678
FXHW40 KWBC 211331
PMDHCO
Prognostic Discussion for Long-Lead Hawaiian Outlooks
NWS Climate Prediction Center College Park MD
830AM EST Thu Nov 21 2024

MONTHLY FORECAST DISCUSSION VALID DECEMBER 2024

Sea-surface temperatures (SSTs) surrounding the Hawaiian islands have been
slightly above average during the past few weeks.



From January through October 2024, rainfall total accumulations were:



Lihue Airport 24.79 inches  (90 percent of average)



Honolulu Airport 10.28 inches  (86 percent of average)



Kahului Airport 11.26 inches  (97 percent of average)



Hilo Airport 83.14 inches  (89 percent of average)



Most climate models of the North American Multi-Model Ensemble (NMME) and the
International Multi-Model Ensemble (IMME or C3S) favor near normal SSTs around
the Hawaiian Islands in December 2024. A few solutions lean towards above
normal SSTs, especially for Kauai, while only the NCEP Climate Forecast System
(CFSv2) favors below normal SSTs for this period. Based primarily on these SST
predictions, Equal Chances (EC) of below, near, and above normal temperatures
are favored for the Big Island, Maui, and Oahu in December, and a slight tilt
towards above normal temperatures is favored for Kauai. For the December 2024
precipitation outlook, the C3S generally favors near normal precipitation with
two constituent models leaning towards relatively wet conditions (Meteo-France
and ECMWF), two models supporting relatively dry conditions (DWD and CMCC), and
two favoring mixed conditions (CFSv2 and UKMO). The NMME inputs depicted mixed
results at best. Therefore, EC appears to be the best bet for the December 2024
precipitation outlook. These weak temperature and precipitation signals are to
be expected given the weak ENSO forcing currently ongoing in the Pacific (see
below).

           TEMPERATURE           PRECIPITATION
          FCST   AVE    LIM  FCST  BLW  MEDIAN  ABV
Hilo        EC   72.5   0.4   EC   6.8   10.2   13.6
Kahului     EC   73.5   0.5   EC   1.9   2.7   3.4
Honolulu    EC   74.9   0.6   EC   0.8   1.3   3.8
Lihue      A40   73.3   0.5   EC   1.8   3.2   5.5

SEASONAL FORECAST DISCUSSION VALID DJF 2024 - DJF 2025

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. ENSO-neutral conditions continue
to be observed over the Pacific Ocean. Equatorial sea surface temperatures are
near-to-below-average in the central and eastern Pacific Ocean. Negative
subsurface temperature anomalies remain at depth in the central and eastern
Pacific, with positive subsurface temperature anomalies continuing over the
western Pacific. A relatively small area of low-level easterly wind anomalies
was observed in the east-central equatorial Pacific Ocean, while upper-level
wind anomalies were near average. Suppressed convection was observed over the
vicinity of the Date Line and equator, while near to slightly enhanced
convection was noted across eastern Indonesia. Collectively, the coupled
ocean-atmosphere system reflected ENSO-neutral. La Nia is most likely to
emerge in October-November-December (OND 2024) with a 57% chance, and is
expected to persist through January-February-March (JFM) 2025.



Enhanced probabilities favoring above normal temperatures are indicated for the
Hawaiian islands (Kauai, Oahu, Maui, and the Big Island) in DJF
(December-January-February) 2024-25, consistent with practically all C3S
dynamical model forecasts, a majority of the NMME dynamical model forecasts,
and (for the Big Island and Maui) the statistical ENSO-OCN tool. Probabilities
favoring above normal temperatures are expected to increase from southeast to
northwest across the island chain. Above normal temperatures are favored by
practically all NMME and C3S model inputs during January-February-March (JFM)
and February-March-April (FMA) 2025, though the ENSO-OCN favors near normal
temperatures. Nearly all models that constitute the NMME favor relatively warm
temperatures across the archipelago during March-April-May (MAM) and
April-May-June (AMJ) 2025. Beyond AMJ 2025, the forecast signal weakens at
longer leads, in large part due to the lack of clear forcing from ENSO and the
climatological Spring Barrier. Therefore, EC is indicated for Hawaii beginning
in May-June-July (MJJ) and extending through longer leads.



For DJF 2024-25 precipitation, most NMME and C3S dynamical model forecasts
depict above normal precipitation across Hawaii, with Meteo-France the main
outlier favoring relatively dry conditions. The statistical consolidation tool
(Stat-CON) and its constituents (Canonical Correlation Analysis (CCA), Optimal
Climate Normals (OCN), Constructed Analog (CA) and ENSO-OCN) provide
conflicting indications amid very weak precipitation signals from DJF through
the winter months and into spring 2025. In JFM 2025, above normal precipitation
continues to be favored by most NMME solutions, though the GFDL Spear forecasts
mixed conditions over the islands. The IMME/C3S solutions also mostly favor
relatively wet conditions, though once again the exception is the Meteo-France
model which leans dry. For FMA, the C3S inputs Meteo-France and CMCC (Canadian)
favor a mixed precipitation signal for Hawaii, with the majority of models
favoring above normal precipitation. For the NMME, nearly all models predict
above normal precipitation, except for the relatively dry GFDL-Spear solution.
Most of the NMME suite of models continue to favor the theme of anomalous
wetness through MAM 2025, though by AMJ the uncertainty increases
significantly, favoring EC for the archipelago. The lack of strong forcing from
ENSO warrants EC for the remaining precipitation leads.

                      Hilo
          TEMPERATURE           PRECIPITATION
         FCST   AVE   LIM  FCST   BLW  MEDIAN   ABV
DJF 2025  A40  72.8   0.4   A40   19.6   30.2   33.3
JFM 2025  A50  71.8   0.4   A50   22.0   32.0   44.5
FMA 2025  A50  71.7   0.4   A50   24.6   34.1   45.5
MAM 2025  A50  72.0   0.5   A40   22.5   28.4   34.0
AMJ 2025  A40  72.9   0.5    EC   21.4   23.7   29.0
MJJ 2025   EC  74.0   0.4    EC   20.2   27.5   29.1
JJA 2025   EC  75.2   0.4    EC   19.4   27.2   31.4
JAS 2025   EC  76.1   0.4    EC   25.2   28.6   33.4
ASO 2025   EC  76.4   0.4    EC   26.1   28.8   33.3
SON 2025   EC  76.2   0.4    EC   24.3   30.2   40.8
OND 2025   EC  75.5   0.4    EC   28.3   34.5   42.0
NDJ 2025   EC  74.2   0.4    EC   26.4   36.6   43.0
DJF 2026   EC  72.8   0.4    EC   19.6   30.2   33.3
                      Kahului
          TEMPERATURE           PRECIPITATION
         FCST   AVE   LIM  FCST   BLW  MEDIAN   ABV
DJF 2025  A50  73.8   0.4   A45   4.6    6.9    8.7
JFM 2025  A55  72.5   0.4   A55   4.2    6.2    8.2
FMA 2025  A60  72.3   0.4   A55   3.2    4.1    6.4
MAM 2025  A55  73.0   0.4   A45   2.5    3.5    4.6
AMJ 2025  A45  74.3   0.5    EC   1.2    1.6    2.2
MJJ 2025   EC  76.0   0.5    EC   0.7    1.1    1.8
JJA 2025   EC  77.7   0.4    EC   0.7    1.1    1.5
JAS 2025   EC  79.0   0.4    EC   0.8    1.1    1.6
ASO 2025   EC  79.4   0.4    EC   0.8    1.6    2.5
SON 2025   EC  79.1   0.4    EC   2.1    3.3    4.8
OND 2025   EC  77.8   0.4    EC   4.2    5.3    8.1
NDJ 2025   EC  75.9   0.4    EC   5.2    7.6    9.5
DJF 2026   EC  73.8   0.4    EC   4.6    6.9    8.7
                      Honolulu
          TEMPERATURE           PRECIPITATION
         FCST   AVE   LIM  FCST   BLW  MEDIAN   ABV
DJF 2025  A60  75.3   0.5   A50   3.7    5.6    8.6
JFM 2025  A60  73.9   0.4   A55   2.1    4.6    7.8
FMA 2025  A60  73.8   0.4   A55   1.9    3.2    4.7
MAM 2025  A55  74.8   0.4   A45   1.8    2.6    3.0
AMJ 2025  A45  76.3   0.4    EC   1.2    1.6    1.8
MJJ 2025   EC  78.2   0.4    EC   0.8    1.4    1.6
JJA 2025   EC  79.9   0.4    EC   0.7    0.8    1.3
JAS 2025   EC  81.3   0.4    EC   1.0    1.4    1.7
ASO 2025   EC  81.7   0.4    EC   1.6    2.4    3.1
SON 2025   EC  81.4   0.4    EC   2.5    4.0    5.6
OND 2025   EC  80.0   0.4    EC   4.4    6.4    8.5
NDJ 2025   EC  77.7   0.5    EC   3.9    5.6    8.8
DJF 2026   EC  75.3   0.5    EC   3.7    5.6    8.6
                      Lihue
          TEMPERATURE           PRECIPITATION
         FCST   AVE   LIM  FCST   BLW  MEDIAN   ABV
DJF 2025  A60  73.6   0.4   A50   7.5    8.4    14.0
JFM 2025  A60  72.2   0.4   A60   6.5    8.8    13.8
FMA 2025  A60  72.1   0.5   A60   5.8    8.4    9.9
MAM 2025  A60  72.8   0.5   A50   5.3    6.6    8.0
AMJ 2025  A50  74.2   0.5    EC   4.7    5.5    6.0
MJJ 2025   EC  76.0   0.5    EC   4.9    5.4    5.9
JJA 2025   EC  77.7   0.4    EC   4.4    5.3    6.9
JAS 2025   EC  79.0   0.3    EC   5.3    6.1    7.8
ASO 2025   EC  79.4   0.3    EC   6.2    7.9    8.4
SON 2025   EC  79.1   0.3    EC   9.2    10.0   11.2
OND 2025   EC  77.8   0.3    EC   9.2    11.7   15.6
NDJ 2025   EC  75.7   0.3    EC   8.6    12.1   16.9
DJF 2026   EC  73.6   0.4    EC   7.5    8.4    14.0
FORECASTER: Anthony Artusa

Anomalies are based on the 1991-2020 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 Dec 19, 2024.

$$