The Joint Typhoon Warning Center has issued a Tropical Cyclone Formation Advisory (TCFA) for disturbed weather located southwest of Chuuk in the tropical Pacific. MIMIC Total Precipitable Water fields, above, show the development of a circulation near 150^oE Longitude and 5^oN Latitude between 0000 UTC 17 May and 0000 UTC 19 May. At present the system is very close to the Equator, and the low latitudes may somewhat inhibit its development in the short term. The circulation of the system is also apparent in Advanced Scatterometry (ASCAT) data from MetopB, shown below and available here. The HY-2C satellite returned scatterometry data over the circulation center, also shown below (taken from this site).

What does the future hold for this system? Dynamic Layer Mean Winds, below, (from the SSEC Tropical Weather website), suggest that in the short term the system might be moving to the northeast (consistent with the track from JTWC here).

The invest is moving over very warm waters, and is in a narrow region of modest shear, as shown in the toggle below.

Himawari9 Clean Window infrared imagery, below, from 00 – 17 UTC on 19 May, shows vigorous convective development just west of 150^oE and south of 10^oN (perhaps some of this intensification in the organization is part of the well-known diurnal cycle in tropical cyclone convection as discussed here, for example). Note also the northward and eastward motion to the north of the convection. There appears to be good ventilation away from the storm (strong upper-level divergence is diagnosed, per this 1500 UTC analysis from the SSEC Tropical Weather website).

The ventilating flow from the storm center is perhaps more apparent in the upper-level water vapor imagery, shown below.

You can find more information on this system at following websites: JTWC. NWS Guam (they recently had a map discussion on Facebook live); SSEC Tropical Website; Tokyo RSMC. The next name for western Pacific tropical systems is Mawar, the Malaysian word for ‘Rose’. Residents of the Guam and other Marianas Islands should pay particular attention to this storm as current forecasts have it moving through that island chain next week.

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Visible imagery from near sunset on 16 May 2023, above, shows multiple horizontal cloud lines north of the islands of Oahu and Kauai. Each of the clouds lines is associated with a local modulation of the wind field in the SAR Wind field. The wind /Normalized Radar Cross Section fields are also available online (winds; NRCS). Note that a SAR Wind scene from this ascending Sentinel-1A pass (here) that was taken just before the one above has an hourglass-shaped feature (at 21.2^oN, 158.4^oW) in the derived wind field that is highlights a mismatch between the first guess field used and the NRCS data.

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Southern Wisconsin experienced the convergence of 3 cooling mechanisms during the afternoon hours of 16 May 2023: (1) the arrival of a dense band of smoke aloft — transported southward from wildfires in Alberta and Saskatchewan — which reduced incoming solar radiation, (2) a southward-moving cold front and (3) the inland surge of a lake breeze (or “Pneumonia Front“) from Lake Michigan. Signatures of all 3 features were evident in GOES-16 (GOES-East) True Color RGB images from the CSPP GeoSphere site (above), with the cold front and lake breeze marked by broken lines of cumulus clouds that could be seen through the thick veil of smoke.

In a comparison of GOES-16 Day Land Cloud RGB images at 1826 UTC that include readouts of Aerosol Optical Depth (AOD), MVFR Fog Probability, Land Surface Temperature and Fire Temperature derived products for a point beneath the thick smoke layer (above) and just south of the thick smoke layer (below), the degree to which the smoke was reducing the amount of incoming solar radiation was apparent in a reduction in Land Surface Temperature (78.26ºF beneath the thick smoke where the AOD was 2.08, vs. 83.98ºF just south of the thick smoke where the AOD was negligible). Both points — and the W-E oriented band of thickest smoke — were located south of the approaching cold front (1800 UTC surface analysis).

CIMSS Natural Color RGB images (below) include plots of surface and buoy reports along with frontal analyses — note the significant drop in air temperatures across southeast Wisconsin as the lake breeze moved inland (for example, from the low 80s F to the middle 50s F within a 30-45 minute period at Milwaukee and Racine; further inland, a notable temperature drop was also seen in Madison just after 19:30 or 7:30 PM local time). Water temperatures reported by Buoy 45007 in southern Lake Michigan were in the 44-46ºF range during the day, and just after 1800 UTC the NOAA-20 VIIRS Sea Surface Temperature value over that buoy location was 47ºF.

A plot of lidar backscatter (source) at Madison, Wisconsin (below) depicted increasing smoke within 2 layers: one at an altitude around 3 km, and another within the 5-6 km altitude range.

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True-Color imagery from GOES-East (above, from the CSPP Geosphere site) and GOES-West (below, also from the CSPP Geosphere site) from 1720-1910 UTC show multiple active fires in British Columbia, Alberta and Manitoba, and a wide plume of smoke entrained into a storm centered just north of Saskatchewan (one wonders if the rain from the storm is somewhat muddy) and also moving south of the storm into the atmosphere above the Great Lakes. Drought conditions that have been widespread over Alberta (from this site) likely are contributing to the smoke production (which has been ongoing — see this CIMSS Blog Post from early May).

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