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<p class="HTMLBody" align="center" style="text-align:center;line-height:115%"><b><u><span style="font-size:26.0pt;line-height:115%;font-family:"Monotype Corsiva"">Meteorology Seminar<o:p></o:p></span></u></b></p>
<p class="HTMLBody" align="center" style="text-align:center;line-height:115%"><b><span style="font-size:28.0pt;line-height:115%;font-family:"Monotype Corsiva"">Kyle Ahern</span></b><span style="font-size:28.0pt;line-height:115%;font-family:"Monotype Corsiva""><o:p></o:p></span></p>
<p class="HTMLBody" align="center" style="text-align:center"><span style="font-size:28.0pt;font-family:"Monotype Corsiva"">PhD Meteorology Candidate<o:p></o:p></span></p>
<p class="HTMLBody"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="doublespacedcaps" align="left" style="text-align:left;line-height:normal">
<b><u><span style="font-size:14.0pt">Title</span></u>:</b> Hurricane Boundary Layer Structure During Intensity Change: An Observational and Numerical Analysis<span style="font-size:14.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><u><span style="font-size:14.0pt">Major Professor</span></u></b><b><span style="font-size:14.0pt">: Dr. Mark Bourassa and Dr. Robert Hart</span></b><b><u><span style="font-size:14.0pt;font-family:"Times",serif"><o:p></o:p></span></u></b></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><u><span style="font-size:14.0pt">Date</span></u></b><b><span style="font-size:14.0pt">:</span></b><span style="font-size:14.0pt"> August 8th, 2019
<b><u>Time</u>: 3:30 PM</b></span><span style="font-size:14.0pt;font-family:"Times New Roman",serif"><o:p></o:p></span></p>
<p class="HTMLBody"><b><o:p> </o:p></b></p>
<p class="HTMLBody"><b><u><span style="font-size:14.0pt">Location</span></u></b><b><span style="font-size:14.0pt">:
</span></b><span style="font-size:14.0pt">Werner A. Baum Seminar Room (353 Love Building)<b><o:p></o:p></b></span></p>
<p class="MsoNormal"><b>(Please join us for refreshments served outside room 353 Love @ 3:00 PM)</b><b><span style="font-size:12.0pt"><o:p></o:p></span></b></p>
<p class="MsoNormal" align="center" style="text-align:center"><b><o:p> </o:p></b></p>
<p class="MsoNormal" align="center" style="text-align:center"><b>ABSTRACT<o:p></o:p></b></p>
<p class="MsoNormal" align="center" style="text-align:center"><b><o:p> </o:p></b></p>
<p class="MsoNormal" style="text-align:justify;text-indent:.5in"><span style="mso-ligatures:standard;mso-contextual-alternates:yes">A combination of observational and numerical analyses is used to investigate hurricane boundary layer (BL) structure in the context
of intensity change. These analyses refer to hurricanes in three modes of intensity change: intensifying (IN), steady-state (SS), and weakening (WE). Observations from GPS dropwindsondes launched in Atlantic tropical cyclones between 1998 and 2015 are collected
for compositing based on intensity change. After quality control and sorting, 3,091 dropwindsondes were composited. In non-intensifying hurricanes, lower-tropospheric tangential winds were stronger than IN storms outside the radius of maximum winds (RMW),
which suggests greater inertial stability </span><!--[if gte msEquation 12]><m:oMath><m:sSup><m:sSupPr><span style='font-size:12.0pt;font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes;font-style:italic'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i><span style='font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes'><m:r>I</m:r></span></i></m:e><m:sup><i><span style='font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes'><m:r>2</m:r></span></i></m:sup></m:sSup></m:oMath><![endif]--><![if !msEquation]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;position:relative;top:3.0pt;mso-text-raise:-3.0pt;mso-fareast-language:EN-US"><img width="12" height="19" style="width:.125in;height:.1979in" id="_x0000_i1025" src="cid:image001.png@01D5485C.9FF5B9D0"></span><![endif]><span style="mso-ligatures:standard;mso-contextual-alternates:yes">
outside the RMW in non-intensifying hurricanes. The BL radial inflow is of similar thickness across the three composites, and all composite groups have an inflow maximum situated at the RMW. Non-intensifying hurricanes are associated with stronger near-surface
inflow outside the eyewall, implying more frictionally forced ascent out of the BL at radii outside the RMW. At greater radii, inflow layer
</span><!--[if gte msEquation 12]><m:oMath><m:sSub><m:sSubPr><span style='font-size:12.0pt;font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes;font-style:italic'><m:ctrlPr></m:ctrlPr></span></m:sSubPr><m:e><i><span style='font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes'><m:r>θ</m:r></span></i></m:e><m:sub><i><span style='font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes'><m:r>e</m:r></span></i></m:sub></m:sSub></m:oMath><![endif]--><![if !msEquation]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;position:relative;top:3.0pt;mso-text-raise:-3.0pt;mso-fareast-language:EN-US"><img width="14" height="19" style="width:.1458in;height:.1979in" id="_x0000_i1025" src="cid:image002.png@01D5485C.9FF5B9D0"></span><![endif]><span style="mso-ligatures:standard;mso-contextual-alternates:yes">
is relatively low in the WE composite, suggesting locally enhanced subsidence or downdrafts.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-indent:.5in"><span style="mso-ligatures:standard;mso-contextual-alternates:yes">High-resolution numerical case studies of Hurricane Irma in 2017 and Hurricane Earl in 2010 are used to check results found in
the composite analysis and highlight BL azimuthal structure. The Weather Research and Forecasting Model for Advanced Research (WRF-ARW) is employed for these full-physics simulations. Irma's strong tangential winds were relatively confined to the RMW, leading
to weak </span><!--[if gte msEquation 12]><m:oMath><m:sSup><m:sSupPr><span style='font-size:12.0pt;font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes;font-style:italic'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i><span style='font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes'><m:r>I</m:r></span></i></m:e><m:sup><i><span style='font-family:"Cambria Math",serif;mso-ligatures:standard;mso-contextual-alternates:yes'><m:r>2</m:r></span></i></m:sup></m:sSup></m:oMath><![endif]--><![if !msEquation]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;position:relative;top:3.0pt;mso-text-raise:-3.0pt;mso-fareast-language:EN-US"><img width="12" height="19" style="width:.125in;height:.1979in" id="_x0000_i1025" src="cid:image001.png@01D5485C.9FF5B9D0"></span><![endif]><span style="mso-ligatures:standard;mso-contextual-alternates:yes">
outside the eyewall. Aside from land interactions, Irma tended to steadily intensify, with an inflow maximum at the RMW and BL ascent isolated inward of the RMW. A brief WE period in Irma was associated with shear- and motion-induced asymmetry, whereby drier
air was able to descend into the BL inflow near the RMW.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-indent:.5in">Hurricane Earl had a broader tangential wind field, with high<!--[if gte msEquation 12]><m:oMath><m:sSup><m:sSupPr><span style='font-size:12.0pt;font-family:"Cambria Math",serif;font-style:italic'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i><span style='font-family:"Cambria Math",serif'><m:r>I</m:r></span></i></m:e><m:sup><i><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSup></m:oMath><![endif]--><![if !msEquation]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;position:relative;top:3.0pt;mso-text-raise:-3.0pt;mso-fareast-language:EN-US"><img width="12" height="19" style="width:.125in;height:.1979in" id="_x0000_i1025" src="cid:image001.png@01D5485C.9FF5B9D0"></span><![endif]>
outside the eyewall. Earl's strong BL inflow spread over a large radial band, which was associated with widespread BL convergence and shallow ascent outside the RMW. During a prolonged and progressive decay in Earl's intensity, two regions of BL convergence
became apparent: one inward of the RMW, and the other well outside the RMW. Descent of low-enthalpy air into the BL near the RMW occurred during Earl's WE phases. Despite shear and storm motion of comparable magnitude to Irma, asymmetries were more pronounced
in Earl's BL. Earl's intensity decline was also associated with strong low-level outflow in the upshear-right quadrant, which may have led to structural evolution that promoted an outer region of BL convergence, as well as an inner-eyewall collapse and coincident
secondary eyewall formation.<o:p></o:p></p>
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