Jan 14, 2016

A hui hou to Pali

While Atlantic Hurricane Alex has formed this morning over the Northeast Atlantic, former Central Pacific Hurricane Pali is in a rapid weakening phase.

Pali initially formed on 31 December 2015, as a tropical depression about 1850 miles to the SW of Honolulu. Pali moved toward the NW and on the evening of January 7th (Local Hawaii time) became a tropical storm with winds of 45 mph while located about 800 miles SW of Honolulu. Thereafter Pali took a meandering slow track toward the west and then southwest and south southeast over the following 4 days. Gradually the TS organized and intensified into a Hurricane by late afternoon on the 11th.

Pali remained  hurricane and intensified to a Category 2 hurricane on the 12th. Thru the 13th Pali continue to meander SOUTH towards the equator. Its position was now within 3 degrees latitude north of the equator! Late on the 13th the combination of decreasing latitude (Pali was nearing the equator) and strong SW wind shear aloft cause a rapid weakening of the storm.

Today Pali is now a tropical depression near 2.5°N and 173.0°W. Pali is rapidly weakening and forecast to dissipate during the next 24 hours.

Here is a link    The Life of Hurricane Pali  to a movie on my YouTube channel of Pali's track from inception to its current demise.

From Byers and Riehl, Tropical cyclone characteristics are as follows:
  1.  they have a greater chance to farm during the summer and fall seasons in either hemisphere.
  2. they form over the warmer waters of subtropical and tropical ocean basins, (Usually with ocean temperatures of 26°C or >)
  3. they have no warm or cold fronts associated with them.
  4. pressure and other properties (winds, rain) tend to be distributed symmetrically
  5. they are seldom observed within 5­° of latitude of the equator, This is because the Coriolis force is important in their development.

    What is the Coriolis force? It is an artifact of the earth's rotation. Basically "things" in motion on the surface of the earth experience a deflection of their motion due to the earth's rotation. In the Northern Hemisphere this deflection is to the right of the object's apparent motion. (In the Southern Hemisphere the deflection is to the left.) For a very good and brief explanation on Coriolis check out this link: What is the Coriolis Force ?

What do you know? Alex is a Hurricane !

Morning satellite pictures (Fig. 1) indicate that Alex has intensified and developed an eye and has now been classified as a hurricane in the far northeast Atlantic Ocean.

(Fig 1.) Visible satellite imagery of hurricane Alex

The Azores Meteorological Service has issued a Hurricane Warning for the islands of Faial, Pico, Sao Jorge, Graciosa, and Terceira in the central Azores, and a Tropical Storm Warning for the islands of Sao Miguel and Santa Maria in the eastern Azores.

Alex is forecast to move across the Central Azores with increasing winds expected to begin to affect the islands by late tonight. Here is the past track and forecast track for Alex is shown below in Fig. 2

(Fig. 2) Alex ' past and forecast track
After passing north of the Azore on Friday Alex is forecast to curl towrad the NNW or NW and merge with a large extratropical low south of Greenland over the weekend.

According to the NHC Alex is the first hurricane to form in the month of January since 1938, and the first hurricane to occur in this month since Alice of 1955.