Heavy rainfall and snowfall in Southern California

January 23rd, 2021 |

GOES-17 Air Mass RGB images, with contours of PV1.5 pressure [click to play animation | MP4]

GOES-17 Air Mass RGB images, with contours of PV1.5 pressure [click to play animation | MP4]

As an anomalously-deep 500 hPa low began to move inland over Southern California during the 23 January24 January 2021 period, GOES-17 (GOES-West)  Air Mass RGB images (above) showed a compact Potential Vorticity (PV) anomaly approaching the coast — and the RAP40 model indicated that the “dynamic tropopause” (defined here as the pressure of the PV1.5 surface) was descending to the 675 hPa pressure level at 18 UTC.

A west-to-east oriented cross section of RAP40 model fields along Line A-A’ (below) depicted the descending dynamic tropopause at 19 UTC.

Cross section of RAP40 model fields along line A-A' [click to enlarge]

Cross section of RAP40 model fields along line A-A’ [click to enlarge]

GOES-17 Mid-level Water Vapor (6.9 µm) images (below) showed the increasing reports of rain and snow that resulted as the PV Anomaly moved inland and provided additional forcing for ascent. Near the coast, thunderstorms were reported at Fulton and Long Beach around 03 UTC. Storm total precipitation amounts included rainfall of 1.40 inch and snowfall of 12-18 inches.

GOES-17 Mid-level Water Vapor (6.9 µm) images, with plots of hourly surface weather type [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm) images, with plots of hourly surface weather type [click to play animation | MP4]

GOES-17 Water Vapor images at 2301 UTC and 0246 UTC (below) revealed sporadic lightning activity (indicated by small clusters of GLM Groups).

GOES-17 Mid-level Water Vapor (6.9 µm) image at 2301 UTC, with GLM Groups plotted in red [click to enlarge]

GOES-17 Mid-level Water Vapor (6.9 µm) image at 2301 UTC, with GLM Groups plotted in red [click to enlarge]

GOES-17 Mid-level Water Vapor (6.9 µm) image at 0246 UTC, with GLM Groups plotted in red [click to enlarge]

GOES-17 Mid-level Water Vapor (6.9 µm) image at 0246 UTC, with GLM Groups plotted in red [click to enlarge]

===== 24 January Update =====

GOES-17 Day Snow-Fog RGB images [click t play animation | MP4]

GOES-17 Day Snow-Fog RGB images [click to play animation | MP4]

On the following day, as clouds began to clear the areal extent of resulting fresh snow cover (darker shades of red) was seen in GOES-17 Day Snow-Fog RGB images (above). Even parts of the high desert — north and east of the mountain ranges — received some snowfall (for example, 2-3 inches were reported at Hesperia).

Suomi NPP VIIRS True Color RGB and False Color RGB images (below) showed the snow cover (shades of cyan) at 2036 UTC.

Suomi NPP VIIRS True Color RGB and False Color RGB images [click to enlarge]

Suomi NPP VIIRS True Color RGB and False Color RGB images [click to enlarge]

Hurricane Delta in the Gulf of Mexico

October 8th, 2020 |

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images — with and without an overlay of GLM Flash Extent Density — and “Red” Visible (0.64 µm) images (above) showed showed Hurricane Delta as it intensified from a Category 2 to a Category 3 storm over the Gulf of Mexico during the daytime hours on 08 October 2020. Cloud-top infrared brightness temperatures of -90ºC and colder  (yellow pixels embedded within the darker shades of purple) were occasionally seen within the eyewall region of Delta, along with intermittent bursts of lightning activity.

A toggle between Suomi NPP VIIRS Infrared Window (11.45 µm) and Visible (0.64 µm) images of Hurricane Delta shortly before it intensified to a Category 3 storm are shown below; the coldest cloud-top infrared brightness temperature at that time was -93.0ºC.

Suomi NPP VIIRS Infrared Window (11.45 µm) and Visible (0.64 µm) images [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) and Visible (0.64 µm) images [click to enlarge]

In a time-matched comparison of Infrared images from Suomi NPP and GOES-16 (below), the coldest cloud-top infrared brightness temperature sensed by GOES-16 was 5.6ºC warmer (-87.4ºC); note the small northwestward parallax displacement that is inherent with GOES-16 imagery over the Gulf of Mexico. The same color enhancement is applied to both images.

Infrared images from Suomi NPP and GOES-16 [click to enlarge]

Infrared images from Suomi NPP (11.45 µm) and GOES-16 (10.35 µm) [click to enlarge]

===== 09 October Update =====

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

In a toggle between Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images at 0734 UTC or 2:34 am CDT on 09 October (above), the coldest cloud-top infrared brightness temperature was -93.8ºC (just northwest of the storm center).

1-minute GOES-16 Infrared and Visible images (below) showed Category 2 Hurricane Delta making landfall in southwestern Louisiana at 2300 UTC, producing wind gusts as high as 100 mph at Texas Point, Texas.

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

The MIMIC Total Precipitable Water product (below) indicated that Hurricane Delta was transporting a large amount of moisture northward across the Gulf of Mexico — rainfall totals included 15.64 inches at Evangeline Gardner, Louisiana.

MIMIC Total Precipitable Water product [click to enlarge]

MIMIC Total Precipitable Water product [click to enlarge]

The MIMIC-TC product (below) showed the deterioration of the eye and eyewall structure as Delta approached the Gulf Coast.

MIMIC-TC product

MIMIC-TC product [click to enlarge]

===== 10 October Update =====

Suomi NPP VIIRS True Color RGB images from 04 and 10 October [click to enlarge]

Suomi NPP VIIRS True Color RGB images from 04 October and 10 October [click to enlarge]

A before (04 October) / after (10 October) comparison of Suomi NPP VIIRS True Color RGB images from the VIIRS Today site (above) revealed a marked increase of turbidity within the more shallow shelf waters of Texas and Louisiana, due to extensive mixing from the wind field associated with Delta. A comparison of VIIRS False Color images from those 2 days (below) highlighted inland areas with significant flooding that resulted from heavy rainfall and/or storm surge (darker shades of blue).

Suomi NPP VIIRS False Color RGB images from 04 October and 10 October [click to enlarge]

Suomi NPP VIIRS False Color RGB images from 04 October and 10 October [click to enlarge]

A GOES-16 River Flood Detection product viewed using RealEarth (below) helped to quantify the severity of flooding resulting from the landfall of Delta.

GOES-16 River Flood product [click to enlarge]

GOES-16 River Flood Detection product valid at 1900 UTC on 10 October [click to enlarge]

CMORPH estimates of hourly (and daily) rainfall with Sally

September 16th, 2020 |

CMORPH hourly estimates of precipitation over Mississippi and surrounding states, 1300-2200 UTC 16 September 2020 (Click to enlarge)

Hurricane Sally weakened to a Tropical Storm at 1800 UTC on 16 September. Sally is a prodigious rainfall producer. CMORPH (CPC Morphing Technique) Precipitation estimates (blogged about earlier) are available at this Real Earth website. Hourly estimates from 1300 through 2200 UTC are shown above.  Many locations over southern Mississippi show hourly multi-inch accumulations for much of the day.

Daily precipitation for the 24 hours ending at 00 UTC on 17 September is shown below.  A large area of Mississippi shows values between exceeding 100-150 mm.  Click here to see a 24-h precipitation total image for the period ending 1200 UTC on 17 September (from this website) A series of daily images of 24-hour precipitation (at bottom) shows the evolution of the diagnosed precipitation from 09-16 September.

Daily CMORPH Precipitation Accumulation, valid 0000 UTC on 17 September 2020 (Click to enlarge)

Daily CMORPH estimates of precipitation, 09-16 September 2020 (Click to enlarge)

CMORPH Precipitation Data available

September 3rd, 2020 |

Daily CMORPH maps of of daily precipitation, 26 August – 2 September 2020 (Click to enlarge)

The Climate Prediction Center (CPC) Morphing (CMORPH) technique produces global estimates of hourly precipitation and those data are available in real time at this website. (Other JPSS/ABI-related flood products are available there as well). CMORPH uses microwave data from Polar Orbiters to estimate rainfall. Infrared information is related to those microwave data estimates, and those infrared data (from ABI, AHI, etc) are used to estimate precipitation during times when microwave observations are not present. This morphing technique is thus different from other morphing techniques for Total Precipitable Water (TPW) such as MIMIC that use model data to move quasi-conserved moisture fields to observational data voids. (Training on MIMIC TPW fields).

Hourly and Daily precipitation totals are available at the website. The animation above shows annual precipitation over the course of 6 days. Daily precipitation on 27 August, for example (link), shows the heavy rain accompanying land-falling Hurricane Laura. In the animation, the rains with that system move north to the mid-Mississippi River before being shunted eastward.

Hourly Precipitation, shown below from 12-15 UTC on 3 September 2020, allows for enhanced situational awareness with respect to heavy (or light) rains.

CMORPH Hourly Precipitation from 1200 – 1559 UTC on 3 September 2020 (Click to enlarge)