196  
FXHW01 KWNH 021317  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
816 AM EST SAT DEC 02 2017  
 
VALID 00Z SUN DEC 03 2017 - 00Z SUN DEC 10 2017  
 
INITIALLY, A CLOSED UPPER LOW WILL PASS WELL EAST OF THE HAWAI`IAN  
ISLAND CHAIN WHILE THE TAIL END OF THE HEIGHT FALLS SHOULD LINGER  
OVER THE REGION INTO EARLY NEXT WEEK. THE ELONGATED BAND OF  
VORTICITY IS FORECAST TO DRIFT SOUTHWARD IN TIME TOWARD THE  
EQUATORIAL PACIFIC BY EARLY NEXT WEEK. EVENTUALLY ANOTHER POTENT  
SYSTEM WILL SWING SOUTHWARD OUT OF THE MID-LATITUDES WITH  
ADDITIONAL SHORTWAVE ENERGY FOLLOWING IN ITS WINGS. WHILE THE  
STRONGEST FORCING SHOULD STAY WELL NORTHEAST OF HAWAI`I, A  
LINGERING BATCH OF HEIGHT FALLS SHOULD SWING THROUGH THE REGION BY  
MID-WEEK. WHILE THE GLOBAL GUIDANCE IS IN AGREEMENT WITH THE  
OVERALL FORECAST EVOLUTION THE NEXT WEEK, THEY VARY WITH THE  
DETAILS, PARTICULARLY THE 00Z ECMWF WHICH SHOWS A CUT-OFF UPPER  
LOW LOOMING JUST EAST OF THE STATE BY THE MIDDLE OF NEXT WEEK.  
THIS CLOSED LOW WOULD LINGER JUST EAST OF HAWAI`I THROUGH MUCH OF  
NEXT WEEK AS THE SYSTEM EDGES SLOWLY TOWARD THE EAST. HOWEVER,  
COMPARED TO THE 00Z ECMWF ENSEMBLE MEMBERS, ITS SOLUTION DOES  
APPEAR TO BE OUTLYING TO SOME DEGREE SO WOULD NOT PUT SIGNIFICANT  
STOCK IN ITS FORECAST JUST YET.  
 
AT THE SURFACE, STRONG RIDGING TO THE NORTH WILL ENCOURAGE A  
STEADY PERIOD OF EAST-NORTHEASTERLY WINDS, APPROACHING THE 20 TO  
25 KNOT RANGE AT TIMES. THIS FLOW REGIME SHOULD PERSIST THROUGH  
THE WEEKEND WITH A GRADUAL SLACKENING OF THE WIND FIELDS BY LATE  
SUNDAY/EARLY MONDAY. BY EARLY NEXT WEEK, A DEEPENING CYCLONE TO  
THE NORTH AND EAST SHOULD SUPPORT A STRENGTHENING COLD ADVECTION  
PATTERN AS MODERATE TO OCCASIONALLY STRONG NORTHERLY FLOW ENSUES.  
THIS WILL ULTIMATELY SHUNT A GREAT DEAL OF THE TROPICAL MOISTURE  
EQUATORWARD. BY THE MIDDLE OF NEXT WEEK, A WEAKENING PRESSURE  
GRADIENT WILL EVENTUALLY DECREASE THE STRENGTH OF THE NORTHERLIES  
WITH LIGHTER WINDS EXPECTED THROUGH AT LEAST THE END OF THE WORK  
WEEK. THE NEXT SYSTEM TAKING SHAPE SHOULD LEAD TO AN ADDITIONAL  
FRONTAL PASSAGE BUT DETAILS REMAIN UNCERTAIN AS SUGGESTED BY WHAT  
THE 00Z ECMWF HAD DEPICTED. REGARDING PRECIPITATION THREATS, THE  
INITIAL HIGH PRECIPITABLE WATER ENVIRONMENT WILL BE IN THE PROCESS  
OF DROPPING SOUTH WHICH SHOULD DECREASE THE COVERAGE OF SHOWERS IN  
TIME. BY LATER IN THE WEEKEND, DRIER AIR WILL WORK ITS WAY INTO  
THE REGION WHICH SHOULD FURTHER SHUT OFF ANY APPRECIABLE  
PRECIPITATION CHANCES. THE NEXT FRONTAL SURGE SHOULD BRING ANOTHER  
THREAT FOR SHOWERS BY TUESDAY/WEDNESDAY ALTHOUGH THIS SHOULD BE  
BRIEF GIVEN THE QUICK PROGRESSION OF THE FRONTAL BOUNDARY. AN  
ADDITIONAL THREAT IS POSSIBLY BY THE DAY 6/7, DECEMBER 8/9,  
TIMEFRAME WITH THE NEXT FRONTAL PASSAGE EXPECTED.  
 
RUBIN-OSTER  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page