A potent winter storm is on tap for eastern Colorado (and surroundings) over the weekend.  As with any system bringing heavy snow, knowing the storm path is crucial.  From a recent Boulder WFO Forecast Discussion, available here:   “Recent models runs in the GFS and ECMWF have trended more to the north while the Canadian stays to the south.”  The toggles above and below compare NUCAPS satellite-based observations of tropopause pressure (NUCAPS at 1023 UTC above, at 0843 UTC below) with 40-km Rapid Refresh model estimates (1000 UTC above, 0900 UTC below) of the tropopause pressure.  Can you use the NUCAPS depiction of the tropopause to convince yourself that the model — the Rapid Refresh in this case — has the proper initialization/evolution of the impulse that will generate the snowfall?  (Note that the colormaps for all images are the same).

A challenge with this storm at this time is that the neither of the NOAA-20 NUCAPS fields available in AWIPS themselves sample the entirety of the tropopause fold.  One might use the 0844 UTC imagery above to conclude that the Rapid Refresh is too slow in the eastward progress of the storm.  It’s difficult to make the same conclusion from the 1026 UTC image, however, at top.  Ozone anomalies (shown below) from the NASA SPoRT gridded NUCAPS site (link) include the Suomi-NPP pass (in between the two NOAA-20 passes above) that does more completely sample the tropopause fold at one time;  however, those data are not available in the baseline AWIPS.  Perhaps the afternoon pass from NOAA-20 will offer better coverage.  (Update, below:  It did!)

Gridded Tropopause height fields and gridded ozone fields, shown below, do agree very well; use them interchangeably to identify tropopause folds.  The two fields are derived from different CrIS channels in NUCAPS.

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The 2000 UTC NOAA-20 overpass more completely sampled the upper tropospheric feature.  See below.  The placement of the feature in the Rapid Refresh looks approximately correct over the southwestern United States (that is, NUCAPS observations seem to overlap Rapid Refresh features);  there are some dissimilarities in features over the Dakotas:  farther north in NUCAPS, farther south in the Rapid Refresh.

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US Space Force EWS-G1 Infrared Window (10.7 µm) images (above) displayed the well-defined eye and eyewall structure of Cyclone Habana in the South Indian Ocean on 10 March 2021. This was the second period of Category 4 intensity (ADT | SATCON) during the life cycle of Habana.

Meteosat-8 Infrared images with contours of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) showed that Habana was moving through an environment of relatively low shear.

Meteosat-8 Infrared images with an overlay of 1505 UTC Metop ASCAT winds (below) depicted a fairly uniform distribution of winds within the eyewall region, as Habana developed an annular structure.

SSMIS Microwave (85 GHz) images from DMSP-16 at 1139 UTC and DMSP-18 at 2327 UTC are shown below.

 

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The system that produced the high-impact flooding event on Maui (discussed here) also  caused flooding rains on Oahu on the 9th.   (A Flash Flood Emergency was declared at 348 HST on 9 March:  Link)  How well did quantitative satellite estimates of this event perform?  Hydroestimator values, above, from the 24 hours ending 1200 UTC on 9 March (from this website) show isolated maxima over northern Oahu for and over eastern Maui. Daily totals for the 24 hours ending 1200 UTC on 10 March are shown below.  Again, heavy rain is diagnosed on Maui with lesser amounts over Oahu, where 48-hour  totals  were between  150  and  200  mm.

24-hour totals from JAXA’s GsMAP website, above, show large values mostly north of Oahu, and also just north of Maui.  Values are between 100-150 mm.  24-hour CMORPH-2 values (from RealEarth), below, ending 0000 UTC on 10 March, show values between 50 and 100 mm.  Values over Maui are less than 50 mm.

The GOES-17 Enterprise algorithm totals, below (courtesy Bob Kuligowski, NOAA) , show values close to 50 mm over Oahu, and over 50 mm on Maui.

None of these rain totals captured the exceptional nature (writeup is here;  some totals are here) of this orographically enhanced rainfall. The widespread nature of the rain was captured however.  All methods detected heaviest rain north of the Island chain.

GOES-17 animations, both visible and infrared, combined with situational awareness driven by animations of total precipitable water, such as that below (from this site) will help a forecaster anticipate heavy rains however — when they might start, and when they might end.

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GOES-17 (GOES-West) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) revealed 2 bursts of back-building thunderstorms that produced heavy rainfall (as much as 19.21 inches) and flooding along the northern coast of the Hawaiian island of Maui on 08 March 2021. This heavy rain caused rockslides that closed some roads, and prompted evacuations of a few communities downstream of the Kaupakulua Dam (which began to experience over-topping).

The coldest 10.35 µm infrared brightness temperatures were around -48ºC — for example, at 0000 UTC on 09 March (below).

In closer views of GOES-17 Visible and Infrared images (above), USGS river and rain gauge locations are plotted in large yellow text — the abrupt rise in flow of the Honopau Stream near Huelo (HPOH1) and the rapid accumulation of 17 inches of rainfall at the Wailuaiki rain gauge near Keanae (WWKH1) are shown below.

GOES-17 Water Vapor images with plots of mid-upper level Derived Motion Winds (above) showed the circulation of an upper level low west of the Hawaiian Islands — and with an increase in southwesterly upper-tropospheric wind speeds (as shown in Lihue rawinsonde data). the corresponding upper-level divergence (below) was seen to increase across the island chain by 00 UTC on 09 March (providing a more favorable environment for the development of deep convection).

The MIMIC Total Precipitable Water product spanning the 2 day period leading up to the heavy rainfall (below) showed an axis of higher tropical moisture — with TPW values of 1.50 to 1.75 inches — moving westward across Hawai’i.

The TPW value calculated from Hilo, Hawai’i rawinsonde data increased from 37.8 mm to 42.3 mm (1.49 inches to 1.67 inches) during the day as the lobe of enhanced moisture began to move westward over the Big Island (below).

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