A combination of north swell and King Tides, plus higher sea levels from |an on going La Nina pattern produced an inundation event.
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.
The episode as NWS GUM wrote it up.
A combination of north swell and King Tides, plus higher sea levels from |an on going La Nina pattern produced an inundation event.
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 Dec 3, 9:27 AM UTC, 4 hours 33 minutes earlier.
Area Forecast Discussion
National Weather Service Tiyan GU
727 PM ChST Fri Dec 3 2021
.Marianas Synopsis...
Gentle to moderate southeast winds and mostly clear skies prevail
this evening. Radar shows pinprick sprinkles. Typhoon Nyatoh (27W)
is centered far to the north- northwest near 23N141E. Seas are around
6 feet at Ipan buoy higher seas likely in more exposed parts of the
coastal waters.
&&
.Discussion...
00Z balloon sounding showed a very dry airmass with PWAT < 1" and a
stout inversion at 4000ft. This led to dry conditions today and that
should continue tomorrow (Saturday). A dry-season style shearline
fragment is still expected to bring a slight uptick in clouds and
low-topped showers for Saturday night and the first part of Sunday.
Gentle winds on Saturday may produce some cloud build ups, but a
shallow boundary layer and lack of moisture should suppress shower
development by and large. By Sunday evening we transition back to a
blase gentle to moderate trade-wind pattern with occasional upticks
in showers. The main focus is the marine pattern as discussed below.
&&
.Marine...
Although winds are expected to remain at gentle to moderate levels
through much of next week, there will be two notable swells pushing
through the coastal waters...one from the WNW to NW and another from
the ENE.
Surf is expected to become hazardous along north and west facing
reefs tonight as swell produced from a cold front interacts with
Nyatoh's wind field. This swell will gradually shift to the north
through early next week, allowing surf to focus more along north
facing reefs. Another swell will build from the east-northeast
Saturday night and Sunday. The source region is an area of gale to
strong gale winds northeast of Wake Island. Guidance has been fairly
steady on long-period swell of ~8 feet at 15 seconds arriving Sunday.
This should be enough to produce hazardous surf along east facing
reefs then. These two swells (NW and ENE) should be enough to
generate 10 foot combined seas early next week, which satisfies the
threshold for a Small Craft Advisory. East reefs will see surf and
swell ease towards Tue/Wed but the overall pattern favors elevated
surf for east reefs through much of the week.
&&
.Tropical systems...
Typhoon Nyatoh is centered well to the north-northwest of Guam near
23N141E. A brisk weakening trend is expected to begin tonight as
Nyatoh is absorbed into a mid-latitude front. TC activity looks to
quiet down the next few weeks as indicated by all model guidance.
&&
.Eastern Micronesia...
Sky cover is slowy decreasing over Chuuk and Pohnpei for partly
cloudy skies tonight.
Scattered to numerous showers and isolated thunderstorms continue
over and near Majuro's waters as a weak circulation aided by upper
divergence tracks west across the islands. Plenty of thunderstorms
were seen over Majuro today with gusts to 28 kts reported by the BoM
buoy. This circulation and weather pattern will continue to affect
Majuro Saturday morning, then affect Kosrae tomorrow and Pohnpei
tomorrow night for scattered showers. So far model guidance has not
indicated any strong winds for Kosrae or Pohnpei the next two days.
Any significant upper level divergence is further up north around
12N latitude by tomorrow. But if the pattern persists and comes
further south, then we might be in for stronger winds and more
frequent thunderstorms for Kosrae and Pohnpei.
Combined seas will start to increase across all eastern Micronesia.
Kosrae's and Pohnpei's seas will rise from 5 ft tonight to 8 to 9 ft
by Monday. Majuro will increase from 8 ft tonight to near 11 ft by
Monday. Models show strong northeasterlies coming down near Wake
Island on Saturday which will generate seas for the islands.
&&
.Western Micronesia...
Strong winds over Koror this morning have come down. Models still
indicate a little bit of convective activity through the night with
strong west winds and gusts, so kept the winds higher for tonight.
Expecting a trough to linger around Koror this weekend around Sunday
through tuesday, then a return to trade winds on Wednesday.
Scattered showers tonight for Yap, then clearing out by tomorrow
morning. Expecting Yap to be just north of the passing trough with
trade winds expected on Sunday. Chuuk's next weather is expected on
Tuesday as a surface trough passes through.
For Yap and Koror, combined seas of 8 to 10 ft will gradually
decrease starting Saturday night and drop below hazardous conditions
on Sunday. Hazardous surf is expected to last through Monday.
&&
.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through Monday night for GUZ001>004.
High Surf Advisory until 6 AM ChST Tuesday for GUZ001>004.
MP...None.
Marianas Waters...None.
&&
Marianas: Bukunt
Micronesia: Hong2 coastal flood. Local standard time, as filed.
A combination of north swell and King Tides, plus higher sea levels from an on going La Nina pattern produced an inundation event. Slight inundation was observed during high tide at T Dock in Palau.
After midday on the 5th a combination of north swell and King Tides, plus higher sea levels from an on going La Nina pattern produced an inundation event.
The inundation caused crop damage over a few islands in Chuuk State. Taro, Breadfruit, and Banana crops were the most notable with damage cost totaling $1,855,840. The inundation also caused damage to a sea wall which resulted in damage totaling $1,560,000.
Yap State also saw inundation across a few of it's islands. Ifalik experienced inundation which caused damage to some of the Taro patches. Salt water brought by inundation may have affected some other crops. Residents on Infalik report that some of the breadfruit and coconuts were smaller than usual. Also some of their banana trees had died. |On Woleai-Falalop also saw some damage to a few Taro patches from the inundation.
Pohnei State-Kapingamarangi atoll, the inundation may have caused damage to a 400 plus foot bridge that connects two of the islands there. Some costal damage reported with inundation going 20 to 30 feet inland. 20 percent of the two main islands went underwater.
Nukuroro saw inundation with salt water covering 85 percent of the island.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Guam in 2021Every state in 2021This day in weather historyWarnings in Guam, December 2021
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: 999973, 999975.