By PETER SUR By PETER SUR ADVERTISING Tribune-Herald staff writer Hawaii’s Doppler radars will be shut down, one at a time, beginning in May for upgrades to a next-generation system that will allow for better weather forecasts. This week, the
By PETER SUR
Tribune-Herald staff writer
Hawaii’s Doppler radars will be shut down, one at a time, beginning in May for upgrades to a next-generation system that will allow for better weather forecasts.
This week, the National Weather Service announced plans to close the first of its four Doppler 88D radar systems beginning May 14.
The Kauai radar will be the first to be upgraded. Next to go will be the Kohala radar, around May 28. Each of the closures will take about two weeks.
Upgrades to the radar systems on Molokai and at South Point will be done in early 2013, forecasters said, as part of a nationwide drive to convert all radars to the new standard.
The radars are being converted to use what’s called dual-polarization technology. Basically, current Doppler radar systems transmit and receive pulses in a horizontal orientation, providing a snapshot of the current weather conditions.
Dual-polarization systems, or Dual-Pol radar for short, also transmit and receive pulses in a vertical orientation, helping forecasters get a more accurate picture of weather events. The new technology adds new information about the size and shape of an object, allowing forecasters to distinguish rain from hail, snow and ice pellets.
“It’s going to give us more information for the meteorologists to differentiate what’s going on inside the clouds,” said Derek Wroe, lead forecaster for the NWS Honolulu forecast office.
The addition of a vertical component is helpful in determining, for example, the elevation at which snow turns into sleet or rain. Today, forecasters can only make an educated guess as to where the snow line is on Mauna Kea and Mauna Loa. Dual-Pol radar will allow forecasters to give better snowfall estimates.
The new radars will help generate more accurate forecasts of flash floods and other hazardous weather events, Wroe said. The images won’t look much different from how they appear on the evening newscast, but forecasters will be able to distinguish precipitation from other sources of interference.
“We’ll be making more informed decisions,” Wroe said.
But during the upgrades, “we’ll be without radar” for a while.
“We have other ways of doing readings out there,” he said. “We do have other sources of information.”
Each upgrade costs about $225,000 for parts and labor, the National Weather Service said. The entire program, comprising more than 160 Doppler radar systems, will cost about $50 million.
Email Peter Sur at psur@hawaiitribune-herald.com.
