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The totals (24h) reported by the rain gauges for the 18@12 in south of California are displayed below (inch). They seem to be consistent with the totals generated for the gridded map.
Maps of total precipitable water based on an algorithm using microwave observations from polar orbiting satellites are generated at Cooperative Institute for Meteorological Satellite Studies (CIMSS) are available to the public. Based on these maps we can detect the presence of Atmospheric Rivers (AR) which was responsible for the large amounts of precipitation occurred in California last weekend (see DR of yesterday). A stream of high values of precipitable water stretches from subtropical region, crossing Hawaii Islands towards the coast of Washington state, sliding equatorwards along the coast and reaching South California 2 days later, embedded in the extra-tropical cyclonic circulation.
The development of this AR in central equatorial Pacific seems to coincide with the propagation of a strong MJO event in western equatorial Pacific some days before. Looking at few products that monitor the presence and progression of the MJO we can seen that around 10 February the system, in terms of OLR anomalies was located in western Pacific (top panel). This is also confirmed by the Wheeler and Hendon index based on the forecast initialised on the 9th February (left panel). The extended range forecast initialised on the 26th January shows the progression of an MJO event in Indian Ocean. By day 20 (~15 January) a good fraction of the ENS members predict a strong MJO in the western Pacific.
3. Predictability
3.1 Data assimilation
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The EFI signal of abnormal rainfall over the region 7 days before the event (and SOT values indicating an extreme scenario). As we get close to the event the EFI become higher.
3.4 Monthly forecasts
The series of plot below show weekly precipitation anomalies for 13-19 February (note that the California event was in the end of the week).
3.5 Comparison with other centres
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