Examining Planetary, Synoptic and Mesoscale Features that Enhance Precipitation Associated with Landfalling Tropical Cyclones in North Carolina.
Landfalling tropical cyclones (TCs) over North Carolina often produce excessive
rain well inland from the location of landfall. A three-part study consisting of a
precipitation analysis, climatological analysis and numerical model simulations was
performed to determine the dominant mechanisms that influence precipitation associated
with TCs that move over North Carolina. The goal was to determine the intrinsic or
environmental features that enhance precipitation associated with the TCs influencing
North Carolina and create a conceptual model to enable forecasters to better assess the
likelihood of enhanced precipitation during TCs.
In the precipitation analysis of 28 TCs that made landfall or tracked along North
Carolina?s immediate coastline from 1953-2003, the spread of precipitation and track of
each storm across North Carolina was considered. The potential correlation between
several intrinsic features (i.e. maximum storm intensity, landfall intensity and translation
speed) and the 3-day storm average precipitation from 52 rain gauge stations across
North Carolina were examined. The results indicated no statistically significant
correlation between precipitation and any of the above features. Due to this lack of
correlation, the preexisting synoptic/dynamic environment the TC was entering at
landfall was examined to determine if the environmental features could be the dominant
precipitation enhancing mechanism.
In the climatological analysis the 28 TCs were divided into relatively heavy and
relatively light rainfall groups so that composite analyses of several environmental
features from 72 hours prior to landfall could be examined. The features included 250
hPa geopotential heights, 850-700 hPa and 500-250 hPa potential vorticity, 925-850 hPa
moisture flux, 1000 hPa frontogenesis, temperatures, winds and mean sea level pressure.
The results indicated that there are several significant planetary, synoptic and mesoscale
climatological differences from 72 to 6 hours prior to landfall between the heavy and
light rainfall groups.
The numerical simulations served to test the agreement between the
climatological analysis and two case studies. The two case studies used were Hurricane
Floyd (1999) and Tropical Storm Arthur (1996) which represented heavy and light rain
events, respectively. All numerical simulations were performed using the Non-
Hydrostatic Mesoscale Atmospheric Simulation System (NHMASS) model. The model
was run at four different scales to allow features from the synoptic to meso- ß scales to be
examined. The results were consistent with the climatological study, showing that
preexisting environmental features influence the mesoscale environment, leading to
enhanced precipitation well inland from the location of landfall. A conceptual model
from 72-hours prior to landfall is now available for forecasters to incorporate into the ir
tropical forecasting routine.
Advisor:Michael Kaplan; Gary Lackmann; Lian Xie
School:North Carolina State University
School Location:USA - North Carolina
Source Type:Master's Thesis
Keywords:marine earth and atmospheric sciences
Date of Publication:10/31/2005