Question regarding El Nino

[boca]

If their is a weak El Nino why is the weather here in S Florida so bone dry. I thought with a El Nino the weather pattern changes for the SE US.

[CaluWxBill]

During the winter months, particularly Jan, Feb, and Mar. Before this the pattern can be remarkable different. The correllation is weaker but precip is generally stronger in the Missippi Valley. There is no significant El Nino effect on Autumn in OCT and NOV, except for possibly with the tropics.

[wxguy25]

If their is a weak El Nino why is the weather here in S Florida so bone dry. I thought with a El Nino the weather pattern changes for the SE US.

It does, but you must understand not all El Nino events are exactly the same as far as intensity and the resulting effects over North America are concerned.

During an El Nino event, the Southern branch of the jet stream becomes energized and a corresponding increase in storminess occurs across the southeast US. This is the reason why Florida sees above normal precipitation during the Dry season when El Nino conditions are present.

This El Nino (which will be with us through the winter) is not close to being in the league of those which you might remember such as 1982-83 and 1997-98. Those years saw near record dry season wetness which was the result of the strong Sub-tropical jet and well above normal numbers of extratropical storms.

The existence of either an El Nino, la Nina or neither is not the complete equation. Other teleconnection patterns have an equal influence and may at times overshadow the ENSO phase. This fall, we have been dealing with a persistent RNA pattern where the mean trough position has been over the western part of the United States and the mean ridge in the east. This is a DRY PATTERN for the state of Florida during all calendar months—not just the dry season or the transition months. The NAO also plays a significant role. A –NAO would favor above normal precipitation over the state.

The reason why the state has not seen much in the way of substantial rainfall since Hurricane Jeanne is due to the fact that the EL Nino (already weak) has been overshadowed by the persistent RNA pattern (western trough/eastern ridge—storm track stays away from the SE US). The unrelenting RNA pattern is being anchored by the SSTA configuration over the North pacific (which is similar to 1968) where the Aleutian low is weak, and the trough is over the west.

In 2002—another historic dry season—the El Nino was somewhat stronger, the East pacific pattern was reversed, so what you ended up with was a persistent PNA pattern (strong Aleutian low, western ridge, PV near Hudson bay and deep EUS trough) which combined w/ a mainly –NAO, allowed a favorable synoptic situation to recur regularly and lead to near historic wetness across the northern and central Peninsula, especially in DEC 2002.