Super Typhoon Megi

October 18th, 2010 |
MTSAT-1R 0.68 µm visible channel images

MTSAT-1R 0.68 µm visible channel images

MTSAT-1R 0.68 µm visible channel images (above) tracked the eye of Super Typhoon Megi making landfall across the northern portion of the island of Luzon in the Philippines on 17-18 October 2010.

The Morphed Integrated Microwave Imagery at CIMSS (MIMIC) product (below) showed the well-defined eye of Megi prior to making landfall, along with the effect that the rugged terrain of Luzon had on the typhoon before it later emerged into the South China Sea.

Morphed Integrated Microwave Imagery at CIMSS (MIMIC)

Morphed Integrated Microwave Imagery at CIMSS (MIMIC)

A Terra MODIS 11.0 µm IR image (below; zoomed-in version) revealed the eye and surrounding concentric eyewall structure of Megi at 02:30 UTC on 19 October — the coldest IR brightness temperature seen at that time was -82º C (purple color enhancement) to the south of the eye.

Terra MODIS 11.0 µm IR image

Terra MODIS 11.0 µm IR image

Strong winds in the Alaska Panhandle region

October 12th, 2010 |
POES AVHRR visible, IR, and Mean Sea Level Pressure contours

POES AVHRR visible, IR, and Mean Sea Level Pressure contours

AWIPS images of POES AVHRR visible and IR channel data with an overlay of Mean Sea Level Pressure contours (above) showed a very intense Storm Force low that was approaching the Alaska Panhandle region at 20:42 UTC on 12 October 2010. This large storm was producing widespread reports of strong winds and heavy rainfall, with wind gusts as high as 126 mph reported from a boat equipped with wind instruments in Thomas Basin near Ketchikan. There were also reports of multiple trees down in nearby Saxman.

The cloud features at 20:42 UTC could be further characterized examining the POES AVHRR Cloud Type, Cloud Top Temperature (CTT), and Cloud Top Height (CTH) products (below). CTT values within portions of the large “comma cloud” were as cold as -50 to -55º C, with CTH values as high as 8-9 km.

POES AVHRR Cloud Type, Cloud Top Temperature, and Cloud Height products

POES AVHRR Cloud Type, Cloud Top Temperature, and Cloud Height products

The evolution of this Storm Force low can be seen in a series of POES AVHRR IR images (below) — from the tell-tale “cusp” cloud feature indicative of strong cyclogenesis early in the day, to a closed-off, almost eye-like cloud structure later in the day.

POES AVHRR IR images

POES AVHRR IR images

A POES AVHRR visible image with an overlay of 1-hour-interval GOES-derived Atmospheric Motion Vector (AMV) winds (below) showed the broad swath of strong winds associated with a low-level jet that was moving inland — a large number of AMVs had speeds in excess of 60 knots.

POES AVHRR visible image + GOES-derived Atmospheric Motion Vector winds

POES AVHRR visible image + GOES-derived Atmospheric Motion Vector winds

A comparison of an 8-km resolution GOES-11 water vapor image with the corresponding 1-km resolution MODIS water vapor image (below) revealed a well-defined dry slot moving inland. Strong momentum aloft was being transported downward to lower altitudes within this dry slot, contributing to the high winds that were being reported at the surface.

MODIS water vapor image + GOES-11 water vapor image

MODIS water vapor image + GOES-11 water vapor image

An animation of GOES-11 6.7 µm water vapor channel images (below) depicted the evolution of this dry slot during the day.

GOES-11 water vapor channel images

GOES-11 water vapor channel images

A comparison of the 12:00 UTC GOES-11 water vapor image with the corresponding MIMIC Total Precipitable Water product (below) indicated that a long atmospheric river of rich moisture was feeding into the developing cyclone. Note that not all  of the  “moist” features on the water vapor image necessarily correspond to areas of high total precipitable water content.

GOES-11 water vapor image + MIMIC Total Precipitable Water product

GOES-11 water vapor image + MIMIC Total Precipitable Water product

Hurricane Alex

June 30th, 2010 |
GOES-13 10.7 µm IR imagery

GOES-13 10.7 µm IR imagery

GOES-13 10.7 µm IR imagery from the CIMSS Tropical Cyclones site (above) showed the development of large convective bursts around the center of Hurricane Alex during the 29 June30 June 2010 period. Alex became the first June hurricane in the Atlantic Basin since the 1995 tropical cyclone season (which produced Hurricane Allison).

An AWIPS image of POES AVHRR 11.0 µm IR channel data (below) showed very cold IR brightness temperatures of -80 to -90º C (violet color enhancement) associated with the convective bursts as well as the distant bands of intense convection surrounding the hurricane.

POES AVHRR 10.8 µm IR image

POES AVHRR 10.8 µm IR image

Deep layer wind shear (below) over the western Gulf of Mexico remained very light, which was favorable factor for further intensification prior to making landfall.

GOES-13 IR image + deep layer wind shear

GOES-13 IR image + deep layer wind shear

DMSP SSMI/S 85 GHz microwave imagery (below) showed the possible development of some inner banding structure, as well as the larger and more intense bands of convection far from the center of Alex.

SSMI/S microwave image

SSMI/S microwave image

AWIPS images of the MIMIC Total Precipitable Water product (below) indicated that a rich source of moisture remained in place across the entire Gulf of Mexico region (with TPW values in excess of 60 mm).

MIMIC Total Precipitable Water product

MIMIC Total Precipitable Water product

UPDATE: AWIPS images of the MODIS 0.65 µm visible and 11.0 µm IR channel data with an overlay of ASCAT scatterometer surface winds (below) depicted the eye of Hurricane Alex at 16:58 UTC on 30 June.

MODIS 0.655 µm visible and 11.0 µm IR images + ASCAT scatterometer winds

MODIS 0.655 µm visible and 11.0 µm IR images + ASCAT scatterometer winds

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POES AVHRR Cloud Top Temperature, Cloud Top Height, and Cloud Type products

POES AVHRR Cloud Top Temperature, Cloud Top Height, and Cloud Type products

Later in the day, AWIPS images of the POES AVHRR Cloud Top Temperature (CTT), Cloud Top Height (CTH), and Cloud Type products at 22:05 UTC (above) displayed a large area of CTT values in the -80 to -83º C range (violet color enhancement), with CTH values as high as 17 km (darker blue color enhancement). The Cloud Type product categorized a large portion of the coldest/highest cloud tops surrounding the eye as “overshooting(lighter violet color enhancement), in general agreement the the GOES InfraRed/Water Vapor difference overshooting top detection technique of Olander and Velden (2009).


GOES-15 and GOES-13 0.63 µm visible channel images

GOES-15 and GOES-13 0.63 µm visible channel images

The eye of Hurricane Alex became more well-defined on GOES visible imagery as it approached the coast of Mexico, as seen on a comparison of GOES-15 and GOES-13 visible images at 15 minute intervals (above) and also on GOES-13 Rapid Scan Operations (RSO) images at 5-10 minute intervals (below). An impressive convective burst was evident just as the eye was nearing the coastline — in fact, Alex rapidly intensified into a 90 knot Category 2 hurricane just prior to making landfall, as can be seen on this plot of the CIMSS Automated Dvorak Technique. This made Alex the first Category 2 or stronger hurricane to occur in the month of June since Hurricane Alma back in 1966.

GOES-13 0.63 µm visible channel images (Rapid Scan Operations)

GOES-13 0.63 µm visible channel images (Rapid Scan Operations)

Historic heavy rainfall event at Nashville, Tennessee

May 2nd, 2010 |
GOES-13 10.7 µm IR images

GOES-13 10.7 µm IR images

During 01 May02 May 2010 the 2-day total precipitation at Nashville, Tennessee was 13.57 inches — by far the wettest 2-day period on record for that location (the old record was 6.68 inches on 13-14 September 1979, in association with Hurricane Fredrick). With 7.25 inches falling on 02 May (5.57 inches of that in just 6 hours!), this also set a record for the wettest calendar day on record. And, remarkably, only 2 days into the month May 2010 is already the wettest May on record for Nashville. An animation of 24-hour observed precipitation can be seen here.

AWIPS images of 4-km resolution GOES-13  10.7 µm IR channel data (above) showed several rounds of deep convection moving northeastward across the region during the period, with some cells exhibiting IR cloud top brightness temperatures as cold as -74º C. This convection was developing along and ahead of a slow-moving cold frontal boundary.

Images of 1-km resolution MODIS  11.0 µm IR data (below) revealed even colder cloud top IR brightness temperature values of -82º C with some of the stronger convection developing over far western Tennessee. The 1-km resolution AVHRR Cloud Top Temperature (CTT) product also indicated CTT values as low as -80º C for some of the stronger thunderstorms.

MODIS 11.0 µm IR image

MODIS 11.0 µm IR image

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Blended Total Precipitable Water (TPW) product

Blended Total Precipitable Water (TPW) product

However, more important than the cold convective cloud top temperatures was the plume of rich moisture that was feeding northward across the Gulf of Mexico and into the Tennessee Valley. The Blended Total Precipitable Water (TPW) product (above) showed that TPW values began to exceed 50 mm across the Lower Mississippi River Valley late in the day on 01 May, with TPW within the moisture plume reaching 75 mm over the Gulf of Mexico late in the day on 02 May. TPW values were greater than 200% of normal across most of the Mississippi and Tennessee Valleys, as well as within the northward-moving moisture plume.

With the greater areal coverage on AWIPS of the MIMIC TPW product (below), it could be seen that the plume of moisture moving meridionally (northward) across the Gulf of Mexico actually originated from the zonal band of deep moisture associated with the Inter-Tropical Convergence Zone (ITCZ) that was located between the Equator and 10º N latitude over the far eastern Pacific Ocean. MIMIC TPW values over the Gulf of Mexico became greater than 60 mm late in the day on 02 May; GOES-13 Sounder TPW values were also as high as 66 mm over the Gulf of Mexico on 02 May.

Incidentally, this case also serves as a great example of why you can’t always identify and track important TPW plumes on standard water vapor imagery — the water vapor channel is often sensing radiation from a layer that is above that of the bulk of the TPW plume (comparison of GOES water vapor image and MIMIC TPW image).

 

MIMIC Total Precipitable Water (TPW) product

MIMIC Total Precipitable Water (TPW) product

Rawinsonde data from Nashville (below) generally revealed a very moist atmosphere throughout much of the troposphere during the period, with TPW values as high as 2.00 inches at 00 UTC on 02 May.

Nashville, Tennessee rawinsonde data

Nashville, Tennessee rawinsonde data

===== 03 MAY UPDATE =====

Before (29 April) and after (03 May) MODIS false color RGB images

Before (29 April) and after (03 May) MODIS false color RGB images

A comparison of before (29 April 2010) and after (03 May 2010) 250-meter resolution MODIS  Red/Green/Blue (RGB) false color images (above) from the SSEC MODIS Today site shows dramatic changes in some of the smaller rivers across western and central Tennessee following the record-setting rainfall that occurred on 01-02 May. On the false color images (created using MODIS bands 7/2/1 as the R/G/B channels), water appears as darker shades of blue,  while dense vegetation appears as brighter shades of  green.

On the corresponding set of before/after MODIS true color images (created using MODIS bands 1/4/3 as the R/G/B channels), increased river water turbidity (varying shades of light brown) can be seen — a result of  high amounts of sediment transport (below).

Before (29 April) and after (03 May) MODIS true color images

Before (29 April) and after (03 May) MODIS true color RGB images

AWIPS images of the MODIS 0.645 µm visible channel and the 2.1 µm near-IR “snow/ice channel” data (below) demonstrate how the 2.1 µm imagery can be used to better identify flooded areas that do not show up as well on the visible channel imagery. Water (like snow and ice) is a strong absorber at the 2.1 µm wavelength, and thus appears very dark on the  “snow/ice” image.

MODIS 0.645 µm visible channel and 2.1 µm near-IR "snow/ice" channel images

MODIS 0.645 µm visible channel and 2.1 µm near-IR “snow/ice” channel images

CIMSS has been supplying a variety of MODIS images and products in AWIPS (some of which are displayed on this page) to a number of NWS forecast offices as a part of the GOES-R Proving Ground effort.

===== 05 MAY UPDATE =====

MODIS false color images from 03, 04, and 05 April 2010

MODIS false color images from 03, 04, and 05 May 2010

A comparison of 250-meter resolution MODIS false color images from 03 May, 40 May, and 05 May 2010 (above) showed that while some of the smaller rivers and tributaries appeared to be receding somewhat, a number of the larger rivers did appear to remain swollen, with many areas still inundated with flood waters.

Related sites:

NWS Nashville precipitation total map
AccuWeather WeatherMatrix blog
Weather Underground blog