A tropical wave over the west-central Caribbean, designated Invest 91L by the National Hurricane Center (NHC) on Thursday morning, is likely to develop into a tropical depression or into Tropical Storm Gamma as early as Saturday. This system is a heavy rain threat to Mexico’s Yucatan Peninsula, Belize, and western Cuba.
Conditions for development of 91L were favorable on Thursday, with sea surface temperatures (SSTs) near 30.5 degrees Celsius (87°F), light wind shear less than 10 knots, and a moist atmosphere with a mid-level relative humidity of 80%. Satellite images showed that 91L’s heavy thunderstorm activity was steadily increasing in intensity, areal coverage, and organization as the system moved west-northwest at about 10 mph. An Air Force hurricane hunter aircraft is scheduled to investigate 91L on Friday afternoon.
Forecast for 91L
The ridge of high pressure steering 91L should keep it moving to the west-northwest through Sunday, a track on which all of the major computer models agree. This motion should bring 91L to the coast of Mexico’s Yucatan Peninsula on Saturday, though it is possible the system could slide just north of Cancun and pass through the Yucatan Channel between Cuba and Mexico. It appears unlikely that 91L will be a threat to the U.S. Gulf Coast next week. In a 2 p.m. EDT Thursday Tropical Weather Outlook, NHC gave 91L 2-day and 5-day odds of development of 40% and 70%, respectively.
The track of 91L beyond this weekend will be complicated because it is embedded in a large area of low pressure over Central America called a Central American Gyre (CAG). Further complications may arise as another tropical wave now moving into the Lesser Antilles Islands arrives in the western Caribbean next week. In a 2 p.m. EDT Thursday Tropical Weather Outlook, NHC gave this second tropical wave two-day and five-day odds of development of 0% and 20%, respectively.
Conditions currently favoring development of 91L will become more hostile on Sunday, when the system will encounter a large trough of low pressure extending from Mexico into the southeastern U.S., associated with a cold front that moved through the Gulf of Mexico early this week. This trough will bring high wind shear of 20 – 30 knots to 91L Sunday through Tuesday. In addition, plenty of dry air over the Gulf of Mexico will interfere with development, as will land interaction with the Yucatan Peninsula. Because of these obstacles, the models are not bullish that 91L will achieve hurricane strength.
Heavy rains possible in Florida
The trough of low pressure that 91L will encounter this weekend will also act to shunt tropical moisture from the system to the northeast over Florida. This is a favorable setup for what is referred to as a Predecessor Rain Event (PRE), which could bring heavy rain and flooding to parts of central Florida.
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Editor’s note: this post was updated at 2 p.m. EDT October 1 to include the latest forecast information from NHC.
Posted on October 1, 2020 (12:51 p.m.EDT).
gee some location got 9 inches of rain or more in one day.. yesterday? wow drive and stay safe over there
How did you east coast of Florida folks make out yesterday with over 6 inches of rain or more?…any bad flooding etc?
HWRF, GFS, and GFS Para send the center of 91L into the central gulf and then turn it west towards the western gulf; these models, especially the HWRF separate the Mid level circulation from the Low Level Circulation, due to strong shear that can be seen looking at the mid levels on the models. The Mid Level Circulation accelerates NE towards the Florida Peninsula, and that combined with the moisture and the front bring bands of heavy rain across Florida Sunday and Monday. The center tracks west and encounters more favorable conditions in the Western Gulf, potentially intensifying and threatening areas in the Western Gulf. Quite a bit of rain on the way for the Florida Peninsula, especially central and south. 3-4 inches with higher amounts localized. Parts of the SE Coast of FL have already seen a lot of Flooding from yesterday’s deluge.
2 more invests coming soon. 92L in the central caribbean and a very impressive TW near 8n 31w to be 93L. The wave in the eastern atlantic is below the westerly shear and should be in an area conducive for development for the next few days
that stalled out front in south Florida may have saved us,storm cant go north..https://www.tropicaltidbits.com/analysis/models/gfs/2020100200/gfs_mslp_uv850_watl_50.png
https://uploads.disquscdn.com/images/ffc8b8ae8431bb152d5c8f2f7fa238e4e37f2936f04ccd5359d2afc30dcf8df8.png?w=600&h=396 there is 91L
Starting to get some blues and purples in the GOM…..must be October…..cold fronts getting farther south….
Thanks for this, Dr. Masters. Very much appreciated!
Thanks Dr. Jeff for this update.
Evening everyone….moisture prevalent in the Caribbean…..animated loop….
And a new gust of 186 km / h at Belle-Ile, violent sting jet in place. The Morbihan coast can expect gusts> 140/150 km / h. #TempeteAlex
172 km / h at Belle-Ile when the winds change to the west. New absolute wind record, beating the 162 km / h of the famous storm of October 1987. #TempeteAlex
gee up to 6 inhes already fallen wow..be safe east coasters………………………BULLETIN – IMMEDIATE BROADCAST REQUESTED
National Weather Service Melbourne FL
257 PM EDT Thu Oct 1 2020
Martin FL-St. Lucie FL-
257 PM EDT Thu Oct 1 2020
The National Weather Service in Melbourne has issued a
* Flood Warning for…
Northeastern Martin County in east central Florida…
Eastern St. Lucie County in east central Florida…
* Until 600 PM EDT.
* At 257 PM EDT, Doppler radar and automated rain gauges indicated
heavy rain due to thunderstorms. Flooding is already occurring in
the warned area. Up to 6 inches of rain have fallen so far today.
An additional 1 to 3 inches are expected through 6pm.
Some locations that will experience flooding include…
Port Saint Lucie, Walton, Fort Pierce, White City, Jensen Beach,
Indian River Estates, Nettles Island, North River Shores,
Hutchinson Island South, and Waveland.
A Flood Warning means that flooding is imminent or occurring. All
interested parties should take necessary precautions immediately.
Turn around, don`t drown when encountering flooded roads. Most flood
deaths occur in vehicles.
LAT…LON 2748 8043 2749 8031 2750 8026 2748 8025
2747 8025 2741 8023 2726 8016 2726 8023
2726 8024 2727 8023 2726 8028 2721 8029
thanks Jeff!! 🙂
so a storm somewhere in gulf around the 10th of OCT huh…https://www.tropicaltidbits.com/analysis/models/icon/2020100112/icon_mslp_pcpn_us_60.png
it looks like the east coast of Florida getting some storms over there now…https://static.baynews9.com/images/wx/bn9/radar/7_county/1601577312.jpg
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