Tropical Depression Nine in the Atlantic Ocean, above, shows characteristics of a heavily sheared storm (longer sunrise-to-sunset animations: gif | mp4). The low-level circulation is displaced south and west of the strongest convection (which is vigorous enough to produce occasional overshooting tops, below, as shown on this page).

Metop-B overflew Tropical Depression Nine’s circulation just after 1300 UTC on 17 September (Orbital tracks for Metop-B are here). The image below shows a circulation with 20-30 knot winds displaced to the south and west of cold 10.7 µm brightness temperatures indicating high cloud tops detected by the GOES-13 Imager.

Total Precipitable Water images from MIMIC (above) suggest the circulation of Tropical Depression Nine is on the northern edge of deep moisture in the Intertropical Convergence Zone. Its projected path to the north and west is towards dryer air. The projected path (below) does take the storm towards warmer waters; however, it also moves it towards a region of even higher deep-layer wind shear (plots below were taken from the CIMSS Tropical Cyclones site). Only the warmer waters argue that this storm will persist; everything else suggests a struggle to survive. Several tropical cyclones this season have succumbed to wind shear while over the tropical Atlantic. Tropical Depression Nine may add to that total.

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Some locations in southern California received record daily precipitation on 15 September 2015. A time series plot of weather conditions for Los Angeles International Airport is shown above; the 1.80 inches of rainfall received there made it the wettest September day on record.

As mentioned in the NWS Los Angeles record event report, the moisture source for this heavy rainfall event was the remnants of Hurricane Linda (storm path); the MIMIC Total Precipitable Water product covering the period 06-15 September (below) showed the evolution of the moisture associated with Linda, which originally tapped rich moisture from the Intertropical Convergence Zone (ITCZ).

A closer look at the MIMIC Total Preciptable Water product (below) showed how the moisture was becoming more concentrated just offshore, in advance of an approaching upper level trough and a decaying surface cold front.

GOES-15 Infrared (10.7 µm) images (below) revealed that the cloud-top IR brightness temperatures were actually quite warm (> -20º C) over coastal southern California during the period of the heavy rainfall event.

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The Aurora Forecast shown above was issued on the night of 08 September 2015 by the NOAA Space Weather Prediction Center, with the accompanying text:

Following the G2 (moderate) geomagnetic storms from last night, observations of the solar wind at the ACE spacecraft near L1 indicate the potential again this evening for more activity. G1 (minor) conditions have already been observed by the global network of ground-based near real-time magnetometers. A forecast warning for G2 has been issue from 09/0500 – 09/1000 UTC (1am to 6am EST). These could be some prime hours to possibly see the Aurora in the northern most regions of the lower 48 states.

A composite of Suomi NPP VIIRS Day/Night Band (0.7 µm) images viewed using the SSEC RealEarth web map server (above) showed the bright and complex signature of the aurora borealis across southern Canada and the northern United States during the subsequent nighttime hours. Two of the individual Day/Night Band image swaths as viewed using AWIPS-2 are shown below.

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GOES-15 Visible (0.63 µm) images (above; click image to play animation) showed the low-level circulation center (LLCC) of Tropical Storm Jimena becoming exposed as the tropical cyclone encountered increasing amounts of westerly deep-layer wind shear. Jimena had rapidly intensified to a Category 4 hurricane over the East Pacific Ocean in late August and early September (path | ADT plot).

Before sunrise, Suomi NPP VIIRS imagery (below; click to enlarge) was useful to help locate the LLCC, as was noted in a discussion issued by the Central Pacific Hurricane Center.

A DMSP-18 SSMIS Microwave (85 GHz) image at 1733 UTC (below; click to enlarge) showed a signature of significant rainfall rates (orange to red color enhancement) within the deep convection that remained well to the east of the LLCC.

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