textproduct: Honolulu

SYNOPSIS

Moderate trades deliver showers windward and mauka through the weekend. A few afternoon showers are possible as well, for south shores and leeward sections today and Thursday.

SHORT TERM UPDATE

Early morning soundings had a bit of a southerly component to the winds off the surface, which has veered low cloud motions toward the WNW. The various HREF/REFS CAMs and University of Hawaii high resolution guidance all have their various opinions on what will happen, but the general idea is higher than climo PoPs over the south shore and leeward Oahu this afternoon into the early evening, thanks to low level convergence from Maui County. Downwind convergence could carry afternoon showers to other islands too. Plenty of subsidence aloft will limit shower intensity, as the upper low about 550 miles NW of Kauai is not having any significant effect on our local stability. Current forecast grids seem to have this well in hand and no updates anticipated at this time.

The start of Kilauea volcano episode 51 occurred at about 830 am, and we are watching radar and in close coordination with USGS to determine what advisories or warnings may be needed. In the meantime, a Special Weather Statement was issued yesterday and remains out. Model guidance shows low level winds 10000 feet and below would likely push any ash cloud toward the WSW, while winds at 20000 feet and higher would carry any ash able to reach that height toward the NNE.

PREV DISCUSSION

Issued at 347 AM HST Wed Jul 15 2026 Little change for the next several days as moderate trades deliver showers windward and mauka into next week. Upper air pattern remains blocky with a closed upper low positioned northwest of Kauai and downstream ridging established over and east of the remainder of the state. As the upper low is drawn northward and absorbed into the westerlies, heights gradually rebound over the islands topping out around 591dm at 500mb by this weekend. Attendant subsidence will reinforce high stability during this time. Brief veering of flow through the lowest 10kft of the atmosphere as this adjustment occurs potentially sets the stage for showers to develop within the convergent leeward Molokai plume and extend over portions of Leeward Oahu this afternoon into this evening. High stability will limit potential for vertical shower development and should keep shower intensity in check, but some enhanced coverage of showers compared to normal will be possible.

AVIATION

Moderate trades expected through the forecast period. Expecting mainly scattered low clouds and showers. Brief MVFR conditions are possible in passing showers, but VFR should prevail across the state.

MARINE

Issued at 347 AM HST Wed Jul 15 2026 High pressure far north of the islands will maintain a trade wind pattern, however as the high has weakened and lifted away from the islands, trade winds are not quite as strong. Winds across the coastal waters remain below Small Craft Advisory levels. Winds could rebound Thursday into the weekend as the high sinks southward, tightening the pressure gradient over the islands and bringing Small Craft Advisory winds back to the typical windy waters.

A small bump in the otherwise fading medium-period southwest swell (around 2.5 ft with a 13 second period) should bring a slight increase in south surf today, particularly this morning. The southwest will return to a gradually decline by tonight and continue through the rest of the week. A series of overlapping small south and southwest swells will maintain small south shore surf, with a larger south swell expected early next week.

Surf along east-facing shores will be slightly below seasonal averages through Thursday with lighter trade winds. Surf may then climb back up somewhat as trades strengthen through the weekend.

A series of small, long to medium period west to west-northwest swells generated by former Super Typhoon Bavi will be possible throughout the rest of the week. Otherwise, no significant north or northwest swells are expected.

HFO WATCHES/WARNINGS/ADVISORIES

None.