Name: Hurricane in Guam, September 15 to 16, 2009
Start: 2009-09-15T01:00
End: 2009-09-16T13:00
Location: Guam

The toll

Deaths: 0
Injuries: 1
Property damage: $20,000
Crop damage: $10,000
Events: 1

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS GUM wrote it up.

Tropical Depression 15W developed from a disturbance about 700 miles east of Guam on the 12th of September, and quickly intensified into Typhoon Choi-wan on the 13th. Moving steadily west-northwest toward the far northern Marianas, Choi-wan became a super typhoon just before passing directly over Alamagan Island at about 1600 GST on the afternoon of September 15th with maximum sustained winds of 150 mph.

On Alamagan, all six wood-and-tin residential structures were destroyed, and the 14 residents were left without food or water. Supplies were airlifted in by helicopter on the morning of the 17th, and a family of six, including a baby born on the 13th, was evacuated to Saipan for medical evaluation. One young girl sustained minor injuries. The remaining eight residents were evacuated on the 29th. Total damage is estimated at $25,000.

On Agrihan, about 75 miles north of Alamagan, winds peaking at an estimated 75 mph caused relatively minor damage to the two houses and to crops. The island's four residents were unharmed, and declined evacuation. Total damage is estimated at $5,000.

What forecasters said that day

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 Guam wrote its last area forecast discussion before the first event at Sep 14, 8:03 AM UTC, 6 hours 57 minutes earlier.

Area forecast discussion, Sep 14, 8:03 AM UTC, 6 hours 57 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
603 PM CHST MON SEP 14 2009

.SYNOPSIS...TYPHOON CHOI-WAN LOCATED ABOUT 150 MILES EAST-
NORTHEAST OF SAIPAN CONTINUES TO MOVE SLOWLY WEST AND INTENSIFY.
SATELLITE IMAGERY SHOWS A POORLY DEFINED EYE...EXTENSIVE DEEP
CONVECTION NEAR THE CENTER AND A LARGE BAND OF CLOUDS AND SHOWERS
WRAPPING AROUND THE CYCLONE FROM THE NORTHEAST THROUGH E AND S.
RADAR SHOWS THE OUTER FRINGE OF THE EYE WALL ABOUT 250 MILES AWAY.
&&

.DISCUSSION...FORECAST IS BASED ON EXPECTED MOVEMENT OF THE
TYPHOON THROUGH THE MARIANAS NORTH OF SAIPAN. WINDS WILL INCREASE
TO TROPICAL STORM-FORCE AT TINIAN AND SAIPAN TONIGHT AND REMAIN
STRONG AND GUSTY TUESDAY. WINDS AT GUAM AND ROTA WILL INCREASE
SIGNIFICANTLY ONCE THE TYPHOON PASSES NEAR 145E AND THE CYCLONE
TAIL EXTENDS ACROSS THE SOUTHERN MARIANAS.
&&

.MARINE...WINDS AND SEAS WILL INCREASE IN STRONG SOUTHWEST MONSOON
FLOW SOUTH OF THE STORM CENTER AND PERSIST SEVERAL DAYS AFTER THE
TYPHOON MAKES ITS CLOSEST APPROACH TO THE MARIANAS. A SMALL CRAFT
ADVISORY IS IN EFFECT FOR THE COASTAL WATERS OUTSIDE THE TROPICAL
STORM WARNING AND TYPHOON WATCH AREA.
&&

.TROPICAL SYSTEMS...A TROPICAL STORM WARNING AND TYPHOON WATCH
REMAIN IN EFFECT FOR ISLANDS IN THE CNMI FROM TINIAN NORTHWARD.
TROPICAL STORM-FORCE WINDS ARE EXPECTED AT TINIAN AND SAIPAN
TONIGHT AND TUESDAY AS THE TYPHOON PASSES NORTH OF SAIPAN NEAR
ANATAHAN. TYPHOON-FORCE WINDS ARE POSSIBLE...BUT NOT EXPECTED.
&&

.EASTERN MICRONESIA...
DECENT LOW-LEVEL CONVERGENCE TO THE SOUTH OF AN EAST TO WEST
ORIENTED SURFACE TROUGH CONTINUES OVER THE POHNPEI AND KOSRAE
VICINITY THIS AFTERNOON. THIS HAS TRIGGERED WIDESPREAD
CONVECTION...MAINLY OVER POHNPEI. EXPECT THAT THIS SHOWER
ACTIVITY WILL CONTINUE THROUGH TOMORROW AHEAD OF LIGHT EASTERLIES
RETURNING TO THE REGION ON WEDNESDAY. A WEAK SURFACE TROUGH JUST
TO THE EAST OF THE MARSHALL ISLANDS WILL MOVE OVER MAJURO TONIGHT.
SCATTERED SHOWERS NEAR THE TROUGH AXIS WILL LINGER OVER THE AREA
THROUGH TOMORROW MORNING BEFORE WEAK RIDGING BUILDS IN.

&&

.WESTERN MICRONESIA...
MONSOON TAIL ASSOCIATED WITH TYPHOON CHOI-WAN APPEARS TO BE
VACILLATING OVER WESTERN MICRONESIA THIS EVENING...WHICH HAS MADE
FOR A DIFFICULT...LOW CONFIDENCE FORECAST. FOR NOW...HAVE CONTINUED
WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FOR YAP AND KOROR
THROUGH MIDWEEK AS POSITIONING OF MONSOON TAIL PER LATEST VIS LOOP
AND MODEL GUIDANCE SUPPORTS THIS. FOR CHUUK...RIDGING SOUTH OF
CHOI-WAN WILL ALLOW FOR MAINLY FAIR WX DURING THE NEXT COUPLE DAYS.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...HIGH SURF ADVISORY UNTIL 6 AM CHST THURSDAY FOR GUZ001-002.
     WIND ADVISORY UNTIL 6 AM CHST THURSDAY FOR GUZ001-002.
     TYPHOON WATCH FOR GUZ003-004.
     TROPICAL STORM WARNING FOR GUZ003-004.

MARIANAS WATERS...TYPHOON WATCH FOR PMZ153-154.
     TROPICAL STORM WARNING FOR PMZ153-154.
     SMALL CRAFT ADVISORY UNTIL 6 AM CHST THURSDAY FOR PMZ151-152.

&&

MUNDELL/LEE/CHAN

Event by event

1 hurricane (typhoon). Local standard time, as filed.

Hurricane (Typhoon), Northern Marianas

When: September 15, 1:00 AM GST to September 16, 1:00 PM GST
Where: Northern Marianas forecast zone
Category: 4
Injuries: 1 direct, 0 indirect
Property damage: $20,000
Crop damage: $10,000
Reported by: Newspaper

What these are

Hurricane (Typhoon): A tropical cyclone with sustained winds of 64 knots (74 mph) or more, filed per forecast zone for its wind, and with separate events for its flooding, surge and tornadoes.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Guam in 2009 Every state in 2009 This day in weather history Warnings in Guam, September 2009 The 2009 hurricane season

Sources

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: 197872.