2024 Hurricane Risk for Tampa Bay Update

The 2024 Hurricane Season is predicted to be well above normal due to two primary factors: El Nino and warm ocean water.

Hurricane Ian approaching Florida West Coast

The Averages

On average, a tropical storm will pass within 50 miles of Tampa Bay about once every other year, while hurricanes pass within 50 miles about once every 4 years and major hurricanes, about once every decade. Direct major hurricane hits on Tampa Bay are rare, with only 2 ever recorded; a Cat 4 storm in 1848 and a Cat 3 storm in 1921. 

Worst Case Scenario

A 2010 study called Project Phoenix, funded by FEMA, took a look at the Tampa Bay area if it was directly hit by a Cat 5 hurricane. In this “worst case” scenario, power outages would be widespread with all of Pinellas County being without power and with Pasco and Hillsborough Counties experiencing nearly total power outages as well. The associated storm surge would be as high as 26 feet in Tampa, 24 feet in Apollo Beach, and 20 feet in St. Petersburg.

Project Phoenix

All told, a Cat 5 storm could result in up to 2,000 people dead, 2 million injured, and almost 500,000 homes and businesses destroyed.  All three bridges between Tampa Bay and the Courtney Campbell Causeway would “sustain either structural damage or have their approaches washed away by water and waves.”  

What is the risk for Tampa Bay in 2024?

It is not all bad news for this season, however.  Although there is an overall higher risk for tropical cyclone activity in the North Atlantic this season, perhaps even setting records, the risk for a hurricane directly hitting the Tampa Bay area may actually be no greater than average, and possibly slightly less than average. 

Based on analysis from Colorado State University, the risk for a named tropical storm passing within 50 miles of Pinellas County this year is about 64% which is 10% higher than the long-term (1880-2020) average of 54%. The risk for a hurricane passing within 50 miles of the coast, however, this season is 26% which is actually slightly lower than the long-term average of 27%. The risk for a major hurricane (Cat 3-5) passing within 50 miles of the coast this year is 10%, also slightly below the long-term average of 11%.

Analog Years

The North American Multi-Model Ensemble (NMME) is a seasonal prediction system that combines data from computer climate models in the U.S. and Canada to produce monthly and three-month averages. The NMME has been releasing global forecasts every month since 2011, and its information is used by NOAA to inform their seasonal outlooks.

The best analog years for the 2024 hurricane season based on NMME sea surface temperature anomalies are 1970, 1999, 2007, 2010, and 2011. The resulting outlook suggests hurricane tracks are more likely in the red-shaded areas vs. blue-shaded areas. Most of Florida is in the blue zone, except for extreme South Florida and the Keys.

Source: Tropical Tidbits.com 

Wind Radius

With hurricanes, size does matter. Typically, for a Cat 1 hurricane, the radius of hurricane force winds will extend out only about 25 miles, with only about 10% of storms being large enough to have hurricane force winds out to over 45 miles. Major hurricanes tend to be larger, with hurricane force winds extending outward about 45 miles, on average, with a few extending outward some 75 miles or more. Damaging winds of 50-64 kt (58-73 mph) usually extend out farther, typically to about 80-110 miles from the center and often cause roof damage, uprooted trees, and significant power outages.

Depiction of a hurricane passing 50 miles off the coast showing wind radii of 25 and 50 miles. 

Hurricane Winds Over Land

Tropical cyclone winds over land are reduced due to land friction by 20% to 50%, however, gustiness will increase from about 10% over water to 20-30% over land. For example, a wind of 80 mph over the ocean would be reduced to about 64 mph over the immediate coastal beaches and to 40-50 mph farther inland. Wind gusts, however, still could reach 75-80 mph along the beaches and 55-65 mph farther inland.

Peak winds over land often are significantly less than the “max winds” reported in a hurricane, especially when the center passes to the east of our area. Even storms passing to the west, like Hurricane Gladys in 1968, will have winds reduced over land. The key issue is whether the center passes east or west of Tampa Bay and how far-out hurricane-force winds extend at that time. 

Some examples of hurricanes passing near Tampa 

1921 Hurricane nearing Tampa Bay

The October 25, 1921 Tampa Bay hurricane  had a peak wind of 125 mph at landfall near Tarpon Springs, just 25 miles northwest of Tampa.  In Tampa, however, a peak wind of 68 mph with a gust to 75 mph recorded atop a tall building in downtown Tampa. The adjusted surface peak wind was later estimated to have  been 56 mph. Most of the damage done by this storm in Tampa and St. Petersburg was due to the storm surge. The 10.5 foot storm surge in Tampa Bay was the highest since the Great Gale of 1848

 

The center of the 1935 Labor Day Hurricane that decimated portions of the Florida Keys, later passed 45 miles west of Tampa with max winds of 120 mph, while Tampa recorded a peak 5 minute wind of 75 mph with a peak gust of 84 mph.

In October of 1944, a hurricane with max winds of about 95 mph passed just 15 miles southeast of downtown Tampa. The maximum sustained wind reported at Tampa was 66 mph.

In September of 1960, Hurricane Donna passed about 38 miles east of downtown Tampa with max winds about 92 mph. The highest sustained wind reported at Tampa was 62 mph with a gust to 75 mph. 

In October 1968, Hurricane Gladys passed about 40 miles northwest of Tampa with max winds of 100 mph, in Tampa the max wind was 37 mph.

More recently, Hurricane Charley passed about 45 miles southeast of Tampa with max winds of 115 mph while the highest wind reported at Tampa was 23 mph with a gust to 30 mph.

Forecasting Hurricane Tracks

The National Hurricane Center’s average track forecast error has improved significantly over time, however, even today the average error just 48 hours out is about 50 nm (58 statute miles) which is close to the average extent of hurricane force winds for major hurricanes. This, unfortunately, makes it difficult to predict where the major impact will occur.

  NOAA NHC Track Forecast Error over Time

Storm Surge 

In most cases, it is the storm surge that does most of the damage in a hurricane. Water (due to flooding by storm surge or heavy rainfall) is the number one killer during a hurricane or tropical storm in the U.S., accounting for nearly 90% of all tropical cyclone deaths. If you are in an evacuation zone, it is imperative to monitor local evacuation zone messages as a storm approaches.

Tampa Bay Evacuation Zones

Fred Pickhardt

Meteorologist

Ocean Weather Services

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Top Tropical Cyclone Tracking Sites

Now that the hurricane season is approaching, here are my thoughts on the best tropical  cyclone  tracking sites:

A view of Hurricane Florence is shown churning in the Atlantic Ocean in a west, north-westerly direction heading for the eastern coastline of the United States, taken by cameras outside the International Space Station, September 12, 2018. NASA/Handout

 

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2024 Atlantic Hurricane Outlook Update

Hurricane Irma 2017

The 2024 Hurricane Season outlook is predicted to be well above normal by just about every forecast center due to two primary factors: Developing La Nina and warm ocean water in the Main Development Region (MDR).

 

 

 

Currently, a rapidly weakening El Niño is expected to transition to a La Niña state by late this summer. This transition should produce low wind shear conditions, favoring tropical cyclone development over the North Atlantic. Additionally, the Atlantic Main Development Region (MDR) remains at record warm levels, increasing the probability of major hurricanes. 

2023 Hurricane Season

Despite a strong El Niño, the Atlantic experienced its fourth most active season in 2023. There were 20 named storms, including 7 hurricanes, with 3 reaching major hurricane strength. The strong El Niño also significantly impacted the Azores-Bermuda Ridge, leading to its weakening. Consequently, most of the tropical cyclones that developed last year tracked northward and remained well out over the Atlantic. The weakened ridge also resulted in weaker trade winds and less Saharan dust, both contributing factors to warming sea surface temperatures.

2023 North Atlantic Tropical Cyclone Tracls

 

Primary Storm Factors for 2024

Wind Shear: During La Niña events, wind shear in the tropical Atlantic typically decreases. Wind shear refers to the change in wind speed and direction with altitude. Reduced wind shear creates favorable conditions for the development and intensification of tropical cyclones. With weaker wind shear, disturbances in the tropics can organize more effectively, potentially leading to more and stronger storms.

Vertical Wind Shear affects Hurricanes

 

 

Sea Surface Temperature: Another key reason for concern this year is the persistent above normal sea surface temperatures (SST) in the tropical North Atlantic. The North Atlantic main development region (MDR) is where many of the stronger hurricanes form and currently SSTs remain well above normal with the ocean heat content at levels in April, more typical for early July.

Atlantic Main Develpment Region

 

Saharan Dust: Hot, dusty air blown westward off the coast of Africa over the main development region from late spring to early fall tends to suppress the formation of tropical cyclones by restricting needed moisture and vertical air motion, as well as reducing the amount of sunlight reaching the sea surface and lowering ocean temperatures.  During 2023 the weakened Azores-Bermuda ridge significantly reduced dust levels, helping to promote tropical cyclone development.

NOAA image Saharan Dust over the eastern North Atlantic

 

 

Azores-Bermuda Ridge (Trade Winds and Storm Paths)
During La Niña years the Azores-Bermuda Ridge (a high-pressure system located in the North Atlantic), tends to be stronger than normal. This ridge is a key factor as to how far west tropical cyclones will move before turning northward. As the Azores-Bermuda Ridge strengthens during this hurricane season, I would expect an increased risk of tropical cyclone landfalls farther to the west than in 2023. Highest risk areas include the Caribbean, the US East Coast, and the Gulf Coast. On the plus side, a stronger Azores-Bermuda ridge increases trade winds which tend to cool sea surface temperatures. As the season progresses, it will be essential to stay informed about the evolving conditions and their potential impact on hurricane activity.

Azores-Bermuda ridge has a strong effect of tropical cyclone tracks

 

Hurricane Season Analogs for 2024
The North American Multi-Model Ensemble (NMME) is an experimental multi-model seasonal forecasting system consisting of coupled models from various modeling centers in the US and Canada. The NMME SST forecast analogs since 1966 for sea surface temperature anomaly currently show the closest matches to this year as 1970, 1975, 1999, 2010 and 2011. Based on these analog years, the highest frequency tropical cyclone tracks are shown below.  Areas in red have higher than average probability and areas in blue, lower than average probability.

NMME SST forecast analogs storm tracks

 

2024 Hurricane Forecast Numbers
Most prognosticators of Atlantic Hurricanes are looking for a much above-normal season, some are predicting possibly record activity. In an average season, we normally see 14-15 named tropical cyclones, of which 7-8 become hurricanes and 3-4 become major hurricanes.  This season is forecasted range is for 17-33 named storms, 8-16 hurricanes and 4-8 major hurricanes.

Selected Forecast Center Predictions 

                                              Named Storms           Hurricanes            Major Hurricanes

Colorado State University                  23                                11                                5            AccuWeather                                      20-25                           8-10                           4-7 WeatherBell                                        25-30                          14-16                          6-8
University of Arizona                           21                                11                                5
NOAA                                                  17-25                             8-13                           4-7

Most Likely                                     23                                    9                               6

Fred Pickhardt

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La Niña and the Azores-Bermuda Ridge: Impact on the 2024 Hurricane Season

Catagory 5 Hurricane Dorian

Introduction

During the 2023 hurricane season, a strong El Niño event had significant effects on the Azores-Bermuda Ridge, leading to a weakening of this high-pressure system. As a result, surface winds, especially in the tropical Atlantic, decreased. This reduction in surface winds had several consequences, including unusual sea surface warming due to decreased ocean mixing and evaporation. Additionally, other factors, such as a strong  Atlantic Multi-decadal Oscillation (AMO), reduced sulfate particles from cleaner shipping fuels, the Hunga-Tonga volcanic eruption, and lower levels of African dust, may have contributed to the overall climate conditions.

June 2023 Surface Pressure Anomaly

 

 

In this analysis, I will explore the transition from El Niño to La Niña and its potential impact on the 2024 hurricane season.

La Niña and Wind Shear

El Niño to La Niña Transition

Currently, El Niño is weakening rapidly, and meteorologists anticipate the development of a La Niña event by the main 2024 hurricane season. La Niña is characterized by cooler-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean. Just how will this transition affect the Atlantic hurricane environment?

Wind Shear and Tropical Cyclones

During La Niña events, wind shear in the tropical Atlantic typically decreases. Wind shear refers to the change in wind speed and direction with altitude. Reduced wind shear creates favorable conditions for the development and intensification of tropical cyclones. With weaker wind shear, disturbances in the tropics can organize more effectively, potentially leading to stronger storms.

The Strengthened Azores-Bermuda Ridge

Trade Winds and Storm Paths

La Niña tends to strengthen the Azores-Bermuda Ridge, a high-pressure system located in the North Atlantic. As this ridge strengthens, trade winds increase. These trade winds play a crucial role in steering tropical cyclones. Here’s how:

  1. Westward Movement: A stronger Azores-Bermuda Ridge tends to steer Atlantic tropical cyclones farther west. This westward shift increases the risk of landfalls in regions such as the Caribbean, the US East Coast, and the Gulf Coast.
  2. Trade Wind Enhancement: Stronger trade winds enhance ocean surface mixing. This process involves cooler water from deeper ocean layers rising to the surface. Consequently, the sea surface temperatures may gradually cool during the hurricane season.
  3. Evaporation and Moisture Transport: The intensified winds also lead to increased evaporation and moisture transport. This contributes to further cooling of the sea surface.

Azores-Bermuda Ridge controls Tropical Cyclone Tracks

Sea Surface Temperature Anomalies

Outlook for 2024

Given the current very high sea surface temperature anomaly in the tropical North Atlantic, it is likely to remain above normal as we move into the peak of the 2024 hurricane season. However, the strengthening La Niña and the associated changes in wind patterns may gradually mitigate this anomaly.

Tropical North Atlantic Sea Surface Temperatre Anomaly

In summary, the transition from El Niño to La Niña could significantly influence the behavior of tropical cyclones in the Atlantic. If the Azores-Bermuda Ridge strengthens during this hurricane season we can expect an increased risk of tropical cyclone landfalls in regions such as the Caribbean, the US East Coast, and the Gulf Coast. As wind shear decreases, tropical cyclone frequency and intensity can increase so it will be essential to stay informed about the evolving conditions and their potential impact on hurricane activity.

Ocean Weather Service

 

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Gulf Low to produce Heavy Rains and Strong Winds

NOAA Surface Forecast for Saturday morning

A low is forecast to form over the south-central Gulf of Mexico Friday night into early Saturday morning, deepening and moving northeast across northern Florida Saturday night, reaching the coast of Georgia by early Sunday before turning northeast to north across the Mid Atlantic States Monday.

 

 

 

NOAA Surface Forecast Monday Morning

A heavy rain event with possible flash flooding is expected across Florida Saturday afternoon and Saturday night with gale force winds developing over the northeastern Gulf of Mexico beginning late Friday night with gale to storm force winds building seas 5-10 meters (16-33 feet) likely over the ocean off the Southeast US East Coast Saturday night and Sunday then spreading northward.

NOAA Precipitation Forecast

 

 

Ocean Weather Service

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Heavy Rains and Gale Winds along Florida Coast

A gale low over the northeastern Gulf of Mexico will move slowly east bringing beneficial rains to drought-stricken areas of the central and eastern Gulf Coast. A secondary low center will form along the Florida East Coast early Thursday and will produce some heavy rainfall in southeast Florida from West Palm Beach and Fort Lauderdale down through Miami and Homestead. In addition, strong to gale force winds are likely with seas building 3-5 meters (10-16 Feet) north of the developing secondary low center Thursday.

NOAA WPC Surface Forecast Wednesday Night

Extremely heavy rainfall rates are possible which may approach or exceed 2 to 3 inches per hour and may produce rainfall totals upwards of 3 to 6 inches with some isolated max amounts approaching 10 inches.

NOAA NWS 24 Hour Rainfall Forecast

NOAA NHC Wave Forecast Thursday Evening

Ocean Weather Services

 

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A Second Hurricane-Force Storm heads for English Channel Approaches

NOAA OPC Surface Analysis

A 2nd rapidly deepening storm low east of Newfoundland will move east then east-southeast with winds to 65 kts building significant wave heights to 14 meters (46 feet) during the next 36 hours over the eastern North Atlantic north of the Azores.  Thereafter the low will begin to weaken and move across southern England into the North Sea.

NOAA OPC Surface Forecast 1200Z 04 November

Again ship delays are likely for both inbound and outbound English Channel traffic as well as north and southbound traffic in the Bay of Biscay.

 

NOAA OPC Wave Height Forecast 1200Z 04 November

Ocean Weather Services

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Two Hurricane-Force North Atlantic Storms

Meteosat Image North Atlantic

A hurricane-force storm low over the eastern North Atlantic will move rapidly across southern England and into the North sea with winds to 70 kts and significant wave heights to 12 meters (about 40 feet) in the English Channel Approaches and portions of the Bay of Biscay during the next 18-24 hours.

 

 

NOAA OPC Surface Analysis 1200 UTC 01 Nov 2023

 

A second low developing SSE of New England will move NE then E and deepen rapidly into another hurricane-force storm low over the Central North Atlantic with wind to 70 kts and significant wave heights building 12-14 meters 40-46 feet) over the next 48-72 hours, approaching the English Channel Approaches by the 4th. 

NOAA OPC Surface Forecast 0000Z 03 Nov. 2023

NOAA OPC Wave Height Forecast

Both storm systems will negatively impact both east and west bound shipping lanes for next few days.

 

Ocean Weather Services

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Intense Storm Heads for English Channel Approaches

NOAA OPC Surface Analysis 1200 UTC 31 October

A gale low over the western North Atlantic will move ENE at 45 kts, deepening rapidly into a hurricane-force 953 mb storm low over the English Channel Approaches by 0000 UTC November 2nd with winds to 70 kts and significant wave heights to 12 meters (about 40 ft) south of England and Ireland and portions of the Bay of Biscay. Thereafter the storm center will move across southern England and into the Northsea.

NOAA OPC Surface Forecast 0000 UTC 2 November

 

 

 

 

 

 

 

 

 

 

 

 

Significant shipping delays are possible for both inbound and outbound English Channel traffic.

 

 

 

 

 

 

 

 

 

 

 

Ocean Weather Services

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Hurricane-Force Storm to affect Bay of Biscay and English Channel Approaches

NOAA OPC Surface Forecast 1200 UTC 31 October

A low pressure disturbance will move off the New England coast early Monday, moving rapidly ENE deepening to a gale low south of Newfoundland then deepening rapidly into a hurricane force storm reaching the English Channel Approaches by 0000 UTC November 2nd with winds of 65-75 kts and significant wave heights building to 12-14 meters (40-46 feet) over the Bay of Biscay and Channel approaches.  This will likely cause issues, particularly with westbound shipping. 

ECMWF Wind Forecast for 0000 UTC 2nd November via windy.com

Ocean Weather Services

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