Hazardous Conditions: Winter

• The greatest concern to ship operations in winter are the 'Xaloc' events. These events occur about 7 times per year and are fierce but short-lived. More widely known as Sirocco, they result from wind flow in the warm sector of cyclones located north of the area. Southeasterly waves, both sea and swell, of 10 to 13 ft can be generated. The waves can cause considerable motion of ships in the roadstead but good holding qualities of the bottom preclude any need to weigh anchor and seek better protection.

• The rugged topography of the island of Mallorca, and the location of the Port of Palma at the north end of the well-defined Bay of Palma, protects the port from many of the hazardous weather conditions of the region. Consequently, the primary threats to the port are those which come from the south quadrant.

• Prevailing winds are northwest clockwise through northeast. The mean wind speed during February and March (tied with November for the highest mean speed) is 5 kt. The remaining months of the year have a 4 kt mean, so the winter winds are only slightly stronger, on average, than the rest of the year. Gale force winds associated with heavy northwesterly squalls, force 8 (34-40 kt) or greater, have a higher frequency of occurrence during January and February than during the other months of the year, averaging between 2 and 3 events each month.

• Southwesterly winds and waves also reach the port area. Broad scale southwesterly flow may precede cold frontal passage (and follow a southeasterly Xaloc event), raising waves in the Mallorca area. Called the Vendaval, the winds are not long lived. They may generate waves of 10 to 13 ft near Punta de Cala Figuera (about 8 n mi southwest of the port), but they diminish somewhat before they reach the Palma roadstead. Because of the good holding quality of the bottom, problems in the anchorage are minimized, and ships can remain at anchor. The southwesterly conditions have little effect on inner harbor operations.

• The northwesterly Mistral winds which are common over the Gulf of Lion in late winter and early spring sometimes extend as far southward as Mallorca. Locally known as the Tramuntana, the effects can be felt on the northwest coast and northeast Mallorcan bays but have no effect on Palma port operations. It is during Mistral events that Palma experiences its best visibility.

• Precipitation is common at Palma during the season, with each of the winter months having 5 or 6 days during which 0.04 inch or more of moisture is recorded. Thunderstorms are rare after the autumn season.

• Easterly winds (Levante) have little effect on port operations, but indicate that cloudy, rainy weather can be expected for 3 days after onset.

• Greatest occurance of low visibility is in winter. January has an average of 5 days when the visibility decreases to less than 1100 yd. The frequency of occurrence decreases as the season progresses. The airport, 7 miles east of the port, experiences a greater occurance of low visibility.

• Temperatures are moderate during the season. January is the coldest month, with a mean daily maximum of 57 deg F, and mean daily minimum of 44 deg F. Wind chill--the cooling effect of temperature combined with wind--is not normally a problem at Palma, but in December 1982, a ship experienced ice pellets, snow, and rain showers with a wind chill of 19 deg F. Wind chill must be considered on cool and windy winter days.