MODIS false-color images show areas of flooding in Montana

August 26th, 2014
Before (12 August) and after (26 August) MODIS false-color RGB images

Before (12 August) and after (26 August) MODIS false-color RGB images

Some locations in northeastern Montana received up to 7-8 inches of rainfall over a 5-day period (NWS Glasgow rainfall map), which led to flooding in many areas. A comparison of before (12 August) and after (26 August) 250-meter resolution MODIS false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed the areal extent of flooding (cyan to darker blue areas on the 26 August image). The RGB images use MODIS bands 7/2/1 to help highlight the areas of of floodwater.

The maps below show the total observed rainfall, the departure from normal, and the percent of normal for the 7-day period ending on 26 August.

Observed 7-day rainfall

Observed 7-day rainfall

7-day rainfall departure from normal

7-day rainfall departure from normal

7-day rainfall percent of normal

7-day rainfall percent of normal

GOES-14 SRSOR: Mesovortices in the eye of Hurricane Marie

August 25th, 2014
GOES-14 0.63 µm visible channel images (click to play YouTube video)

GOES-14 0.63 µm visible channel images (click to play YouTube video)

The GOES-14 satellite was in Super Rapid Scan Operations for GOES-R (SRSOR) mode, providing 1-minute interval images of Category 4 intensity Hurricane Marie over the East Pacific Ocean on 25 August 2014. Even though the eye was cloudy, the 1-minute imagery revealed a number of mesovortices circulating within the eye of Hurricane Marie (above; click image to play YouTube video). Note: the YouTube video is best viewed in Full Screen mode, and clicking on the “Gear” icon to select “1080p HD”.

On the previous day, the eye was less cloudy and mesovortices were more easily seen on GOES-15 0.63 µm visible channel images (below; click to play Animated GIF); however, the GOES-15 images were only available at the routine 15-minute interval, which made tracking the evolution and motion of the mesovortices more difficult. On this day (24 August) Hurricane Marie had rapidly intensified to a Category 5 storm (plot of CIMSS ADT).

GOES-15 0.63 µm visible channel images (click to play Animated GIF)

GOES-15 0.63 µm visible channel images (click to play Animated GIF)

The effect of wind shear on Tropical Storm Karina

August 24th, 2014
GOES-15 0.63 µm visible channel  images (click to play Animated GIF)

GOES-15 0.63 µm visible channel images (click to play Animated GIF)

GOES-15 0.63 µm visible channel images (Animated GIF | MP4 movie | YouTube video | QuickTime movie) showed the decoupling of the upper-level and lower-level circulations of Tropical Storm Karina in the East Pacific Ocean on 24 August 2014. This decoupling was caused by strong wind shear along the western periphery of Category 5 Hurricane Marie, which was located to the east-southeast of Karina (large-scale view). Kudos to Dennis Chesters (NASA/Goddard) for bringing this interesting case to our attention (and providing the QuickTime movie linked to above).

The corresponding GOES-15 10.7 µm IR channel images (Animated GIF | MP4 movie | YouTube video) showed the cold clouds (red to black to white to purple color enhancement) associated with the upper-level circulation moving northward and quickly dissipating; the signature of the warmer clouds (darker cyan color enhancement) associated with the lower-level circulation can also be seen emerging from beneath the cold cloud shield and moving eastward.

GOES-15 10.7 µm IR channel images (click to play Animated GIF)

GOES-15 10.7 µm IR channel images (click to play Animated GIF)

A closer view provided by a Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image from the SSEC RealEarth web map server (below) showed the separation of the upper-level and lower-level circulations around 21:53 UTC.

Suomi NPP VIIRS true-color RGB image

Suomi NPP VIIRS true-color RGB image

A sequence of 4 images (15, 18, 21, and 00 UTC) from the CIMSS Tropical Cyclones site (below) shows GOES-15 6.5 µm water vapor channel images with overlays of deep-layer wind shear (derived from satellite winds). To the east of Karina (which was located in the center of the images), the large anticylcone aloft associated with Category 5 Hurricane Marie can be seen, with increasing vales of southeasterly wind shear moving over Karina.

GOES-15 6.5 µm water vapor images with overlays of deep layer wind shear

15 UTC GOES-15 6.5 µm water vapor images with overlays of deep layer wind shear

The 3 image comparisons below show the separation of the centers of upper-level divergence (yellow) and lower-level convergence (cyan) as the decoupling process was occurring at 18 UTC, 21 UTC, and 00 UTC.

18 UTC GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

18 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

21 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

21 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

00 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

00 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

===== 25 August Update =====

GOES-15 0.63 µm visible channel images, with Metop ASCAT surface scatterometer winds

GOES-15 0.63 µm visible channel images, with Metop ASCAT surface scatterometer winds

Even though the southeastward-moving low-level circulation of Karina had been downgraded to a Tropical Depression with 30 knot winds, there was still an impressive burst of convection just west of the center as it began to move back over warmer water on 25 August. Metop ASCAT surface scatterometer winds (above) showed a small pocket of winds in the 30.0-39.9 knot range (green wind barbs) at 18:29 UTC.

There were also some Tropical Overshooting Top (TOT) targets detected within the convective burst (below); TOT symbols: Red = 0-1 hour previous, Green = 1-2 hours previous, Blue = 2-3 hours previous.

GOES-15 Infrared - Water Vapor difference product, and Tropical Overshooting Tops product (TOT symbols: Red = 0-1 hour previous, Green = 1-2 hours previous, Blue = 2-3 hours previous)

GOES-15 Infrared – Water Vapor difference product, and Tropical Overshooting Tops product (TOT symbols: Red = 0-1 hour previous, Green = 1-2 hours previous, Blue = 2-3 hours previous)

GOES-14 SRSOR: Thunderstorms over Florida

August 21st, 2014
GOES-14 0.63 µm visible channel images (click to play YouTube movie)

GOES-14 0.63 µm visible channel images (click to play YouTube movie)

The GOES-14 satellite was in Super Rapid Scan Operations for GOES-R (SRSOR) mode, providing images at 1-minute intervals over the southeastern US on 21 August 2014. An animation of 0.63 µm visible channel images (above; click to play YouTube movie) showed the development of numerous large thunderstorms, many of which were focused along surface boundaries such as the sea breeze and  convective outflow boundaries from adjacent storms. The YouTube video is best viewed in Full Screen mode, using the “Gear” icon to select 1080p HD resolution.