018  
FXHW40 KWBC 151231  
PMDHCO  
PROGNOSTIC DISCUSSION FOR LONG-LEAD HAWAIIAN OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
830AM EDT THU APR 15 2021  
 
MONTHLY FORECAST DISCUSSION VALID MAY 2021  
 
SEA SURFACE TEMPERATURE (SST) ANOMALIES FROM ZERO DEGREE TO NEGATIVE ONE-HALF  
DEGREE CELSIUS WERE OBSERVED OVER NORTHWESTERN ISLANDS (KAUAI AND OAHU), WHILE  
NEGATIVE ONE-HALF DEGREE TO NEGATIVE ONE DEGREE CELSIUS SST ANOMALIES WERE OVER  
SOUTHEASTERN ISLANDS (MAUI AND BIG ISLAND) DURING THE PREVIOUS WEEK.  
 
FOR JANUARY THROUGH MARCH 2021, RAINFALL TOTAL ACCUMULATIONS WERE:  
 
- LIHUE AIRPORT 17.67 INCHES (153 PERCENT OF NORMAL)  
 
- HONOLULU AIRPORT 8.98 INCHES (142 PERCENT OF NORMAL)  
 
- KAHULUI AIRPORT 14.06 INCHES (195 PERCENT OF NORMAL)  
 
- HILO AIRPORT 55.59 INCHES (172 PERCENT OF NORMAL)  
 
THE NCEP CLIMATE FORECAST SYSTEM (CFS) AND OTHER CLIMATE MODELS OF THE NORTH  
AMERICAN MULTI-MODEL ENSEMBLE (NMME) PREDICT ABOVE NORMAL MONTHLY MEAN AIR  
TEMPERATURES FOR KAHULUI, HONOLULU AND LIHUE IN MAY 2021. EQUAL CHANCES (EC)  
FOR ABOVE, NEAR, OR BELOW NORMAL PRECIPITATION ARE INDICATED BY MOST DYNAMICAL  
AND STATISTICAL MODELS FOR THE HAWAIIAN ISLANDS DURING MAY 2021.  
 
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
HILO EC 74.0 0.5 EC 4.1 7.4 8.7  
KAHULUI A50 75.8 0.6 EC 0.2 0.5 0.8  
HONOLULU A60 78.0 0.6 EC 0.2 0.4 0.8  
LIHUE A60 75.8 0.6 EC 1.3 1.5 2.3  
 
SEASONAL FORECAST DISCUSSION VALID MJJ 2021 - MJJ 2022  
 
REFER TO THE PROGNOSTIC DISCUSSION OF THE LONG-LEAD SEASONAL OUTLOOKS FOR THE  
CONUS AND ALASKA FOR A DESCRIPTION OF THE ENSO OUTLOOK AND OTHER CLIMATE  
CONDITIONS RELEVANT TO THE SEASONAL OUTLOOK. LA NINA CONDITIONS ARE PRESENT  
ACROSS THE PACIFIC OCEAN, WITH BELOW AVERAGE SEA SURFACE TEMPERATURES (SSTS)  
FROM THE WEST-CENTRAL TO EASTERN EQUATORIAL PACIFIC OCEAN. NEGATIVE SUBSURFACE  
TEMPERATURE ANOMALIES HAVE WEAKENED AND NOW ONLY REMAIN IN A LAYER CLOSE TO THE  
SURFACE, WHILE A LARGE AREA OF POSITIVE SUBSURFACE TEMPERATURE ANOMALIES IN THE  
WESTERN PACIFIC HAS SHIFT EASTWARD TO AROUND 110W. TROPICAL CONVECTION IS  
SUPPRESSED OVER THE WESTERN AND CENTRAL PACIFIC. LOW-LEVEL EASTERLY WIND  
ANOMALIES WERE OBSERVED ACROSS THE EQUATORIAL PACIFIC, WHILE UPPER-LEVEL  
WESTERLY WIND ANOMALIES WERE OBSERVED OVER MOST OF THE TROPICAL PACIFIC. A  
TRANSITION FROM LA NINA TO ENSO-NEUTRAL IS LIKELY IN THE NEXT MONTH OR SO, WITH  
AN 80 PERCENT CHANCE OF ENSO-NEUTRAL DURING MAY-JULY 2021.  
 
ENHANCED PROBABILITIES FOR BELOW NORMAL TEMPERATURES ARE INDICATED OVER HILO  
FROM JJA 2021 TO ASO 2021, WHILE ABOVE NORMAL TEMPERATURES ARE FORECAST OVER  
HONOLULU FROM MJJ TO JJA 2021, AND OVER LIHUE FROM MJJ 2021 TO ASO 2021,  
SUPPORTED BY MOST DYNAMICAL AND STATISTICAL FORECAST TOOLS.  
 
ENHANCED PROBABILITIES FOR BELOW NORMAL PRECIPITATION ARE LIKELY OVER THE  
 
HAWAIIAN ISLANDS FROM SUMMER(JJA) 2021 TO OND 2021, CONSISTENT WITH MOST  
DYNAMICAL MODELS. DUE TO CONSIDERABLE UNCERTAINTY IN THE PRECIPITATION  
FORECASTS FROM DYNAMICAL AND STATISTICAL MODELS OVER THE HAWAIIAN ISLANDS IN  
NDJ 2021 AND LONGER LEADS, EQUAL CHANCES (EC) FOR ABOVE, NEAR OR BELOW NORMAL  
PRECIPITATION ARE INDICATED.  
 
HILO  
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
MJJ 2021 EC 74.0 0.4 EC 20.2 27.5 29.1  
JJA 2021 B40 75.2 0.4 B40 19.4 27.2 31.4  
JAS 2021 B40 76.1 0.4 B50 25.2 28.6 33.4  
ASO 2021 B40 76.4 0.4 B60 26.1 28.8 33.3  
SON 2021 EC 76.2 0.4 B50 24.3 30.2 40.8  
OND 2021 EC 75.5 0.4 B40 28.3 34.5 42.0  
NDJ 2021 EC 74.2 0.4 EC 26.4 36.6 43.0  
DJF 2022 EC 72.8 0.4 EC 19.6 30.2 33.3  
JFM 2022 EC 71.8 0.4 EC 22.0 32.0 44.5  
FMA 2022 EC 71.7 0.4 EC 24.6 34.1 45.5  
MAM 2022 EC 72.0 0.5 EC 22.5 28.4 34.0  
AMJ 2022 EC 72.9 0.5 EC 21.4 23.7 29.0  
MJJ 2022 EC 74.0 0.4 EC 20.2 27.5 29.1  
KAHULUI  
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
MJJ 2021 EC 76.0 0.5 EC 0.7 1.1 1.8  
JJA 2021 EC 77.7 0.4 B40 0.7 1.1 1.5  
JAS 2021 EC 79.0 0.4 B50 0.8 1.1 1.6  
ASO 2021 EC 79.4 0.4 B60 0.8 1.6 2.5  
SON 2021 EC 79.1 0.4 B50 2.1 3.3 4.8  
OND 2021 EC 77.8 0.4 B40 4.2 5.3 8.1  
NDJ 2021 EC 75.9 0.4 EC 5.2 7.6 9.5  
DJF 2022 EC 73.8 0.4 EC 4.6 6.9 8.7  
JFM 2022 EC 72.5 0.4 EC 4.2 6.2 8.2  
FMA 2022 EC 72.3 0.4 EC 3.2 4.1 6.4  
MAM 2022 EC 73.0 0.4 EC 2.5 3.5 4.6  
AMJ 2022 EC 74.3 0.5 EC 1.2 1.6 2.2  
MJJ 2022 EC 76.0 0.5 EC 0.7 1.1 1.8  
HONOLULU  
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
MJJ 2021 A40 78.2 0.4 EC 0.8 1.4 1.6  
JJA 2021 A40 79.9 0.4 B40 0.7 0.8 1.3  
JAS 2021 EC 81.3 0.4 B50 1.0 1.4 1.7  
ASO 2021 EC 81.7 0.4 B60 1.6 2.4 3.1  
SON 2021 EC 81.4 0.4 B50 2.5 4.0 5.6  
OND 2021 EC 80.0 0.4 B40 4.4 6.4 8.5  
NDJ 2021 EC 77.7 0.5 EC 3.9 5.6 8.8  
DJF 2022 EC 75.3 0.5 EC 3.7 5.6 8.6  
JFM 2022 EC 73.9 0.4 EC 2.1 4.6 7.8  
FMA 2022 EC 73.8 0.4 EC 1.9 3.2 4.7  
MAM 2022 EC 74.8 0.4 EC 1.8 2.6 3.0  
AMJ 2022 EC 76.3 0.4 EC 1.2 1.6 1.8  
MJJ 2022 EC 78.2 0.4 EC 0.8 1.4 1.6  
LIHUE  
TEMPERATURE PRECIPITATION  
FCST AVE LIM FCST BLW MEDIAN ABV  
MJJ 2021 A50 76.0 0.5 EC 4.9 5.4 5.9  
JJA 2021 A45 77.7 0.4 B40 4.4 5.3 6.9  
JAS 2021 A40 79.0 0.3 B50 5.3 6.1 7.8  
ASO 2021 A40 79.4 0.3 B60 6.2 7.9 8.4  
SON 2021 EC 79.1 0.3 B50 9.2 10.0 11.2  
OND 2021 EC 77.8 0.3 B40 9.2 11.7 15.6  
NDJ 2021 EC 75.7 0.3 EC 8.6 12.1 16.9  
DJF 2022 EC 73.6 0.4 EC 7.5 8.4 14.0  
JFM 2022 EC 72.2 0.4 EC 6.5 8.8 13.8  
FMA 2022 EC 72.1 0.5 EC 5.8 8.4 9.9  
MAM 2022 EC 72.8 0.5 EC 5.3 6.6 8.0  
AMJ 2022 EC 74.2 0.5 EC 4.7 5.5 6.0  
MJJ 2022 EC 76.0 0.5 EC 4.9 5.4 5.9  
FORECASTER: LUKE HE  
 
ANOMALIES ARE BASED ON THE 1981-2010 MEANS.  
 
CLARIFICATION: EC INDICATED EQUAL CHANCES THAT THE PREDICTED PARAMETER WILL  
FALL INTO ANY ONE OF THE THREE CATEGORIES, WHOSE BOUNDARIES ARE SPECIFIC IN THE  
TABLES ABOVE. A FORECAST SPECIFICATION OF EC MEANS THERE IS NO PARTICULATE TILT  
OF THE ODDS TOWARD ABOVE NORMAL OR BELOW NORMAL CONDITIONS IN THE OUTLOOK. FOR  
EXAMPLE A40 MEANS A 40% CHANCE THAT THE AVERAGE TEMPERATURE OR TOTAL  
PRECIPITATION WILL BE IN THE ABOVE NORMAL CLASS, B40 MEANS A 40% CHANCE THAT  
THE AVERAGE TEMPERATURE OR TOTAL PRECIPITATION WILL BE IN THE BELOW NORMAL  
CLASS, AND N35 MEANS A 35% PROBABILITY THAT THE AVERAGE TEMPERATURE OR TOTAL  
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 THE VALID  
PERIODS. WITHIN ANY VALID PERIOD, OBSERVATIONS AND SHORTER RANGE FORECASTS  
SHOULD BE CONSULTED. ALSO, THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE  
ISSUANCES OF THE NEW SET NET MONTH, ON THU MAY 20, 2021.  
 

 
 
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