CoCoRaHS

FLORIDA

A Community Collaborative

Rain, Hail & Snow Network

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Winter 2024-25 Newsletter

Greetings from the Coordinators,

We are pleased to present the winter 2024-25 quarterly newsletter. In this issue, we share highlights from the network during the past few months, discuss the 2024 Atlantic hurricane season and fall precipitation trends, and peak into the winter season outlook.


Mean temperatures this fall (September - November) were above average across Florida. Most places recorded one of their top 10 warmest falls on record. Precipitation was generally above normal for the season, and several central Florida stations had one of their top 3 wettest falls on record.

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Florida was directly impacted by three hurricanes this season, including two major back-to-back hurricanes - Helene and Milton. While this hurricane season was above-average, it was not quite as active as predicted, likely due to a combination of factors that include a delayed La Niña in the tropical equatorial Pacific Ocean and a stormier pattern over West Africa during August and early September that inhibited tropical development during the typical peak of the season. Following Hurricane Milton, a drying pattern set in and drought developed across the Panhandle in November.


As always, your contributions to this network are greatly appreciated. Thank you for your continued support and dedication to the CoCoRaHS program. We hope you have a wonderful holiday season and a happy new year!


Sincerely,


Emily Powell

epowell@coaps.fsu.edu

Ivetta Abramyan

ivetta.abramyan@fscj.edu

Florida CoCoRaHS Program Fall Highlights

During fall 2024, 55,442 reports were submitted through daily and multi-day reports. There were an additional 57 significant weather reports and 104 condition monitoring reports submitted during the months of September, October, and November. These reports provided near real-time data and post-event data and analysis for use by forecasters and other stakeholders across the state.

Fall Rainfall Departures and Rankings


The map below shows the general patterns of rainfall departures from normal from September 1 - November 30 using a combination of station networks, including CoCoRaHS, courtesy of the High Plains Regional Climate Center. Seasonal rainfall totals were above normal across the Peninsula and central Panhandle regions. Areas impacted by Hurricanes Helene and Milton were over 8 inches above normal for the season (and much more in some locations), while much of the Big Bend and north-central Florida were well below normal.

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Some stations recorded record or near-record wet conditions this fall. Tampa had its wettest fall on record (135 years) with 29.27", which was 19.44" above normal. Daytona Beach had its 2nd-wettest fall (88 years) with 26.90" of rain for the season, which was 12.14" above normal. Several additional locations had their 3rd-wettest fall on record, including Apalachicola (30.08" total), Titusville (26.89" total), Leesburg (18.08" total), and Vero Beach (28.38" total).

2024 Atlantic Hurricane Season Recap

The 2024 Atlantic hurricane season had a total of 18 named storms, which is considered above average. Of those, 11 storms became hurricanes and 5 of those became major hurricanes (category 3 or higher). Five hurricanes make landfall in the U.S., all of them along the Gulf Coast; and 2 major hurricanes made landfall, both in Florida.

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(Click on the image above to view a larger version.)

In late June, major Hurricane Beryl developed and became the earliest major hurricane (category 3+) and earliest category 5 hurricane to form in the Atlantic basin on record. Beryl did not impact Florida; the storm made landfall in the western Gulf of Mexico near Matagorda, Texas as a Category 1 hurricane, impacting parts of Texas and Louisiana.


Early season activity was followed by a lull in tropical development during the time when it is typically most active from about mid-August to mid-September. According to NOAA, this lull was the result of stormier weather over Western Africa. Easterly waves that track west and often develop into hurricanes in the Atlantic's Main Development Region exited the African continent further north than usual where they were met with a more hostile environment, inhibiting storm development. The second half of the hurricane season picked back up, with 12 named storms forming after the climatological peak. Florida was directly impacted by three landfalling storms this season – Debby, Helene, and Milton – two of which were major hurricanes and all three of which impacted Florida’s western Gulf coast.


Florida experienced major damages from these hurricanes, including severe coastal erosion and the displacement of large volumes of beach sand, record high storm surge along Florida's west coast, and a record tornado outbreak with 47 tornadoes occurring during Hurricane Milton. Category 3 Milton made landfall on the west coast in Sarasota County just less than 2 weeks after Hurricane Helene struck Taylor County in the Big Bend as a major category 4 hurricane, compounding clean up and recovery efforts. The two storms set a new record for number of days between two major hurricane landfalls in Florida (at 13 days), breaking the old record set in 1950 (44 days between Hurricanes Easy and King).

How CoCoRaHS Data Helped Meteorologists During Hurricanes Helene and Milton

From: Austen Flannery, National Weather Service - Tampa Bay Area

Hurricanes Helene and Milton were two of the most impactful storms for the West Coast of Florida in the last one hundred years, rivaled only by storms as infamous as Hurricane Charley (2004), Hurricane Irma (2017), and Hurricane Ian (2022). Unlike past storms, however, the scope of impacts was much larger. From historic storm surge that impacted the entire West Coast, some of the highest wind speeds recorded in the Tampa Bay Area, a prolific tornado outbreak across Central and South Florida, to historic flooding rainfall that caused new record water levels on area rivers, these two storms touched everyone's lives in some way across the region.


Using data from CoCoRaHS, meteorologists with the NWS were able to gain better insight into the scope of impacts. Flash Flood emergencies were issued for portions of Florida along the West Coast as hurricane Milton made landfall. Rainfall observations as high as 20 inches were recorded in portions on St. Petersburg, FL, with the peak rainfall observation noted during the storm from a CoCoRaHS observer. After the storm passed, these data could be incorporated with other observational systems to provide a visual depiction of where the highest rainfall occurred to assess lingering impacts and to begin to forecast where the greatest river flooding was expected.

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Hurricanes Helene and Milton are a reminder of just how important this data can be. Thank you to all the volunteers helping us to provide a more detailed picture and better forecast for high-impact events. Interested in seeing more of the data? Check out the Preliminary Tropical Cyclone Reports from the Tampa Bay NWS office at this link:

https://www.weather.gov/tbw/TropicalEventSummary, and head over to this link for more interactive data and a review of the impacts:

https://storymaps.arcgis.com/stories/ca76a6bf17be46f68f60bec6cccdef8e.

Additional Post-Tropical Cyclone Reports and articles about storm impacts are available:


Fall Extremes Across Florida CoCoRaHS


Between 1 September 2024 and 30 November 2024:

  • Highest seasonal rainfall total: 37.84" in Boca Raton, Palm Beach Co. (PB-127)
  • Lowest seasonal rainfall total: 3.72" in Lake City, Columbia Co. (CB-25)
  • Highest daily rainfall total: 18.75" reported on October 10 in Gibsonia, Polk Co. (PK-93)

*based on stations with at least 90% completeness

Significant Weather Reports


Between 1 September 2024 and 30 November 2024, there were:

  • 58 total Significant Weather reports submitted.
  • 23 reports of Minor flooding.
  • 15 reports of Unusual flooding.
  • 4 reports of Severe flooding.

Observer Comment Corner


Observer comments are encouraged! Thanks to the many who regularly post comments with their reports. Comments provide valuable context to observations, which can be very helpful to those who later use the observations. Below are a select few of the comments shared during the past few months. We’ll continue to share your comments in these newsletters.

1. 26 September, Islamorada 7.8 SW, Monroe County (MN-39) - 0.25 inches:


"In Islamorada, Florida Keys, we are under a tornado watch with Hurricane Helene. High tide was about 2' higher than normal. Wind gusts up to 50 mph."

2. 27 September, Graceville 7.0 S, Jackson County (JK-7) - 7.37 inches:


"When it rains, it pours. Rained all day and into the darkness. Winds were never a problem here where Jackson, Washington, and Holmes County intersect. No lightning detected nearby anytime during Helene."

3. 27 September, Tallahassee 5.2 E, Leon County (LN-47) - 2.65 inches:


"Hurricane Helene, winds here only 50-60 mph, minimal tree damage, branches and palm fronds down but thankful it wasn’t worse!"

4. 2 October, Rockledge 1.1 WSW, Brevard County (BV-13) - 2.93 inches:


"Deluge ~6pm within 1 hour. Lots of thunder."

5. 10 October, Bradenton 3.5 WNW, Manatee County (MA-20) - 12.38 inches:


"Gauge was recorded and emptied at 6:00PM on 10/9/24 (6.64 inches). The rest was recorded and emptied this a.m. at (5.74 inches)."

6. 10 October, Lake Helen 0.9 S, Volusia County (VL-90) - 15.37 inches:


"Hurricane Milton - 4.28" between 7 am and 7:30 pm on 10/9/2024, plus 11.07 between 7:30 pm and 7 am on 10/10/2024. Rain gauge possibly overflowed this morning. We only had power fluctuations and lots of tree limbs down. Some roads are flooded due to lakes overflowing their banks."

7. 10 October, St. Petersburg 3.2 NNW, Pinellas County (PN-34) - 10.05 inches:


"Most I have ever had in one day and since I joined."

8. 11 November, Archer 5.5 E, Alachua County (AL-2) - Trace:


"Pastures turning brown from lack of rain!"

Fall Drought Development


The CoCoRaHS Condition Monitoring (CM) chart below shows a wet start to fall followed by gradual drying following Hurricane Milton in early October. This chart displays observers' reports of on-the-ground conditions as a percentage of the total number of reports submitted each week. In early September, most local CM reports indicated normal to wet conditions. As fall progressed, more CM reports indicated near normal to dry conditions, with an increasing number of reports indicating dry conditions beginning in late October and persisting through November.

Condition Monitoring Reports Submitted by CoCoRaHS Observers 

(August 27, 2024 - December 2, 2024)

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A lack of rainfall following Hurricanes Helene and Milton led to a drying pattern in late October through November. Drought development occurred in the Panhandle in early November. Tallahassee recorded 30 consecutive days without measurable rainfall from October 6 - November 6, while the rest of the Panhandle saw between 26 and 29 consecutive days without measurable rainfall (defined as <0.01 inches). By late November, about 16% of the state was in moderate drought (D1); another 36% was considered abnormally dry (D0), according to the U.S. Drought Monitor.

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La Niña Watch


Sea surface temperatures in the central and eastern equatorial Pacific Ocean have been near average and show evidence of ENSO-neutral conditions. The latest weekly Niño indices of sea surface temperature anomalies ranged from +0.2°C (Niño-4) to -0.3°C (Niño-3.4), according to the Climate Prediction Center. There is a 57% chance that La Niña will develop soon (December 2024), which is now considered to be a delayed arrival. Forecasters expect this to be a weak event, at most. Nevertheless, a weak La Niña can still exert an influence on our temperatures and rainfall patterns. Once it arrives, it will likely persist through January – March 2025.

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Winter Season Outlook


Despite a cold start to December, the NOAA Climate Prediction Center's outlook for this winter is leaning toward a warmer than normal winter on average, December - February, in Florida and the southern tier of the U.S. Winter precipitation is leaning below normal in Florida with drought development expected.

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Important Reminders

New Mobile App for CoCoRaHS Has Launched

The new mobile app, available at mobile.cocorahs.org, is a mobile-enabled web application. It looks like an app, acts like an app, and you can download it from either Google Play or the Apple store as an app. Our app will work across platforms (Android and iOS phones, tablets, computers) and browsers. This new app is full featured, allowing observers to enter data for any of our data types (significant weather, hail, etc.) and provides easy access to our current web site.


What will become of the old app, "CoCoRaHS Observer"? Both the iOS and Android versions will continue to be available as long as they work. However, they are no longer supported, i.e. there will be no bugs fixed or improvements made.


Learn more here: https://cocorahs.blogspot.com/2024/11/new-mobile-app-opens-up-world-of.html 

Install options here: https://www.cocorahs.org/Content.aspx?page=app-install

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The home page of the new mobile web app in the light and dark modes.

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Don't forget to tune into our regular webinar series, featuring experts on various weather and climate topics. The next webinar will be January 9 at 1pm ET by meteorologist Greg Corbin who will review significant weather events of 2024. Register and view recordings of past webinars at: https://www.cocorahs.org/Content.aspx?page=wxtalk.

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