Alert archive / Guam / Flash Flood Warnings in 2021

Flash Flood Warning 3, NWS Guam

July 30, 2021

NWS Guam issued this flash flood warning at Jul 30, 2021, 10:15 PM CDT. It was in force for 66 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: Jul 30, 2021, 10:15 PM CDT (03:15 UTC)
Expired: Jul 30, 2021, 11:21 PM CDT
In force: 66 min
Issued by: NWS Guam
Area: Storm-based polygon
Flood severity: None

The radar

The Andersen AFB radar (PGUA), 22 km from the middle of the area, began a volume at 03:18 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.

517 
WGMY50 PGUM 310315
FFWGUM
GUC010-310445-
/O.NEW.PGUM.FF.W.0003.210731T0315Z-210731T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Tiyan GU
115 PM ChST Sat Jul 31 2021

The National Weather Service in Tiyan has issued a

* Flash Flood Warning for...
  Guam Island in the Marianas...

* Until 245 PM ChST.

* At 115 PM ChST, Doppler radar and automated rain gauges indicate 
  thunderstorms producing heavy rain with rain rates of 2-3 inches 
  per hour across portions of southern Guam including Umatac and 
  Merizo. Rain gauges show that 1-2 inches of rain has already 
  fallen. Additional heavy showers approaching from the south are 
  expected to bring an additional 2-3 inches to parts of southern 
  Guam. Flash flooding is ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and automated 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 flash flooding include...
  Merizo and Umatac.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 1335 14464 1336 14463 1334 14469 1330 14470
      1328 14476 1327 14475 1328 14475 1327 14474
      1325 14472 1325 14468 1324 14468 1325 14467
      1327 14466 1333 14465 1334 14463

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL...2-3 INCHES IN 1 HOUR

$$

WBA

1 follow-up statement

707 
WGMY70 PGUM 310421
FFSGUM

Flash Flood Statement
National Weather Service Tiyan GU
221 PM ChST Sat Jul 31 2021

GUC010-310431-
/O.CAN.PGUM.FF.W.0003.000000T0000Z-210731T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Guam GU-
221 PM ChST Sat Jul 31 2021

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

Radar imagery shows that heavy rains have subsided and are no longer 
expected. Additionally, rain and stream gauges show that rainfall 
has diminished with stream levels also decreasing. Flooding is no 
longer expected to pose a threat.

LAT...LON 1335 14464 1336 14463 1334 14469 1330 14470
      1328 14476 1327 14475 1328 14475 1327 14474
      1325 14472 1325 14468 1324 14468 1325 14467
      1327 14466 1333 14465 1334 14463

$$

WBA

The office that day

Everything else NWS Guam issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 30, 9:11 PM CDT	Areal Flood Advisory	GUM		2 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.