scholarly journals The influence of the coastal front on heavy rainfall events along the east coast

2019 ◽  
Author(s):  
◽  
Chasity B. Henson
Keyword(s):  
Tropical Cyclone ◽  
Heat Release ◽  
Latent Heat ◽  
Heavy Rainfall ◽  
East Coast ◽  
Latent Heat Release ◽  
Rainfall Events ◽  
Upper Level ◽  
Heavy Rainfall Events ◽  
Frontal Boundary

Coastal fronts are commonly found along the East Coast of the United States and can often be associated with intense rainfall and flooding due to elevated convection on the cold side of the boundary. Five heavy rainfall events ([greater to or equal than] 250 mm 24 hr-1) during the fall months along the East Coast were investigated using numerical weather prediction (NWP) models to determine the influence of an upper-level trough/cut-off low, an offshore tropical cyclone, a frontal boundary, and a moisture plume on the intense precipitation. Using experimental NWP simulations, it was determined that the tropical cyclone had an impact on the moisture plume and subsequent location of precipitation due to an associated deformation zone. The tropical cyclone prolonged the events by 6 hours, but inhibited the amount of moisture and resulting precipitation by deterring southeasterly flow. Evaporation from precipitation (surface heat fluxes) contributed to less than 25% (33%) of the precipitation, while latent heat release had the largest impact on the rain totals due to positive feedback from convection and an influence on the frontal boundary. Terrain also impacted the frontal boundary in each event, altering precipitation totals. Parcel trajectories confirmed regions of frontogenesis to be the main source of lift for the release of gravitational instability and convective initiation in each event, while the extratropical cyclone provided upper-level support for ascent and organized the plume of deep tropospheric moisture perpendicular to the front. Three of the five events lasted multiple days due to negative PV advection by the irrotational wind, in response to latent heat release in the region of convection, acting to slow the propagation of the upper-level low.

scholarly journals The Poleward Motion of Extratropical Cyclones from a Potential Vorticity Tendency Analysis

2016 ◽  
Vol 73 (4) ◽  
pp. 1687-1707 ◽  
Author(s):  
Talia Tamarin ◽  
Yohai Kaspi
Keyword(s):  
Heat Release ◽  
Latent Heat ◽  
Potential Vorticity ◽  
Growth Stage ◽  
Baroclinic Instability ◽  
Propagation Time ◽  
Latent Heat Release ◽  
Low Level ◽  
Upper Level ◽  
Tendency Analysis

Abstract The poleward propagation of midlatitude storms is studied using a potential vorticity (PV) tendency analysis of cyclone-tracking composites, in an idealized zonally symmetric moist GCM. A detailed PV budget reveals the important role of the upper-level PV and diabatic heating associated with latent heat release. During the growth stage, the classic picture of baroclinic instability emerges, with an upper-level PV to the west of a low-level PV associated with the cyclone. This configuration not only promotes intensification, but also a poleward tendency that results from the nonlinear advection of the low-level anomaly by the upper-level PV. The separate contributions of the upper- and lower-level PV as well as the surface temperature anomaly are analyzed using a piecewise PV inversion, which shows the importance of the upper-level PV anomaly in advecting the cyclone poleward. The PV analysis also emphasizes the crucial role played by latent heat release in the poleward motion of the cyclone. The latent heat release tends to maximize on the northeastern side of cyclones, where the warm and moist air ascends. A positive PV tendency results at lower levels, propagating the anomaly eastward and poleward. It is also shown here that stronger cyclones have stronger latent heat release and poleward advection, hence, larger poleward propagation. Time development of the cyclone composites shows that the poleward propagation increases during the growth stage of the cyclone, as both processes intensify. However, during the decay stage, the vertical alignment of the upper and lower PV anomalies implies that these processes no longer contribute to a poleward tendency.

scholarly journals Numerical Study of Explosively Developing Extratropical Cyclones in the Northwestern Pacific Region

2008 ◽  
Vol 136 (2) ◽  
pp. 712-740 ◽  
Author(s):  
Akira Kuwano-Yoshida ◽  
Yoshio Asuma
Keyword(s):  
Pacific Ocean ◽  
Heat Release ◽  
Latent Heat ◽  
Moisture Distribution ◽  
Northwestern Pacific ◽  
Extratropical Cyclones ◽  
Latent Heat Release ◽  
Northwestern Pacific Ocean ◽  
Asian Continent ◽  
Upper Level

Abstract Numerical simulations of six explosively developing extratropical cyclones in the northwestern Pacific Ocean region are conducted using a regional mesoscale numerical model [the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)]. Cyclones are categorized according to the locations where they form and develop: Okhotsk–Japan Sea (OJ) cyclones originate over the eastern Asian continent and develop over the Sea of Japan or the Sea of Okhotsk, Pacific Ocean–land (PO–L) cyclones also form over the Asian continent and develop over the northwestern Pacific Ocean, and Pacific Ocean–ocean (PO–O) cyclones form and develop over the northwestern Pacific Ocean. Two cases (the most extreme and normal deepening rate cases for each cyclone type) are selected and simulated. Simulations show that the extreme cyclone of each type is characterized by a different mesoscale structure and evolutionary path, which strongly reflect the larger-scale environment: an OJ cyclone has the smallest deepening rates, associated with a distinct upper-level shortwave trough, a clear lower-level cold front, and a precipitation area that is far from the cyclone center; a PO–L cyclone has moderate deepening rates with high propagation speeds under zonally stretched upper-level jets; and a PO–O cyclone has the strongest deepening rates associated with large amounts of precipitation near its center. Sensitivity experiments involving the latent heat release associated with water vapor condensation show that PO–O cyclones rarely develop without a release of latent heat and their structures are drastically different from the control runs, while OJ cyclones exhibit almost the same developments and have similar structures to the control runs. These tendencies can be seen in both extreme and normal deepening rate cases. These results reveal that the importance of latent heat release to explosive cyclone development varies among the cyclone types, as is reflected by the cyclone origin, frontal structure, moisture distribution, and jet stream configuration.

scholarly journals The Influence of Incipient Latent Heat Release on the Precipitation Distribution of the 24–25 January 2000 U.S. East Coast Cyclone

2005 ◽  
Vol 133 (7) ◽  
pp. 1913-1937 ◽  
Author(s):  
Michael J. Brennan ◽  
Gary M. Lackmann
Keyword(s):  
Heat Release ◽  
Latent Heat ◽  
Moisture Transport ◽  
East Coast ◽  
Weather Prediction ◽  
Lower Troposphere ◽  
Latent Heat Release ◽  
Precipitation Distribution ◽  
Balanced Flow ◽  
The Impact

Abstract The role of a diabatically produced lower-tropospheric potential vorticity (PV) maximum in determining the precipitation distribution of the 24–25 January 2000 U.S. East Coast cyclone is investigated. Operational numerical weather prediction (NWP) models performed poorly with this storm, even within 24 h of the event, as they were unable to properly forecast the westward extent of heavy precipitation over the Carolinas and mid-Atlantic. The development of an area of incipient precipitation (IP) around 0600 UTC 24 January over the southeastern United States prior to rapid cyclogenesis was also poorly forecasted by the operational NWP models. It is hypothesized that the lower-tropospheric diabatic PV maximum initially produced by the IP was important to subsequent inland moisture transport over the Carolinas and mid-Atlantic. A PV budget confirms that latent heat release in the midtroposphere associated with the IP led to the initial formation of a PV maximum in the lower troposphere that propagated eastward in association with the IP to the Atlantic coast late on 24 January. The impact of this PV maximum on the westward moisture transport was quantified by piecewise Ertel PV inversion. Results from the inversion show that the balanced flow associated with this evolving cyclonic PV maximum contributed substantially to the onshore moisture flux into the Carolinas and Virginia. The balanced flow associated with the PV anomaly also contributed to quasigeostrophic forcing for ascent in the region. These findings suggest that accurate numerical prediction of the precipitation distribution in this event requires adequate representation of the IP and its associated impacts on the PV distribution.

scholarly journals Using Satellite Observations to Evaluate the Relationships between Ice Condensate, Latent Heat Release, and Tropical Cyclone Intensification in a Mesoscale Model

2021 ◽  
Vol 149 (1) ◽  
pp. 113-129
Author(s):  
Shun-Nan Wu ◽  
Brian J. Soden ◽  
Yoshiaki Miyamoto ◽  
David S. Nolan ◽  
Stefan A. Buehler
Keyword(s):  
Tropical Cyclone ◽  
Heat Release ◽  
Water Content ◽  
Latent Heat ◽  
Satellite Observations ◽  
Latent Heating ◽  
Latent Heat Release ◽  
Model Simulations ◽  
Ice Water Content ◽  
Ice Water

AbstractThis study examines the relationship between frozen hydrometeors and latent heating in model simulations and evaluates the capability of the Weather Research and Forecasting (WRF) Model to reproduce the observed frozen hydrometeors and their relationship to tropical cyclone (TC) intensification. Previous modeling studies have emphasized the importance of both the amount and location of latent heating in modulating the evolution of TC intensity. However, the lack of observations limits a full understanding of its importance in the real atmosphere. Idealized simulations using WRF indicate that latent heating is strongly correlated to the amount of ice water content, suggesting that ice water content can serve as an observable proxy for latent heat release in the mid- to upper troposphere. Based on this result, satellite observations are used to create storm-centered composites of ice water path as a function of TC intensity. The model reasonably captures the vertical and horizontal distribution of ice water content and its dependence upon TC intensity, with differences typically less than 20%. The model also captures the signature of increased ice water content for intensifying TCs, suggesting that observations of ice water content provide a useful diagnostic for understanding and evaluating model simulations of TC intensification.

Role of baroclinic trough in triggering vertical motion during summertime heavy rainfall events in Korea

2021 ◽  
Author(s):  
Chanil Park ◽  
Seok-Woo Son ◽  
Jung-Hoon Kim
Keyword(s):  
Heavy Rainfall ◽  
Vertical Motion ◽  
The West ◽  
Rainfall Events ◽  
Synoptic Conditions ◽  
Upper Level ◽  
Diabatic Forcing ◽  
Upper Level Jet ◽  
Q Vector ◽  
Heavy Rainfall Events

AbstractThe nature of the vertical motion responsible for the summertime (June–September) heavy rainfall events (HREs) in Korea is quantitatively examined. By compositing 318 HREs in 1979–2018, it is found that the synoptic conditions of the HREs are typically characterized by a developing surface cyclone with a southwesterly low-level jet on its southeastern flank and an upper-level trough to the west of the HREs. This baroclinic environment allows for well-organized vertical motion over Korea at the equatorward side of the upper-level jet entrance. The relative importance of dynamic and diabatic forcings in driving the vertical motion is further quantified by solving the quasi-geostrophic omega equation. It turns out that the dynamic forcing, defined as Q-vector convergence, is comparable to the diabatic forcing in the developing stage of the HREs. The diabatic forcing, however, becomes more important in the mature stage as latent heating rapidly increases. The decomposition of Q-vector into the transverse and shearwise components reveals that the dynamic uplift is largely caused by the shearwise Q-vector convergence which is closely related to the developing trough in the upper-to-middle troposphere on the west of the HREs. This result indicates that the HREs in Korea are organized by the baroclinic trough coupled to moist processes, with a minor contribution of the thermally-direct secondary circulation at the entrance region of the upper-level jet.

scholarly journals Impact of Assimilating Upper-Level Dropsonde Observations Collected during the TCI Field Campaign on the Prediction of Intensity and Structure of Hurricane Patricia (2015)

2019 ◽  
Vol 147 (8) ◽  
pp. 3069-3089 ◽  
Author(s):  
Jie Feng ◽  
Xuguang Wang
Keyword(s):  
Heat Release ◽  
Latent Heat ◽  
Inner Core ◽  
Motion Vector ◽  
Latent Heat Release ◽  
Field Campaign ◽  
Cyclone Intensity ◽  
Warm Core ◽  
Upper Level ◽  
The Impact

Abstract The dropsondes released during the Tropical Cyclone Intensity (TCI) field campaign provide high-resolution kinematic and thermodynamic measurements of tropical cyclones within the upper-level outflow and inner core. This study investigates the impact of these upper-level TCI dropsondes on analyses and prediction of Hurricane Patricia (2015) during its rapid intensification (RI) phase using an ensemble–variational data assimilation system. In the baseline experiment (BASE), both kinematic and thermodynamic observations of TCI dropsondes at all levels except the upper levels are assimilated. The upper-level wind and thermodynamic observations are assimilated in additional experiments to investigate their respective impacts. Compared to BASE, assimilating TCI upper-level wind observations improves the accuracy of outflow analyses verified against independent atmospheric motion vector (AMV) observations. It also strengthens the tangential and radial wind near the upper-level eyewall. The inertial stability within the upper-level eyewall is enhanced, and the maximum outflow is more aligned toward the inner core. Additionally, the analyses including the upper-level thermodynamic observations produce a warmer and drier core at high levels. Assimilating both upper-level kinematic and thermodynamic observations also improves the RI forecast. Compared to BASE, assimilating the upper-level wind induces more upright and inward-located eyewall convection, resulting in more latent heat release closer to the warm core. This process leads to stronger inner-core warming. Additionally, the initial warmer upper-level inner core produced by assimilating TCI thermodynamic observations also intensifies the convection and latent heat release within the eyewall, thus further contributing to the improved intensity forecasts.

scholarly journals The role of surface fluxes in the development of a tropical-like cyclone in southern Italy

2008 ◽  
Vol 2 (1) ◽  
pp. 35-39 ◽  
Author(s):  
M. M. Miglietta ◽  
S. Davolio ◽  
A. Moscatello ◽  
F. Pacifico ◽  
R. Rotunno
Keyword(s):  
Tropical Cyclone ◽  
Numerical Simulations ◽  
Heat Release ◽  
Latent Heat ◽  
Initial Phase ◽  
Southern Italy ◽  
Surface Fluxes ◽  
Mature Stage ◽  
Latent Heat Release

Abstract. Numerical simulations of a tropical-like cyclone in southern Italy have been performed with two different modelling systems (BOLAM-MOLOCH and WRF) with the aim of discussing the role of the surface fluxes in the development of the vortex and evaluating their intensity during the mature stage of the cyclone. Although significant differences emerge in their intensity, both the modelling systems agree in showing that the surface fluxes are more important than the latent heat release associated with convection in the initial phase of the vortex lifecycle, while they are less relevant (although more intense) when the minimum assumes the characteristic of a tropical cyclone.

scholarly journals Heavy Rainfall Events in Southern China Associated with Tropical Cyclones in the Bay of Bengal: A Case Study

Atmosphere ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 574
Author(s):  
Junpeng Yuan ◽  
Jiao Lü ◽  
Dian Feng ◽  
Mengni Mao ◽  
Tao Feng ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Bay Of Bengal ◽  
Heavy Rainfall ◽  
Southern China ◽  
Southwestern China ◽  
Rain Event ◽  
Rainfall Events ◽  
Main Contributor ◽  
Heavy Rainfall Events

We use a case study to show that a continuous heavy rainfall process in southern China was closely related to tropical cyclone activity in the Bay of Bengal. The continuous heavy rainfall that occurred in southern China on 11–13 May 2002 can be considered as two different processes. The first process, referred to as a predecessor rain event, occurred over southwestern China before landfall of the tropical cyclone. The second process occurred after dissipation of the tropical cyclone when its remnant caused heavy rainfall that expanded from southwestern China to the middle to lower reaches of the Yangtze–Huaihe river basin. Both of the heavy rainfall processes were closely related to the transport of warm, moist air associated with a tropical cyclone originating over the Bay of Bengal, but the mechanisms in the two processes were quite different. Low-level orographic forcing was the main contributor to the predecessor rain event, whereas baroclinic frontogenesis induced by thermal advection was the main contributor to the tropical cyclone remnant event. Both heavy rainfall events occurred beneath the equatorial entrance of the upper level East Asian subtropical jet.

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