127  
FXHW01 KWNH 121219  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
718 AM EST MON FEB 12 2018  
 
VALID 00Z TUE FEB 13 2018 - 00Z TUE FEB 20 2018  
 
HIGHLY AMPLIFIED MID-LATITUDE FLOW WILL PREVAIL OVER THE CENTRAL  
PACIFIC WHILE THE SOUTHERN EXTENSION OF HEIGHT FALLS SHOULD CLOSE  
OFF NORTHWEST OF THE HAWAI`IAN ISLANDS BY LATER TONIGHT. AS THIS  
CIRCULATION EDGES CLOSER TO 165W LONGITUDE, THE LOW-LEVEL WIND  
FIELDS SHOULD PICK UP A BIT AS SOUTH-SOUTHEASTERLY WARM ADVECTION  
ENSUES. THIS WILL ALSO BE ACCOMPANIED BY A SLIGHT INCREASE IN  
SHOWER ACTIVITY AS HIGHER PRECIPITABLE WATER AIR LIFTS OUT OF THE  
EQUATORIAL PACIFIC. OVER THE FOLLOWING DAYS, THE PARENT  
LOW/MID-LEVEL CIRCULATION SHOULD REMAIN SLOW MOVING WITH A  
POSITION JUST TO THE NORTH OF KAUAI AND NI'IHAU ON THURSDAY  
MORNING. THIS WILL ULTIMATELY AFFORD A FRONTAL PASSAGE BY MID-WEEK  
WHILE THE BOUNDARY SHOULD EVENTUALLY STALL AND BEGIN TO SHEAR OUT  
BY LATER IN THE WEEK. WHILE A BULK OF THE RAINFALL WITH THIS  
SYSTEM SHOULD OCCUR IN CLOSER PROXIMITY TO THE UPPER LOW WHERE  
BETTER DYNAMICS WILL RESIDE, MODELS DO AFFORD A FAIR AMOUNT OF  
PRECIPITATION ALONG THIS MENTIONED BOUNDARY. UNSETTLED CONDITIONS  
COULD LINGER INTO EARLY FRIDAY OVER THE BIG ISLAND AS SHOWN BY THE  
06Z GFS AND 00Z CMC/UKMET SOLUTIONS.  
 
LOOKING OUT TO FRIDAY ONWARD, THE GUIDANCE GRADUALLY ALLOW THE  
UPPER LOW TO WEAKEN AND BECOME ABSORBED BY A BROADER-SCALE  
LONGWAVE TROUGH INTERCEPTING FROM THE NORTH. WITHIN THIS SAME  
FEATURE, THERE IS A GROWING CONSENSUS THAT AN ADDITIONAL  
CIRCULATION MAY PEEL OFF AND LOOM NORTH OF THE HAWAI`IAN ISLANDS  
OVER THE WEEKEND. BY DAY 6/7, FEBRUARY 18/19, THE 06Z GFS AND 00Z  
CMC/ECMWF ALL INDICATE A BROAD UPPER LOW MAY SIT RIGHT OVER  
HAWAI`I WHICH IS ACCOMPANIED BY A FAIR SHARE OF ENSEMBLE SUPPORT.  
WHILE THIS WILL AFFORD A THREAT FOR INCREASED SHOWER ACTIVITY,  
OUTSIDE OF THE WETTER 00Z CMC, IT APPEARS THE BETTER MOISTURE  
FLUXES WOULD RESIDE WELL TO THE EAST. THERE SHOULD ALSO BE DECENT  
LOW-LEVEL SUPPORT FOR SHOWERS AS A NORTH-SOUTH ORIENTED  
CONVERGENCE ZONE SETS UP. THIS SOLUTION IS PARTICULARLY EVIDENT IN  
THE 06Z GFS ALTHOUGH OVERALL WIND FIELDS ARE ON THE LIGHTER SIDE.  
 
RUBIN-OSTER  
 

 
 
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