An upper trough near the islands caused southwest to west winds to exceed 50 knots over the summits of Mauna Kea and Mauna Loa on the Big Island of Hawaii. There were no reports of significant injuries or property damage.
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The episode as NWS HFO wrote it up.
An upper trough near the islands caused southwest to west winds to exceed 50 knots over the summits of Mauna Kea and Mauna Loa on the Big Island of Hawaii. There were no reports of significant injuries or property damage.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Honolulu, HI wrote its last area forecast discussion before the first event at Apr 19, 9:20 PM HST, 3 hours 24 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 920 PM HST SUN APR 19 2009 .SYNOPSIS... A COLD FRONT CONTINUES TO APPROACH THE ISLANDS FROM THE NORTHWEST. CLOUDS AND SHOWERS FORMING AHEAD OF THE FRONT WILL MOVE OVER OAHU AND MOLOKAI TONIGHT...BEFORE STALLING AND WEAKENING ON MONDAY. MOISTURE ASSOCIATED WITH THE FRONT WILL KEEP SKIES CLOUDY...AND RAIN CHANCES ELEVATED...UNTIL THE MIDDLE OF THE WEEK. SHOWERS ALONG THE FRONT MAY BECOME HEAVY THROUGH TUESDAY...WITH THESE HEAVY SHOWERS FOCUSED OVER WINDWARD SLOPES. WINDS AHEAD OF THE FRONT WILL BE SOUTHWEST AND WEST...AND WILL SHIFT TO THE NORTH AND NORTHEAST AFTER THE FRONT PASSES. && .DISCUSSION... NO HUGE SURPRISES THIS EVENING. THE FIRST CLOUD BAND IS MOVING OVER OAHU...SPREADING RAIN ACROSS THE ISLAND. WINDS ATOP MAUNA KEA HAVE CONTINUED TO INCREASE...SO HAVE UPDATED THE GRIDS TO REFLECT THE HIGHER WINDS. HAVE UPGRADED THE ADVISORY TO A HIGH WIND WARNING. && .PREV DISCUSSION... ISSUED AT 330 PM REGIONAL SATELLITE IMAGERY REVEALS THREE NORTHEAST TO SOUTHWEST ORIENTED BANDS OF MOISTURE OVER THE WESTERN END OF THE ISLAND CHAIN THIS AFTERNOON. THE FIRST CLOUD BAND IS ABOUT 60 MILES WIDE...IS CURRENTLY IN THE KAUAI CHANNEL...AND BROUGHT A PERIOD OF HEAVY RAIN TO KAUAI THIS AFTERNOON. THIS BAND IS ANALYZED AS A PRE-FRONTAL CONVERGENCE BAND...HAVING DEVELOPED AHEAD /EAST AND SOUTHEAST/ OF AN APPROACHING COLD FRONT. THE SECOND BAND...WHOSE LEADING EDGE IS NOW ABOUT 100 MILES NORTHWEST OF KAUAI...IS ANALYZED AS A WEAKENING COLD FRONT...AND DOES NOT CONTAIN THE SAME INTENSITY RAINFALL AS THAT OBSERVED IN THE PRE-FRONTAL BAND. THE THIRD BAND IS ANALYZED AS A COLD FRONT...AS IT APPEARS TO MARK THE LEADING EDGE OF A DISTINCT AIR MASS CHANGE...AND IT/S LEADING EDGE IS ABOUT 275 MILES NORTHWEST OF KAUAI. NORTH TO NORTHEAST LOW-LEVEL WINDS LIE NORTH OF THIS BOUNDARY...THAT CONTAINS BROKEN TO OVERCAST SHOWERY OPEN-CELLED CUMULUS...BUT NOT DEEP CONVECTION. ALL THE BANDS MENTIONED ABOVE HAVE DEVELOPED IN RESPONSE TO A MID-LEVEL SHORT WAVE TROUGH THAT IS UNSEASONABLY STRONG IN IT/S SOUTHWARD PROTRUSION...AND IT/S ASSOCIATED DEVELOPING SURFACE LOW. THE SHORT WAVE TROUGH...CURRENTLY ALONG 157W LONGITUDE FROM 26N TO 39N...IS EXPECTED TO DEVELOP INTO A CUT-OFF LOW ABOUT 1000 MILES NORTH-NORTHEAST OF THE ISLANDS LATER TONIGHT. THE LOW WILL BECOME CUT-OFF FROM THE FLOW ALOFT...AND WILL THUS BE A RELATIVELY LONG-LIVED FEATURE NORTH AND NORTHEAST OF THE ISLANDS THAT WILL PERSIST FOR MUCH OF THE UPCOMING WEEK. THE LOW ALOFT HAS A SURFACE REFLECTION IN THE FORM OF A DEEPENING LOW...CURRENTLY NEAR 33N 155W...THAT IS FORECAST TO GAIN STORM FORCE WINDS...BUT OVER WATERS WELL NORTH OF THE ISLANDS. ONCE AGAIN A DIFFICULT FORECAST...AS GLOBAL MODEL GUIDANCE STILL CONTAINS SOME DIFFERENCES WITH TIMING AND INTENSITY OF THE FRONT OVER THE ISLANDS THE NEXT COUPLE OF DAYS. THE FORECAST PRESENTED HERE CONTAINS MORE THAN THE USUAL AMOUNT OF UNCERTAINTY...AND REPRESENTS A BLEND OF THE VARIOUS MODELS...WITH A NOD TO CURRENT CONDITIONS FOR THE SHORT-TERM FORECAST. FORECAST PHILOSOPHY MOVES THE PRE-FRONTAL BOUNDARY EASTWARD TOWARD OAHU THIS EVENING WHILE WEAKENING...BUT HOLDING TOGETHER SUFFICIENTLY TO BRING SHOWERS TO OAHU THIS EVENING AND OVERNIGHT. THIS BAND IS EXPECTED TO SPREAD AS FAR EAST AS MOLOKAI LATE TONIGHT BEFORE SLOWING...WEAKENING...AND MERGING WITH THE SECOND BAND THAT WILL BE WEAKER...AND MOVING OVER KAUAI LATER TONIGHT. THE THIRD BAND WILL MOVE OVER KAUAI ON MONDAY AND MONDAY NIGHT...FOLLOWED BY INCREASING NORTHEAST WINDS. MOISTURE ASSOCIATED WITH THESE FEATURES IS NOT EXPECTED TO SPREAD TO THE REMAINDER OF MAUI COUNTY OR THE BIG ISLAND TONIGHT OR TOMORROW. FROM MONDAY NIGHT THROUGH TUESDAY NIGHT...THE COMBINED MOISTURE OF THE THREE BANDS WILL BE NEARLY EAST-WEST ORIENTED OVER THE ISLAND CHAIN...AND SAGGING SOUTHWARD SLOWLY. A LOBE OF VORTICITY WRAPPING AROUND THE LARGE CUT-OFF LOW TO THE NORTH WILL DESTABILIZE THE ATMOSPHERE...AND RE-ENERGIZE CONVECTION ALONG THE STALLED BOUNDARY. WITH NORTHEAST WINDS PREVAILING NEAR THE SURFACE...THESE ENHANCED SHOWERS WILL PRIMARILY AFFECT WINDWARD SLOPES. THE BOUNDARY WILL WEAKEN ON WEDNESDAY AND THURSDAY...BUT NEW LOW PRESSURE IS FORECAST TO DEVELOP WEST OF THE ISLANDS...POSSIBLY BEGINNING A NEW ROUND OF DISTURBED WEATHER AS WE HEAD INTO NEXT WEEKEND. SURFACE WINDS WILL FAVOR A W AND SW DIRECTION TONIGHT AND MONDAY... BEFORE THE WIND SHIFT TO THE NORTHEAST KICKS IN BEHIND THE THIRD BAND OF MOISTURE. BRISK NE FLOW INITIALLY BEHIND THE FRONT WILL GRADUALLY WEAKEN...AS THE LOW TO THE NORTH RETROGRADES AND WEAKENS AND DISPLACES THE HIGH TO THE NORTH. IN THE MID-LEVELS...A TIGHT GRADIENT WILL MAINTAIN AT LEAST ADVISORY LEVEL WINDS OVER THE BIG ISLAND SUMMITS AND UPPER ELEVATIONS FOR AT LEAST THE NEXT COUPLE OF DAYS...AND THE ADVISORY WAS EXTENDED AN ADDITIONAL 24 HOURS. ALL IN ALL...A RATHER DYNAMIC WEATHER PATTERN IS IN STORE FOR THE NEXT WEEK OR SO...AND FORECAST ADJUSTMENTS MAY BE RADICAL AT TIMES TO ACCOUNT FOR MODEL AND OBSERVED TRENDS. && .MARINE... THE SURFACE LOW WILL DELIVER A SHORT-PERIOD NORTH-NORTHEAST SWELL WHICH WILL BUILD ON TUESDAY...PEAK ON WEDNESDAY AND THURSDAY...AND LOWER ON FRIDAY AND SATURDAY. THE SWELL WILL LIKELY BE LARGE ENOUGH TO EXCEED THE 8 FOOT ADVISORY THRESHOLD ALONG EAST FACING SHORES. && .HFO WATCHES/WARNINGS/ADVISORIES... HIGH WIND WARNING FOR MAUNA KEA AND MAUNA LOA SUMMITS UNTIL 10 AM HST TUESDAY. &&
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Hawaii in 2009Every state in 2009This day in weather historyWarnings in Hawaii, April 2009
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 158307.