHOW  
THE 570-DM CLOSED CIRCULATION GRAZING THESE NORTHERN MOST ISLANDS.  
AMONGST THE OPERATIONAL MODELS, THE 00Z CMC IS ON THE SOUTHERN  
EXTENT OF THE SPREAD WHICH LEADS TO A MUCH WETTER SOLUTION. THE  
GENERAL CONSENSUS IS FOR THIS WEAKENING CIRCULATION TO BE ABSORBED  
BY A BROADER SCALE TROUGH DROPPING DOWN FROM THE NORTH BY THE END  
OF THE WORK WEEK. THIS WOULD ENSURE MAINTAINING AN AXIS OF LOWER  
HEIGHTS INTO NEXT WEEKEND AS PERHAPS ANOTHER CLOSED LOW MAY SPIN  
OFF OVER THE HAWAI`IAN ISLANDS NEXT WEEKEND. HOWEVER, GIVEN HOW  
MUCH THE CURRENT FORECAST HAS CHANGED, WILL LIKELY SEE A MULTITUDE  
OF CHANGES DURING THE NEXT FEW DAYS OF MODEL RUNS. ENSEMBLE  
SPAGHETTI PLOTS SHOW QUITE A BIT OF SPREAD WHICH VERIFIES THIS  
NOTION.  
 
CONSIDERING THE SURFACE PATTERN NEXT WEEK, GENERAL  
EAST-SOUTHEASTERLY FLOW WILL TAKE SHAPE AS A WARM ADVECTION REGIME  
ENSUES AHEAD OF THE APPROACHING BAROCLINIC ZONE. DEPENDING ON THE  
STRENGTH AND POSITION OF THE PARENT SURFACE CYCLONE TO THE  
NORTHWEST OF HAWAI`I, THE WIND FIELDS VARY AMONG THE GUIDANCE. A  
FRONTAL PASSAGE WOULD APPEAR LIKELY BY MID-WEEK WITH THE SURFACE  
WAVE POSSIBLY LINGERING TO THE NORTH INTO THURSDAY. IT IS  
DIFFICULT TO SAY WITH CONFIDENCE WHAT THE SURFACE WIND FIELDS WILL  
LOOK LIKE LATER IN THE WEEK GIVEN INCREASING MODEL SPREAD. LIKE  
YESTERDAY, GFS SOLUTIONS REMAIN QUICKER AND FAVOR A COLD ADVECTION  
PATTERN BY THURSDAY. IT DOES SEEM LIKELY THAT AN INVERTED SURFACE  
TROUGH WILL LIKELY TAKE A NORTH/SOUTH ORIENTATION INTO NEXT  
WEEKEND WITH POSITIONS QUITE VARIABLE. ONE THING THAT SEEMS  
CERTAIN IS DAILY RAINFALL CHANCES ARE IN THE PICTURE, PARTICULARLY  
LATER IN THE PERIOD AS THAT MENTIONED INVERTED TROUGH SETS UP.  
MODELS SHOW PRECIPITABLE WATER VALUES EXCEEDING 1.50 INCHES WITH A  
BROAD AXIS OF PRECIPITATION SPREAD OVER THE REGION.  
 
RUBIN-OSTER  
 

 
 
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