Ship routing services are delivered to U.S. Navy ships and staffs, Military Sealift Command, the U.S. Coast Guard, NOAA, National Science Foundation, DoD contract carriers, U.S. Army, and NATO ships.
FWC Norfolk’s area of responsibility (AOR) roughly covers the South and North Atlantic and Mediterranean Sea, while the FWC San Diego AOR covers the Pacific and Indian Oceans.
The specific requirements to produce the optimal track ship routes are heavily dependent on the ship’s wind and significant wave height limits to operate safely. The FWCs will issue area Weather and Wave Advisories (WWA), ship-specific advisories, and divert recommendations based on ship limit criteria in coordination with the ship’s captain or navigator.
To meet the FWC’s mission, the OTSR program relies on round-the-clock meteorology technicians whose job it is to integrate NWP model guidance, in-situ, and remotely sensed measurements with ship-specific information. The FWCs output several maritime weather products utilized by ship’s navigator or captain, meteorological technicians, or to Navy staff responsible for the various fleets.
While safety, fuel consumption and timing are important parameters considered by ship routers, the users of the FWC’s weather forecast products have other vessel or mission specific objectives that create other criteria to be met. This is a key difference between FWC ship routing and the requirements of merchant marine vessels whose primary objectives are driven by commerce.
Since the US Navy and its allies operate nearly global, there are several wind/seas phenomena that ship routing officers must focus particular attention on. They can be broken into a few categories that roughly align with scale of the phenomena (in descending order): (i) mid-latitude cyclone, (ii) tropical cyclone, and (iii) fleet concentration area forecasts.
Since forecast products are generated multiple times per day, the FWCs forecast product time horizon is normally within 48 hours. At these forecast horizons, NWP model guidance has improved significantly over the past 20 years. While the forecast product only extends 48 hours, the decisions that go into that product have to consider the entire route and longer term forecasts.
For mid-latitude cyclones, special attention is given to rapidly developing cyclones which are most often encountered off the east coast of continents (i.e., the Northwestern Atlantic and Northwestern Pacific). This is where the potential spatial and temporal errors are largest. The ship router will always be thinking ahead to potential divert options should one (or all) forecast model guidance be off. This is a more involved process where the ship router works closely with the ship staff to understand the mission objectives, geopolitical sensitivities and safety of crew and vessel.
US Navy ship routers will use other forecasting tools and human resources for advisories and route recommendations associated with Tropical Cyclones. Whereas route forecast considerations for mid-latitude cyclones assume translating waves from west to east (or northwest to southeast), US Navy ship routing associated with tropical cyclones have a different set of procedures owing to their potential for inflicting serious damage to ships in port and at-sea. The US Navy uses 5 levels of Tropical Cyclone Conditions Of Readiness (TCCOR) corresponding to surface wind speed levels at specific forecast horizons (US Navy CNIC Instruction 3440.17) The issuance of a TCCOR requires the implementation of protective measures that increase the level of safety of the installation and range from lowest level of readiness (TCCOR 5) to highest level of readiness (TCCOR 1). For the Indian and Pacific Oceans, FWC San Diego will work with Joint Typhoon Warning Center (JTWC) meteorologists and fleet and base commanders to discuss and agree on level of TCCOR. Similarly, for the Atlantic Ocean, FWC Norfolk joins National Hurricane Center briefs for latest guidance and expert consulting. A similar process takes place for US Navy base Sortie decisions in which all vessels take action to safeguard their vessels or get underway to leave port. There are four levels of Sortie that take into account surface wind forecast conditions at different time horizons to allow for protective actions as appropriate.
For ships at sea in the vicinity of tropical cyclones, the FWC ship routers will often make divert or course of action recommendations to slow down or speed up based on close coordination with partner agencies and close inspection of NWP model guidance.
The FWCs are also responsible for issuing area forecasts in regions of high concentration of vessels. In contrast to ship-specific forecasts that are moving over time, the area forecast is done in coordination and consistent with the National Weather Service when the area is a US territory (e.g., CONUS, Alaska, Hawaii, Guam, etc..).The forecasts are more automated and take full advantage of satellite, model surface analysis and text products of sensible weather elements including aviation and maritime-specific elements (e.g., visibility, sky conditions, combined seas). Further automation of these forecasts is expected as the Navy utilizes the Advanced Weather Interactive Processing System (AWIPS).
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