Hey Everyone & Welcome to Miami!
*cues Will Smith* …Party in the city where the heat is on!… (Sorry, couldn’t resist 😊)
For those of you who don’t know me, I’m Chelsea, a meteorologist, sailor, and UMiami Alum/South Florida local. Find out what I’m up to with my company SeaTactics at the bottom of this blog and download our FREE Weather Resource Guide. Wondering what the best free sites are to use for this forecasting challenge? I promise this guide will help!
FORECAST LOCATION- KMIA
Miami International Airport is located approx. 5 nautical miles inland from the sea as the crow flies. (Or it can take an hour by car 😉) The weather station at the airport is on the southwest side – See images below.
One thing we can certainly expect in Miami is the sea breeze. The inland extent of the sea breeze boundary is often located quite close to MIA- which, as we’ll see later, can often queue up thunderstorms. However, keep in mind the sea breeze at the airport is certainly not as strong as it is on Biscayne Bay – 50% is probably a good estimate.
The end of Spring is a transition time for Florida from the drier winter season into the rainy season, marked by our lovely afternoon deluges you can set your watch by. (one of my favorite parts about Florida) Depending on the year, this transition can happen from late April/early May to mid-June.
This year, we are having a somewhat later transition. We actually had a couple of cold fronts push through South Florida in early May (!) and we are just now starting to move into our typical summertime pattern. The exception being: the unusually wet weather last week (May 23-27) from the tropical disturbance that eventually became Tropical Storm Bertha!
Just for fun, here’s the rainfall totals from South Florida over a 4 day period ending May 27 (courtesy of NWS Miami)…
…and this from the MIA station showing a total of 14.93 inches in the last 168 hours!! (as of May 28)
** You guys, be glad we were forecasting for PVD last week, not MIA! **
Okay, now that I’ve weather-geeked out for a minute… back to business where I’ll talk a little more about the typical summertime weather.
In the tables below you can see the normal temperatures don’t vary much. Temps may be one of the easier things to predict, while precip amounts will be more challenging. (more on that below..)
|Date||Max Temp||Min Temp||Daily Precip (in)|
|Date||Highest Max Temp||Lowest Min Temp||Highest daily Precip (in)|
Forecasting Tip: looking at the model guidance (such as the MOS tables) and the NWS Miami office will help get you in the right ballpark. The main reason for temps to drop significantly (sometimes 10 degrees) this time of year is due to a storm bringing cooling air from its downdraft (aka rain).
We know it’s becoming summer in South Florida when the weather is dominated by the Atlantic subtropical high, which is a semi-permanent feature (similar to the Azores high) that usually resides around 30 degrees north. It’s ridge axis is what provides the typical easterly winds along the coast.
*Side note: Interestingly, we haven’t had an uber stable subtropical high set up off the Southeast coast yet this year, hence the lack of a “normal” summertime pattern.*
When the subtropical high is farther away from the coast and more towards the middle of the Atlantic, or if the ridge axis is north of Miami, our gradient winds can be weaker which opens the possibility for onshore sea breezes.
How do we know if there will be a sea breeze? If the gradient wind in the morning is either very light/nil, or moderate from the W, AND the land is at least 5 degrees F warmer than the water, then we can get a sea breeze to develop in the afternoon. (see image below)
Getting the timing down will be the tricky part for a 12pm wind forecast. Often that is close to the time of the sea breeze fill on the coast, plus you want to allow some time for it to build inland towards the airport. It will all depend on the prevailing wind and how hot the land gets.
The sea breeze direction in Miami starts as E-SE and builds while clocking (clockwise) to become SSE-S late in the afternoon. Even when we have a gradient breeze and not a sea breeze, it is most often from the E to SE, so it’s a pretty safe wind direction to bet on. However, if a thunderstorm approaches from the Everglades and you get a gust of 30mph from the W, it can easily be a bust.
What about wind speeds? Typically this time of year, wind speeds are not very strong and usually run in the 8-15 kt range (especially inland at the airport- winds are stronger in Biscayne Bay). This is partly because of the dominance of the subtropical high extending over the area. It’s also partly because the water is quite warm and so is the land, so the sea breeze can be on the weak side.
The exceptions to the light winds are: wind gusts from thunderstorms that can reach up to 40-50kt (see my blog on thunderstorms below), and tropical systems.
The wind rose shows mainly SE breeze under 17kts because of the light sea breezes, and lighter winds from the subtropical high typically over the area.
Forecasting Tips: Keep in mind thunderstorm gusts for the daily high wind speed forecast – if a strong storm rolls by, you can easily see 35-45 knots!
Model preferences for wind would be the NAM, HRRR, and SailFlow’s 2km high resolution model.
I’ve already mentioned thunderstorms a bit already, but they really are the wild card in the South Florida forecasting game.
Here is a blog I wrote recently on the life cycle of a thunderstorm and the wind impacts that I recommend.
A couple things to know about thunderstorms in Miami:
- by nature they are usually pop-up, isolated cells that are difficult to predict the exact location (although meteorologists can narrow down whether they will be focused inland, on the coast, or offshore, for example.)
- A very common place for the thunderstorms to pop up is along the sea breeze boundary. This is where the sea breeze pushing inland meets a converging prevailing breeze, causing air to rise and storms to form. An interesting application of this is when the west coast FL sea breeze meets the east coat FL sea breeze, shown below. This leads to large convective storms in the middle of the state, that often hedge more E or W depending on the relative strength of the two sea breezes.
Forecasting Tip: NWS Miami’s experimental precipitation forecast can be found here: https://www.weather.gov/crh/pqpf?sid=mfl
Hurricane season officially starts June, 1 but we are already teeing up the “C” storm after Arthur and Bertha both formed in the last weeks in May.
NHC and other syndicates are forecasting a more active than normal hurricane season, with potentially more US landfalls. Buzz is also generating in the meteorological world of an approaching La Nina, which usually means active an active Tropics.
In June and July (before the peak of season Aug-Sept), we see more storms that are “homegrown”, or develop close to the US like in the Gulf of Mexico or just off of Florida, like Bertha last week. As the season goes on, the generation area shifts more towards the Caribbean and Atlantic Ocean west of Africa.
Forecasting temps will be on the easier side with it being so warm and summer-like already, but precip will be a challenge along with max wind speeds.
The long-range models for next week are hinting at interesting weather with a possible cold front moving down the southeast coast ahead of a new high pressure cell heading towards Bermuda. If that holds, we’ll see a mix of light wind days along with fresher wind days.
Tropically speaking, we are also watching enhanced moisture and energy that could potentially be brewing in the western Caribbean Sea or Yucatan area. Should be interesting and plenty of fun!!
Best of Luck, Chelsea
Chelsea Carlson is a meteorologist, sailor, and the founder of SeaTactics, a company with the goal of providing useful and clear marine weather knowledge for safety and strategy.
She has worked with mariners ranging from retired cruisers leisurely sailing around the world to high-performance racing teams. Chelsea is currently the US Olympic Sailing Team meteorologist for Tokyo 2020ne.
In addition to her years forecasting marine weather, Chelsea is also a lifelong sailor who has sailed across the Pacific, navigated in various distance and day races, and is passionate about protecting our environment and oceans (which is why 1% of annual gross sales go to nonprofits specifically working to ocean conservation).
Ways to join in on the weather fun:
– Watch our free webinar: “Weather Strategy 101” on www.sea-tactics.com
– Follow us on Instagram @sea_tactics and check out #WeatherWednesday where we post weather & sailing tips!
– Join one of our upcoming webinars or work with Chelsea as a private weather coach