* Iselle weakens to tropical storm from hurricane
* Some 2,000 people head to shelters; 23,000 without power
* Stronger Julio makes it way toward islands (Adds 23,000 people without power, governor's comments)
By Ken Wills
KAPAAU, Hawaii, Aug 8 (Reuters) - Tropical Storm Iselle pummeled the Hawaiian Islands with high winds and heavy rain on Friday, forcing hundreds to seek shelter and knocking out power to 23,000 people as residents kept a wary eye on an even more powerful storm headed their way.
Iselle weakened into a tropical storm before reaching Hawaii and officials said it was blunted to some extent by the state's mountainous Big Island, though high winds and heavy rain were still expected to lash smaller islands in the chain.
"The fact that the storm appears a bit benign at the moment is due to the fact that it hit the Big Island. This is not Kansas, this is not Florida," Governor Neil Abercrombie told a news conference.
"Mauna Kea and Mauna Loa are formidable topographical features, and the storm smacked into these great volcanic mountains and (that) helped to break it apart, but the wind and rain part of it are still moving," he said. "We are going to get hit with huge amounts of rain coming down and gusting winds that can put debris out there."
As Iselle passed over the Big Island with winds up to 50 miles per hour and pummeled eastern areas from Puna to Hilo with heavy rains, some 2,000 people hunkered down in evacuation shelters across the state.
Another 23,000 people were left without power on the Big Island and Maui, according to utility companies, and the National Weather Service issued flash flood warnings for the entire Big Island as well as the windward side of Oahu, where forecasters predicted heavy rain in windward areas. All ports were closed.
Abercrombie said that even as the eye of the storm moved south past the Big Island, a broader cone of wind and rain could still affect other islands, warning residents: "Do not be fooled by the fact that there may appear to be a lull right now."
There were no reports of major injuries from Iselle, but residents who believed the worst had passed were left still bracing for Hurricane Julio, tracking right in her wake.
'NOW THERE'S JULIO'
Julio, which was downgraded to a Category 2 storm on Friday, was barreling toward the islands at about 16 miles per hour, carrying maximum sustained winds of 105 miles per hour (169 kph), and expected to affect the islands as early as Sunday.
"It's raining hard here, but I guess I can expect that the worst of Iselle is over. Now there's Julio to worry about," said Pepeekeo resident Rae Miyashiro, who experienced power outages overnight but was otherwise unscathed.
Prediction models showed Julio weakening still further as it nears Hawaii, and officials said its latest model showed it would track about 150 miles (240 km) north of the archipelago early on Sunday.
"Julio will be passing over cooler waters compared to Iselle and is forecast to weaken to a tropical storm before nearing Hawaii waters," Dan Kottlowski of AccuWeather said. "Rainfall could still be locally heavy, especially in the higher terrain as a result of the tropical flow of moisture."
But even if the storm veers away from the Hawaiian Islands, forecasters said, it could still bring high winds and considerable amounts of rain.
In anticipation of the rare back-to-back storms, Hawaii residents have scrambled to stock up on supplies. Abercrombie signed an emergency proclamation freeing up funds and resources, and authorities advised residents to prepare seven-day disaster supply kits and cautioned them against driving except in an emergency.
Hawaii's schools and many stores and offices were closed on Friday, but authorities planned to keep airports open so planes could land in an emergency, although some airlines had canceled flights, officials said.
Power was out at the Olinda Water Treatment plant in a rural area of Maui, and officials told some 700 water customers to conserve water, County of Maui spokesman Rod Antone said. (Additional reporting by Malia Mattoch McManus in Honolulu and Dan Whitcomb in Los Angeles, Writing by Dan Whitcomb; Editing by Sandra Maler, Bill Trott and Bernard Orr)