Here we are in the peak of summer, trade winds present almost daily as one would expect for this time of the year. It seems boring and uneventful. However, the interaction of the trade winds with our complex island terrain can create widely varying local weather conditions around the state. This is especially true for the Big Island, where its large size produces very interesting local circulations and patterns that are sensitive to even small changes in the large scale weather conditions.
In the South Kohala District of the Big Island (see map below), the persistent summer trade wind pattern is generally dry. But variations in the strength of the large scale trade winds can produce significant day-to-day variability in the winds, cloud cover, and temperature due to how the daily sea breeze sets up.
Map of the districts in the northern portion of the Big Island. The South Kohala District is between Mauna Kea and the Kohala Mountains, and includes Waimea and Waikoloa Village as its main communities.
On July 29, the remnant circulation of Hurricane Fausto passed north of the state and cut off the ubiquitous trade wind flow. This allowed land and sea breezes to dominate local conditions for a couple of days across the main Hawaiian Islands. After Fausto’s remnant moved northwest of the island chain, trade winds filled in behind it, and reached strong levels on August 1. This sequence allowed for a nice comparison of how the sea breeze sets up over the South Kohala District during a large scale light wind pattern versus a strong trade wind pattern.
The two visible satellite loops below cover the period from 7 AM to 1 PM HST on July 29 and August 1. On July 29 (first loop), skies are mostly clear at 7 AM with a combined land breeze and downslope (katabatic) flow around the entire island. The only significant cloud feature is a plume cloud from what’s left from episode 52 of Kīlauea’s ongoing eruption. Sea breezes and upslope (anabatic) flow quickly initiates after sunrise, producing clouds along all of the slopes. The end of the loop shows the “tail” of Fausto nearing the east tip of the Big Island (Cape Kumukahi), marking the leading edge of the trade winds filling in behind the tropical cyclone remnant.
In the August 1 loop, clouds are present along the windward slopes from the initial frames as the strong trades jam up against the island. The South Kohala District and the leeward side of the North Kohala District start off with scattered clouds but become increasingly cloud free through the middle of the day.
NOAA/NESDIS visible image loop centered on the Big Island. The loop covers the period from 7:00 AM to 1:00 PM HST, July 29, 2026.
Same as previous, but for August 1, 2026.
What’s going on at the surface? The following plots are from the National Weather Service’s (NWS) Weather and Hazards Data Viewer and they show surface observations in the South Kohala District and the surrounding areas. My main focus is on the winds, and each weather station observation includes a “wind barb” and a peak wind value in red. The long shaft on the wind barb shows the direction the wind is blowing towards. Each full barb on the shaft is a 10 knot (nautical miles per hour) increment. A half barb is 5 knots. Unfortunately, it appears the viewer is inconsistent with units (cardinal sin!) and the peak gusts in red are in statute miles per hour (MPH) instead of knots! Air temperature values (degrees F) are plotted in black. I wasn’t trying to point out anything about the temperatures. I just forgot to turn off the values when I captured the data. For each data plot, I’ve annotated the wind direction with red arrows. Where appropriate, solid red lines mark the approximate location of the sea breeze/upslope flow convergence zones.
Starting at 7 AM HST on July 29, the day with light winds around the Big Island, the surface observations show most of the winds either calm or blowing towards a downslope direction. The corresponding satellite image from that time shows clear skies over the South Kohala District.
Plot of observations in the South Kohala District and surrounding areas at 7 AM HST, July 29, 2026 from the observations archive on the National Weather Service Weather and Hazard Data Viewer. The red arrows were added to highlight the direction of the near surface wind flow. Where appropriate, a solid red line shows the approximate location of the sea breeze/upslope flow convergence zones.
NOAA/NESDIS visible image from 7:00 AM HST, July 29, 2026 centered on the Big Island. The red box shows the approximate region in the surface observations plot.
At 8 AM, the sea breeze and upslope flow have already commenced at Kawaihae and to the south at Puako. The flow front has made it halfway up the Kawaihae Road, but hasn’t quite reached Waikoloa Village. The corresponding satellite image shows that the upslope flow hasn’t developed enough to form clouds.
Same as the above surface observation plot, but for 8 AM HST.
Same as the above satellite image, but for 8 AM HST.
By 10 AM, the wind data indicate that the southern end of the sea breeze front has pushed above Waikoloa Village and the Māmalahoa Highway near the junction with the Daniel K. Inouye Highway. The northern end made it above the Kohala Mountain Road, but stalled before reaching Waimea town. The 10 AM satellite image shows clouds developing near and upslope from the Māmalahoa Highway, and over the Kohala Mountain Road.
Same as the above surface observation plot, but for 10 AM HST.
Same as the above satellite image, but for 10 AM HST.
Conditions were quite a bit different in the South Kohala District on August 1 on a day with strong trade winds hitting the Big Island. At 7 AM, winds are downslope, but very gusty down through the Waimea Saddle between Mauna Kea and the Kohala Mountains, and down the Kawaihae Road to Kawaihae Harbor. Even at Waikoloa Village and the old Saddle Road Junction, winds are a bit gusty and reflected a direction more from trades forced across the Waimea Saddle than a pure downslope direction as on July 29. The satellite image shows clouds jammed up along the windward slopes and a nearly stationary line peeling off the north flank of Mauna Kea on the south side of the Waimea Saddle.
Same as the above surface observation plot, but for 7 AM HST, August 1.
Same as the above satellite image, but for 7 AM HST, August 1.
Unlike July 29, the surface observations for 10 AM on August 1 show no hint of a sea breeze from Kawaihae to Waikoloa Village. Instead, all you can see are surging gusty trade winds through the Waimea Saddle with a few peak wind values over 40 MPH. These winds converged with a modified upslope flow south of Waikoloa Village and near the Waikoloa Road-Māmalahoa Highway junction. The satellite image shows a narrow northwest-southeast cloud line likely from the surface wind convergence.
Same as the above surface observation plot, but for 10 AM HST.
Same as the above satellite image, but for 10 AM HST.
At 1 PM, the west end of the convergence zone is a bit farther south down the Queen Kaʻahumanu Highway but appears to be in the same general area over the Māmalahoa Highway. The winds are also still very gusty throughout most of the South Kohala District north of the convergence zone. The satellite image shows clouds from the convergence zone a bit farther south than the 10 AM image. Cloud cover over the district overall appears to be lower.
Same as the above surface observation plot, but for 1 PM HST.
Same as the above satellite image, but for 1 PM HST.
The observation plots focus on near-surface conditions and you can’t tell how deep the upslope flow is based on the available data. However, a field observation project conducted in 1978 found sea breeze depth using tethered balloons to be often over 1,000 feet deep and almost reached 5,000 feet on one occasion (Schroeder, 1981).
So why care? Other than being really interesting to a weather enthusiast, most people may not really care what the South Kohala sea breeze does on a day-to-day basis. My guess, though, is that any agency tasked with fighting brush fires in the district pays close attention to what’s going on with the local circulations. Large portions of the South Kohala District contain grasslands that usually become quite dry during the summer months. Following the above normal wet season rainfall this year, grasses were quite abundant but have become rather dry since then. In July, a brush fire ignited and threatened the Waikoloa Village community, with evacuations ordered by the county. Local wind conditions play a huge role in determining fire behavior, and understanding what the sea breeze is doing can help firefighters determine tactical plans to attack the fire effectively. The NWS helps with these efforts by providing tailored weather forecasts to fire fighting agencies, and in some cases deploy on-site Incident Meteorologists (IMETs) for specialized support. Effective support means understanding highly localized circulations like the South Kohala sea breeze.
Reference
Schroeder, T. A., 1981: Characteristics of local winds in northwest Hawaiʻi. J. Appl. Meteor., 20, 874-881.