Alberto

May 25th, 2018 |

GOES-16 ABI Band 10 (7.34 µm, low-level water vapor) Infrared imagery, 0822-1632 UTC on 25 May 2018 (Click to animate)

The National Hurricane Center has assigned the name ‘Alberto’ to region of low pressure that has persisted near the northwest Caribbean Sea for the past week. The low-level water vapor (7.34 µm) animation, above, shows abundant mid-tropospheric moisture to the east of the system. Dryer mid-level conditions are apparent west of Alberto: the storm structure is very asymmetric. Sheared systems such as this one typically do not strengthen quickly.

A plot of shear (from this site), below, shows Alberto in a region of westerly shear, with a forecast path towards a region that currently has higher shear — part of which is outflow. However, forecast models suggest the shear along the forecast path will decrease with time.  Sea-surface temperatures are warm enough to support tropical cyclones, and the forecast path is towards warmer waters.

Shear Analysis and Satellite imagery at 1500 UTC on 25 May 2018 (Click to enlarge)

Visible imagery, below, shows one low-level circulation center (others may be masked by the convection to the east) that is south and west of the main convection over the Caribbean.

GOES-16 ABI Visible (0.64 µm) Imagery, 1137-1642 UTC on 25 May 2018 (Click to animate)

Suomi-NPP overflew this region at 0723 UTC, and a toggle between the Window Channel Infrared (11.45 µm) and the Day Night Band Visible (0.70 µm) imagery (courtesy William Straka) is shown below. The low-level circulation is apparent in the Day Night Band to the west of the deep convection over the northwest Caribbean.

Suomi-NPP VIIRS Infrared (11.45 µm) and Day Night Band Visible (0.70 µm) Imagery at 0735 UTC on 25 May 2018 (Click to enlarge)

Total Precipitable Water, 1600 UTC on 24 May 2018 to 15 UTC on 25 May 2018 (Click to enlarge)

A MIMIC Total Precipitable Water animation, above, shows abundant moisture over the northwest Caribbean. As Alberto lifts to the north, that moisture will shift north as well, and flooding rains are possible over the southeastern United States. Flood Watches have been raised over Louisiana, Mississippi, Alabama and Georgia (below, from this site).

Hazards at 1700 UTC on 25 May 2018 (Click to enlarge)

The Geostationary Lightning Mapper (GLM) on GOES-16 observed lightning in the deep convection to the east of the system center. GLM is overlain on both infrared (top) and visible (bottom) imagery below (animations courtesy Dave Santek, CIMSS). The updating infrared animations are available here. GLM data for this system can also be viewed in RealEarth.

GOES-16 Infrared (10.3 µm) Imagery over Alberto at 5-minute time-steps, 1747 – 1832 UTC,  along with GLM observations of group density plotted every minute (See legend in image for times of GLM plots) (Click to enlarge)

GOES-16 Visible (0.64 µm) Imagery over Alberto at 5-minute time-steps, 1747 – 1832 UTC, along with GLM observations of group density plotted every minute (See legend in image for times of GLM plots) (Click to enlarge)

Updates on this system are sent every six hours from the National Hurricane Center. You can find more information there, or at the CIMSS Tropical Weather Website.

Cyclone Mekunu in the northwest Indian Ocean

May 23rd, 2018 |
Meteosat-8 Infrared 10.8 µm imagery, 1630 UTC 22 May - 1715 UTC 23 May 2018 (Click to animate)

Meteosat-8 Infrared 10.8 µm imagery, 1630 UTC 22 May – 1715 UTC 23 May 2018 (Click to animate)

Cyclone Mekunu in the northwest Indian Ocean was approaching Oman and Yemen on the Arabian Peninsula on 23 May 2018, as shown in the animation above. Morphed Microwave Imagery, below, (from this site) for the 24 hours ending at 1900 UTC on 23 May 2018, shows the storm at the periphery of deep tropical moisture.  This moisture will likely lead to devastating floods in the desert regions of Oman and Yemen as the storm approaches. (News Link 1, 2 and 3).  Cyclone Chapala that affected the region in 2015 also caused devastating floods.

Microwave-based Total Precipitable Water for 24 hours ending 1900 UTC on 23 May 2018 (Click to enlarge)

Microwave imagery, below, (from this site) shows how the organization of the storm changed in the 24 hours ending around 1600 UTC on 23 May 2018.   AMSU microwave imagery for this storm can be found here (off of this website).

Morphed Microwave Imagery over Mekunu for the 24 hours ending at 1600 UTC (Click to enlarge)

Satellite intensity estimates for the storm are shown below (taken from this website). The Meteosat-8 infrared animation, above, shows a periodic increase and decay in the strong convection near the center. Satellite estimates of strength (below) show a consistent lowering of the central pressure of the storm, however; winds have consistently increased.

Satellite-based estimates of Mekunu’s central pressure (Click to enlarge)

Mekunu is traversing a region with very high Sea Surface Temperatures and modest shear. Significant weakening is not forecast.

Sea Surface Temperatures and Shear over the northwest Indian Ocean (Click to enlarge)

More information on this unusual tropical cyclone can be found at the CIMSS Tropical Weather Website (link) and the CIRA Tropical Weather Website (link).

=============== Added, 24 May 2018 ==============

Suomi-NPP overflew Mekunu at 2133 UTC on 23 May 2018, and the toggle below (between the Day Night Band and the 11.45 µm infrared;  Click here for a zoomed-in toggle between the Day Night Band and the 11.35 µm infrared image) shows the storm well-illuminated by a waxing gibbous Moon.  Strong convection with lightning is apparent north of the island of Socotra.  (VIIRS imagery courtesy Will Straka, CIMSS)

Suomi NPP VIIRS Infrared (11.45 µm) and Day Night Band Visible (0.70 µm) imagery over Mekunu, 2133 UTC on 23 May 2018 (Click to enlarge)

=============== Added, 25 May 2018 ==============

Mekunu is approaching the coast of Oman on 25 May 2018 from the southeast.  The animation below of visible (0.6 µm, left) and Infrared (10.8 µm ,right) imagery shows a compact storm with deep convection around an eye.  Microwave Imagery for the 24 hours ending at 1300 UTC on 25 May (here, from this site) suggest Mekunu is strengthening as it nears the coast. (Satellite-estimated winds and pressure also suggest strengthening near landfall).

Meteosat-8 Visible (0.6 µm, left) and Infrared (10.8 µm, right) imagery over Mekunu, 1145 UTC on 24 May to 1215 UTC on 25 May 2018 (Click to animate)

Visible Imagery from 1045 to 1430 UTC, below, suggests landfall will occur shortly after sunset east of the Oman/Yemen border.  Infrared Imagery (at bottom) shows a landfall near 1800 UTC.

Meteosat-8 Visible (0.6 µm, left) imagery over Mekunu, 1045 UTC to 1430 UTC on 25 May 2018 (Click to animate)

Meteosat-8 Infrared (10.8 µm, left) imagery over Mekunu, 1415 UTC to 1830 UTC on 25 May 2018 (Click to animate)

Surface observations from Salalah, in southern Oman (click here), show sustained tropical-storm force winds, with gusts to 60 knots, from the east for several hours today. Normal annual precipitation for the region is about 5″.

Subtropical cyclone formation off the coast of Chile

May 9th, 2018 |

GOES-16

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

A very unusual subtropical cyclone formed off the coast of Chile during the 07-08 May 2018 period (Weather Channel | Weather Underground). The system transitioned from a typical cold core baroclinic mid-latitude cyclone to a shallow warm core cyclone with some deep convection around the center of circulation. GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) showed the evolution from 06 May to 09 May. The surface report plotted in the lower right corner of the images is Concepción, Chile.

A Suomi NPP VIIRS True-color Red-Green-Blue (RGB) image viewed using RealEarth (below) depicted the circulation once it had drifted to a position northwest of Santiago, Chile at 1839 UTC on 08 May.

Suomi NPP VIIRS Ttue-color RGB image [click to enlarge]

Suomi NPP VIIRS Ttue-color RGB image [click to enlarge]

The hourly MIMIC Total Precipitable Water product (below) initially showed a long ribbon of subtropical moisture which was being transported ahead of a cold front into the baroclinic low on 05 May — then during the transition to a subtropical low, a small pocket of modest TPW migrated slowly northward  with the surface circulation.

MIMIC Total Precipitable Water product [click to play animation | MP4]

MIMIC Total Precipitable Water product [click to play animation | MP4]

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]