Paper on new observations of rapid intensification during Hurricane Karl published in The Journal of the Atmospheric Sciences

Posted on November 6, 2016 by

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Read the paper at http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-16-0026.1.

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Two-part paper on the intensification of Hurricane Edouard published in Monthly Weather Review

Posted on November 5, 2016 by

Summary: Hurricane Edouard (2014) is examined using radar onboard NOAA P-3 aircraft that flew the storm. Two periods are shown, one when the storm was intensifying to a major hurricane and the other when the storm was weakening. The location of strong thunderstorms, and how they changed over time, is examined to see if there is a difference over time and to determine what caused those differences.

Important Conclusions: (two – three)

  1. Strong thunderstorms that extend above 50,000 ft altitude are seen when Edouard was intensifying; when Edouard was weakening, no such thunderstorms are seen.
  2. When Edouard is intensifying, thunderstorms cover a large area and are located close to and inside where the strongest winds exist.
  3. More thunderstorms occur when the wind in the lowest few thousand feet flowing toward the central low pressure reaches past the eyewall where the strongest winds exist. Because this air flows inward from all directions, it must rise in the eyewall, and thunderstorms develop. These strength and longevity of these thunderstorms depends on the warmth of the ocean below the storm and the moisture in the air around it.

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You can access Part I at http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-16-0018.1 and Part II at http://journals.ametsoc.org/doi/full/10.1175/MWR-D-16-0017.1.

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HRD Seminar – Dr. Andy Hazelton, Princeton University and NOAA/GFDL – 28 October 2016

Posted on October 28, 2016 by

Dr. Hazelton presented a seminar on “Convective Burst Development and Evolution in Two Simulated Atlantic TCs”.

Abstract

Understanding the structure and evolution of the tropical cyclone (TC) inner core remains an elusive challenge in tropical meteorology, especially transient asymmetric features such as localized strong updrafts known as convective bursts (CBs).  This study investigates the formation of CBs and their role in TC structure and evolution using high-resolution simulations of two hurricanes (Dean 2007 and Bill 2009) with the Weather Research and Forecasting (WRF) model. 

Several different aspects of the dynamics and thermodynamics of the TC inner-core region are investigated with respect to their influence on TC convective burst development.   Radius-height composites with CBs show stronger radial inflow in the lowest 2 km, and stronger radial outflow from the eye to the eyewall around z = 2-4 km, than composites without CBs.  Asymmetric vorticity associated with eyewall mesovortices appears to be a major factor in leading to some of the radial flow anomalies that lead to CB development.  Analysis of individual CBs and parcel trajectories show that many parcels are pulled into the eye, move outward into the eyewall, and rapidly ascend in CBs.  The positive buoyancy observed along the parcel paths support the importance of eye-eyewall exchange in CB development.

            Analysis of intensity change in the simulations shows that there are more inner-core CBs during times when the TCs are intensifying, while weakening/steady times appear to be associated with more CBs outside the radius of maximum wind (RMW), consistent with observational studies and theoretical work.  However, times when the TC has already been intensifying and continues to do so have more CBs than times when the TC has been weakening but then intensifies.  This result suggests that CB development may not always be predictive of intensification, but rather may occur as a result of ongoing intensification.  Rapid intensification (RI) in the simulations is found to be associated with an even higher density of CBs inside the RMW than slower intensification.  Lag correlations between CBs and intensity reveal a broad peak in correlation, with the CBs leading pressure falls by 0-3 hours.  These results confirm the notion that convective heating inside the RMW (where inertial stability is higher) is favorable for intensification.  However, it is shown that the relationship can vary in different cases depending on environmental conditions and the previous evolution of the TC.

A recording of the presentation is available on the anonymous ftp site:

ftp://ftp.aoml.noaa.gov/pub/hrd/blog/seminars/2016/Hazelton_HRD_Seminar_20161028.mp4

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95th Anniversary of Tarpon Springs hurricane

Posted on October 26, 2016 by
Ship stranded by storm surge of 1921 hurricane (Florida State Archives)

Ship stranded by storm surge of 1921 hurricane
(Florida State Archives)

On October 25th, a severe hurricane struck the Tampa area bringing a surge of 10 to 12 feet (3 to 3.5 m) in Tampa Bay.

The storm originated somewhere in the southwestern Caribbean Sea, but was not detected until Oct. 20th, by which time it was already at tropical storm strength.  Like many late-October storms, the system moved northward from its breeding ground and brushed Nicaragua and Honduras with winds and waves.  Three days after first being observed, it moved through the Yucatan Channel as a major hurricane.  Although it dumped heavy rains on the western tip of Cuba, no major damage was caused.

Once in the Gulf of Mexico, the hurricane turned northeastward, and picked up forward speed.  By the evening of the 25th, the storm center made landfall at Tarpon Springs with maximum sustained winds estimated at 115 mph (185 km/hr).  But the majority of the damage was caused by the storm surge on Florida’s west coast from Punta Gorda to Tampa.  The storm weakened passing over Florida, exiting north of Cape Canaveral.  It moved eastward out to sea and was tracked for four days before it became extratropical east of Bermuda.

During its crossing of Florida the hurricane was responsible for eight deaths and US$10 million in damages.

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HRD Seminar – Dr. Andy Hazelton, Princeton University and NOAA/GFDL – 25 October 2016

Posted on October 25, 2016 by

Dr. Hazelton presented a seminar on “Evaluation of Tropical Cyclone Structure in High-Resolution FV3 Simulations”.

Abstract

The FV3 dynamical core with GFS physics has shown skill both in global forecasting and the ability to simulate high-impact weather events.   Here, a regionally stretched and nested version of the model, centered over the Atlantic Basin with a grid spacing of approximately 3 km, is used to evaluate tropical cyclone (TC) forecasts of track, intensity, and structure. Two different configurations are tested: one in which the convective parameterization is turned on on the 3- km nest, and one in which the convective parameterization is turned off.  In addition, a new modified version of the Lin Microphysics (called GFDL Microphysics) is tested against the two simulations using the original Zhao and Carr (1997) microphysics. Simulations are performed on 3 TCs: Earl 2010, Edouard 2014, and Gonzalo 2014

In addition to verification of track and intensity, the model is evaluated by comparison of the model data with high-resolution airborne Doppler radar composite from the NOAA-P3 aircraft.   Structural metrics analyzed include the radius of maximum wind (RMW), the slope of the RMW, and the depth of the vortex. Preliminary results indicate that keeping the convective parameterization turned on results in the best forecast of structure (particularly more realistic RMW and vortex depth) as well as a better forecast of intensity and rapid intensification.  In addition,  the  new  microphysics  scheme  appears  to  produce  more  realistic  TC  structure. Simulations of more TCs are planned in order to generalize the results and investigate further ways to improve FV3 TC forecasts.

A recording of the presentation is available on the anonymous ftp site:

ftp://ftp.aoml.noaa.gov/pub/hrd/blog/seminars/2016/Hazelton_HRD_Seminar_20161025.mp4

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HRD Debrief for missions into Hurricane Matthew – 20 October 2016

Posted on October 23, 2016 by

HRD researchers discussed the results from the 9 P-3, 9 G-IV, and 3 Global Hawk missions into Hurricane Matthew (30 September to 8 October 2016). The agenda for the discussion was:

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Slides from the debrief are available at:

ftp://ftp.aoml.noaa.gov/pub/hrd/blog/meetings/2016/HFP/MatthewDebrief_10202016.pptx

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Posted in Data Assimilation, Dynamics and Physics, HFIP-Hurricane Forecast Improvement Project, Impacts, Modeling and Prediction, Observations, Presentations | Tagged , , , , , , , , , , , , , , , , , , , | Leave a comment

Frank Marks talks to the History News Network about Hurricane Matthew

Posted on October 20, 2016 by

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You can read the article at http://historynewsnetwork.org/article/164176.

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Paper on the formation of the secondary eyewall of Hurricane Edouard published in Monthly Weather Review

Posted on October 20, 2016 by

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You can read the article at http://journals.ametsoc.org/doi/full/10.1175/MWR-D-15-0421.1.

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20th Anniversary of Hurricane Lili

Posted on October 18, 2016 by
Hurricane Lili at Catagory 3 status east of the Bahamas, Oct. 19, 1996 (NOAA)

Hurricane Lili at Catagory 3 status east of the Bahamas, Oct. 19, 1996
(NOAA)

On October 18, 1996, Hurricane Lili slammed into Cuba with over 100 mph (160 km/hr) winds and heavy rains.  The storm, during its life cycle, would leave destruction from Central America to the British Isles.

Lili formed from a tropical depression which developed on Oct. 15th in the typical breeding grounds for mid-October, the western Caribbean Sea.  It crawled slowly northward over the next couple of days, becoming more organized.  By the 17th, it reached hurricane strength and turned to the northeast picking up forward speed.

That afternoon, NOAA42 was dispatched by NHC to perform a reconnaissance mission as the storm approached the Isle of Youth.  During the flight, the storm strength remained even and its forward progress stalled.  But afterward, it resumed its northeastly track and, that night, crossed the Isle of Youth and Cuba, gaining strength as it did so.  The following day, the storm re-emerged from Cuba’s north shore.

NOAA 42 lower fuselage radar depiction of Hurricane Lili at 01:30 UTC Oct. 19, 1996 (NOAA/AOML/HRD)

NOAA 42 lower fuselage radar depiction of Hurricane Lili at 01:30 UTC Oct. 19, 1996
(NOAA/AOML/HRD)

As it did so, NOAA42 flew another reconnaissance mission into the hurricane. Lili’s central pressure dropped during this flight and its rain bands were becoming more organized.  The storm pounded the Bahamas and south Florida with heavy rains, up to 12″ in isolated areas.  The hurricane intensified to Category-3 status in the following 24 hour period, with its winds peaking at 115 mph (185 km/hr) as it departed from the Bahamas.

It continued to move toward the northeast maintaining hurricane strength.  It even slowed at mid-ocean where it ramped back up to Category-2 status. But from there it began to weaken and became extratropical.  The system was tracked over the British Isles where it was considered to be the strongest storm to affect the islands since 1961.  It produced wind gusts up to 92mph (148 km/hr) in Wales.  Waves of 40 ft (12 m) dislodged an oil platform in the North Sea, and a 4-ft (1.2-m) storm surge moved up the Thames River.  It moved into the North Sea and was absorbed into a frontal zone.  During its life, Lili was responsible for 22 deaths and US$660 million in damages; almost half of the total damage was in the United Kingdom.

Paper written by HRD scientists using data from Hurricane Lili

Dunion, J. P., S. H. Houston, C. S. Velden, and M. D. Powell, 2002: Application of surface-adjusted GOES low-level cloud0drift winds in the environment of Atlantic tropical cyclones.  Part II:  Integration into surface wind analyses.  Mon. Wea. Rev., 130, 1347-1355.

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Frank Marks talks to the Cosumnes River College Connection about Hurricane Matthew

Posted on October 18, 2016 by

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Read the article at http://crcconnection.com/2016/10/18/hurricane-matthew-leaves-nearly-1-2-mln-in-u-s-southeast.html.

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