NWS forecast office use of MODIS TPW product

August 27th, 2011 |
MODIS Total Precipitable Water product

MODIS Total Precipitable Water product

The National Weather Service forecast office in Salt Lake City, Utah referred to the MODIS Total Precipitable Water (TPW) product (above) in their afternoon forecast discussion on 27 August 2011:

FXUS65 KSLC 272201
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
355 PM MDT SAT AUG 27 2011

.SYNOPSIS...HIGH PRESSURE NEAR THE FOUR CORNERS WILL DRIFT WEST AND
WEAKEN ON SUNDAY. A VERY MOIST AIRMASS WILL REMAIN IN PLACE SUNDAY
BRINGING SCATTERED THUNDERSTORMS TO UTAH. WESTERLY FLOW WITH A
GRADUAL DRYING TREND IS THEN EXPECTED ON MONDAY AND TUESDAY.

.DISCUSSION...UPPER LEVEL AREA OF HIGH PRESSURE REMAINS CENTERED
NEAR THE FOUR CORNERS AREA THIS AFTERNOON...KEEPING A VERY MOIST
AIRMASS IN PLACE ACROSS UTAH. GPS-MET SENSOR CONTINUES TO SHOW THAT
COLUMN PRECIPITABLE WATER IS HOVERING AROUND 1.20 INCHES IN SALT
LAKE CITY.  AFTERNOON MODIS IMAGERY INDICATES THAT PRECIPITABLE
WATER VALUES ARE GENERALLY 1.0 TO 1.25 INCHES STATEWIDE.

The MODIS TPW values were in general agreement with those seen on the GOES sounder TPW product (below), but with finer spatial resolution (4-km MODIS, vs 10-km GOES) the various TPW gradients appear smoother on the MODIS image.

GOES sounder Total Precipitable Water product

GOES sounder Total Precipitable Water product

The Blended TPW product (below) displayed complete coverage (even in cloudy areas), but lacked the finer scale definition of the MODIS or GOES products due to the use of only Global Positioning System derived TPW data over inland areas.

Blended Total Precipitable Water product

Blended Total Precipitable Water product

The Percent of Normal TPW product (below) indicated that the TPW values present across the region were generally 150-200% above normal for the date.

Percent of Normal TPW product

Percent of Normal TPW product

Their forecast discussion went on to state:

AIRMASS QUICKLY DESTABILIZED IN THE EARLY AFTERNOON WITH SCATTERED
CONVECTION FORMING IN THE SOUTH AND EAST AND MORE ISOLATED COVERAGE
IN THE NORTHWEST.

The MODIS 0.65 µm visible channel image (below) showed the areas where organized convection had already developed across Utah and the surrounding states.

MODIS 0.65 µm visible chanel image

MODIS 0.65 µm visible chanel image

CIMSS participation in GOES-R Proving Ground activities includes making a variety of MODIS images and products available for National Weather Service offices to add to their local AWIPS workstations. Currently there are 49 NWS offices receiving MODIS imagery and products from CIMSS. In addition, the VISIT training lesson “MODIS Products in AWIPS” is available to help users understand these products and their applications to weather analysis and forecasting.