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HOME > Expert Assessments > East Pacific Hurricane Outlook
 
NOAA PRESS RELEASE
 
NOAA: 2014 Eastern Pacific Hurricane Season Outlook

Issued: 22 May 2014

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The 2014 eastern Pacific hurricane season outlook is an official product of the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC), and is produced in collaboration with scientists from the NOAA National Hurricane Center (NHC). The eastern Pacific hurricane region covers the eastern North Pacific Ocean east of 140oW north of the equator.

Interpretation of NOAA's eastern Pacific hurricane season outlook
This outlook is general guide to the expected overall activity during the upcoming hurricane season. It is not a seasonal hurricane landfall forecast, and it does not imply levels of activity for any particular region.

Preparedness
Hurricane disasters can occur whether the season is active or relatively quiet. It only takes one hurricane (or even a tropical storm) to cause a disaster. Therefore, residents, businesses, and government agencies of coastal and near-coastal regions are urged to prepare for every hurricane season regardless of this, or any other, seasonal outlook. NOAA, the Federal Emergency Management Agency (FEMA), the NHC, the Small Business Administration, and the American Red Cross all provide important hurricane preparedness information on their web sites.

NOAA does not make seasonal hurricane landfall predictions
NOAA does not make seasonal hurricane landfall predictions. Hurricane landfalls are largely determined by the weather patterns in place as the hurricane approaches, which are only predictable when the storm is several days of making landfall.

Nature of this Outlook and the "likely" ranges of activity
This outlook is probabilistic, meaning the stated "likely" ranges of activity have a certain likelihood of occurring. The seasonal activity is expected to fall within these ranges in 7 out of 10 seasons with similar climate conditions and uncertainties to those expected this year. They do not represent the total possible ranges of activity seen in past similar years.

This outlook is based on predictions of large-scale climate factors and conditions known to strongly influence seasonal eastern Pacific hurricane activity, along with climate model forecasts. The outlook also takes into account uncertainties inherent in such climate outlooks.

Sources of uncertainty in this seasonal outlook

  1. Predicting El Niño and La Niña (also called ENSO) impacts is an ongoing scientific challenge facing climate scientists today. Such forecasts made during the spring generally have limited skill.
  2. Many combinations of named storms and hurricanes can occur for the same general set of climate conditions. For example, one cannot know with certainty whether a given climate signal will be associated with several short-lived storms or fewer longer-lived storms with greater intensity.
  3. Weather patterns that are unpredictable on seasonal time scales can sometimes develop and last for weeks or months, possibly affecting seasonal hurricane activity.

2014 Eastern Pacific Hurricane Outlook Summary

NOAA's 2014 eastern Pacific Hurricane Season Outlook indicates a near- or above-normal season is likely, with a 50% chance of an above-normal season, a 40% chance of a near-normal season, and a 10% chance of an below normal season. See NOAA definitions of above, near-, and below- normal seasons. The eastern Pacific hurricane region covers the eastern North Pacific Ocean east of 140oW north of the equator.

The main climate factor guiding the outlook is the likely development of El Niño during the summer. El Niño decreases the vertical wind shear over the eastern tropical Pacific, favoring more and stronger tropical storms and hurricanes. The eastern Pacific has been in an era of lower hurricane activity since 1995 (Fig. 3), but this pattern will be offset in 2014 by El Niño.

Historically, this combination of factors produces a near- or above-normal eastern Pacific hurricane season. We estimate a 70% chance of occurrence for each of the following ranges of activity this season:

  • 14-20 named storms,
  • 7-11 hurricanes,
  • 3-6 major hurricanes,
  • An ACE range 95%-160% of the median.

The seasonal activity is expected to fall within these ranges in 7 out of 10 seasons with similar climate conditions and uncertainties to those expected this year. They do not represent the total possible ranges of activity seen in past similar years.

The predicted ranges are centered near or above the official NHC 1981-2010 seasonal averages of 15 named storms, 8 hurricanes, and 4 major hurricanes.

There will be no further updates to this outlook.

DISCUSSION

1. Expected 2014 Activity

Evolving climate signals, combined with dynamical and statistical model forecasts, indicate that a near- or above-normal eastern Pacific hurricane season is likely during 2014. This outlook calls for a 50% chance of an above-normal season, a 40% chance of a near-normal season, and a 10% chance of a below-normal season.

Predictions from NOAA's Climate Forecast System (CFS), NOAA Geophysical Fluid Dynamics Lab (GFDL) model FLOR-FA, the European Centre for Medium Range Weather Forecasting (ECMWF), and the EUROpean Seasonal to Inter-annual Prediction (EUROSIP) ensemble are all suggesting near- or above-normal tropical cyclone activity in the eastern Pacific this season, though their forecast skill for the region is limited at this lead time.

An important measure of the total seasonal activity is NOAA's Accumulated Cyclone Energy (ACE) index, which accounts for the combined strength and duration of tropical storms and hurricanes during the season. We estimate a 70% chance that the 2014 seasonal ACE index will be in the range of 95%-160% of the median. According to NOAA's definitions of season strength, an ACE value above 115% of the 1981-2010 median indicates an above-normal season, and a value of 80%-115% of the median indicates a near-normal season. Consistent with the expected ACE range, other likely (70% chance) ranges of activity for 2014 are 14-20 named storms, 7-11 hurricanes, and 3-6 major hurricanes.

2. Science behind the outlook

a. El Niño

The 2014 seasonal hurricane outlook reflects the likely development of El Niño. El Niño reduces the vertical wind shear in the eastern Pacific hurricane basin, making atmospheric conditions more conducive to hurricane activity.

At present, equatorial Pacific SSTs are above average, with the largest departures (exceeding 1oC) centered on the date line. SST anomalies in all of the Niño regions are also increasing, and anomalies in the Niño 3.4 region, which spans the central and east-central equatorial Pacific between 120oW-170oW, are currently 0.4,sup>oC. This value is approaching the CPC's lower threshold for El Niño (+0.5oC).

Observations show that the atmosphere is also trending to an El Niño state. For example, a time-longitude section of 200-hPa velocity potential anomalies shows anomalous upper-level divergence since January over the central equatorial Pacific. This signal is consistent with enhanced convection near the date line, a key feature of El Niño.

Anomalous westerly trade winds across the western equatorial Pacific, along with several westerly wind bursts, have also been present since January. A westerly wind burst triggered a strong downwelling equatorial oceanic Kelvin wave in February, and this wave subsequently reached the west coast of South America in late April. This Kelvin wave acted to shift the oceanic thermocline deeper into the ocean, resulting in above-average temperatures and increased heat content between the thermocline and the ocean surface.

A depth-longitude section of sub-surface temperature anomalies and a time series of the upper-ocean heat content highlight the substantial sub-surface warmth associated with this Kelvin wave. The persistence of the westerly wind anomalies has helped to lock in this anomalous warmth, further setting the stage for El Niño.

The average forecast of the dynamical prediction models (closed markers) contained in the suite of IRI/ CPC Niño 3.4 SST forecasts (yellow line) predicts El Niño to form during the May-July (MJJ) season and to reach moderate strength (SST values of 1oC - 1.5oC) during ASO. The statistical model forecasts (open markers) are generally cooler than the dynamical model predictions, and show a weak El Niño during the ASO season.

There are also differences in the predicted timing and strength of El Niño within models having a similar formulation. For example, NOAA's high-resolution CFS model (T-382) is forecasting a delay in the development of El Niño, while the lower resolution model (T-126) is predicting El Niño to develop during JJA. These results produce some uncertainty as to exactly when El Niño will develop and how strong it will become. Despite these differences, both CFS models predict upper-level westerly wind anomalies and reduced vertical wind shear across the eastern Pacific hurricane region during JJA and ASO.

b. Low-activity era for eastern Pacific hurricanes

Eastern Pacific hurricane seasons have been less active since 1995, while the Atlantic Basin has been more active. During 1995-2013, 42% of eastern Pacific hurricane seasons were below normal, 37% were near normal, and only 21% were above normal. Seasons during this period averaged about 13 named storms, 7 hurricanes, and 3 major hurricanes, with an ACE value of 88% of the median.

These levels of activity contrast sharply with the more active period 1982-1994. For the eastern Pacific, 62% of hurricane seasons during 1982-1994 were above normal, 23% were near normal, and only 15% were below normal. Seasons during this period averaged about 18 named storms, 10.5 hurricanes, and 5 major hurricanes, with an ACE value of 150% of the median. This ACE value falls within NOAA's definition for an above-normal season.

NOAA FORECASTERS

Climate Prediction Center
Dr. Gerald Bell, Meteorologist, Gerry.Bell@noaa.gov
Dr. Jae Schemm, Meteorologist, Jae.Schemm@noaa.gov

National Hurricane Center
Eric Blake, Hurricane Specialist, Eric.S.Blake@noaa.gov
Todd Kimberlain, Hurricane Specialist, Todd.Kimberlain@noaa.gov

Dr. Christopher Landsea, Meteorologist, Chris.Landsea@noaa.gov


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Page Author: Climate Prediction Center Internet Team
Page last modified: May 22, 2014
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