Tropical Depression (update: Tropical Storm Surigae) over the western Pacific

April 13th, 2021 |

Himwari-8 Clean Window (10.41 µm) Band 13 Infrared imagery, 1220 – 2050 UTC on 13 April 2021 (Click to animate)

Himawari-8 Window Channel infrared imagery (10.41 µm), above, shows a well-defined tropical disturbance (Tropical Depression #2 has become become Tropical Storm Surigae by 0900 UTC on 14 April; this website shows Pacific basin names and includes audio pronunciation examples) moving between Yap and Palau in the western Pacific to the southwest of Guam. The disturbed weather in this region has persisted for many days as it has moved towards the west-northwest, as shown in the rocking MIMIC Total Precipitable Water animation below.

10-day animation of MIMIC Total Precipitable Water over the western Pacific Ocean, 2-12 April 2021 (Click to animate)

NOAA-20 NUCAPS estimates of tropopause Heights, below, show the storm in a region with a very high tropopause, around 120 hPa. The system is moving towards a region with similarly high tropopauses.

Himawari-8 Clean Window (10.41 µm) infrared imagery overlain with NUCAPS estimates of Tropopause Heights, 1540 UTC on 13 April 2021 (Click to enlarge)

Water Vapor imagery (6.24 µm and 7.3 µm) from near sunrise of 14 April show moist air in the immediate environment surrounding the storm (Link).  Visible imagery at sunrise on 14 April, below, show strong and persistent deep convection.

Himawari-8 Visible (0.64 µm) imagery, 2027 – 2114 UTC on 13 April 2021 (Click to enlarge)


It is interesting to note that during the ~12 hours prior to the disturbance (dubbed Tropical Invest 94W) being named Tropical Depression 02W at 12 UTC on 13 April, 2.5-minute interval Himawari-8 Visible (0.64 µm) images from 0002-0802 UTC (below) revealed a trio of low-level vorticies circulating around the incipient storm center. The northernmost vortex appeared to play a role in the initiation of a small cluster of sheared convection. While an exposed low-level circulation center is common in deteriorating highly-sheared tropical cyclones, the presence of 3 vortices during the formative stages of development is rather unusual.

Himawari-8 Visible (0.64 µm) images [click to play animation | MP4]

Himawari-8 Visible (0.64 µm) images [click to play animation | MP4]


Imagery from the CIMSS Tropical Weather Site (link), below, shows the system in a region of very warm Sea Surface Temperatures and modest shear.  Strengthening is forecast as it moves towards the Philippines.

Screencaptures from the CIMSS Tropical Weather Website ca. 2100 UTC on 13 April 2021 (Click to enlarge)


Himawari-8 Imagery courtesy of JMA, the Japan Meteorological Agency.

Thunderstorms northeast of Guam

April 2nd, 2021 |

Himawari-8 Band 13 Clean Window infrared imagery (10.41 µm) from 2300 UTC on 1 April through 1100 UTC 2 April (Click to enlarge)

The animation above shows Himawari full-disk imagery from 2300 UTC on 1 April through 1140 UTC on 2 April and depicts a cluster of thunderstorms over the Pacific Ocean far to the northeast of Guam.  A particular challenge in diagnosing atmospheric events over the open Pacific is the lack of data.  In this case, a timely NOAA-20 overpass (around 0300 UTC), below, allowed for the use of NOAA-Unique Combined Atmospheric Processing System (NUCAPS) profiles to describe the atmosphere in and around this ongoing convection.

NOAA-20 NUCAPS Sounding Availability points, 0300 UTC on 2 April 2020 (click to enlarge)

The toggles below shows Total totals index and Tropopause heights over the Pacific Ocean around Guam and northeastward over the developing convection.  Modest instability surrounds the convective cluster (TT values from 40-44);  somewhat more unstable air (TT > 46) is diagnosed to the northwest of the convection.   Tropopause heights surrounding the convection are high, around 200 mb.  Much lower tropopause heights are diagnosed over the northern part of the domain, and the more unstable TT values are in a region where the tropopause height is sloping.

HImawari-8 Clean Window infrared imagery (10.41 µm) overlain with NUCAPS-derived Total Totals indices (with and without labels) at 0312 UTC on 2 April 2021 (click to enlarge)

Himawari-8 Clean Window infrared imagery (10.41 µm) overlain with NUCAPS-derived estimates of tropopause heights, 0312 UTC on 2 April 2021 (Click to enlarge)

Himawari-8 infrared (Clean Window, 10.41 µm) imagery and NUCAPS-derived lapse rates, 925-700 mb, 0312 UTC on 2 April 2021

NUCAPS can also show you lapse rates within the atmosphere.  It is important when viewing lapse rates to consider that the vertical resolution of NUCAPS profiles is typically not greater than 10 layers within the tropopause.  The toggle above shows lapse rates from 925-700 mb; lapse rates from 850-500 mb are shown below. These domains are is a bit larger than the domain used in showing the tropopause height and Total Totals index above.  The 925-700 mb lapse rates show two regions:  relatively weak stability, with lapse rates around 5 or 6 C/km south of 30 N Latitude, and much stronger stability (Lapse rates closer to 3 C / km ) north of that latitude, to the east of Japan.

The 850-500 mb lapse rates similarly show two general regions:  not as stable south of 30 N, much more stable east of Japan.  There is a more concentrated region of lower stability, however, along the leading edge of the sloped tropopause, at 850-500 mb compared to 925-700 mb, and the 850-500 mb values show larger lapse rates in the air to the east of Japan.  This toggle shows the 925-700 and 850-500 mb lapse rates directly.

Himawari-8 infrared (Clean Window, 10.41 µm) imagery and NUCAPS-derived lapse rates, 850-500 mb, 0312 UTC on 2 April 2021


This region of the Pacific Ocean is scanned by both the Advanced Himawari Imager (AHI) on JMA’s Himawari-8 satellite and the similar Advanced Meteorological Imager (AMI) on KMA’s GK2A satellite.  The animation below combines visible imagery from the two satellites at 0100, 0110, 0230 and 0400 UTC to create a pseudostereocopic image of the convection.

Himawari-8 (left) and GK2A (right) visible imagery (0.64 µm) at 0100, 0110, 0230 and 0400 UTC 2 April (Click to enlarge)

Developing (and ongoing) thunderstorms are usually locations of turbulence. The CIMSS Turbulence product, shown below for the region from 0000 UTC to 0350 UTC, and available online here, does show elevated turbulence probabilities over the convection (located over the western part of the domain shown below).

Turbulence probability plotted on top of Himawari-8 grey-scale water vapor imagery, 0000 – 0350 UTC on 2 April 2021 (Click to enlarge)

Himawari-8 imagery in this blog post courtesy of JMA; GK2A imagery in the blog post courtesy of KMA. Thanks to Brandon Aydlett, WFO Guam, for alerting us to this interesting case.

NUCAPS’ description of a post-frontal atmosphere

March 31st, 2021 |

GOES-16 ABI Band 02 (0.64 µm) visible imagery, 1901 UTC, and NUCAPS estimates of Lapse Rate and Mixing Ratio at 925-700 mb, and 700-300 mb (Click to enlarge)

The animation above cycles through GOES-16 Visible Imagery (0.64 µm) at 1901 UTC as well as simultaneous observations (from NUCAPS) of Lapse Rates (925-700 mb and 700-300 mb) and Mixing Ratio (925-700 mb and 700-300 mb). Thermodynamic information from NUCAPS complements information about the atmosphere that can be inferred by the GOES-16 imagery.

There are very strong low-level (925-700) lapse rates around Missouri behind the cold front that stretches over the south.   The atmosphere there is also very dry.  The smaller lapse rates at higher altitudes (700-300) also are in a region of very dry air.   NUCAPS Soundings from Des Moines, Kansas City and St Louis show the inversion that exists between the steep low-level lapse rates and smaller upper-level lapse rates. There is a much smaller change in lapse rates over the southeastern United States, with small stability all through the troposphere.

NUCAPS themrodynamic fields also capture the relatively moist air within the cloud features in northeastern Iowa, with strong low-level lapse rates on either side of the cloud field there.

Monitoring severe weather as it happens

March 17th, 2021 |

NUCAPS/MADIS Lifted Index, GLM Group Density, GOES-16 Band 13 Infrared Imagery, and ProbSevere polygons, all at ~0939 UTC on 17 March 2021 (Click to enlarge) All imagery from RealEarth

When NOAA’s Storm Prediction Center issues a High Risk of severe weather (below), people sit up and take notice. Are there easily accessible tools to monitor the state of the atmosphere in/around a region of expected severe weather?

The toggle above shows products (early in the morning on 17 March — at 439 AM CDT) in RealEarth that can help. NOAA-Unique Combines Atmospheric Processing System (NUCAPS)/MADIS (Meteorological Assimilation Data Ingest System) Lifted Indices combine tropospheric information from NUCAPS profiles with lower-tropospheric/surface information from MADIS to create Lifted Index fields, twice daily. These fields are generated using HEAP (Hyper-spectral Enterprise Algorithm Package) software (incorporated into CSPP — the Community Software Processing Package) at the UW-CIMSS Direct Broadcast site. A Suomi-NPP (or NOAA-20) overpass will quickly yield stability information. Today’s afternoon Suomi-NPP overpasses occurs around 1730 UTC (east of the High Risk area) and 1915 UTC (Link, from this site.) The toggle above also includes GOES-16 Band 13 infrared (Clean Window, 10.3 µm) information, GLM Group Density, and NOAA/CIMSS ProbSevere (ProbSevere has a stand-alone RealEarth-based site here).  All of these products are useful in monitoring this evolving, dangerous event.   As is often the case, the strongest convection was occurring at 0939 UTC along the edges of the most unstable air, that is, in the instability gradient.

People within the region of elevated risk of Severe Weather on 17 March 2021, especially the region High Risk, should pay especial attention to the weather.

NOAA Storm Prediction Center Risk assessment for 17 March 2021, issued 1300 UTC on 17 March (Click to enlarge)

Added: the Geosphere site (link) gives rapid access to GOES-16 imagery (including mesoscale sectors) and can be used to monitor this evolving situation.

The afternoon image of stability is shown below.

NUCAPS/MADIS Lifted Index, GLM Group Density, and GOES-16 Band 13 Infrared Imagery, all at ~1830 UTC on 17 March 2021 (Click to enlarge) All imagery from RealEarth