East Hawaii saw a wet start to the work week, but rainfall totals in Hilo for the month and year remain well below the norm.
The rain gauge at Hilo International Airport measured 1.23 inches in the 13 hours between midnight and 1 p.m. Monday. That brought rainfall totals for the month to 5.8 inches and the yearly total to 15.26 inches, lagging behind the monthly norm of 7.41 inches and the year-to-date average of slightly more than 40 inches.
Tom Birchard, a National Weather Service forecaster in Honolulu, said Monday’s rain was the product of “the remnants of a front that extends well to the northeast of us.”
“There’s a low (pressure system) between us and California, and there’s a trailing cloud band associated with that low that came through the smaller islands (Sunday and Sunday night) and through the Big Island (Sunday night and Monday),” he said. “It’s expected to shift to the south of the Big Island (today).”
That low-pressure front left its largest mark on Hawaii Island’s windward-side rain gauges. Kawainui Stream, above Waipio Valley, received 3.78 inches in the 24-hour period ending at 2 p.m. Monday.
Other 24-hour totals during that period include 2.11 inches at Saddle Quarry, 1.94 inches at the Waimea upper gauge, 1.8 inches in Piihonua and at Waiakea Experimental Station, 1.31 inches in Waimea and 1.2 inches in Mountain View.
Most leeward sites saw little if any rain, but there were exceptions, with Kahua Ranch reporting 0.8 inches and lower Kahuku 0.57 inches. At the end of March, Kahua had received 9.89 inches, 47 percent of its normal year-to-date total of 21.17 inches, while lower Kahuku had received just 3.79 inches going into April, a scant 23 percent of its usual total of 16.67 inches.
“The severe drought that has been ongoing is mostly on the leeward side,” Birchard said. “And even though it’s been cloudy with some moisture, they’re not getting all that much rain.”
The parched conditions have contributed to a spate of brush fires, some thought to be maliciously set, on the leeward side. And although it’s wetter on the windward side, rainfall totals remain significantly short of normal, with Hilo registering about a third of its norm so far this year.
“Since the beginning of the year, we’re 25 inches below normal,” Birchard said. “And half of what we had last year, where it was fairly dry. Officially, the Climate Prediction Center is calling for a slightly above normal rainfall level for the summertime, but it’s only slightly above. And with El Nino weakening and possibly transitioning to La Nina, we’re not expecting the hurricane season to be nearly as active.”
Birchard said it’s unlikely windward residents will see average year-to-date rainfall totals catch up to the norm anytime soon.
“For moisture sources, trade wind flow is normally what we get during the summer months, so it doesn’t look like we’re going to have too many tropical (storm) systems in the area,” he said. “… So an educated guess is that you’re going to continue to run a (rainfall) deficit there in Hilo through the summer.”
Email John Burnett at jburnett@hawaiitribune-herald.com.
