026  
FXHW01 KWNH 011230  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
730 AM EST THU FEB 01 2018  
 
VALID 00Z FRI FEB 02 2018 - 00Z FRI FEB 09 2018  
   
..HEAVY RAIN THREAT FOR KAUAI AND OAHU THROUGH THE WEEKEND
 
 
VERY DEEP TROUGHING TO THE WEST OF HAWAI'I NEAR THE DATELINE  
(500MB HEIGHT ANOMALIES AROUND -4 STANDARD DEVIATIONS) WILL HOLD  
IN PLACE UNTIL THIS WEEKEND WHEN IT WILL MOVE EASTWARD. THIS WILL  
DRIVE A FRONT THROUGH THE REGION EARLY IN THE WEEK WITH  
NORTHWESTERLY UPPER FLOW BEHIND IT BY THURSDAY.  
 
THE MODELS AND ENSEMBLES WERE IN GOOD AGREEMENT THROUGH ABOUT NEXT  
TUESDAY/WEDNESDAY WITH THE APPROACH OF THE FRONT (EARLY MONDAY IN  
THE NORTHWESTERNMOST ISLANDS). THROUGH THE WEEKEND, OLD SURFACE  
BOUNDARIES (MOISTURE AXES) TO THE NORTHWEST OF THE REGION WILL  
MAINTAIN A MOIST SOUTHERLY TO SOUTHEASTERLY FLOW AND THE CONTINUED  
RISK OF MODEST TO LOCALLY HEAVIER RAIN FOR OAHU/KAUAI/NI'IHAU.  
PRECIPITABLE WATER VALUES WILL BE IN EXCESS OF 1.5 INCHES OR +2 TO  
+3 STANDARD DEVIATIONS. THE APPROACHING COLD FRONT ON MONDAY WILL  
PUSH THE RAIN TO THE SOUTHEAST THROUGH THE REST OF THE REGION ON  
TUESDAY AND THE TO THE EAST OF THE BIG ISLAND ON WEDNESDAY. BY  
THEN, THE ENSEMBLES DIVERGE IN TIMING WITH THE GEFS MEMBERS  
GENERALLY QUICKER WITH THE UPPER TROUGH THAN THE ECMWF/CANADIAN  
MEMBERS. THE DETERMINISTIC RUNS WERE GENERALLY CLOSE IN TIMING TO  
THEIR ENSEMBLE MEMBERS. PREFER A TIMING SLOWER THAN THE GEFS  
MEMBERS NEAR THE ECMWF ENSEMBLE MEAN, WHICH WAS A BIT WEAKER THAN  
THE DETERMINISTIC 00Z ECMWF.  
 
FRACASSO  
 

 
 
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