Morphed Total Precipitable Water (click image to play animation)

The “cutoff low” system that had been slowly moving across the country for the past week spawned heavy rains which caused flooding in parts of the New York City (NYC) metropolitan area on the morning of 08 May 2013. The image above, of MIMIC Total Precipitable Water, showed a plume of moisture-rich air moving northwestward from the tropical Atlantic towards New York (in advance of the surface frontal system associated with the cutoff low). This region of enhanced precipitable water was seen on the previous day as well. The blended Total Precipitable Water Product (as described here) also showed a plume of higher-than-normal precipitable water air moving over New York City — values of 170+% of normal are over New York City, with a value exceeding 200% (in yellow) sits over the Atlantic Ocean.

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

High values of Total Precipitable Water were being been entrained by the circulation of the upper-level low, as shown in the animation of GOES-13 water vapor channel images above. The cyclonic circulation had drawn the moisture north and west into the NYC metropolitan region, and convection developing in the cyclonic flow was responsible for the heavy rainfall. A Suomi/NPP VIIRS 11.45 µm IR image, below, overlain with model-based 500-mb geopotential height fields, showed the strong convection and the cyclonic flow moving into New York. It is interesting to note that the southern tail end of the convection sat right over the Gulf Stream.

Suomi/NPP VIIRS 11.45 µm imagery

The GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-10 minutes. Discrete convective cells with cloud-top IR brightness temperatures colder than -60º C (darker red color enhancement) can be seen developing and moving northwestward over the NYC area on 4-km resolution GOES-13 10.7 µm IR channel images (below).

GOES-13 10.7 µm IR channel images (click image to play animation)

A closer view using 1-km resolution POES AVHRR 0.63 µm visible channel and 10.8 µm IR channel images at 10:09 UTC or 6:09 AM local time (below) revealed the texture and shadowing of overshooting tops on the visible image, with cloud-top IR brightness temperature values as cold as -67º C (dark red color enhancement).

POES AVHRR 0.64 µm visible channel and 10.8 µm IR channel images

GOES-13 0.63 µm visible channel imagery (below) showed the different bands of convection that developed offshore and moved inland across the NYC metropolitan area.

GOES-13 Visible Imagery (0.63 µm) (click image to play animation)

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GOES-13 10.7 µm IR channel images (click image to play animation)

McIDAS images of 4-km resolution GOES-13 10.7 µm IR channel images (above; click image to play animation) showed the development of large thunderstorms that produced heavy rainfall (including 5.18 inches at San Sebastian) which led to flash flooding over parts of Puerto Rico (Local Storm Report) on 07 May 2013. Since their primary Doppler radar was out of service due to an upgrade to Dual-Polarization technology, the National Weather Service forecast office at San Juan had requested that the GOES-13 (GOES-East) satellite be placed into Rapid Scan Operations (RSO), which provided images as frequently as every 5-10 minutes (instead of the nominal 15-minute image interval). The coldest cloud top IR brightness temperature seen on the GOES-13 IR image sequence above was -69º C at 17:10 UTC.

Due to a full-disk scan at 18:00 UTC, there was a 30-minute gap between the 17:45 UTC and 18:15 UTC GOES-13 images. A timely overpass of the NOAA-19 polar-orbiting satellite at 18:03 UTC provided a 1-km resolution AVHRR 10.8 µm IR image during this 30-minute GOES-13 gap (below), which revealed that a new convective cell had rapidly developed over the northwestern portion of Puerto Rico (exhibiting a cloud-top IR brightness temperature as cold as -79º C).

NOAA-19 AVHRR 10.8 µm IR channel image

AWIPS images of the MIMIC Total Precipitable Water (TPW) product (below; click image to play animation) showed that an elongated plume of high TPW (50 to 60 mm or 2.0 to 2.4 inches, darker orange color enhancement) was rotating across the Puerto Rico region during this period, providing ample moisture to fuel the development of deep convection and heavy rainfall. Surface analyses suggest that the eastern portion of the TPW  plume was associated with the remnants of a cold frontal boundary, while an impulse over the Caribbean Sea was helping to transport higher TPW values from the south (TJSJ is the station identifier for San Juan, Puerto Rico).

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

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Suomi NPP VIIRS 0.64 µm visible and 3.74 µm shortwave IR images

A comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and 3.74 µm shortwave IR channel data (above) showed 2 signatures of an ongoing low-level eruption of the Cleveland Volcano located on the Aleutian Island chain of Alaska: a “hot spot” of 45.5º C (red color enhancement) on the shortwave IR image, and a thin plume of gas, steam, and minor amounts of ash streaming eastward at 22:33 UTC on 04 May 2013. The Cleveland volcano began the eruption around 13:00 UTC earlier that day. The volcano is located on the western portion of Chuginadak Island (denoted by the cyan range ring centered on the island) — however, note that the mapping navigation is slightly off on the images (making the volcano hot spot and plume source appear as if they were located in the waters just west of the island).

Several hours later, a Suomi NPP VIIRS 0.7 µm Day/Night Band image at 12:18 UC on 05 May (below) showed the bright night-time glow of the erupting Cleveland volcano.

Suomi NPP VIIRS 0.7 µm Day/Night Band image

Another feature of interest was the von Karman vortex street further to the east, as seen on 2 consecutive Suomi NPP VIIRS 0.64 µm visible channel images (below). Northwesterly flow within the marine boundary layer was being perturbed by the high terrain of the Aleutian Range on the tip of the Alaska Peninsula, with the resulting vortex street streaming southeastward downwind of the peninsula.

Suomi NPP VIIRS 0.64 µm visible channel images

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GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

A comparison of McIDAS images of 1-km resolution GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel data (above; click image to play animation) showed the smoke plume from the Springs Fire near Camarillo, California on 02 May 2013. GOES-15 (positioned over the Equator at 135º West longitude) had a better viewing angle of the smoke plume, while GOES-13 (positioned at 75º West longitude) was in Rapid Scan Operations (RSO) mode and was therefore able to provide more frequent images.

AWIPS images of 4-km resolution GOES-15 3.9 µm shortwave IR data (below; click image to play animation) showed the development and rapid growth of the fire “hot spot” signature (dark black enhancment) after 14:01 UTC (7:01 AM local time). At Point Mugu (station identifier KNTD), the surface winds gusted to 27 knots from the southwest at 17 UTC, then shifted and gusted to 30 knots from the northwest at 19 UTC, and then shifted again and gusted to 30 knots from the southwest at 20 UTC. Surface visibility at this site was reported to be as low as 2 miles to the north and northeast of the station, with an overcast layer of smoke during most of the day. Not far inland at Sandberg (station identifier KSDB), winds gusted to 46 knots and the dew point temperature dropped to -19º F (making for a relative humidity of 2%!).

GOES-15 3.9 µm shortwave IR images (click image to play animation)

===== 03 May Update =====

AWIPS images of 1-km resolution Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band data at 09:41 UTC or 2:41 AM local time on 03 May (below) showed a very large fire “hot spot” (yellow to red to black color enhancement) on the shortwave IR image, and the Day/Night Band revealed the hazy signature of smoke aloft that had drifted offshore and south and southeastward along the southern California coast.

Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band images

During the following afternoon on 03 May, 250-meter resolution true-color and false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed the dense smoke plume continuing to drift offshore; the hottest active fire regions appeared as light red features on the false-color image.

MODIS true-color and false-color Red/Green/Blue (RGB) images

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