630  
FXHW01 KWNH 141212  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
711 AM EST SUN JAN 14 2018  
 
VALID 00Z MON JAN 15 2018 - 00Z MON JAN 22 2018  
 
A RELATIVELY WEAK FLOW PATTERN WILL BE IN PLACE ACROSS HAWAI'I  
INITIALLY, WITH RIDGING CENTERED EAST AND WEST OF THE STATE, AND A  
MORE ACTIVE MID-LATITUDE FLOW PATTERN TO THE NORTH OF THE STATE.  
OVER THE NEXT FEW DAYS, MODELS SHOW GOOD AGREEMENT THAT UPPER  
RIDGING WILL MIGRATE EASTWARD ACROSS HAWAI'I, WITH THE SURFACE  
HIGH CENTERED NORTH OF THE STATE. THIS WILL ALLOW BRISK LOW-LEVEL  
EAST TO EAST-NORTHEAST FLOW TO RESUME (REACHING THE 20-30 KT RANGE  
BY MIDWEEK), BUT WILL KEEP THE DEEPEST MOISTURE SUPPRESSED SOUTH  
OF THE STATE. THUS, EXPECT A MODEST INCREASE THROUGH MIDWEEK IN  
SHOWER ACTIVITY ALONG WINDWARD TERRAIN DUE TO THE INCREASING  
LOW-LEVEL FLOW, BUT WIDESPREAD PRECIPITATION IS NOT ANTICIPATED  
DUE TO PWATS REMAINING WELL BELOW 1 INCH THROUGH MUCH OF THE WEEK.  
 
BY LATE IN THE WEEK, A MAJORITY OF THE MODELS/ENSEMBLES SHOW A  
WEAKNESS IN THE RIDGE DEVELOPING WEST OF HAWAI'I AS A PIECE OF  
ENERGY SEPARATES FROM THE HIGHER LATITUDE FLOW. THIS SHOULD RESULT  
IN A GRADUAL INCREASE IN PWATS ACROSS HAWAI'I INTO THE 1.0-1.2  
INCH RANGE BY THE WEEKEND, WITH VALUES PERHAPS INCREASING FURTHER  
BY EARLY NEXT WEEK. A COLD FRONT IS SHOWN BY BOTH THE ECMWF AND  
GFS STALLING NORTH OF HAWAI'I BY LATE NEXT WEEKEND. AT THIS TIME  
BOTH MODELS SHOW THE GREATEST MOISTURE POOLING ALONG THIS FRONT,  
REMAINING NORTH OF HAWAI'I ALONG WITH MOST OF THE PRECIPITATION.  
EVEN IF THAT IS THE CASE, THE GRADUALLY INCREASING MOISTURE ACROSS  
THE STATE SHOULD YIELD A GRADUAL INCREASE IN WINDWARD SHOWER  
ACTIVITY THROUGH NEXT WEEKEND.  
 
RYAN  
 

 
 
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