Moist air over the tropical western Pacific Ocean

July 22nd, 2021 |
MIMIC Total Precipitable Water, 0000 UTC 21 July – 1200 UTC 22 July

Microwave estimates of total precipitable water over the western Pacific Ocean (available here) show a moist airmass — out of which Typhoon In-Fa (seen near Taiwan in the animation) emerged — over the western Pacific Ocean. (The circulation of Tropical cyclone Cempaka is also apparent near the Gulf of Tonkin) This rich moisture has led to very heavy rains and Flash Flood alerts on the island of Guam (at 13.4 N, 144.5 E). Are there any indications that a new tropical cyclone will emerge out of the moisture?

The toggle below shows Himawari-8 10.41 µm “Clean Window” infrared imagery (notice In-Fa in the northwest part of the image). A distinct trough is apparent in the scatterometery north of the Marianas islands (and north of 20 N latitude), with west-southwesterly surface winds bordered by east-southeasterlies to the north. Weaker winds are indicated south of Guam. (For a recent primer on Scatterometer winds, click here; ASCAT winds can be found online here)

ASCAT Scatterometry winds and Himawari-8 Band 13 infrared (10.41 µm)imagery, 1200 UTC on 22 July 2021

NOAA-20 overflew this region at 1600 UTC on 22 July. The imagery below shows Tropopause Heights as well as Total Precipitable water — along with Band 13 imagery (over a different location) at that time. NUCAPS estimates of TPW are in the 60-70 mm range (in agreement with the MIMIC animation above); Very high tropopauses are Equatorward of 20 N Latitude.

A ribbon of small wind shear exists, as shown in the 200-850 wind shear analysis below, taken from the CIMSS Tropical Website. Meteorologists continue to monitor this region of tropical activity.

200-850 mb wind shear, 1800 UTC on 22 July 2021, over the western Pacific Ocean.

Tropical Storm Elsa forms in the Atlantic

July 1st, 2021 |

Night Time Microphysics (at night) and True-Color imagery (during the day) over the eastern Atlantic, 0920 – 1220 UTC on 1 July 2021

Tropical Storm Elsa has formed over the tropical eastern Atlantic Ocean.  True-color imagery from CSPP Geosphere (link) shows the storm with occasional bursts of deep convection.  Elsa has formed at the southern edge of a large area of Saharan Air (shown below, link, from this site), and the storm’s future could be influenced by this dry air.

Saharan Air Layer analysis, 1200 UTC on 1 July 2021 (Click to enlarge)

The abundant dry air to the north of Elsa is also apparent in the low-level water vapor imagery, as shown below.

GOES-16 ABI infrared low-level water vapor (Band 10, 7.34 µm) at 1240 UTC on 1 July 2021. NHC prediction of the 1300 UTC position of Elsa along with 34-knot wind radii are shown (Click to enlarge)

The dry air associated with the SAL shows up nicely in gridded NUCAPS fields, too. The toggle below steps through the CIMSS True Color RGB and GOES-16 Band 10 imagery (7.34 µm) along with 850-700 mb relative humidity from gridded NUCAPS.

CIMSS True Color RGB, GOES-16 ABI Band 10 infrared water vapor (7.34 µm), 850-700 mb relative humidity, 1510 UTC on 1 July 2021 (Click to enlarge)

For more information on Elsa, see the SSEC Tropical Website. Official forecasts are on the website of the National Hurricane Center (link; direct link to Elsa’s webpages there)

Tropical Storm Claudette makes landfall along the central Gulf Coast

June 19th, 2021 |

MIMIC Total Precipitable Water (TPW) estimates, 1900 UTC 18 June 2021 – 1800 UTC 19 June 2021 (Click to enlarge)

The Potential Tropical Cyclone that has been moving northward through the Gulf of Mexico made landfall southwest of New Orleans, LA on Saturday 19 June as a minimal Tropical Cyclone. The animation of total precipitable water, above, from the MIMIC TPW website, shows that most of the storm’s moisture is east of the center. (The circulation of Pacific Tropical Storm Dolores is also apparent, making landfall near Punta San Telmo in Mexico) A percent-of-Normal plots from NOAA/NESDIS/OSPO, below, shows values about 150% of normal over much of the southeast USA. Consequently, Flash Flood Watches are in effect over much of southern Alabama northeastward into western North Carolina, as shown below.

Percent-of-normal Blended Total Precipitable Water, 1800 UTC on 19 June 2021 (Click to enlarge)

Weather hazards at 1911 UTC on 19 June 2021 (Click to enlarge)

A True-Color image from CSPP Geosphere, below, taken from this link, shows the storm inland over southwestern Alabama; much of the rain and deep moisture with the storm remains to the east of the center.

True-Color imagery, 1921 UTC on 19 June 2021, from CSPP Geosphere (Click to enlarge)


24-hour precipitation ending 1200 UTC on 20 June 2021 (Click to enlarge)

24-hour precipitation totals (from this site) are shown above. The analysis shows a few spots in northern Alabama received 6-8″ of rain.

CMORPH2 estimates for the 24-hours of precipitation ending at 0000 UTC on 20 June (that is, 12 hours before the estimate above), from RealEarth, are shown below.

24-hour CMORPH2 precipitation total estimates for the time ending 0000 UTC on 20 June 2021 (Click to enlarge)

GSMaP (link) also shows satellite-derived precipitation estimates. The 24-hour estimate ending at 0000 UTC on 20 June is shown below.

GSMaP precipitation estimate for the 24 hours ending 0000 UTC on 20 June 2021 (Click to enlarge)

Near-surface winds over the south Pacific Ocean

June 14th, 2021 |

SAR Winds over the South Pacific, latitude/longitudes as indicated, at 0544 UTC on 14 June 2021 (click to enlarge)

Synthetic Aperture Radar (SAR) winds from RCM1 (RADARSAT Constellation Mission 1) over the south Pacific Ocean, from this site, show a gradient in wind speeds between 165 W and 168 W. Are there other ways to view this type of wind change over the open ocean?

GOES-17 Derived Motion wind vectors, below, showing 0500 UTC wind speeds between 950 and 800 mb (a different level than the near-surface winds from the SAR data), from Real Earth, below, do not clearly show the difference in winds over this same domain.

GOES-17 Enhanced window infrared (10.3 µm, Band 13) and 950-800 mb winds, 0500 UTC on 14 June 2021 (click to enlarge).  Note that the latitude lines shown are 19.5, 22 and 24.5 South.  The cold cloud top feature near the edge of this scene is also apparent at the beginning of the animation below.

GOES-17 Shortwave infrared imagery from the same time in that region, below, shows consistent westward motion at low levels (it’s hard to distinguish from this animation if the low-level wind speeds change across the domain; the cloud motions are all similar) with eastward motion aloft (that, is: considerable shear!)

GOES-17 3.9 µm imagery over the South Pacific, latitudes/longitude lines shown, from 0500 to 0600 UTC on 14 June 2021 (Click to enlarge)

SAR winds can give information over the open ocean that is difficult to find in other places.