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 Paula

October 11th, 2010
GOES-13 0.63 µm visible images

GOES-13 0.63 µm visible images

Tropical Storm Paula formed just off the coast of Honduras on 11 October 2010. GOES-13 0.63 µm visible channel images from the CIMSS Tropical Cyclones site (above) showed the well-defined convective clusters associated with Paula.

The canopy of cold cloud tops was evident on GOES-13 10.7 µm IR channel images (below).

GOES-13 10.7 µm IR images

GOES-13 10.7 µm IR images

A comparison of a GOES-13 10.7 µm IR image with the corresponding Aqua AMSR-E 89 GHz microwave image (below) revealed a large area of heavy precipitation over a good portion of eastern Honduras.

GOES-13 IR image + Aqua AMSR-E 89 GHz microwave image

GOES-13 IR image + Aqua AMSR-E 89 GHz microwave image

========== 12 OCTOBER UPDATE ==========

GOES-15 0.63 µm visible images

GOES-15 0.63 µm visible images

Paula rapidly intensified (CIMSS ADT plot) into a Category 2 hurricane on 12 October 2010. Paula briefly exhibited an eye during the morning hours on 1-km resolution GOES-15 0.63 µm visible channel imagery (above) and on 4-km resolution GOES-15 10.7 µm IR channel imagery (below). At 15:45 UTC,  ASCAT scatterometer winds were measured at 46 knots  surrounding the northern periphery of the center of Paula.

GOES-15 10.7 µm IR images

GOES-15 10.7 µm IR images

AWIPS images of the POES AVHRR Cloud Top Temperature (CTT), Cloud Top Height (CTH), and Cloud Type products at 18:46 UTC  (below) showed that the coldest CTT value was -86º C, with a large area of maximum CTH values of 16 km (much of that overshooting the tropopause, as indicated by the violet color enhancement on the Cloud Type product).

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

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

Valley fog across the Appalachian Mountains region

October 8th, 2010
MODIS and GOES-13 fog/stratus product images

MODIS and GOES-13 fog/stratus product images

AWIPS images showing comparisons of the 4-km resolution GOES-13 fog/stratus product with the 1-km resolution MODIS fog/stratus product (above) and also the 1-km resolution POES AVHRR fog/stratus product (below) offer further demonstration of the importance of improved spatial resolution for the detection of the small-scale filaments of valley fog that were forming across parts of the Appalachian Mountains region during the pre-dawn hours on 08 October 2010.

POES AVHRR and GOES-13 fog/stratus product images

POES AVHRR and GOES-13 fog/stratus product images

Severe thunderstorms in Arizona

October 5th, 2010
GOES-11 (left), GOES-15 (center), and GOES-13 (right) visible images

GOES-11 (left), GOES-15 (center), and GOES-13 (right) visible images

Multiple rounds of severe thunderstorms moved northward across southern Arizona on 05 October 2010, producing hail as large as 2.5 inches in diameter, wind gusts as high as 75 mph, and rainfall in excess of 2 inches at some locations (SPC Storm Reports). According to a Phoenix Public Information Statement, the 2.5 inch diameter hail was some of the largest hail ever reported in Arizona.

A 3-panel comparison of visible channel images from GOES-11, GOES-15, and GOES-13 (above; also available as a QuickTime movie) showed the large clusters of convection, some of which moved through the Phoenix area (station identifier PHX). After 18:30 UTC, the GOES-11 satellite was placed into Rapid Scan Operations (RSO) mode, allowing images as frequently as every 5-7 minutes (in contrast to the standard operational 15-minute image interval on GOES-15 and GOES-13).

AWIPS images of the MODIS 0.65 µm visible channel and 11.0 µm IR Window channel (below) showed a closer view of the storms at 21:01 UTC (3:01 pm local time). MODIS cloud top IR brightness temperatures were as cold as -61º C (darker red color enhancement). Cloud-to-ground lightning strikes, severe reports of hail and wind, and surface METAR reports are also overlaid on the MODIS images.

MODIS 0.65 µm visible and 11.0 µm IR Window images

MODIS 0.65 µm visible and 11.0 µm IR Window images

An AWIPS image of the POES AVHRR Cloud Top Temperature (CTT) product (below) displayed a minimum CTT value of -63º C just southeast of Chandler/Williams Air Force Base (station identifier KIWA) at 21:23 UTC (3:23 pm local time).

POES AVHRR Cloud Top Temperature product

POES AVHRR Cloud Top Temperature product