Chan-Hom approaches the coast of China

July 10th, 2015


The video above shows 5 hours of Himawari-8 10.35 µm Infrared imagery from Typhoon Chan-Hom as it moves through the Yellow Sea towards the coast of China (original animated gif here; mp4 here). The location of Shanghai is indicated in the first frame, and this blog post talks about the history of typhoon landfalls near Shanghai. The appearance of the storm in the animation above is relatively constant.

Himawari-8 10.35 µm infrared imagery, 1447-2002 UTC on 6 July 2015 (Click to animate)

Himawari-8 6.2 µm (top), 6.9 µm (middle) and 7.3 µm (bottom) water vapor infrared imagery, 0000 UTC 8 July 2015 – 1500 UTC 10 July 2015 (click to animate)

The three water vapor channels from Himawari-8, above, over the course of the past 3 days show a steady northwestward motion and a decrease in the cold cloud tops surrounding the storm, consistent with the weakening that has been observed after peak intensity at ~1500 UTC on July 9. Typhoon Nangka remains southeast of Chan-Hom; Typhoon Linfa has dissipated after having made landfall over south China. Chan-Hom’s path (below) is over progressively colder water and significant intensification is not expected before landfall.

Sea-Surface Temperatures over the Yellow Sea, along with Chan-Hom's past and projected path (Click to enlarge)

Sea-Surface Temperatures over the Yellow Sea, along with Chan-Hom’s past and projected path (click to enlarge)

A DMSP SSMIS 85 GHz microwave image at 0946 UTC on 10 July, below, showed that Category 3 Typhoon Chan-Hom was undergoing an eyewall replacement cycle as the small inner eyewall was being replaced by a much larger outer eyewall. Also on the image are 1244 UTC Metop ASCAT surface scatterometer winds, which displayed a large area with winds in the 50-59.9 knot range along the western periphery of the tropical cyclone.

DMSP SSMIS microwave image at 0946 UTC, and Metop ASCAT winds at 1244 UTC (click to enlarge)

DMSP SSMIS microwave image at 0946 UTC, and Metop ASCAT winds at 1244 UTC (click to enlarge)

Tropical Storm Ela east of Hawai’i

July 9th, 2015
Suomi NPP VIIRS visible (0.64 µm) and Infrared (11.45 µm) images of Tropical Depression 4E at 2224 UTC on 08 July

Suomi NPP VIIRS visible (0.64 µm) and Infrared (11.45 µm) images of Tropical Depression 4E at 2224 UTC on 08 July

Tropical Storm Ela began as Tropical Depression 4E about 900 miles east of Hilo, Hawai’i around 03 UTC on 08 July 2015. A comparison of daytime images of Suomi NPP VIIRS 0.64 µm Visible channel and 11.45 µm Infrared channel images (above) showed the somewhat disorganized appearance of TD 4E at 2224 UTC on 08 July — the low-level circulation center (LLCC) was located to the southwest of the clusters of deep convection associated with the system.

About 12 hours later, a nighttime comparison of VIIRS 0.7 µm Day/Night Band (DNB) and 11.45 µm Infrared channel images at 1052 UTC on 09 July (below) continued to show a similar disconnect between the LLCC and clusters of deep convection in the eastern semicircle of recently-upgraded Tropical Storm Ela. The coldest cloud-top IR brightness temperature in the convection closest to the storm center was -78º C. Even though the Moon was in the Waning Crescent phase (at 43% of Full), it still provided enough illumination to aid in the location of the LLCC, as noted in a discussion issued by the CPHC:

TROPICAL STORM ELA DISCUSSION NUMBER   7
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP042015
500 AM HST THU JUL 09 2015

A 1052Z VIIRS DAY/NIGHT BAND IMAGE WAS INSTRUMENTAL IN HELPING TO LOCATE THE PARTIALLY EXPOSED CENTER OF ELA THIS MORNING.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared (11.45 µm) images of Tropical Storm Ela at 1052 UTC on 09 July

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared (11.45 µm) images of Tropical Storm Ela at 1052 UTC on 09 July

According to satellite-derived winds products from the CIMSS Tropical Cyclones site, there was strong divergence and a well-defined outflow channel in the northern quadrant of Ela (below), whose center was located at 19.3º N 145.1º W at 09 UTC on 09 July.

GOES-15 water vapor (6.5 µm) images with satellite wind derived upper tropospheric divergence and winds

GOES-15 water vapor (6.5 µm) images with satellite wind derived upper tropospheric divergence and winds

The reason that the LLCC remained exposed from the elements of deep convection was the fact that Ela was encountering increasing amounts of southwesterly deep-layer wind shear as it tracked northwestward  (below).

GOES-15 Infrared (10.7 µm) images, with an overlay of deep-layer wind shear at 18 UTC on 09 July

GOES-15 Infrared (10.7 µm) images, with an overlay of deep-layer wind shear at 18 UTC on 09 July

========================= Added July 10 2015 ============================

The southwesterly shear over the storm decoupled the surface circulation from the overlying convection, and Ela was downgraded to a depression early on 10 July 2015. The 0700 UTC 10 July 2015 image below shows ASCAT Scatterometer winds depicting a low-level swirl well east of Hawai’i; deep convection with the system is hundreds of kilometers to the northeast.

ASCAT Scatterometer winds and GOES-15 infrared (10.7 µm) imagery, 0700 UTC 10 July 2015

ASCAT Scatterometer winds and GOES-15 infrared (10.7 µm) imagery, 0700 UTC 10 July 2015 (Click to enlarge)

The long-lasting remnants of Tropical Storm Bill

June 21st, 2015
Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images (click to enlarge)

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images (click to enlarge)

Advisories on Tropical Storm Bill were initiated when the system organized and intensified off the coast of Texas at 03 UTC on 16 June 2015 (GOES-13 IR image animation). Bill moved inland during the afternoon hours on 16 June, as can be seen in a comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 1916 UTC (above).

Late in the day on 17 June, the general appearance of downgraded Tropical Depression Bill on GOES-13 6.5 µm water vapor channel imagery (below) began to suggest that the system might be undergoing an extratropical transition (intrusion of dry air in the southern quadrant, along with a blosominig comma head signature on the northern quadrant) — but Bill maintained sufficient tropical characteristics to continue being named a tropical depression.

GOES-13 6.5 µm water vapor channel images, with surface pressure and frontal analyses (click to play animation)

GOES-13 6.5 µm water vapor channel images, with surface pressure and frontal analyses (click to play animation)

The circulation of TD Bill maintained its identity on satellite imagery as the storm remained over land for the next 3+ days, curving northeastward and moving across the Ohio River Valley region. Slow-moving TD Bill dropped over 12 inches of rain at some locations in Texas and Oklahoma, with amounts exceeding 8 inches in Missouri and 6 inches in Indiana (WPC storm total rainfall totals), before being designated a post-tropical feature at 21 UTC on 20 June (WPC advisories).

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

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

The history of Bill can be followed in a multi-day animation of GOES-13 10.7 µm IR channel imagery (above); in addition, the lower-tropospheric circulation of Bill can be followed using the CIMSS 850 hPa relative vorticity product (below).

GOES-13 850 hPa relative vorticity product (click to play animation)

GOES-13 850 hPa relative vorticity product (click to play animation)

As the post-tropical remnants of Bill emerged over the Atlantic Ocean early in the day on 21 June, it still appeared to be associated with an arc of deep convection as seen on a comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 1742 UTC (below). A similar comparison of Terra MODIS visible and IR images at 1514 UTC can be seen here.

Soumi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Soumi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Hurricane Blanca in the eastern Pacific Ocean

June 4th, 2015
Suomi NPP VIIRS Day Night Band 0.70 µm Visible and 11.35 µm infrared imagery over Blanca, 0829 UTC 4 June 2015 (Click to enlarge)

Suomi NPP VIIRS Day Night Band 0.70 µm Visible and 11.35 µm infrared imagery over Blanca, 0829 UTC 4 June 2015 (Click to enlarge)

Suomi NPP overflew Hurricane Blanca early in the morning on 4 June, during a near-full Moon, and the Day Night Band imagery, above, toggled with the 11.35 µm imagery, show the hurricane. (Day/night band imagery of the eye is here, the entire storm is here, and zoomed out is here; click for 11.35 µm imagery of the eye, the entire storm, and zoomed out). Deep convection overnight did not wrap all the way around the storm. Evidence of dry air entrained into the circulation is apparent.

GOES-15 Imager 10.7 µm infrared channel images (click to play animation)

GOES-15 Imager 10.7 µm infrared channel images (click to play animation)

The 3-hourly animation of 10.7 micron imagery, above, from 3-4 June 2015 shows Hurricane Blanca southwest of the Mexican coast, drifting southwestward. Cold cloud tops that were apparent at the start of the loop warm by the end, perhaps because convection is being suppressed by the presence of dry air. MIMIC Total Precipitable Water (below) suggests that dry air is being entrained into Blanca’s circulation from the north. (Update on Andres, also apparent in the MIMIC Total Precipitable Water animation: This overlay of Metop ASCAT winds on top of GOES 10.7 imagery from ~0530 UTC on June 4 shows a swirl that is offset from the convection. Andres is forecast to become post-tropical later on June 4.)

MIMIC Total Precipitable Water animation for the 72 hours ending 1300 UTC on 4 June 2015 (click to enlarge)

MIMIC Total Precipitable Water animation for the 72 hours ending 1300 UTC on 4 June 2015 (click to enlarge)

Visible imagery from GOES-13 from June 3 and June 4, below, show a less distinct/cloudier eye on 4 June compared to 3 June. Multiple overshooting tops persist in the circulation of the system, but the coarse 30-minute temporal resolution of the imagery cannot capture the lifecycle of these quickly evolving events.

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

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

Water vapor imagery from GOES-13 from June and June 4, below, also confirm a consistently less organized storm. The dry air penetrating from the north is apparent in the imagery, but it appears not to have entered into the circulation of the storm, at least not at levels detected by the water vapor channel.

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

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

Morphed Microwave Imagery (MIMIC) from this website shows the evolution of the central eye structure, below. The eyewall that was much closer to the storm center at the start of the animation has been replaced by a weaker, larger eyewall.

Morphed Microwave Imagery, 48 hours ending 1500 UTC 4 June 2015 (click to enlarge)

Morphed Microwave Imagery, 48 hours ending 1500 UTC 4 June 2015 (click to enlarge)

For more information on this storm, please visit the National Hurricane Center website or the SSEC/CIMSS Tropical Weather website.