The Contribution of Eastern North Pacific Tropical Cyclones to the Rainfall Climatology of the Southwest United States

Abstract

Forty-six years of summer rainfall and tropical cyclone data are used to explore the role that eastern North Pacific tropical cyclones (TCs) play in the rainfall climatology of the summer monsoon over the southwestern United States. Thirty-five TCs and their remnants were found to bring significant rainfall to the region, representing less than 10% of the total number of TCs that formed within the basin. The month of September was the most common time for TC rainfall to occur in the monsoon region as midlatitude troughs become more likely to penetrate far enough south to interact with the TCs and steer them toward the north and east. On average, the contribution of TCs to the warm-season precipitation increased from east to west, accounting for less than 5% of the rainfall in New Mexico and increasing to more than 20% in southern California and northern Baja California, with individual storms accounting for as much as 95% of the summer rainfall. The distribution of rainfall for TC events over the southwest United States reveals three main categories: 1) a direct northward track from the eastern Pacific into southern California and Nevada, 2) a distinct swath northeastward from southwestern Arizona through northwestern New Mexico and into southwestern Colorado, and 3) a broad area of precipitation over the southwest United States with embedded maxima tied to terrain features. Differences in these track types relate to the phasing between, and scales of, the trough and TC, with the California track being more likely with large cutoff cyclones situated off the west coast, the southwest-northeast track being most likely with mobile midlatitude troughs moving across the intermountain west, and the broad precipitation category generally exhibiting no direct interaction with midlatitude features.

The Impact of Horizontal Resolution on North American Monsoon Gulf of California Moisture Surges in a Suite of Coupled Global Climate Models

“…4) results in a great improvement in the modeled wind variability in the GoC, particularly at the synoptic time scales (#10 days). In this time window, the summertime GoC wind variability is mainly associated with the passage of tropical easterly waves (TEWs) or tropical cyclones (TCs)-often triggered by a TEW (e.g., Lorenz and Hartmann 2006)-south of the GoC (Serra et al 2008(Serra et al , 2010Corbosiero et al 2009;Wood and Ritchie 2013). The low energy in the CM2.1 power spectrum at synoptic time scales suggests an overly weak TEW and/or TC variance in CM2.1, consistent with findings in Lin et al (2008).…”

“…6c,d) reveals that, in reanalyses, the most intense GoC surge-related wind anomalies occur in September ('7 vs '4 m s 21 in JulyAugust). This is most likely due to the passage of TCs south of the Baja California peninsula (Higgins and Shi 2005;Corbosiero et al 2009;Wood and Ritchie 2013). This seasonal pattern with a maximum in September is also seen in the moisture flux ('14 vs '10 m s 21 g kg 21 in…”

“…Also evident are a concomitant progression of a TEW, or the passage of a TC (Higgins and Shi 2005;Corbosiero et al 2009;Wood and Ritchie 2013), to the south of the GoC and a midlatitude westerly disturbance over the central United States (e.g., Pascale and Bordoni 2016). In CM2.1-the model with the lowest resolutionGoC surges do not feature a realistic structure.…”

Comparing the Spatial Patterns of Rainfall and Atmospheric Moisture among Tropical Cyclones Having a Track Similar to Hurricane Irene (2011)

“…This limits the ability to investigate rainfall produced on the right side of the storm's track. Previous studies have used this dataset to examine rainfall from TCs [6,41], supporting its use in the current study. The fact that strong winds near the TC's center causes undercatch in rain gauges leading to lower rainfall totals should also be noted [42][43][44].…”

On the distinct interannual variability of tropical cyclone activity over the easter North Pacific

“…Since most TCs tend to move westward and/or northwestward, TCs in the ENP make landfall less frequently when compared to other basins; hence, TC activity in the ENP basin has possibly received relatively less attention. However, ENP TC activity is an important factor in the summer precipitation regime across Central America and southwestern North America Douglas, 2001, 2002;Corbosiero et al, 2009;Wood and Ritchie, 2013). These regions are projected to experience prolonged drought-like condition in the future climate, so a better understanding of TC activity in the ENP basin has not only scientific relevancy but also a profound socioeconomic impact.…”