A bizarre hurricane

Matthew is a bizarre hurricane. It is moving slowly along the coastline with the potential for landfall anywhere from northeastern Florida to southeastern North Carolina, and landfall could happen multiple times. There is no other hurricane on record with a similar track!

Hurricane Matthew is expected to turn offshore after reaching North Carolina. This is because a high pressure system over the northern United States prevents the storm from moving further north.

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Because of the approaching Hurricane Nicole, Matthew is predicted to loop back in almost a complete circle and affect Bahamas and the east coast of Florida again. It should be significantly weakened than the first round, because the temperature and heat content of the ocean where it passed over are significantly reduced, thus providing less “fuel” for Matthew to strengthen again.

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Storm prediction using CNAPS – a fully coupled atmosphere-ocean-wave modeling system

Hurricane Matthew is on track to become the first major hurricane to make landfall on U.S. shores since Wilma in 2005. National Hurricane Center (NHC) predicted Matthew could make landfall in Florida early Friday as a Category 4 hurricane. At the same time, Nicole to its east was just upgraded to Category 1 hurricane (Figure 1).

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Figure 1. Visible image on Oct. 6 at 1:00 p.m. EDT from NOAA’s GOES-East satellite shows Hurricane Matthew as it regained Category 4 hurricane status. Hurricane Nicole is visible to the right. Image credit: NASA/NOAA GOES Project.

This is a rare phenomenon and how exactly the two tropical cyclones will interact with one another is too early to tell. NHC predictions suggest Nicole will likely nudge Matthew back to Florida and Bahamas again in a loop-de-loop early next week (Figure 2). The underlying three-dimensional ocean conditions will play a key role throughout this process. Accurately resolving the dynamic ocean temperature field and the momentum, heat and moisture flux exchanges across the air-sea-wave interface is in particular crucial for hurricane intensity forecast.

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Figure 2: NHC prediction of hurricane Matthew’s track and intensity as of Thursday, Oct 6, 8 pm EDT.

At North Carolina State University, Ocean Observing and Modeling Group (OOMG) is using their Coupled Northwest Atlantic Prediction System (CNAPS) to closely monitor and predict Hurricanes Matthew and Nicole. CNAPS is a fully coupled Atmosphere-Ocean-Wave Modeling System, providing a unique capability to account for complex but important air-sea-wave interaction dynamics during storms and generate forecasts of simultaneous atmosphere, ocean and wave conditions.

CNAPS is operated on NC State’s high-performance supercomputer, providing daily nowcast and 3-day forecast for the entire Northwest Atlantic ocean. Routine model output include sea level air pressure, 10-m wind, significant wave height and directions, 3-dimensional ocean circulation, temperature and salinity (Figure 3).

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Figure 3. Snapshots of CNAPS predicted concurrent marine weather, ocean, and wave conditions at 21:00 EDT, October 6. 2016, showing Matthew is accompanied with strong wind, current, and wave; so is Nicole, albeit with smaller size and scale. 

Near-real time model validations against HF radar surface currents and buoy measurements have been implemented and continue to be refined in CNAPS (Figure 4).  

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Figure 4. Comparison between HF radar observed and CNAPS predicted surface current fields off Miami at 2100 EDT, October 5, 2016. CNAPS prediction shows that Matthew had a strong interaction with the northward flowing Gulf Stream and an energetic  cyclonic surface current gyre was generated. (HF data courtesy: Nick Shay, University of Miami)

Other interactive functions built into CNPAS include: isosurface maps of ocean current, temperature, salinity; visualizations of user defined station profiles and hydrographic transects, as well as 72-hour surface trajectory simulations of user defined “virtual particles” (Figure 5).

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Figure 5. Virtual particle trajectories simulated by CNAPS.

To check out CNAPS predictions of Matthew and Nicole, and their concurrent ocean circulation and wave conditions, use this link.