Development of Convective Systems over Baja California during Tropical Cyclone Linda (2003)

Abstract Characteristics of the life cycle and motion of convective systems that occurred over the Baja California Peninsula were determined from a case study in September of 2003. This note applies data from satellite imagery, regular observations from upper-air and surface networks, and operational analyses. Changes in environmental conditions over northwestern Mexico are documented and these are associated with the development of Tropical Cyclone Linda in the eastern Pacific Ocean. When Linda became a tropical storm and was located several hundred kilometers away to the southwest, a convective outbreak occurred over land. An examination of large-scale conditions indicated that flow from the eastern flank of Linda supplied low- to midlevel moisture. Significant convection is associated with specific thresholds for precipitable water, CAPE, and lifted index. Convective systems initiated in the early afternoon remained active for several hours and provided localized areas of precipitation along the western side of the peninsular mountains. An assessment of all the available surface data was performed to determine regional elements that played a role in the development of these systems. Results include documentation of a sea breeze from the Gulf of California onto the mountain slopes when organized convection was first detected.

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Influence of Tropical Cyclones on Humidity Patterns over Southern Baja California, Mexico

Monthly Weather Review ◽

10.1175/mwr3356.1 ◽

2007 ◽

Vol 135 (4) ◽

pp. 1208-1224 ◽

Cited By ~ 16

Author(s):

Luis M. Farfán ◽

Ira Fogel

Keyword(s):

Tropical Cyclones ◽

Gulf Of California ◽

Large Scale ◽

Baja California ◽

Deep Convection ◽

Precipitable Water ◽

Operational Model ◽

Western Mexico ◽

Surface Station ◽

Northwestern Mexico

Abstract The influence of tropical cyclone circulations in the distribution of humidity and convection over northwestern Mexico is investigated by analyzing circulations that developed in the eastern Pacific Ocean from 1 July to 21 September 2004. Documented cases having some impact over the Baja California Peninsula include Tropical Storm Blas (13–15 July), Hurricane Frank (23–25 August), Hurricane Howard (2–6 September), and Hurricane Javier (15–20 September). Datasets are derived from geostationary satellite imagery, upper-air and surface station observations, as well as an analysis from an operational model. Emphasis is given to circulations that moved within 800 km of the southern part of the peninsula. The distribution of precipitable water is used to identify distinct peaks during the approach of these circulations and deep convection that occurred for periods of several days over the southern peninsula and Gulf of California. Hurricane Howard is associated with a significant amount of precipitation, while Hurricane Javier made landfall across the central peninsula with a limited impact on the population in the area. An examination of the large-scale environment suggests that advection of humid air from the equatorial Pacific is an important element in sustaining tropical cyclones and convection off the coast of western Mexico.

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Improved moist-convective rotating shallow water model and its application to instabilities of hurricane-like vortices

10.31219/osf.io/nfhkz ◽

2018 ◽

Author(s):

LMD

Keyword(s):

Tropical Cyclone ◽

Shallow Water ◽

Water Vapour ◽

Large Scale ◽

Precipitable Water ◽

Water Model ◽

Moist Convection ◽

Shallow Water Model ◽

Atmospheric Motions ◽

Rotating Shallow Water

We show how the two-layer moist-convective rotating shallow water model (mcRSW), which proved to be a simple and robust tool for studying effects of moist convection on large-scale atmospheric motions, can be improved by including, in addition to the water vapour, precipitable water, and the effects of vaporisation, entrainment, and precipitation. Thus improved mcRSW becomes cloud-resolving. It is applied, as an illustration, to model the development of instabilities of tropical cyclone-like vortices.

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Characteristics of mesoscale convection over northwestern Mexico, the Gulf of California, and Baja California Peninsula

International Journal of Climatology ◽

10.1002/joc.6752 ◽

2020 ◽

Author(s):

Luis M. Farfán ◽

Bradford S. Barrett ◽

G. B. Raga ◽

Julián J. Delgado

Keyword(s):

Gulf Of California ◽

Baja California ◽

Baja California Peninsula ◽

Mesoscale Convection ◽

Northwestern Mexico

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Evaluating Forecast Skills of Moisture from Convective-Permitting WRF-ARW Model during 2017 North American Monsoon Season

Atmosphere ◽

10.3390/atmos10110694 ◽

2019 ◽

Vol 10 (11) ◽

pp. 694 ◽

Cited By ~ 1

Author(s):

Christoforus Bayu Risanto ◽

Christopher L. Castro ◽

James M. Moker ◽

Avelino F. Arellano ◽

David K. Adams ◽

...

Keyword(s):

North American ◽

Monsoon Season ◽

Precipitable Water ◽

Weather Forecast ◽

Moisture Flux ◽

Rain Gauge ◽

North American Monsoon ◽

Convective Systems ◽

The North ◽

Northwestern Mexico

This paper examines the ability of the Weather Research and Forecasting model forecast to simulate moisture and precipitation during the North American Monsoon GPS Hydrometeorological Network field campaign that took place in 2017. A convective-permitting model configuration performs daily weather forecast simulations for northwestern Mexico and southwestern United States. Model precipitable water vapor (PWV) exhibits wet biases greater than 0.5 mm at the initial forecast hour, and its diurnal cycle is out of phase with time, compared to observations. As a result, the model initiates and terminates precipitation earlier than the satellite and rain gauge measurements, underestimates the westward propagation of the convective systems, and exhibits relatively low forecast skills on the days where strong synoptic-scale forcing features are absent. Sensitivity analysis shows that model PWV in the domain is sensitive to changes in initial PWV at coastal sites, whereas the model precipitation and moisture flux convergence (QCONV) are sensitive to changes in initial PWV at the mountainous sites. Improving the initial physical states, such as PWV, potentially increases the forecast skills.

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Numerical Study on the Formation of Typhoon Ketsana (2003). Part I: Roles of the Mesoscale Convective Systems

Monthly Weather Review ◽

10.1175/2011mwr3649.1 ◽

2012 ◽

Vol 140 (1) ◽

pp. 100-120 ◽

Cited By ~ 5

Author(s):

Xinyan Lu ◽

Kevin K. W. Cheung ◽

Yihong Duan

Keyword(s):

Large Scale ◽

Numerical Study ◽

Wrf Model ◽

Precipitable Water ◽

Relative Vorticity ◽

Formation Time ◽

Mesoscale Convective Systems ◽

Low Level ◽

Convective Systems ◽

Mesoscale Convective

Abstract The effects of multiple mesoscale convective systems (MCSs) on the formation of Typhoon Ketsana (2003) are analyzed in this study. Numerical simulations using the Weather Research and Forecasting (WRF) model with assimilation of Quick Scatterometer (QuikSCAT) and Special Sensor Microwave Imager (SSM/I) oceanic winds and total precipitable water are performed. The WRF model simulates well the large-scale features, the convective episodes associated with the MCSs and their periods of development, and the formation time and location of Ketsana. With the successive occurrence of MCSs, midlevel average relative vorticity is strengthened through generation of mesoscale convective vortices (MCVs) mainly via the vertical stretching mechanism. Scale separation shows that the activity of the vortical hot tower (VHT)-type meso-γ-scale vortices correlated well with the development of the MCSs. These VHTs have large values of positive relative vorticity induced by intense low-level convergence, and thus play an important role in the low-level vortex enhancement with aggregation of VHTs as one of the possible mechanisms. Four sensitivity experiments are performed to analyze the possible different roles of the MCSs during the formation of Ketsana by modifying the vertical relative humidity profile in each MCS and consequently the strength of convection within. The results show that the development of an MCS depends substantially on that of the prior ones through remoistening of the midtroposphere, and thus leading to different scenarios of system intensification during the tropical cyclone (TC) formation. The earlier MCSs are responsible for the first stage vortex enhancement, and depending on the location can affect quite largely the simulated formation location. The extreme convection within the last MCS before formation largely determines the formation time.

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The Effects of the Gulf of California SSTs on Warm-Season Rainfall in the Southwestern United States and Northwestern Mexico: A Regional Model Study

Journal of Climate ◽

10.1175/jcli3584.1 ◽

2005 ◽

Vol 18 (23) ◽

pp. 4970-4992 ◽

Cited By ~ 8

Author(s):

Jinwon Kim ◽

Jongyoun Kim ◽

John D. Farrara ◽

John O. Roads

Keyword(s):

Water Vapor ◽

Gulf Of California ◽

Monsoon Rainfall ◽

Land Development ◽

Warm Season ◽

Sea Breeze ◽

Western Slope ◽

Mesoscale Circulation ◽

Low Level ◽

Northwestern Mexico

Abstract The impacts of the sea surface temperatures (SSTs) in the northern Gulf of California (GC) on warm-season rainfall in the Arizona–New Mexico (AZNM) and the northwestern Mexico (NWM) regions associated with the North American monsoon (NAM) are examined from two sets of seasonal simulations in which different SSTs were prescribed in the GC. The simulations reproduced important features in the low-level mesoscale circulations and upper air fields around the time of monsoon rainfall onset in AZNM such as sea-breeze-like diurnal variations in the low-level winds between the GC and the land, development of south-southeasterly winds over the GC and the western slope of the Sierra Madre Occidental after the onset of rainfall, and the strengthening of the 500-hPa high over AZNM around the onset of monsoon rainfall in AZNM. The simulated temporal variations in the upper air fields and daily rainfall, as well as the mesoscale circulation around the GC, suggest that the GC SSTs affect the water cycle around the GC mainly by altering mesoscale circulation and water vapor fluxes, but they have minimal impacts on the onset timing of monsoon rainfall in NWM and AZNM. With higher SSTs in the NGC, rainfall in NWM and AZNM increases in response to enhanced water vapor fluxes from the GC into the land. The enhanced onshore component of the low-level water vapor fluxes from the GC with higher GC SSTs results from two opposing effects: weakened sea-breeze-like circulation between the GC and the surrounding lands that tends to reduce the water vapor fluxes from the GC, and increased evaporation from the GC that tends to increase the water vapor fluxes. The simulations also suggest that the development of south-southeasterly low-level winds over the GC after monsoon rainfall onset plays an important role in enhancing rainfall as longer fetches over the GC can provide more water vapor into the low atmosphere.

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A Numerical Study of Tropical Cyclone Formation from Two Mesoscale Convective Systems in a Large-scale Convective System

SOLA ◽

10.2151/sola.2006-015 ◽

2006 ◽

Vol 2 ◽

pp. 57-60 ◽

Cited By ~ 3

Author(s):

Masanori Yamasaki

Keyword(s):

Tropical Cyclone ◽

Large Scale ◽

Numerical Study ◽

Mesoscale Convective Systems ◽

Convective System ◽

Tropical Cyclone Formation ◽

Convective Systems ◽

Mesoscale Convective

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Tropical Cyclone Mekkhala’s (2008) Formation over the South China Sea: Mesoscale, Synoptic-Scale, and Large-Scale Contributions

Monthly Weather Review ◽

10.1175/mwr-d-14-00119.1 ◽

2015 ◽

Vol 143 (1) ◽

pp. 88-110 ◽

Cited By ~ 11

Author(s):

Myung-Sook Park ◽

Hyeong-Seog Kim ◽

Chang-Hoi Ho ◽

Russell L. Elsberry ◽

Myong-In Lee

Keyword(s):

Tropical Cyclone ◽

Large Scale ◽

Wave Train ◽

Critical Role ◽

Intraseasonal Variability ◽

The Philippines ◽

Synoptic Scale ◽

Low Level ◽

Convective Systems ◽

Mesoscale Convective

Abstract Tropical cyclone formation close to the coastline of the Asian continent presents a significant threat to heavily populated coastal countries. A case study of Tropical Storm Mekkhala (2008) that developed off the coast of Vietnam is presented using the high-resolution analyses of the European Centre for Medium-Range Weather Forecasts/Year of Tropical Convection and multiple satellite observations. The authors have analyzed contributions to the formation from large-scale intraseasonal variability, synoptic perturbations, and mesoscale convective systems (MCSs). Within a large-scale westerly wind burst (WWB) associated with the Madden–Julian oscillation (MJO), synoptic perturbations generated by two preceding tropical cyclones initiated the pre-Mekkhala low-level vortex over the Philippine Sea. Typhoon Hagupit produced a synoptic-scale wave train that contributed to the development of Jangmi, but likely suppressed the Mekkhala formation. The low-level vortex of the pre-Mekkhala disturbance was then initiated in a confluent zone between northeasterlies in advance of Typhoon Jangmi and the WWB. A key contribution to the development of Mekkhala was from diurnally varying MCSs that were invigorated in the WWB. The oceanic MCSs, which typically develop off the west coast of the Philippines in the morning and dissipate in the afternoon, were prolonged beyond the regular diurnal cycle. A combination with the MCSs developing downstream of the Philippines led to the critical structure change of the oceanic convective cluster, which implies the critical role of mesoscale processes. Therefore, the diurnally varying mesoscale convective processes over both the ocean and land are shown to have an essential role in the formation of Mekkhala in conjunction with large-scale MJO and the synoptic-scale TC influences.

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Composite Life Cycle of Maritime Tropical Mesoscale Convective Systems in Scatterometer and Microwave Satellite Observations

Journal of the Atmospheric Sciences ◽

10.1175/2008jas2746.1 ◽

2009 ◽

Vol 66 (1) ◽

pp. 199-208 ◽

Cited By ~ 37

Author(s):

Brian Mapes ◽

Ralph Milliff ◽

Jan Morzel

Keyword(s):

Life Cycle ◽

Large Scale ◽

Surface Wind ◽

Precipitable Water ◽

Satellite Observations ◽

Mesoscale Convective Systems ◽

Convective Systems ◽

Mesoscale Convective ◽

The Common ◽

Cloud Tops

Abstract This study examines scatterometer-observed surface wind divergence and vorticity, along with precipitable water (PW), across the life cycle of tropical maritime mesoscale convective systems (MCSs) as resolved in 0.5° data. Simple composites were constructed around first appearances of cold (<210 K) cloud tops in infrared (IR) data at 3-hourly resolution. Many thousands of such events from the tropical Indo-Pacific in 2000 were used. Composites of subpopulations were also constructed by subdividing the dataset according to IR event size and duration, as well as by prevailing values of PW and vorticity at a 5° scale. The composite MCS life cycle here spans about a day and covers a few hundred kilometers, with a remarkable sameness across subpopulations. Surface wind convergence and PW buildup lead cold cloud appearance by many hours. Afterward there are many hours of divergence, indicative of downdrafts. Contrary to motivating hypotheses, the strength of this divergence relative to convergence is scarcely different in humid and dry subpopulation composites. Normalized time series of composite vorticity show an evolution that seems consistent with vortex stretching by this convergence–divergence cycle, with peak vorticity near the end of the period of convergence (3 h prior to cold cloud appearance). In rotating conditions, the common 1-day MCS life cycle is superposed on large-scale mean vorticity and convergence, approximately in proportion, which appear to be well scale-separated (covering the whole of the 48-h and 5°–10° averages) and are as strong as or stronger than the MCS signature.

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