Flash Floods in Hawaii

May 10th, 2011 |
MIMIC TPW over the eastern Pacific Ocean

MIMIC TPW over the eastern Pacific Ocean

Images of MIMIC Total Precipitable Water, above, show moist air emerging from the Intertropical Convergence Zone and streaming north over the western islands of Hawaii.

GOES Imager Water Vapor imagery

GOES Imager Water Vapor imagery

GOES-West water vapor imagery (the rocking animation, above) shows the circulation north of the Hawaiian islands that is drawing moisture northward. Because the water vapor channel on the Imager is most accurate at sensing the temperature at the top of the moist layer, however, water vapor imagery can significantly underestimate the amount of water vapor that is in the atmospheric column. The warm temperatures evident over the western Hawaiian Islands (the blue and yellow enhancements) suggest that the water vapor that is emitting radiation sensed by the satellite is warm and confined to lower levels in the atmosphere. Images of Total Precipitable Water give a better indication of how much water vapor is available for precipitation.

Flash flood watches continue through late Tuesday, 10 May, for the western Islands of Hawaii (Oahu, Kauai and Niihau) as the moisture plume continues to drift westward.

The CIMSS MIMIC Total Precipitable Water product is also available for NWS forecast offices to add to their local AWIPS workstations (via Unidata LDM subscription) — a sample animation is shown below. To learn more about the MIMIC TPW product and its applications, a VISIT lesson is also available.

 

MIMIC Total Precipitable Water product (click image to play animation)

MIMIC Total Precipitable Water product (click image to play animation)

Occluded cyclone off the New England coast

May 9th, 2011 |
MODIS 6.5 µm water vapor channel image + surface pressure and surface fronts

MODIS 6.5 µm water vapor channel image + surface pressure and surface fronts

An AWIPS image of the MODIS 6.7 µm “water vapor channel” with an overlay of surface pressure and surface fronts (above) showed a large occluded cyclone off the New England coast on 09 May 2011.

McIDAS images of GOES-13 6.5 µm water vapor channel data (below; click image to play animation) displayed the evolution of the classic signature that indicates a cyclone has reached the occluded stage: the formation of a well-defined “dry swirl” that wraps around the center of the circulation.

GOES-13 6.5 µm water vapor channel images (click image to play animation)

GOES-13 6.5 µm water vapor channel images (click image to play animation)

A comparison of AWIPS images of the 1-km resolution MODIS water vapor channel image with the corresponding 4-km resolution GOES-13 water vapor channel image (below) demonstrates the advantage of improved spatial resolution for analyzing the complex water vapor gradients as the system was becoming occluded.

MODIS 6.7 µm water vapor image + GOES-13 6.7 µm water vapor image

MODIS 6.7 µm water vapor image + GOES-13 6.7 µm water vapor image

Fire in the Okefenokee Swamp region of of Georgia

May 6th, 2011 |
GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 0.63 µm visible channel images (click image to play animation)

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the smoke plume emanating from a large fire that was burning in the Okefenokee Swamp in far southern Georgia on 06 May 2011. This fire originally began on 28 April as a result of a cloud-to-ground lightning strike.

AWIPS images of GOES-13 3.9 µm shortwave IR data (below; click image to play animation) displayed the rapid growth in size of the associated fire “hot spot” (black to red to yellow color enhancement). The hot spot first became apparent around 17:31 UTC (1:31 pm local time), and quickly grew as drier air moved across the region in the wake of a passing cold frontal boundary.

GOES-13 3.9 µm shortwave IR images (click image to play animation)

GOES-13 3.9 µm shortwave IR images (click image to play animation)

A comparison of AWIPS images of 1-km resolution POES AVHRR 3.7 µm and 4-km resolution GOES-13 3.9 µm shortwave IR data (below) demonstrated the advantage of better spatial resolution for locating the fire boundaries. CIMSS participation in GOES-R Proving Ground activities includes making a variety of POES AVHRR images and products available for National Weather Service offices to add to their local AWIPS workstations. A “POES and AVHRR Satellite Products in AWIPS” VISIT training lesson is also available to help users understand the products and their applications to weather analysis and forecasting.

POES AVHRR 3.7 µm + GOES-13 3.9 µm shortwave IR image comparison

POES AVHRR 3.7 µm + GOES-13 3.9 µm shortwave IR image comparison

===== 07 MAY UPDATE =====

On the following day, a comparison of 250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) revealed the dense smoke plume (which appeared as varying shades of  gray on the true color image), as well as the large size of the burn scar (which appeared as darker shades of darker red to brown on the false color image) resulting from this fire that had been burning for several days. Also evident was the fact that several active, very hot fires were burning at this time along the edges of the burn scar — these hot fires appeared as the brighter pink areas on the false color image. Many of these fire “hot spots” could even be detected through the dense smoke.

MODIS true color and false color images

MODIS true color and false color images

Flooding at the confluence of the Mississippi and Ohio Rivers

May 4th, 2011 |
MODIS 0.65 µm visible channel image + MODIS 2.1 µm near-IR "snow/ice channel" image

MODIS 0.65 µm visible channel image + MODIS 2.1 µm near-IR "snow/ice channel" image

 

A comparison of AWIPS images of the 1-km resolution MODIS 0.65 µm visible channel (first shown with a map overlay and location of METAR sites) and the corresponding 1-km resolution MODIS 2.1 µm near-IR “snow/ice channel” (above) shows the areal coverage of flood waters across the region of the confluence of the Mississippi River and the Ohio River on 04 May 2011. Since water happens to be a strong absorber at the 2.1 µm wavelength, it shows up as a very dark feature on the MODIS “snow/ice channel” image — making it more useful for locating areas of flooding than just a simple visible channel image.

A similar near-IR channel will be on the ABI instrument of the future GOES-R satellite. 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.

MODIS True-color imagery from the SSEC MODIS Today website can be used to compare data from this year and last year, shown below. In the linked-to-images, the Mississippi River north of Memphis (located at the bottom edge of each image) meanders through the center part of the images. There are several former meanders of the river in Arkansas and Tennessee that are filled with water this year, but not last.

 

MODIS true color images (04 May 2010 and 04 May 2011)

MODIS true color images (04 May 2010 and 04 May 2011)