Hilo
Tonight: Cloudy. Isolated showers early in the evening, then scattered showers in the late evening and overnight. Lows 56 to 66 near the shore to 46 to 53 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.
Sunday: Cloudy with scattered showers. Highs around 77 near the shore to 62 to 67 at 4000 feet. Northwest winds up to 10 mph shifting to the northeast around 10 mph in the afternoon. Chance of rain 50 percent.
Sunday Night: Mostly cloudy with scattered showers. Lows 57 to 67 near the shore to 48 to 54 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.
Kona
Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 68 near the shore to 46 to 51 near 5000 feet. Northwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.
Sunday: Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 79 to 84 near the shore to around 65 near 5000 feet. Light winds. Chance of rain 30 percent.
Sunday Night: Mostly cloudy with isolated showers. Lows around 69 near the shore to 46 to 52 near 5000 feet. Light winds. Chance of rain 20 percent.
Waimea
Tonight: Mostly cloudy with isolated showers. Lows 57 to 67 near the shore to 49 to 57 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.
Sunday: Partly sunny with isolated showers. Highs around 76 near the shore to 66 to 73 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.
Sunday Night: Mostly cloudy with isolated showers. Lows 58 to 68 near the shore to 51 to 59 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.
Kohala
Tonight: Mostly cloudy with isolated showers. Lows 57 to 67 near the shore to 49 to 57 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.
Sunday: Partly sunny with isolated showers. Highs around 76 near the shore to 66 to 73 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.
Sunday Night: Mostly cloudy with isolated showers. Lows 58 to 68 near the shore to 51 to 59 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.
South Big Island
Tonight: Partly cloudy. Lows around 70 near the shore to around 51 near 5000 feet. East winds up to 15 mph.
Sunday: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81 near the shore to around 64 near 5000 feet. East winds up to 20 mph. Chance of rain 30 percent.
Sunday Night: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Lows around 71 near the shore to around 52 near 5000 feet. East winds up to 20 mph.
Puna
Tonight: Cloudy. Isolated showers early in the evening, then scattered showers in the late evening and overnight. Lows 56 to 66 near the shore to 46 to 53 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.
Sunday: Cloudy with scattered showers. Highs around 77 near the shore to 62 to 67 at 4000 feet. Northwest winds up to 10 mph shifting to the northeast around 10 mph in the afternoon. Chance of rain 50 percent.
Sunday Night: Mostly cloudy with scattered showers. Lows 57 to 67 near the shore to 48 to 54 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.
Waikoloa
Tonight: Partly cloudy. Lows around 68 near the shore to 47 to 52 above 4000 feet. Northeast winds up to 15 mph shifting to the southeast after midnight.
Sunday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 79 to 84 near the shore to 62 to 69 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 30 percent.
Sunday Night: Partly cloudy in the evening then becoming mostly cloudy. Lows around 69 near the shore to 48 to 53 above 4000 feet. North winds up to 10 mph in the evening becoming light.
Synopsis
Mostly dry and pleasant trade wind weather will continue into Monday, with brief passing showers favoring windward and mauka areas. A significant pattern change is then expected by Tuesday into midweek as an upper disturbance and surface low pressure evolve northwest of the islands. This setup is expected to draw deep tropical moisture northward over the state, leading to an extended period of southerly winds, increasing chances for widespread rainfall, and renewed flooding concerns from Tuesday through next weekend. Given recent flood events and soils that remain only partially recovered, the potential for runoff and flash flooding impacts may increase rapidly.
Discussion
A relatively benign trade wind pattern remains in place across the Hawaiian Islands this evening and is expected to persist into Monday. Moderate easterly trades will continue to focus mainly light showers along windward and mauka slopes, while leeward areas remain dry.
Global guidance remains in good agreement and depicts a notable amplification of the large-scale pattern across the central Pacific by Monday. A series of shortwave troughs digging southeastward toward the state will translate to large-scale upper height falls a cross the region. The surface ridge to the north will gradually erode as an attendant broad surface trough evolves to the west. This will disrupt the typical trade wind flow by Monday night and allow low-level winds to gradually veer out of the southeast to south Tuesday through Wednesday.
This transition to southerly flow will draw deep tropical moisture northward into the islands beginning Tuesday and especially by Wednesday. Precipitable water values are forecast to climb toward 2 inches or higher, signaling a marked increase in moisture. This increasing moisture combined with daytime heating, sea breezes, and a potent shortwave trough moving through may even trigger some heavy showers over interior areas on Tuesday.
Confidence is increasing that the second half of the week may present the highest potential for widespread rainfall and flooding impacts across the state. During this time, upper-level forcing is expected to strengthen as a strong shortwave rounds the base of the trough, potentially enhancing lift over the region while low pressure organizes west of the islands. The combination of deep moisture, increasing large-scale forcing for ascent, and gusty southerly winds favors a transition toward a more widespread and organized rainfall event. In addition to the rainfall concerns during this period, some strong to severe thunderstorms along with gusty downsloping winds for north and windward sides of the islands can’t be ruled out, especially by Thursday and into Friday.
Although forecast confidence begins to lower by next weekend due to model differences, the general large-scale pattern could linger. This scenario suggests the potential for rain may persist through next weekend and beyond for at least parts of the state or where the deep moisture axis anchors.
Regardless of the precise evolution, antecedent conditions remain a significant concern. The islands have experienced significant flash flood events in recent weeks, and despite several days of drier trade wind weather, soils remain vulnerable in many areas. As a result, any period of heavy rainfall next week may quickly lead to enhanced runoff, renewed rises in streams and reservoirs, and localized flash flooding concerns.
This system will continue to be monitored closely over the coming days, as additional adjustments to timing, duration, and impact messaging are likely as this change in the pattern evolves.
Aviation
Moderate trade winds will slowly weaken over the next 24 hours. Isolated light showers will continue to be carried in to the windward slopes, with brief MVFR conditions are possible. Otherwise, VFR conditions are expected to prevail.
No AIRMETs are in effect and none are expected overnight.
Marine
Moderate to locally fresh trades will persist during the next couple days as high pressure north of the islands moves slowly eastward. Winds will ease and shift southeasterly Monday night through Wednesday as a front stalls out and merges with a trough just west of the islands. The winds will turn more southerly and increase to moderate and strong levels on Thursday as a storm system develops along the trough west of the state.
A series of overlapping small northwest swells will keep some small surf in place along north facing shores through Monday. A new long-period northwest swell will fill in Monday night and Tuesday, giving a more noticeable boost to north shore surf late Tuesday through Wednesday, followed by a gradual decline Thursday into next weekend.
Overlapping southerly swells will keep some small surf in place along south facing shores through Monday. A new long duration, and slightly larger long-period south swell, will fill in Monday night. This swell will give a more noticeable boost to south shore surf Tuesday into next weekend. Strengthening southerly winds could lead to choppy conditions by late next week.
East shore surf will remain small and below climatological levels during the next 7 days due to a lack of strong trade winds over and upstream of the islands.
HFO Watches/Warnings/Advisories
None.
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Data Courtesy of NOAA.gov
‘ The preceding article may include information circulated by third parties ’
‘ Some details of this article were extracted from the following source bigislandnow.com ’
