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“Talking the Tropics With Mike” - deep dive on the tropics updated everyday through Nov. 30th.
I’ve fielded quite a few questions about the “September soaker” during roughly the first two weeks of September (Sept. 3 through the 15th specifically). The rainfall amounts were not unprecedented. But all that rain without a tropical system is a pretty rare set-up for NE Fl./SE Ga. The multiple days of rain & clouds were essentially caused by a stalled front nearby... high pressure centered over or near the Northeast U.S./NW Atlantic helping to produce onshore flow... & upper level disturbances moving from west to east. What was rather uncommon was how stagnant the set-up was lasting nearly 2 weeks. Similar rainfall amounts - or more - occurred in a shorter period of time but driven by tropical cyclone inflences including Irma in 2017, Matthew in 2016, Debby in 2012 & Fay in 2008.
It’s that time of year - ‘king tides’. King tides are higher than avg. tides in Sept., Oct. & Nov. naturally caused each by the approximate alignment of the sun, earth & moon. Add in all the rain during the rainy season which has well above avg. since July + a good deal of onshore flow & even higher tides are resulting in at least moderate flooding at times of high tide along the St. Johns River & its tributaries with minor flooding along the intracoastal & beaches.
The higher than avg. tides for the St. Johns River continues through mid December. Below are the peaks for the river supplied by Al Sandrik, Jax N.W.S.:
1. Today through September 26th , peaking between the 19th and 21st
2. October 11 to October 24th , peaking between 10/16 to 10/21
3. November 11th to November 21st , peaking between Nov 14th to Nov 18th
4. December 12th to December 19th , peaking between December 13th to the 16th
The autumnal equinox is Sunday, September 22nd. The Northern Hemisphere has approximately equal hours of day & night as the sun’s rays are just about directly over the equator. Avg. high temps. in the mid to upper 80s drop to the mid 60s(!) by the winter solstice (Dec. 21).
NOAA image:
Interesting research:
One of World’s Fastest Ocean Currents is Remarkably Stable, Study Finds
Study challenges previous assertions of Gulf Stream slowdown
A new study by scientists at the Cooperative Institute for Marine and Atmospheric Studies (CIMAS), the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML), and the National Oceanography Centre found that the strength of the Florida Current, the beginning of the Gulf Stream system and a key component of the global Atlantic Meridional Overturning Circulation, or AMOC, has remained stable for the past four decades.
There is growing scientific and public interest in the AMOC, a three-dimensional system of ocean currents that act as a “conveyer belt” to distribute heat, salt, nutrients, and carbon dioxide across the world’s oceans. Changes in the AMOC’s strength could impact global and regional climate, weather, sea level, precipitation patterns, and marine ecosystems.
In this research, measurements of the Florida Current were corrected for the secular change in the geomagnetic field to find that the Florida Current, one of the fastest currents in the ocean and an important part of the AMOC, has remained remarkably stable over the past 40 years.
The study published in the journal Nature Communications, the scientists reassessed the 40-year record of the Florida Current volume transport measured on a decommissioned submarine telecommunications cable in the Florida Straits, which spans the seafloor between Florida and the Bahamas. Due to the Earth’s magnetic field, as salt ions in the seawater are transported by the Florida Current over the cable, a measurable voltage is induced in the cable. The cable measurements were analyzed together with measurements from regular hydrographic surveys that directly measure the Florida Current volume transport and water mass properties. In addition, the transport was inferred from cross-stream sea level differences measured by altimetry satellites.
“This study does not refute the potential slowdown of AMOC, it shows that the Florida Current, one of the key components of the AMOC in the subtropical North Atlantic, has remained steady over the more than 40 years of observations,” said Denis Volkov, lead author of the study and a scientist at CIMAS which is based at the Rosenstiel School. “With the corrected and updated Florida Current transport time series, the negative tendency in the AMOC transport is indeed reduced, but it is not gone completely. The existing observational record is just starting to resolve interdecadal variability, and we need many more years of sustained monitoring to confirm if a long-term AMOC decline is happening.”
Understanding the state of the Florida Current is very important for developing coastal sea level forecast systems, assessing local weather and ecosystem and societal impacts.