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Thunderstorms across Puerto Rico and the US Virgin Islands

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed thunderstorms that moved across Puerto Rico and the US Virgin Islands on 06 February 2024. These storms produced up to 4-5 inches of rainfall in parts of central Puerto Rico, with wind gusts as high as... Read More

1-minute GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.3 µm, bottom) images, from 1600-2200 UTC on 06 February [click to play animated GIF | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed thunderstorms that moved across Puerto Rico and the US Virgin Islands on 06 February 2024. These storms produced up to 4-5 inches of rainfall in parts of central Puerto Rico, with wind gusts as high as 41 kts (47 mph).

These thunderstorms were fueled by a plume of tropical moisture that was moving north-northeastward from northern South America, which passed directly over Puerto Rico during the entire day — as depicted by the MIMC TPW product (below).

MIMIC Total Precipitable Water product, hourly from 0300 UTC on 06 February to 0200 UTC on 07 February

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Ongoing tropical activity in the SPCZ near American Samoa

As tropical storm Nat moves away from the Samoan Islands and towards Tahiti, another Invest area, 98P, has developed north of the Samoan Islands. The animation above, from the MIMIC Total Precipitable Water site (link), shows a cyclonically-rotating concentration of moisture just north of Samoa, and moving east-southeastward toward Olosega... Read More

MIMIC Total Precipitable Water fields, 1900 UTC 5 February – 1800 UTC 6 February 2024 (Click to enlarge)

As tropical storm Nat moves away from the Samoan Islands and towards Tahiti, another Invest area, 98P, has developed north of the Samoan Islands. The animation above, from the MIMIC Total Precipitable Water site (link), shows a cyclonically-rotating concentration of moisture just north of Samoa, and moving east-southeastward toward Olosega and Ta’u. The Tropical Cyclone Formation Alert (TCFA) graphic (click here for text explanation) from the Joint Typhoon Warning Center (link), below, moves the center of the disturbed weather towards those islands. skirting the larger islands of Samoa. Flood watches and Heavy Surf Warnings are in effect for all of American Samoa.

Tropical Cyclone Formation Alert graphic, 1730 UTC on 6 February 2024 (Click to enlarge)

Imagery from the CIMSS Tropical Weather website, below, helps gauge the threat of the storm. The imagery shows the Invest location at 1200 UTC along with the 1730 UTC infrared imagery, then the Invest Location with the 1730 UTC water vapor imagery along with the 1500 UTC analysis of 850-mb vorticity (notice its motion east-southeastward from the 1200 UTC Invest location, and also the vorticity associated with Tropical Storm Nat at the eastern edge of the domain), then the 1500 UTC analysis of 200-850 mb shear overlain on top of the infrared imagery (note that Nat has moved poleward into stronger shear, but invest 98P to the north of Samoa is within a persistent corridor of low shear that has existed for days), and finally the deep layer mean motion appropriate for a fairly weak system, motion that moves the system towards the eastsoutheast.

Invest area 98P near Samoa and derived fields and satellite imagery that can be used to diagnose the strength and motion of the system. See text above for details (Click to enlarge)

Scatterometry is a useful tool to find circulation centers, but observations over the center must happen! The animation below (from this source) shows MetopB and MetopC observations in the past 2 days. The circulation of Tropical Cyclone Nat is sampled well on the 5th, but the region north of Samoa, where 98P is developing, has not had good coverage.

MetopB and MetopC ASCAT observations, 5-6 February 2024 (Click to enlarge) The nominal times of the ASCAT observations are shown in blue along the bottom of the plot

However, HY-2B and HY-2C satellites from China (available at this website), shown below, had good coverage over the region, as shown below. The 0930 UTC image shows the circulation (with much stronger winds towards the Equator) associated with 98P.

HY-2B and HY-2C Scatterometer winds, 0330, 0630, 0930 UTC on 6 February 2024 (Click to enlarge)
GOES-West Night Microphysics (at night) and True-Color imagery (during daytime) 1640-2030 UTC on 6 February 2024

GOES-West imagery (taken from the CSPP Geosphere site) over the South Pacific on 6 February, above, shows 98P north of American Samoa, and Tropical Storm Nat to the east. Nat is showing the effects of increasing shear as the low-level circulation starts to emerge from beneath the deep convection by the end of the animation. One of the GOES-West mesosectors has been positioned over Samoa to monitor the evolution of the system. A 2-hour animation, below, of visible imagery shows the active convection, and low-level flow to the northwest (north of Tutuila).

GOES-18 Mesoscale Sector #2 Visible Imagery (Band 2, 0.64 µm), 1835 – 2105 UTC on 6 February 2024 (Click to enlarge)

Added, 2200 UTC: Advisories on Tropical Depression 11P have started from JTWC and on Tropical Cyclone 08F from the Fiji RSMC. Despite the different numbers, they’re the same system.

The animation below (source), from 2130 UTC 6 February to 0120 UTC 7 February, shows the continued spin-up of the Tropical Depression in American Samoa waters. The GLM does not show lightning near the center of the storm. Meanwhile, Tropical Storm Nat, to the east, continues to exhibit characteristics of a sheared storm, with the low-level circulation separated from convection.

GOES-18 GeoColor animation with GLM FED overlain, 2136 UTC 6 February – 0126 UTC 7 February 2024 (Click to enlarge)

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Atmospheric Rivers Drench California

2024 has seen several strong storms hit the U.S. West Coast delivering repeated rounds of widespread rains and mountain snow, with Southern California experiencing the heaviest rainfall totals. Total Precipitable Water imagery (MIMIC TPW) conveying data acquired by microwave sensors on polar-orbiting satellites is a key tool for meteorologists tracking atmospheric... Read More

2024 has seen several strong storms hit the U.S. West Coast delivering repeated rounds of widespread rains and mountain snow, with Southern California experiencing the heaviest rainfall totals. Total Precipitable Water imagery (MIMIC TPW) conveying data acquired by microwave sensors on polar-orbiting satellites is a key tool for meteorologists tracking atmospheric rivers associated with these storm systems, as seen in this loop from 30 January to 6 February.

Numerous daily rainfall records have been set so far this year. Below are 3-day observed precipitation totals across the state of California ending at 4am PST on February 7th, with an impressive maximum of 19.97 inches from southwest California.

GOES-18 (GOES West) monitors all storms over the Pacific Ocean and U.S. West Coast. The following animation toggles between Mid-level Water Vapor (ABI band 9) and Air Mass RGB imagery on January 31st.

A second storm directed a significant Atmospheric River at southern California on the 3rd and 4th of February as seen in the following loop of GOES West Water Vapor imagery.

As seen in the accompanying graphic, a majority of the major water supply reservoirs in California are at or above historical averages, an astonishing rebound from the dire drought conditions at the end of 2022. This turn-around commenced last winter when an historic run of nine atmospheric rivers inundated California between December 2022 and January 2023.

Now the concern has shifted to damaging floods, falling trees, mudslides and debris flows.

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Blowing snow signature over northern Hudson Bay

At the CIMSS Satellite Blog, we occasionally get emails from our readers. Yesterday’s (6 February 2024) email included this one: I was doing some forecasting for the Canadian Arctic today and noticed a veryimpressive blowing snow signature on satellite; not that blowing snow isuncommon up there, but rather that the... Read More

At the CIMSS Satellite Blog, we occasionally get emails from our readers. Yesterday’s (6 February 2024) email included this one:

I was doing some forecasting for the Canadian Arctic today and noticed a very
impressive blowing snow signature on satellite; not that blowing snow is
uncommon up there, but rather that the signature was so strong given the lower
resolution and parallax at that latitude.

The email included this link to the CIRA SLIDER, where a Day Snow Fog image loop was displayed, including the frame below. The linear structures that appear in the RGB between, for example, Southampton and Nottingham Islands (here’s a map with islands labeled) are characteristic of blowing snow. (See this blog post for more information on RGB detection of blowing snow) Other linear features are north of Southampton Island.

Day Snow Fog RGB north of Hudson Bay, 1740 UTC on 6 February 2024 (Click to enlarge)

This was happening south of strong storm (with a central pressure of 991 mb) even farther north than northern Hudson Bay, shown in the map below.

North America Surface Analysis, 1500 UTC on 6 February 2024 (Click to enlarge)

The Day Snow Fog Quick Guide (here, one of many Quick Guides developed over the years by scientists at CIMSS, CIRA and SPORT) describes the components of the RGB. I decided to create the RGB using CSPPGeo‘s geo2grid software, and the way to do that is to insert definitions into two different yaml files within the geo2grid file structure.

First, define the RGB in $GEO2GRID_HOME/etc/polar2grid/composites/abi.yaml by adding the lines below. I called this Day Snow Fog RGB ‘dsfog’: the ‘Red’ component is Band 3 (0.86 µm); the ‘Green’ component in Band 5 (1.61 µm); the blue component is a difference field, Band 7 – Band 13 (3.9 µm – 10.3 µm). When invoking geo2grid, the -p dsfog flag tells the software to create Day Snow Fog imagery.

  dsfog:
    compositor: !!python/name:satpy.composites.GenericCompositor
    prerequisites:
      - name: C03
      - name: C05
      - compositor: !!python/name:satpy.composites.DifferenceCompositor
        prerequisites:
        - name: C07
        - name: C13
    standard_name: dsfog

Then, assign bounds and gamma in $GEO2GRID_HOME/etc/polar2grid/enhancements/abi.yaml, shown below. Band 3 reflectance values range from 0 to 100, band 5 reflectance values range from 0 to 70, and the Band 7 – Band 13 brightness temperature difference ranges from 0 to 30oC. In addition, a gamma of 1.7 is applied to each of the RGB bands.

  dsfog_abi:
    standard_name: dsfog
    name: dsfog
    operations:
      - name: stretch
        method: !!python/name:satpy.enhancements.stretch
        kwargs:
          stretch: crude
          min_stretch: [0.0, 0.0, 0.0]
          max_stretch: [100.0, 70.0, 30.0]
      - name: gamma
        method: !!python/name:satpy.enhancements.gamma
        kwargs:
          gamma: [1.7, 1.7, 1.7]

Use the p2g_grid_helper.sh shell script to define a grid (‘MyMap’, defined in ‘MyMap.yaml’ as used in the geo2grid call below) onto which data will be displayed. Then two geo2grid calls create the imagery and put georeferencing onto it. I used ImageMagick to annotate the imagery, and the animation is shown below. Characteristic linear features that are a bit greener than the underlying red surface show where blowing snow is occurring. In the absence of surface observations, this can give important information.

$GEO2GRID_HOME/bin/geo2grid.sh -r abi_l1b -w geotiff -g MyMap --grid-configs MayMap.yaml -p dsfog -f /path/to/goes16/abi/L1b/RadF/*s2024037[time]*
../add_coastlines.sh --add-coastlines --coastlines-resolution f --add-grid --grid-D 5.0 5.0 --grid-d 5.0 5.0 --grid-text-size 14 GOES-16_ABI*dsfog*.tif
Day Snow Fog RGB over northern Hudson Bay, 1500-2100 UTC on 6 February 2024 (Click to enlarge)

Another (higher-contrast) version of the GOES-16 Day Snow-Fog RGB along with the Day Cloud Phase Distinction RGB was also created using Geo2Grid, as shown below. The higher-contrast RGB imagery depicted the areal coverage of horizontal convective roll clouds — which often highlight the presence of blowing snow — a bit more clearly as they streamed eastward from Southampton Island (and even Coats Island, just to the south). The higher contrast also helped to accentuate the polynyas that were slowly opening just downwind of the islands.

GOES-16 Day Snow-Fog RGB (left) and Day Cloud Phase Distinction RGB (right) images from 1500-2050 UTC on 06 February (courtesy Scott Bachmeier CIMSS) [click to play animated GIF | MP4]


Thanks to Brad Vrolijk for alerting us to this far north event!

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