637  
FXHW40 KWBC 191254  
PMDHCO  
PROGNOSTIC DISCUSSION FOR LONG-LEAD HAWAIIAN OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
830AM EDT THU APR 19 2018  
 
MONTHLY FORECAST DISCUSSION VALID MAY 2018  
 
SEA SURFACE TEMPERATURE (SST) ANOMALIES ARE CURRENTLY AROUND ZERO TO POSITIVE  
ONE-HALF DEGREE C OVER MOST OF THE NORTHERN HAWAIIAN ISLANDS, AND ABOUT  
POSITIVE ONE-HALF DEGREE TO ONE DEGREE C OVER THE SOUTHEASTERN ISLANDS.  
 
FOR JANUARY 2018 THROUGH THE END OF MARCH 2018, RAINFALL TOTAL ACCUMULATIONS  
WERE:  
 
- LIHUE AIRPORT 18.62 INCHES (162 PERCENT OF NORMAL)  
 
- HONOLULU AIRPORT 6.75 INCHES (107 PERCENT OF NORMAL)  
 
- KAHULUI AIRPORT 8.85 INCHES (112 PERCENT OF NORMAL)  
 
- HILO AIRPORT 41.01 INCHES (127 PERCENT OF NORMAL)  
 
THE NCEP CLIMATE FORECAST SYSTEM (CFS) AND OTHER CLIMATE MODELS RUN AS A PART  
OF THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) PREDICT ABOVE NORMAL SSTS  
AROUND THE HAWAIIAN ISLANDS FOR MAY 2018. THIS ELEVATES THE CHANCES OF ABOVE  
NORMAL MONTHLY MEAN AIR TEMPERATURES FOR LIHUE, HONOLULU, KAHULUI, AND HILO IN  
MAY 2018. MOST DYNAMICAL TOOLS ALSO FAVOR ABOVE NORMAL PRECIPITATION FOR HILO,  
KAHULUI, HONOLULU AND LIHUE DURING MAY 2018.  
 
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
HILO A60 74.0 0.5 A50 4.1 7.4 8.7  
KAHULUI A60 75.8 0.6 A50 0.2 0.5 0.8  
HONOLULU A50 78.0 0.6 A50 0.2 0.4 0.8  
LIHUE A40 75.8 0.6 A50 1.3 1.5 2.3  
 
SEASONAL FORECAST DISCUSSION VALID MJJ 2018 - MJJ 2019  
 
REFER TO THE PROGNOSTIC DISCUSSION ON LONG-LEAD SEASONAL OUTLOOKS FOR THE CONUS  
AND ALASKA FOR A DISCUSSION OF THE FORECASTS OF EQUATORIAL PACIFIC SSTS, AND  
FOR THE GENERAL BACKGROUND FOR THE SEASONAL FORECAST, INCLUDING DETAILS ON THE  
CURRENT STATE OF THE ATMOSPHERE AND OCEAN. WEAK LA NINA CONDITIONS CURRENTLY  
ARE PRESENT ACROSS THE EQUATORIAL PACIFIC OCEAN. EQUATORIAL SEA SURFACE  
TEMPERATURES (SSTS) ARE BELOW AVERAGE ACROSS THE EAST-CENTRAL AND EASTERN  
PACIFIC OCEAN, AND ABOVE AVERAGE IN THE WESTERN PACIFIC. POSITIVE SUBSURFACE  
TEMPERATURE ANOMALIES AT DEPTH HAVE SHIFTED EASTWARD TO 110W, WHILE NEGATIVE  
ANOMALIES PERSIST CLOSER TO THE SURFACE BETWEEN 150W AND 120W. CONVECTION WAS  
SUPPRESSED NEAR AND EAST OF THE DATE LINE AND ENHANCED OVER THE FAR WESTERN  
TROPICAL PACIFIC OCEAN, WHILE LOW-LEVEL WIND ANOMALIES WERE EASTERLY OVER THE  
EAST-CENTRAL PACIFIC, AND WESTERLY OVER THE FAR WESTERN PACIFIC. MOST MODELS  
INDICATE A TRANSITION FROM LA NINA TO ENSO NEUTRAL IS MOST LIKELY (GREATER THAN  
50% CHANCE) DURING THE APRIL-MAY SEASON, WITH NEUTRAL CONDITIONS LIKELY TO  
CONTINUE THROUGH THE NORTHERN HEMISPHERE SUMMER 2018.  
 
 
 
ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE INDICATED FOR HAWAII  
FROM MJJ 2018 TO OND 2018 DUE TO PREDICTED ABOVE NORMAL SEA SURFACE  
TEMPERATURES ACROSS THE REGION. EQUAL CHANCES (EC) FOR ABOVE, NEAR, OR BELOW  
NORMAL TEMPERATURES ARE INDICATED AT ALL LOCATIONS FOR NDJ 2018 AND BEYOND.  
 
DYNAMICAL TOOLS FAVOR ABOVE NORMAL PRECIPITATION FOR HAWAII IN FROM MJJ TO ASO,  
2018. THE STATISTICAL TOOLS (CANONICAL CORRELATION ANALYSIS, AND ENSO-OCN)  
PREDICT BELOW NORMAL PRECIPITATION DURING THE SUMMER. THEREFORE THE  
PROBABILITIES OF ABOVE NORMAL PRECIPITATION ARE LOWERED. THERE IS CONSIDERABLE  
UNCERTAINTY ACROSS THE HAWAIIAN ISLANDS IN THE PRECIPITATION FORECAST AMONG  
AVAILABLE DYNAMICAL AND STATISTICAL TOOLS (CONSTRUCTED ANALOG, CANONICAL  
CORRELATION ANALYSIS, AND ENSO-OCN) IN SON AND LONGER LEADS, SO EQUAL CHANCES  
(EC) FOR ABOVE, NEAR, OR BELOW NORMAL PRECIPITATION ARE INDICATED.  
 
HILO  
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
MJJ 2018 A65 74.0 0.4 A40 20.2 27.5 29.1  
JJA 2018 A60 75.2 0.4 A40 19.4 27.2 31.4  
JAS 2018 A55 76.1 0.4 A40 25.2 28.6 33.4  
ASO 2018 A50 76.4 0.4 A40 26.1 28.8 33.3  
SON 2018 A45 76.2 0.4 EC 24.3 30.2 40.8  
OND 2018 A40 75.5 0.4 EC 28.3 34.5 42.0  
NDJ 2018 EC 74.2 0.4 EC 26.4 36.6 43.0  
DJF 2019 EC 72.8 0.4 EC 19.6 30.2 33.3  
JFM 2019 EC 71.8 0.4 EC 22.0 32.0 44.5  
FMA 2019 EC 71.7 0.4 EC 24.6 34.1 45.5  
MAM 2019 EC 72.0 0.5 EC 22.5 28.4 34.0  
AMJ 2019 EC 72.9 0.5 EC 21.4 23.7 29.0  
MJJ 2019 EC 74.0 0.4 EC 20.2 27.5 29.1  
\N KAHULUI  
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
MJJ 2018 A65 76.0 0.5 A40 0.7 1.1 1.8  
JJA 2018 A60 77.7 0.4 A40 0.7 1.1 1.5  
JAS 2018 A55 79.0 0.4 A40 0.8 1.1 1.6  
ASO 2018 A50 79.4 0.4 A40 0.8 1.6 2.5  
SON 2018 A45 79.1 0.4 EC 2.1 3.3 4.8  
OND 2018 A40 77.8 0.4 EC 4.2 5.3 8.1  
NDJ 2018 EC 75.9 0.4 EC 5.2 7.6 9.5  
DJF 2019 EC 73.8 0.4 EC 4.6 6.9 8.7  
JFM 2019 EC 72.5 0.4 EC 4.2 6.2 8.2  
FMA 2019 EC 72.3 0.4 EC 3.2 4.1 6.4  
MAM 2019 EC 73.0 0.4 EC 2.5 3.5 4.6  
AMJ 2019 EC 74.3 0.5 EC 1.2 1.6 2.2  
MJJ 2019 EC 76.0 0.5 EC 0.7 1.1 1.8  
\N HONOLULU  
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
MJJ 2018 A60 78.2 0.4 A40 0.8 1.4 1.6  
JJA 2018 A55 79.9 0.4 A40 0.7 0.8 1.3  
JAS 2018 A55 81.3 0.4 A40 1.0 1.4 1.7  
ASO 2018 A50 81.7 0.4 A40 1.6 2.4 3.1  
SON 2018 A45 81.4 0.4 EC 2.5 4.0 5.6  
OND 2018 A40 80.0 0.4 EC 4.4 6.4 8.5  
NDJ 2018 EC 77.7 0.5 EC 3.9 5.6 8.8  
DJF 2019 EC 75.3 0.5 EC 3.7 5.6 8.6  
JFM 2019 EC 73.9 0.4 EC 2.1 4.6 7.8  
FMA 2019 EC 73.8 0.4 EC 1.9 3.2 4.7  
MAM 2019 EC 74.8 0.4 EC 1.8 2.6 3.0  
AMJ 2019 EC 76.3 0.4 EC 1.2 1.6 1.8  
MJJ 2019 EC 78.2 0.4 EC 0.8 1.4 1.6  
\N LIHUE  
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
MJJ 2018 A60 76.0 0.5 A40 4.9 5.4 5.9  
JJA 2018 A55 77.7 0.4 A40 4.4 5.3 6.9  
JAS 2018 A55 79.0 0.3 A40 5.3 6.1 7.8  
ASO 2018 A50 79.4 0.3 A40 6.2 7.9 8.4  
SON 2018 A45 79.1 0.3 EC 9.2 10.0 11.2  
OND 2018 A40 77.8 0.3 EC 9.2 11.7 15.6  
NDJ 2018 EC 75.7 0.3 EC 8.6 12.1 16.9  
DJF 2019 EC 73.6 0.4 EC 7.5 8.4 14.0  
JFM 2019 EC 72.2 0.4 EC 6.5 8.8 13.8  
FMA 2019 EC 72.1 0.5 EC 5.8 8.4 9.9  
MAM 2019 EC 72.8 0.5 EC 5.3 6.6 8.0  
AMJ 2019 EC 74.2 0.5 EC 4.7 5.5 6.0  
MJJ 2019 EC 76.0 0.5 EC 4.9 5.4 5.9  
\NFORECASTER: LUKE HE  
 
ANOMALIES BASED ON 1981-2010 MEANS  
CLARIFICATION: EC INDICATES EQUAL CHANCES THAT THE CLIMATE WILL FALL INTO ANY  
ONE OF THE THREE RANGES OR CATEGORIES WHOSE BOUNDARIES ARE SPECIFIED IN THE  
TABLES ABOVE. A FORECAST SPECIFICATION OF EC MEANS THERE IS NO PARTICULAR TILT  
OF THE ODDS TOWARD ABOVE-NORMAL OR BELOW-NORMAL CONDITIONS IN THE OUTLOOK. FOR  
EXAMPLE A40 MEANS A 40% CHANCE THAT TEMPERATURE OR PRECIPITATION WILL BE IN THE  
ABOVE CLASS, B40 MEANS A 40% PROBABILITY THAT TEMPERATURE OR PRECIPITATION WILL  
BE IN THE BELOW CLASS, AND N35 MEANS A 35% PROBABILITY THAT TEMPERATURE OR  
PRECIPITATION WILL BE IN THE NEAR-NORMAL CLASS. WHEN EC IS SPECIFIED, ALL  
CATEGORIES ARE EQUALLY LIKELY.  
NOTE - THESE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR VALID  
PERIODS. WITHIN ANY VALID PERIOD OBSERVATIONS AND SHORTER RANGE FORECASTS  
SHOULD BE CONSULTED. ALSO - THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE  
ISSUANCE OF THE NEW SET NEXT MONTH ON THU MAY 17, 2018.  
 

 
 
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