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

A strong storm is bringing high winds and rain to the east coast of the United States from North Carolina northward to New Jersey. This dangerous weather will persist through tomorrow. The weather results from the combination of the extratropically transitioned remnants of Ida — over southern North Carolina — and a strong high pressure system over New England. (See a surface analysis here). Various satellite-derived products can be used to explore this system.

Consider the water vapor loop above. Towards the end of the loop, features in the vapor are developing and moving westward over Virginia and North Carolina. That observation combined with the continued eastward motion in the water vapor signal over the southeast part of the US suggests the formation of a closed circulation. Such a development will slow the eastward progression of the system, prolonging the period of stormy weather on the coast.

Satellite observations of total precipitable water (a blended product from AMSU and SSM/I on the NOAA series of Polar Orbiters) show large values — greater than 200% of normal — over the eastern United States. Superimposed near-surface winds from the QuikScat scatterometer show a broad region of gale-force winds over the Ocean. The long fetch of the wind over open ocean will allow large waves to develop. (A zoomed-in version of the QuikScat winds, here, includes a 57-knot wind with a rain flag of only 1% — meaning it’s a “good” wind. Peak surface wind gusts from reporting stations on land at this time included 44 knots at Norfolk, Virginia, 43 knots at Wallops Island, Virginia, and 42 knots at Elizabeth City, NC). The long duration of the storm event and the winds will exacerbate matters. A loop of precipitable water derived from SSMI and AMSRE (here) shows the tropical origins of the moisture over the eastern part of the United States, and also the movement of more moisture in from the east.

Abundant moisture is leading to large rainfalls. Rainfall rates are estimated using data from the AMSU instrument on the NOAA series of POES spacecraft. There are numerous pixels in the short loop above, including suggesting rains exceeding 20 mm per hour. There is also a westward drift suggested in the loop.

Visible image loops (rocking loops) from GOES-12 and GOES-14 show the westward drift of clouds into western Virginia and the Carolinas as the system starts to close off. A near-surface circulation center can also be inferred over southern North Carolina.