Public Information Statement
Issued by NWS Seattle/Tacoma, WA

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PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE SEATTLE WA
205 PM PST FRI FEB 12 2016

...RAIN VS DRIZZLE VS SHOWERS...

WEATHER FORECASTERS USE TERMS LIKE RAIN...DRIZZLE OR SHOWERS TO
DESCRIBE EXPECTED WET PRECIPITATION. WHAT IS THE DIFFERENCE BETWEEN
THESE TERMS?  WHAT DO THESE TERMS MEAN?

RAIN IS DEFINED AS PRECIPITATION THAT FALLS TO THE GROUND IN DROPS
MORE THAN 0.5 MILLIMETERS IN DIAMETER OR 0.02 INCHES IN DIAMETER.
IN CONTRAST...DRIZZLE IS PRECIPITATION CONSISTING OF NUMEROUS MINUTE
DROPLETS OF WATER LESS THAN 0.5 MILLIMETERS IN DIAMETER. WE FEEL
DRIZZLE...KIND OF LIKE A MIST. RAIN IS APPARENT AS IT LANDS IN
PUDDLES WHILE DRIZZLE USUALLY IS NOT.

SHOWERS DESCRIBE PRECIPITATION CHARACTERIZED BY THE SUDDENNESS WITH
WHICH THEY START AND STOP...BY RAPID CHANGES IN INTENSITY AND
USUALLY BY QUICK CHANGES IN THE APPEARANCE OF THE SKY. HERE IN
WESTERN WASHINGTON...SHOWERS ARE OFTEN ACCOMPANIED BY BREAKS IN THE
CLOUD COVER. DURING THE DAY...MANY RESIDENTS CALL THESE SUN BREAKS.

ANOTHER CONTRAST BETWEEN RAIN OR DRIZZLE AND SHOWERS IS THE
STABILITY OF THE AIR MASS. RAIN OR DRIZZLE IS OFTEN ASSOCIATED WITH
A MORE STABLE AIR MASS IN A FRONTAL SYSTEM OFFERING A MORE STEADY
PRECIPITATION. BEHIND A COLD FRONT IS USUALLY A COOLER UNSTABLE AIR
MASS THAT HELPS GENERATE - HIT AND MISS - SHOWERS WITH CLOUD BREAKS.

A TYPICAL WESTERN WASHINGTON FORECAST INVOLVING WET PRECIPITATION IS
RAIN TURNING TO SHOWERS. THE RAIN WILL BE INVOLVED WITH AN INCOMING
PACIFIC FRONTAL SYSTEM AND SHOWERS FOLLOWING IN ITS WAKE. ON
SATELLITE IMAGERY...RAIN INVOLVED WITH THE FRONTAL SYSTEM HAS A MORE
SOLID CLOUD SHIELD WHILE CLOUDS ASSOCIATED WITH SHOWERS HAVE A
POPCORN LOOK TO THEM.

RAINFALL IS ALSO DESCRIBED BY ITS INTENSITY. LIGHT RAINFALL IS LESS
THAN 0.10 INCH PER HOUR...WHILE MODERATE RAINFALL RANGES FROM 0.10
TO 0.30 INCHES PER HOUR. HEAVY RAINFALL IS MORE THAN 0.30 INCHES PER
HOUR - A HEALTHY RAINFALL AMOUNT. SOME OF THIS REGIONS HEAVY RAIN
EVENTS CAN PRODUCE OVER 0.50 INCHES PER HOUR AND OFTEN RESULT IN
SOME FORM OF FLOODING.

NOW YOU KNOW THE DIFFERENCE BETWEEN RAIN...DRIZZLE AND SHOWERS. FOR
MORE INFORMATION ON WEATHER TERMS...VISIT THE NATIONAL WEATHER
SERVICE GLOSSARY AT HTTP://W1.WEATHER.GOV/GLOSSARY/

$$

BUEHNER


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