Hurricane Hector

August 6th, 2018 |
NOAA-20 and Suomi NPP VIIRS Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 and Suomi NPP VIIRS Infrared Window (11.45 µm) images [click to enlarge]

* GOES-17 images shown here are preliminary and non-operational *

A toggle between NOAA-20 and Suomi NPP VIIRS Infrared Window (11.45 µm) images (above; courtesy of William Straka, CIMSS) showed the well-defined eye of Hurricane Hector after it had reached Category 4 intensity on 06 August 2018 (advisories: EPAC | CPAC).

GOES-17 “Red” Visible (0.64 µm) images (below) revealed cloud-top gravity waves within the eyewall region of the storm, along with thin filaments of transverse banding in the northern semicircle farther from the eye.

GOES-17

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-15 (GOES-West) Visible (0.63 µm) and Infrared Window (10.7 µm) images (below) showed that eyewall cloud-top infrared brightness temperatures were in the -70 to -80ºC range (black to white enhancement).

GOES-15 Visible (0.63 µm, left) and Infrared Window (10.7 µm, right) images [click to play animation | MP4]

GOES-15 Visible (0.63 µm, left) and Infrared Window (10.7 µm, right) images [click to play animation | MP4]

A magnified view of GOES-15 Visible images (below) revealed mesovortices within the eye of Hector.

GOES-15 Visible (0.63 µm) images [click to play animation | MP4]

GOES-15 Visible (0.63 µm) images [click to play animation | MP4]

Metop ASCAT surface scatterometer winds (below) surrounding the eye were near 70 knots around 1930 UTC.

GOES-15 Infrared Window (10.7 µm) image and Metop ASCAT surface scatterometer winds [click to enlarge]

GOES-15 Infrared Window (10.7 µm) image and Metop ASCAT surface scatterometer winds [click to enlarge]

The MIMIC-TC morphed microwave product (below) showed that Hector underwent an eyewall replacement cycle early in the day on 05 August, and then maintained a well-defined eye as it subsequently strengthened to a high-end Category 4 intensity on 06 August (ADT | SATCON).

MIMIC-TC morphed microwave product [click to play animation]

MIMIC-TC morphed microwave product [click to play animation]

===== 07 August Update =====

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A nighttime NOAA-20 VIIRS Day/Night Band (0.7 µm) image (above) revealed the presence of mesospheric airglow waves (reference) propagating northwestward away from Category 4 Hurricane Hector on 07 August. Note that these high-altitude waves were not apparent on the corresponding Infrared Window (11.45 µm) image.

Mesoscale Convective System in the Plains

June 11th, 2018 |

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images, with plots of SPC storm reports [click to play MP4 animation]

A Mesoscale Convective System (MCS) developed over eastern Nebraska early in the evening on 11 June 2018, then propagated southward across the Plains during the subsequent overnight hours. GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images with plots of SPC storm reports are shown above; a Mesoscale Sector was positioned over the region, providing images at 1-minute intervals.

A closer look over Kansas using Infrared imagery from polar-orbiting satellites (below) revealed some very cold cloud-top infrared brightness temperatures, which included -87ºC on MODIS, -90ºC on VIIRS and -92ºC on AVHRR.

POES AVHRR, Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images, with plots of SPC storm reports [click to enlarge]

Metop-B AVHRR, Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images, with plots of SPC storm reports [click to enlarge]

The coldest air temperature on 00 UTC rawinsonde data from Dodge City and Topeka, Kansas (below) was -69.5ºC (at altitudes of 14.6 km/49,900 feet at Dodge City, and 17.6 km/57,700 feet at Topeka) — so in theory air parcels and cloud material within a vigorous overshooting top could have ascended a few km (or thousands of feet) beyond those altitudes to exhibit an infrared brightness temperature of -92ºC.

Plots of rawinsonde data from Dodge City and Topeka, Kansas [click to enlarge]

Plots of rawinsonde data from Dodge City and Topeka, Kansas [click to enlarge]

A toggle between re-mapped versions of the GOES-16 ABI and Metop-B AVHRR Infrared imagery over Kansas at the time of the very cold cloud-top infrared brightness temperature (below) revealed 2 important points: (1) with improved spatial resolution (1 km for AVHRR, vs 2 km *at satellite sub-point* for ABI) the instrument detectors sensed much colder temperatures (-92.6ºC with AVHRR vs -81.2ºC with ABI), and (2) due to parallax. the GOES-16 image features are displaced to the northwest. In addition to the isolated cold overshooting top in south-central Kansas, note the pronounced enhanced-V storm top signature in far northeastern Kansas.

Comparison of GOES-16 ABI and Metop-B AVHRR Infrared images [click to enlarge]

Comparison of GOES-16 ABI and Metop-B AVHRR Infrared images [click to enlarge]

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Tropical Invest 90E in the East Pacific

May 8th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of ship reports [click to play MP4 animation]

An organized area of low pressure (Invest 90E) developed in the East Pacific Ocean on 08 May 2018 — the NHC gave it a 50% chance of becoming a tropical depression within 48 hours. GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the formation of a large convective burst in the northwest quadrant of the circulation after 00 UTC on 09 April.

Metop ASCAT surface scatterometer winds from the CIMSS Tropical Cyclones site (below) showed velocities in the 20.0 to 29.9 knot range (dark blue barbs).

GOES-15 Visible (0.63 µm) image with Metop ASCAT surface scatterometer winds [click to enlarge]

GOES-15 Visible (0.63 µm) image with Metop ASCAT surface scatterometer winds [click to enlarge]

The Invest was located in a region of low deep-layer wind shear, with relatively warm Sea Surface Temperatures and modest values of Ocean Heat Content (below).

GOES-15 Visible (0.63 µm) image, with contours of deep-layer wind shear [click to enlarge]

GOES-15 Visible (0.63 µm) image, with contours of deep-layer wind shear [click to enlarge]

Sea Surface Temperature analysis [click to enlarge]

Sea Surface Temperature analysis [click to enlarge]

Ocean Heat Content analysis [click to enlarge]

Ocean Heat Content analysis [click to enlarge]

The hourly MIMIC Total Precipitable Water product (below) showed that Invest 90E was embedded within the ribbon of high moisture associated with the ITCZ.

MIMIC Total Precipitable Water product [click to enlarge]

MIMIC Total Precipitable Water product [click to enlarge]

ACSPO SSTs in AWIPS at WFO Guam

April 24th, 2018 |

ACSPO SSTs constructed from AVHRR, MODIS and VIIRS data from various overpasses at Guam on 18 April 2018 (Click to enlarge)

Sea Surface Temperatures (SSTs) produced from the Advanced Clear-Sky Processor for Oceans (ACSPO) are now being created in real time at the National Weather Service Forecast Office on Guam (where the National Weather Service day begins). The algorithm is applied to data broadcast from polar orbiter satellites and received at the Direct Broadcast antenna sited at the forecast office.  Because there are so many polar orbiters broadcasting data — NOAA-18, NOAA-19, Metop-A, Metop-B, Suomi-NPP, Terra, Aqua — cloudy pixels on one pass are typically filled in with data from a subsequent pass.  When ACSPO software for NOAA-20 is available, data from that satellite will be incorporated as well.  The result is a very highly calibrated, accurate depiction of high spatial resolution tropical Pacific SSTs.  A composite created every 12 hours from the imagery is also available at the forecast office.