Marine Information

Marine Zone Changes

On March 8, 2023, the National Weather Service office in Lake Charles, LA (LCH) completed changes to the Marine Forecast Zones encompassing Vermilion, West Cote Blanche Bay, East Cote Blanche Bay, and Atchafalaya Bay.

These changes are intended to provide increased flexibility and improved accuracy of forecast, watch, warning, and advisory products in the marine weather program.

1) Marine Zone for GMZ435-Vermilion Bay was renamed GMZ435-Vermilion and West Cote Blanche Bays to reflect the names of both bays this marine zone covers. The zone boundary will remain the same.

2) A new marine zone, GMZ436-Atchafalaya and East Cote Blanche Bays, was created. This area is currently within the northeastern extent of marine zone GMZ455-Lower Atchafalaya River to Intracoastal City out 20 Nautical Miles.

The main justifications for the creation of GMZ436-Atchafalaya and East Cote Blanche Bays marine zone are:

- Marine Fog. This area has much colder water temperatures being emptied from the Atchafalaya River in the winter and spring months, which often leads to persistent marine fog lasting much longer than the remainder of GMZ455-Lower Atchafalaya River to Intracoastal City out 20 Nautical Miles marine zone.

- Wave Height Differences. The shallow waters in the Atchafalaya and East Cote Blanche Bays have lower wave heights than the remainder of GMZ455-Lower Atchafalaya River to Intracoastal City out 20 Nautical Miles marine zone. This area would benefit from the bay waters wave height wording that the Vermilion Bay zone is currently using.

- Low Water Advisories. The shallow waters in the Atchafalaya and East Cote Blanche Bays need the ability for a Low Water Advisory to be issued during periods of strong offshore flow behind strong cold fronts. This is not advisable using the current zone configuration GMZ455-Lower Atchafalaya River to Intracoastal City out 20 Nautical Miles marine zone.

Marine zones before changes:

Marine zones after changes:

NWS Lake Charles, LA marine zones effective March 8, 2023.

Table 1. Old marine zones and corresponding Universal Geographic Codes(UGC) for WFO Lake Charles:

UGC: Old marine zone and corresponding UGC for which WFO Lake Charles issued forecasts and warnings.
----------------------------------------------
GMZ435: Vermilion

Table 2: New marine zones and corresponding UGC for which WFO Lake Charles is issuing forecasts and warnings effective March 8, 2023:

UGC: New Marine Zone Name
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GMZ435: Vermilion and West Cote Blanche Bays
GMZ436: Atchafalaya and East Cote Blanche Bays

Table 3. NWS products affected by the WFO Lake Charles, LA by these Marine forecast zone changes are listed below:

Product Name                   WMO Heading    AWIPS ID
-------------                  -----------    --------
Tsunami Message                WEXX20 PAAQ    TSUAT1
Marine Weather Message         WHUS74 KLCH    MWWLCH
Special Marine Warning        WHUS54 KLCH    SMWLCH
Marine Weather Statement       FZUS74 KLCH    MWSLCH
Coastal Waters Forecast        FZUS54 KLCH    CWFLCH
Area Forecast Discussion       FXUS64 KLCH    AFDLCH
Hazardous Weather Outlook      FLUS44 KLCH    HWOLCH
Watch County Notification      WWUS64 KLCH    WCNLCH

NWS partners and users will need to make necessary changes to their communications systems to accommodate these weather forecast zone changes.

Shapefiles for marine zones are available online at:
https://www.weather.gov/gis/MarineZones

A written and graphical depiction of this change is online at:
https://www.weather.gov/lch/2023MarineZoneChange

For more information, please contact:

Roger Erickson
Meteorologist-In-Charge
NWS Lake Charles, LA
roger.erickson@noaa.gov
337-477-5285 x222

or

Melinda Bailey
NWS Southern Region Headquarters
Fort Worth, TX
melinda.bailey@noaa.gov
904-741-4470 x223

National Service Change Notice 22-114 is available at:
https://www.weather.gov/media/notification/pdf2/scn22-114_marine_forecast_zones_lch.pdf