Alert archive / Guam / Flash Flood Warnings in 2021

Flash Flood Warning 4, NWS Guam

August 18, 2021

NWS Guam issued this flash flood warning at Aug 18, 2021, 12:21 AM CDT. It took effect at Aug 18, 2021, 12:26 AM CDT. It was in force for 86 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 18, 2021, 12:21 AM CDT (05:21 UTC)
In effect from: Aug 18, 2021, 12:26 AM CDT
Expired: Aug 18, 2021, 1:52 AM CDT
In force: 86 min
Issued by: NWS Guam
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

The radar

The Andersen AFB radar (PGUA), 4 km from the middle of the area, began a volume at 05:28 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The text

As transmitted.

372 
WGMY50 PGUM 180526
FFWGUM
GUC010-181015-
/O.NEW.PGUM.FF.W.0004.210818T0526Z-210818T1015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Tiyan GU
321 PM ChST Wed Aug 18 2021

The National Weather Service in Tiyan Guam has issued a

* Flash Flood Warning for...
  Guam   

* Until 815 PM ChST.

* At 321 PM ChST, Doppler radar and automated rain gauges indicate 
  thunderstorms producing heavy rain with rain rates of 1-2 inches 
  per hour across portions of Guam. Rain gauges show that 2-3 inches 
  of rain has already fallen. Additional heavy showers approaching 
  from the southeast are expected to bring an additional 2-3 inches 
  to parts of Guam. Flash flooding is ongoing or expected to begin 
  shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and rain gauges.

  IMPACT...Flash flooding of small creeks and streams, streets as 
           well as other poor drainage and low-lying areas.

* Some locations that will experience flooding include...
  Guam.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

This warning may need to be extended beyond 815 PM ChST if heavy rain
persists.

LAT...LON 1334 14464 1341 14465 1343 14463 1348 14476
      1352 14481 1364 14485 1365 14488 1360 14490
      1359 14495 1353 14494 1342 14478 1328 14476
      1323 14467

FLASH FLOOD...RADAR AND GAGE INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

ZIOBRO/PAVLIUKOIT

1 follow-up statement

569 
WGMY70 PGUM 180652
FFSGUM

Flash Flood Statement
National Weather Service Tiyan GU
452 PM ChST Wed Aug 18 2021

GUC010-180702-
/O.CAN.PGUM.FF.W.0004.000000T0000Z-210818T1015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Guam GU-
452 PM ChST Wed Aug 18 2021

...FLASH FLOOD WARNING HAS BEEN CANCELLED...

Radar imagery shows that the heaviest rainfall have subsided and are 
no longer expected. Additionally, rain and stream gauges show that 
rainfall has diminished with stream levels also decreasing.

LAT...LON 1334 14464 1323 14467 1328 14476 1342 14478
      1353 14494 1359 14495 1360 14490 1365 14488
      1364 14485 1352 14481 1348 14476 1343 14463
      1341 14465

$$

PAVLIUKOIT

The office that day

Everything else NWS Guam issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 17, 10:48 PM CDT	Areal Flood Advisory	GUM		4 hr

Nearby

Flash Flood Warnings in Guam, 2021 Every flash flood warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; radar from the NEXRAD Level II archive.