MIMIC Total Precipitable Water product

AWIPS images of the MIMIC Total Precipitable Water (TPW) product (above) revealed the formation of a long “atmospheric river” of moisture over the North Atlantic Ocean during the 17-19 November 2009 period. MIMIC TPW values were as high as 60 mm (darker orange color enhancement) within the moisture plume.

The surface analysis (below) showed that this moist plume was along and ahead of a cold front that was trailing southward from a deepening mid-latitude cyclone. This plume of moisture was contributing to very heavy rainfall and significant flooding over parts of the United Kingdom — Seathwaite reported a 24-hour rainfall amount of 12.36 inches (314 mm), which if confirmed as accurate will set a new record for 24-hour precipitation in the UK (UK Met Office).

MIMIC TPW with surface analysis

A composite of GOES-12 and Meteosat-9 water vapor imagery (below) suggested that this long atmospheric river tapped into a pocket of deep tropical moisture (associated with the remnants of what was formerly Hurricane/Tropical Storm Ida), and was then brought northward within the warm conveyor belt in advance of the deepening cyclone over the North Atlantic Ocean.

GOES-12 and Meteosat-9 water vapor imagery

The Blended Total Precpitable Water – Percent of Normal product (below) indicated that this moist plume was rather anomalous for the season over the North Atlantic region, containing values of TPW that exceeded 200% of normal (yellow color enhancement).

Blended Total Precipitable Water - Percent of Normal

Meteosat-9 IR images

Meteosat-9 IR images from the CIMSS Tropical Cyclones site (above) showed that Hurricane Fred began to exhibit a well-defined eye as it rapidly intensified to a Category 3 storm on 09 September 2009. As noted in the National Hurricane Center discussion:

IT IS QUITE UNUSUAL TO HAVE SUCH A POWERFUL SYSTEM SO FAR EAST IN
THE BASIN AND FRED IS ONLY THE THIRD MAJOR HURRICANE NOTED EAST OF
35W IN THE TROPICAL ATLANTIC OCEAN...AND THE STRONGEST HURRICANE SO
FAR SOUTH AND EAST IN OUR DATA RECORD.  THIS TYPE OF SYSTEM...
HOWEVER...WOULD HAVE BEEN VERY DIFFICULT TO ACCURATELY OBSERVE
BEFORE SATELLITE PICTURES BEGAN IN THE 1960S.

Terra MODIS visible image

At 12:50 UTC, a “transverse banding” structure was seen on the cold cloud tops surrounding the western periphery of the eyewall region on the  Terra MODIS visible image (above) and the 11.0 µm Terra MODIS IR image (below). MODIS IR brightness temperatures were as cold as -74º C within the transverse bands.

Terra MODIS 11.0 µm IR image

Fred was not expected to undergo much more in the way of intensification, since the cyclone was moving toward increasing values of environmental wind shear and warmer sea surface temperatures (below).

Meteosat-9 IR image with CIMSS wind shear analysis

Hurricane Fred forecast track + Sea Surface Temperature analysis