Moisture Streaming towards Southern California

February 14th, 2019 |

Morphed Microwave Total Precipitable Water, 1800 UTC 13 February to 1700 UTC 14 February 2019 (Click to enlarge)

A potent Atmospheric River is affecting the California Coast on 14 February 2019. The morphed microwave imagery, above (from this site), shows rich moisture from deep in the tropics moving onto the southern California and northwest Mexican coasts.  The animation below shows the Layered Precipitable water — also a product derived from microwave imagery — for the same time period, but at 3-hour time steps (from this site).  An interesting feature is that the 850-700 hPa moisture layer is not as continuous back to the tropics as the other 3 layers.

Advected Layer Precipitable Water, 18z 13 February to 18z 14 February 2019 (Click to enlarge)

You can also infer a large influx of moisture from the low-level water vapor imagery, as shown in the short animation below from GOES-17, from 1617 UTC (just as Loop Heat Pipe issues that cause missing data were ramping down) to 1857 UTC. One might also infer a long-duration event from this animation!

GOES-17 ABI Band 10 Infrared 7.3 µm Imagery (Low-Level Water Vapor Band) from 1617 UTC to 1857 UTC on 14 February 2019 (Click to animate)

The GOES-R All-Sky Total Precipitable Water product (from this site) is as yet produced only from GOES-16 data (The Loop Heat Pipe problems have a strong impact on all Baseline products, including Legacy Profiles that are used to create Total Precipitable Water, which impact is still under investigation). The western Pacific is on the limb of this product, but it does capture the deep moisture moving towards southern California.

GOES-16 All-Sky Total Precipitable Water, 1400 UTC on 14 February 2019 (Click to enlarge)

Much of the San Diego National Weather Service Forecast Office County Warning Area is under Flood and/or Wind Warnings! See the Screen Capture below from 1121 AM Pacific Standard Time.

Warnings (as of 11:21 AM PDT on 14 February 2019) over the San Diego County Warning Area (Click to enlarge)

Dry air over Florida

February 14th, 2019 |

GOES-16 Low-level Water Vapor (7.3 µm) images, with and without a map overlay; rawinsonde sites are plotted in cyan [click to play animation | MP4]

GOES-16 Low-level Water Vapor (7.3 µm) images, with and without a map overlay; rawinsonde sites are plotted in cyan [click to play animation | MP4]

GOES-16 (GOES-East) Low-level Water Vapor (7.3 µm) images, with and without a map overlay (above), revealed that a portion of the western coastline of Florida around and north of Tampa (KTBW) could be seen on the Water Vapor imagery. Although more subtle, the St. Johns River south of Jacksonville (KJAX) and the northeast coast between Jacksonville and Cape Canaveral (KXMR) could also briefly be seen.

A plot of the sounding climatology for the Tampa site (source) showed that the Total Precipitable Water value of 0.18 inch at 12 UTC was just 0.02 inch higher than the record low value for all 14 February/12 UTC soundings (below).

Plot of mean and extreme Total Precipitable Water values for Tampa, Florida [click to enlarge]

Plot of mean and extreme Total Precipitable Water values for Tampa, Florida [click to enlarge]

The GOES-16 Total Precipitable Water product at 1207 UTC (below) showed the extent of the dry air that had moved across central Florida that morning.

GOES-16 Total Precipitable Water product at 1207 UTC [click to enlarge]

GOES-16 Total Precipitable Water product at 1207 UTC [click to enlarge]

Plots of GOES-16 Water Vapor weighting functions calculated using 00 UTC and 12 UTC rawinsonde data from Tampa, Florida (below) indicated that while the peak pressure of the 7.3 µm weighting function remained at 596.31 hPa during those 2 times, a significant radiation contribution was coming directly from the surface at 12 UTC. The presence of unusually dry air within the atmospheric column shifted all 3 water vapor band weighting functions to lower altitudes, thereby allowing a signature of the thermal contrast between land and water to be detected using 7.3 µm imagery.

Plots of GOES-16 Water Vapor weighting functions calculated from 00 UTC and 12 UTC rawinsonde data from Tampa, Florida [click to enlarge]

Plots of GOES-16 Water Vapor weighting functions calculated from 00 UTC and 12 UTC rawinsonde data from Tampa, Florida [click to enlarge]