Tropical Storm Beryl forms in the Atlantic Ocean

July 5th, 2018 |

GOES-16 Band 2 (“Red Visible”, 0.64 µm) Imagery over the Atlantic Ocean, 0915-2130 UTC on 5 July 2018 (Click to animate)

The season’s second named tropical cyclone in the Atlantic Basin has formed.  GOES-16 visible imagery, above (click to play an animated gif), shows Tropical Storm Beryl moving westward just north of 10 º N Latitude between 40 º and 50 º W Longitude.  The infrared imagery (10.3 µm), the Clean Window, below shows a compact storm with cold cloud tops and a central dense overcast.

GOES-16 Band 13 (“Clean Window”, 10.3 µm) Infrared Imagery over the Atlantic Ocean, 0915-2130 UTC on 5 July 2018 (Click to animate)

Much of the tropical Atlantic north of 10 N Latitude shows little convection.  This is because of a Saharan Air Layer, shown below (in red) from a screen capture from the CIMSS Tropical Website (Click here for the latest SAL analysis). An important component of the SAL analysis is the Split Window Difference field (10.3 µm – 12.3 µm) that can diagnose both moisture and dust. The SAL analysis shows considerable dry Saharan air over the Atlantic; Beryl has formed along its southern edge. Compare the SAL analysis to the Split Window Difference field, below, that shows dry air in blue. Similar features are present in both. The GOES-16 Low-Level Water Vapor Infrared Imagery (7.34 µm), here, shows similar features as well. There are multiple ways to diagnose dry air with GOES-16.

Saharan Air Layer (SAL) Analysis, 2100 UTC on 5 July 2018 (Click to enlarge)

GOES-16 Split Window Difference field (10.3 -12.3 µm) Imagery over the Atlantic Ocean, 2100 UTC on 5 July 2018 (Click to enlarge)

NUCAPS Soundings from Suomi NPP can be used to diagnose the thermodynamics of the atmosphere surrounding Beryl. The image below shows NUCAPS Soundings locations between 1500 and 1600 UTC on 5 July 2018, and the points are color-coded to describe the data (as discussed here). A Sounding near 16.3 N, 43.1 W (north of Beryl) shows dryness at mid-levels; total precipitable water is only 1.27″. A Sounding closer to the storm, at 10.3 N, 43.5 W (west of Beryl) is much wetter: total precipitable water is 2.12″. NUCAPS Soundings are available online (over the Continental US only) here.

NUCAPS sounding locations over Beryl at 1500-1600 UTC on 5 July 2018 (Click to enlarge)

Very small (in size) Beryl is forecast to strengthen in the short term. See the National Hurricane Center website and the CIMSS Tropical Website for more information.


==== Update 6 July 2018 ====
Beryl has strengthened and is a hurricane, as of 0900 UTC on 6 July, the first hurricane of the 2018 Atlantic Hurricane season. The sandwich product animation below, courtesy Rick Kohrs and Joleen Feltz, CIMSS, that combines visible (0.64 µm) and clean window infrared (10.3 µm) imagery shows the appearance and subsequent disappearance of a very small eye.

Sandwich product that combines GOES-16 Band 2 (“Red Visible”, 0.64 µm) and Band 13 (“Clean Window”, 10.3 µm) over Beryl, 0815-1515 UTC on 6 July 2018 (Click to enlarge)

Hurricane Bud

June 12th, 2018 |

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

East Pacific Hurricane Bud peaked at Category 4 intensity (ADT | SATCON) around 06 UTC on 12 June 2018 (just 4 days after Hurricane Aletta reached the same intensity) — and a GOES-16 (GOES-East) Mesoscale Sector was positioned over the storm about an hour before that time, providing “Clean” Infrared Window (10.3 µm) images at 1-minute intervals (above).

A post-sunrise comparison of 1-minute GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images is shown below.

GOES-16 "Red" Visible (0.64 µm, left) and "Clean" Infrared Window (10.3 µm, right) images [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images [click to play MP4 animation]

Ocean Heat Content and Sea Surface Temperature analyses, with the track of Hurricane Bud ending at 12 UTC on 12 June [click to enlarge]

Ocean Heat Content and Sea Surface Temperature analyses, with the track of Hurricane Bud ending at 12 UTC on 12 June [click to enlarge]

As mentioned in the NHC discussion at 15 UTC, Bud was beginning to move over water having lower values of Ocean Heat Content and Sea Surface Temperature (above), which would lead to rapid weakening — in fact, an erosion of the northern eyewalll was seen in DMSP-16 SSMIS Microwave imagery at 1105 UTC (below).

DMSP-16 SSMIS Microwave (85 GHz) image [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) image [click to enlarge]

Hurricane Aletta

June 7th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images [click to play MP4 animation]

Tropical Storm Aletta was upgraded to Hurricane Aletta at 21 UTC on 07 June 2018. As was the case on 06 June, a GOES-16 Mesoscale Domain Sector centered over the tropical cyclone provided 1-minute data — and an eye eventually became apparent on  “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) imagery (above).

DMSP-15, DMSP-17 and GPM GMI Microwave (85 GHz) imagery from the CIMSS Tropical Cyclones site (below) showed an increase in organization of the eye structure as the day progressed.

DMSP-15 SSMI Microwave image [click to enlarge]

DMSP-15 SSMI Microwave image [click to enlarge]

DMSP-17 SSMIS Microwave image [click to enlarge]

DMSP-17 SSMIS Microwave image [click to enlarge]

GPM GMI Microwave image [click to enlarge]

GPM GMI Microwave image [click to enlarge]

===== 08 June Update =====

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

Aletta went through a period of rapid intensification (ADT | SATCON), reaching Category 4 status by 15 UTC on 08 June. 1-minute GOES-16 Infrared (10.3 µm) images (above) showed the eye becoming more well-defined during the pre-dawn hours.

After sunrise, GOES-16 Visible images (below) initially hinted at the presence of mesovortices within the eye of Aletta.

GOES-16

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images [click to play MP4 animation]

Aletta had been moving over relatively warm water and within an environment characterized by low values of deep-layer wind shear (below) — both  of which were favorable factors for intensification. An animation of the deep-layer wind shear over the East Pacific Ocean during 06-07 June is available here.

Sea Surface Temperature and Deep-Layer Wind Shear products [click to enlarge]

Sea Surface Temperature and Deep-Layer Wind Shear products [click to enlarge]

Aletta peaked in intensity later in the day on 08 June (ADT | SATCON) — as pointed out by NHC “This is also consistent with GOES-16 measurements of increased inner-core lightning observed to be occurring to the east of the eastern eyewall, which some research suggests corresponds to a halting of the intensification process”. GOES-16 Infrared (10.3 µm) imagery with GLM Group Density counts are shown below.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) with GLM Group Density counts [click to play MP4 animation]

Why Mesoscale Sectors matter: Tropical Storm Aletta

June 6th, 2018 |

GOES-16 Visible (0.64 µm) Imagery, 1422-1741 UTC on 6 June 2018 (Click to animate)

The first Tropical Storm, Aletta, of the eastern Pacific Ocean basin has been named. One-minute imagery from a moveable Mesoscale Sector, above as an animated gif (or here as an mp4), shows a distinct low-or mid-level circulation center moving out from under higher clouds in the northeast quadrant of the storm at about 1621 UTC, being even more obvious at 1636 UTC.

The GOES-16 CONUS Sector scans at 5-minute intervals. The southern boundary of the CONUS sector (15º N Latitude), however, bisects this tropical storm, as shown at this link, and is therefore unhelpful for center diagnostics. Full Disk imagery captures the storm evolution at a 15-minute time step that is too coarse to provide a smooth animation. (Just two years ago, the time resolution for this storm formation would have been every 3 hours, as that was the time cadence for a Full Disk from GOES-13! GOES-16 really is life-changing for those who view satellite animations.)