Guam, 2015

Tropical Storm in Guam, August 15 to 17, 2015

August 15 to 17, 2015 · NWS GUM · 1 event in 1 county or zone

Tropical Storm Goni passes across the Marianas during the middle of the month of August. The storm produced heavy rain across the island of Guam.

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
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 Storm Goni passes across the Marianas during the middle of the month of August. The storm produced heavy rain across the island of Guam.

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 Aug 14, 6:55 AM UTC, 7 hours 5 minutes earlier.

Area forecast discussion, Aug 14, 6:55 AM UTC, 7 hours 5 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
455 PM CHST FRI AUG 14 2015

.SYNOPSIS...
TROPICAL DEPRESSION 16W IS CENTERED ABOUT 380 MILES EAST OF GUAM
NEAR 12N150E. 16W CONTINUES TO BE SHEARED BY STRONG FLOW FROM THE
EAST. LATEST FLAREUP OF CONVECTION WEST OF THE CENTER IS CAUSING
SHOWER COVERAGE TO INCREASE OVER THE FORECAST ZONES.

&&

.DISCUSSION...
WEATHER GRIDS CLOSELY FOLLOW CONTINUITY. ELECTED TO MAINTAIN
SCATTERED SHOWER COVERAGE THROUGH DAY 7. SHOWER COVERAGE WITH 16W
HAS BEEN RATHER SPARSE SO FAR...SO HAVE CAPPED SHOWER COVERAGE AT
SCATTERED UNTIL FUTURE TRACK AND EVOLUTION OF 16W BECOME MORE
CERTAIN. MODEL SOLUTIONS CONTINUE TO RAPIDLY DIVERGE REGARDING THE
TRACK OF 16W...SO WIND FORECAST CONFIDENCE REMAINS LOW. NEXT WEEK
CONTINUES TO LOOK WET AS MONSOONAL FLOW CONTINUES. WIND GRIDS HAVE
SIGNIFICANT UPDATES SUNDAY THROUGH MONDAY NIGHT TO REFLECT THE
PASSAGE OF A TROPICAL CYCLONE DURING THIS TIME FRAME.

&&

.MARINE...
BUOY READINGS AND LATEST ALTIMETRY STILL SHOW COMBINED SEAS IN
THE 3 TO 4-FOOT RANGE. HOWEVER...RELATIVELY BENIGN CONDITIONS WILL
CONTINUE ONLY A LITTLE BIT LONGER. SEAS AND SURF WILL BEGIN TO
RAPIDLY BUILD AS THE WIND FIELD OF 16W BEGINS TO IMPACT THE
FORECAST ZONES BY SATURDAY NIGHT.

&&

.EASTERN MICRONESIA...
THE MONSOON TROUGH EXTENDS EASTWARD FROM NEWLY FORMED TROPICAL
DEPRESSION 16W TO A SECOND CIRCULATION...STILL THE SUBJECT OF A
TROPICAL CYCLONE FORMATION ALERT...CENTERED NORTHWEST OF
KWAJALEIN. WINDS CONTINUE TO SLOWLY SUBSIDE FROM CHUUK EASTWARD TO
MAJURO. MODERATE TO FRESH WINDS WILL CONTINUE OVER THE MARSHALLS
AND KOSRAE STATE THROUGH SATURDAY...THEN DECREASE FURTHER AS THE
TROUGH AND CIRCULATION PULL FARTHER NORTHWESTWARD...ALLOWING WEAK
RIDGING TO BUILD INTO THE AREA. MODERATE TO FRESH WINDS WILL
CONTINUE THROUGH SUNDAY MORNING AT POHNPEI. MOST OF THE CONVECTION
IS NOW WELL NORTH OF ALL THREE FORECAST POINTS AND DRY CONDITIONS
ARE EXPECTED TO CONTINUE AS THE TROUGH DRIFTS FARTHER NORTHWARD
AWAY FROM THE REGION.

SEAS HAVE ALSO SUBSIDED OVER KOSRAE AND MAJURO AS THE MONSOON TROUGH
MOVES FARTHER AWAY FROM BOTH LOCATIONS. THIS HAS ALLOWED SURF TO
FALL BELOW HAZARDOUS LEVELS. LARGE SEAS WILL LINGER A LITTLE
LONGER OVER POHNPEI AND CHUUK...REMAINING AT HAZARDOUS LEVELS FOR
POHNPEI UNTIL SATURDAY AFTERNOON AND CHUUK SUNDAY.

&&

.WESTERN MICRONESIA...
LATEST GFS AND ECMWF ARE SHOWING MUCH DRIER CONDITIONS OVER CHUUK
FOR THE NEXT FEW DAYS. CHOSE TO CONTINUE WITH INHERITED FORECAST
FOR NOW TO SEE IF THIS IS GOING TO BE THE TREND. LATEST SATELLITE
DATA INDICATES THIS SCENARIO IS PLAUSIBLE AS THE MONSOON TROUGH
CONTINUES TO DRIFT FARTHER AWAY FROM CHUUK STATE AS TD 16W MOVES
TOWARD THE NORTHWEST. OTHERWISE...MODERATE TO FRESH MONSOON WINDS
ARE EXPECTED TO CONTINUE ON CHUUK FOR THE NEXT FEW DAYS.

THE MONSOON TROUGH WILL LINGER ACROSS YAP STATE AND PALAU FOR THE
NEXT FEW DAYS. AS TD 16W CONTINUES TO DEVELOP AND MOVE TOWARD THE
NORTHWEST...THE MONSOON PATTERN WILL STRENGTHEN OVER BOTH PALAU
AND YAP STATE. LATEST MODEL RUNS SHOW A LITTLE DRIER OVER
YAP...WITH SCATTERED SHOWERS DEVELOPING A DAY OR SO LATER. BASED
ON CURRENT VIS SATELLITE...CHOSE TO INCREASE SHOWERS TO SCATTERED
AT YAP FOR TONIGHT. CHOSE TO MAINTAIN INHERITED FORECAST FOR THE
REMAINDER OF THE FORECAST SINCE THE MODELS DO KEEP SHOWERS FAIRLY
CLOSE TO YAP WATERS AND FELT THAT DECREASING THE COVERAGE NOW
WOULD BE A BIT PREMATURE. ONCE SCATTERED SHOWERS MOVE TO KOROR
AND BACK INTO YAP SATURDAY NIGHT...MODELS INDICATE THE WET
CONDITIONS WILL CONTINUE THROUGH MOST OF THE WEEK.

RESIDUAL SOUTHWEST TO WEST SWELL WILL MAINTAIN CONDITIONS HAZARDOUS
TO SMALL CRAFT FOR CHUUK THROUGH SATURDAY. THIS SWELL WILL ALSO
MAINTAIN HAZARDOUS SURF CONDITIONS THROUGH THE WEEKEND. SWELL WILL
GRADUALLY SUBSIDE THROUGH THE WEEKEND WITH SEAS FALLING BELOW
HAZARDOUS LEVELS ON SATURDAY. AS THE SEAS SUBSIDE FURTHER SATURDAY
NIGHT...SURF ACROSS CHUUK STATE IS EXPECTED TO FALL BELOW HAZARDOUS
LEVELS SUNDAY. SEA CONDITIONS FOR YAP AND KOROR ARE EXPECTED TO
REMIAN BELOW HAZARDOUS LEVELS AT THIS TIME...BUT NEEDS TO BE
WATCHED CAREFULLY.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...TROPICAL STORM WATCH FOR GUZ001-002.
     TYPHOON WATCH FOR GUZ003-004.

MARIANAS WATERS...TROPICAL STORM WATCH FOR PMZ151-152.
                  TYPHOON WATCH FOR PMZ153-154.

&&

MCELROY/KLEESCHULTE

Event by event

1 tropical storm. Local standard time, as filed.

Tropical Storm, Guam

When
August 15, 12:00 AM GST to August 17, 12:00 AM GST
Where
Guam forecast zone
Reported by
Newspaper

Tropical Depression 16W forms about 380 miles to the east-southeast of Guam in the afternoon of the 14th. By the morning of the 15th the depression becomes Tropical Storm Goni when it was located 190 miles east of Guam. On the morning of the 16th Tropical Goni passes through the Marianas between Rota and Tinian.

While tropical storm force winds were observed on the islands the main event was heavy rainfall. The tropical storm traveled slowly through the local area, prolonging the period of rainfall. At the National Weather Service Office in central Guam 9.64 inches fell on the 15th with an additional 3.94 inches on the 16th. 13.58 inches in total. The wind and rainfall caused sporadic power outages across Guam. The heavy rainfall produced high stream flow in the Ugum River in Guam. This high stream flow increases the turbidity of the water, which hampers the Ugum Water Treatment Plant and its processing of drinking water. The plant had to shut down, which caused|water outages in parts of Guam.|The heavy rain produced flooding which temporarily caused a shutdown of a power sub-station in Tumon creating a power outage there.

The heavy rainfall caused Guam bound flights to be diverted to Saipan. One Delta Airline flight was also canceled. Three flights were also stuck in Saipan, China Eastern, United Star Alliance, and Jin Air all had passengers disembark from the respective flights. Three United Airline flights were diverted to Andersen Air Force Base. The flights came from Honolulu, Manila, and Palau.

What these are

Tropical Storm
A tropical cyclone with sustained winds of 34 to 63 knots (39 to 73 mph).

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

The same day elsewhere

More

Every storm in Guam in 2015Every state in 2015This day in weather historyWarnings in Guam, August 2015The 2015 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: 601889.