Forecasting Florida Dry Season Storminess From the ENSOSignal and Communicating Likelihood of Impacts to

Decision Makers

Bart Hagemeyer and Jacklyn R. AlmeidaNational Weather Service

Melbourne, Florida

Losses From 1997-98 El NinoLosses From 1997-98 El Nino-Deadliest Tornado Outbreak in Florida History

- Most Damaging Tornado Outbreak in South Florida History

- Most Strong and Violent Tornadoes in Florida Since 1983-Extensive Flooding Rains

Decadal Trend in Florida Population GrowthDecadal Trend in Florida Population Growth

Seasonal Storminess - The Accumulated Passage of Significant Extratropical Cyclones

Goal: Predict Dry Season Storminess Over Florida as Far in Advance as Possible From Observed and Predicted Pacific SST’s and other

Telleconnections and Exploit the Results

Conceptual Model of a Significant Extratropical Cyclone inthe Florida Dry Season:

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-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6Storm-Relative Days

Daily MSLP (mb)

Conceptual Model of Significant Extratropical Cyclone or“Storm” Passage Through the Florida Grid -

Daily MSLP Minima 1012.5 From 1 November - 30 April

>Tornadoes – Hailstorms – Damaging Wind – Flooding Rain- Coastal Flooding – Gradient Winds – Marine Hazards>Beneficial Rain>Lack of Storms - Drought - Wildfire

ImprovedImproved StorminessStorminess ClimatologyClimatology

Individual Inspection of “Statistical Storms” 1948-2002 Individual Inspection of “Statistical Storms” 1948-2002 for Validity, Track, and Jet Track – Left 329 Storms for Validity, Track, and Jet Track – Left 329 Storms

Average of 6 Per Dry Season – Mode/Median 5Average of 6 Per Dry Season – Mode/Median 5

Significant Interseasonal Variability

1948 - 2002

Is Seasonal Variability Related to ENSO?

CoolSeasonForecast

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Monthly NINO 3.4 3-Month Moving Average MSLP Anomaly

Monthly Nino 3.4 PredictorsMonthly Nino 3.4 Predictors

Storms

Nino SSTSSTs3.4

Seasonal Forecast Methodology - Find Best Combinationof May to April SST Predictor Variables to Predict

November to April (Seasonal) Storminess Over Florida

Lesson Learned: Limited to Two Variables Due to Multicolinearity

BEST

Many predictor combinations gave similar results Strong relationship between ENSO and above/below normal storminess – Especially extreme phases which generally have most significant impact

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Taylor Russell Diagram of Predicted Versus Observed Storminess

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Scatter Plot of Nino 3.0 and Florida Dry Season Storms (1950-2002)

Updated Historical Conditional Probabilities In Progress

Synthesis of “ensemble” MLR,Conditional historical Probabilities, Recent trends, and Forecaster experience and Judgment.

Monthly Dry Season Nino 3.0 for 2001-02 and 1983-04 Very Similar83-84 4th Stormiest Ever – 2001-02 Tied For Least Stormiest Ever!

The ENSO Neutral Forecast Challenge

Some Issues

PNA Appears to be the Dominant Seasonal Telleconnecton

2001-02

1983-84

PNA

NAO

2001-02 Season – 1 Storm in Neutral ENSO – Near Record Dryness

Our Forecast is Dependent on Other ForecastsOur Forecast is Dependent on Other Forecasts

Accurate ENSO Forecast as far in advance as Accurate ENSO Forecast as far in advance as possible.possible.

Seasonal Outlooks of PNA, NAO etc.Seasonal Outlooks of PNA, NAO etc. Expand MLR to include PNA/NAO with ENSO Expand MLR to include PNA/NAO with ENSO

Stratified by phase.Stratified by phase.

Gulf Low with Gulf Jet or “Florida Cyclone”Gulf Low with Gulf Jet or “Florida Cyclone”

Improved Florida Storm Impact Climatology is UnderwayNot all Storms are Created Equal – Some Don’t Reach Their Potential

Many are purely beneficial

Two Types With Greatest Potential Negative Impact:

Strong Gulf Jet Crossing Strong Trailing Cold FrontStrong Gulf Jet Crossing Strong Trailing Cold Front

There is strong evidence that while these two types of storms are not exclusive to El Nino Seasons

They are more likely in them!

Impacts Can Be Quite Localized – 2002/03 Moderate El Nino – Record DecemberStorminess and Rainfall Across Central Florida (Volusia County Flooding)

Strong El Nino’s Appear More Likely to Impact More Areas…However Ability To Forecast Which Area of State Might Bear the Brunt is Problematic.

Are We In A “Stormier” Period – and Will it Continue?

Questions?

bart.hagemeyer@noaa.gov