P-ETSS' EXPERIMENTAL GUIDANCE New Features in Experimental P-ETSS
1. Extend the CONUS East Coast basin to cover Puerto Rico and Virgin Islands.

2. Upgrade Gulf of Mexico basin to cover a gap over FL caused by upgrading the East Coast basin. Also extending it to cover all of the Gulf of Mexico and the Yucatan Peninsula.

3. At 00Z, 06Z, 12Z and 18Z run ETSS 2.3 using 42 NAEFS ensemble members.

4. Have the models use an initial water level condition in each basin based on the average anomaly of the observations in the domain, (instead of using 0).

5. Operationalize station bias adjustment Post-Processing and image production.

6. Update the point station lists.

7. Have the models use updated and expanded BUFR tanks for observations thereby enabling the models to produce guidance at more stations with matching observations, primarily on the U.S. East-Coast.

For OPERATIONAL GUIDANCE go here

Datums

Horizontal lines in the diagram above represent "datums", or known water levels used as baselines for measuring water depth at known locations. Mean sea level is not constant all over the world, but instead varies at any given location or point in time due to several factors.

Water depth listed as one foot above "mean sea level" is really one foot above "mean sea level at Location A". At Location B, however, the water level may be 1.5 feet above "mean sea level". "Mean sea level" really refers to the mean water level at that point as determined by a long-term record of tidal measurements.

Mean sea level (MSL) is not the only water level determined by long-term tidal measurements. Highest astronomical tide (HAT), for instance, is the highest tide ever seen in the measurement record at a given point. It indicates the grass line, or the level above which most structures are built.

Many other datums exist (just look at the diagram above!). Data displayed on this site is relative to the MSL datum by default. However, the user can change the datum to their preference. Mean lower-lower water (MLLW) is a popular choice as it indicates the average of all daily lowest tide measurements. In a way it shows the average lowest tide, and so is a conservative baseline against which to compare possible flooding levels.

Mean higher-high water (MHHW) has a similar meaning to MLLW, except it is the average of all daily highest tide measurements. The National Hurricane Center (NHC) considers MHHW to be the "above ground" datum. In other words, any water reaching above this datum has potential to cause flooding inland.