Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
079 FXUS62 KKEY 160656 AFDKEY Area Forecast Discussion National Weather Service Key West FL 256 AM EDT Sun Jun 16 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 255 AM EDT Sun Jun 16 2024 An upper-level composite analysis early this morning reveals a building deep layer ridge over most of the eastern United States. During the last 24 hours, geopotential heights over the Florida Keys have risen through the lower and middle troposphere. A comparison of data collected from the Key West Friday and Saturday evening radiosonde balloons shows this clearly. Lower- tropospheric flow has both increased and become more anticyclonic and difluent during the last 12 hours or so, and this more than anything has led to gradual dissipation and suppression of cumulus convection. However, both satellite and surface observations indicate extensive altostratus and cirrostratus layers keeping it mostly cloudy across the Florida Keys and adjacent coastal waters. Current air temperatures in most Keys island communities are holding steady around 83-84F, with dewpoint temperatures 73-77F, yielding heat indices of 91-92F. Breezes have freshened, and winds are blowing mainly out of due east at a steady 10-15 mph over land. Our basic prognostic reasoning remains unchanged from the previous cycle. The lengthy cloudy and wet weather pattern is coming to an end. Sky cover should gradually decrease, with much lower measurable rain chances today through Tuesday. Thereafter, rain chances should spike again as a fairly robust upper-tropospheric cold-core cyclone develops in response to an anticylonic wave break over the western North Atlantic, and then migrates westward. Another interesting development is the potential for a tropical cyclone to emerge northeast of the Bahamas from the coalescence of low-level vorticity over warm sea surface temperatures amidst enhanced deep cumulus convection from ascent forced by a downstream sharp upper trough/jet/incipient upper low. The depth and strength of the deep-layer ridge over the eastern United States will ensure that whatever emerges from this area will move westward or west-northwestward toward Florida, Georgia, or the Carolinas. National Hurricane Center specialists are forecasting a tropical low to form by mid-week, with a 30 percent chance for tropical cyclone formation thereafter. The evolution of this potential system could result in lower than forecast wind speeds locally later this week if it moves north of the service area and disrupts the local gradient flow. However, too much uncertainty exists to adjust the forecast as such for this cycle. && .MARINE... Issued at 255 AM EDT Sun Jun 16 2024 Moderate to fresh east breezes prevail across Florida Keys coastal waters early this morning. Significant wave heights at Satan Shoal have been running 3-4 feet, and it is probably a foot or two higher in the Gulf Stream. Winds and seas should increase further today and tonight, as gradient flow sharpens between an expanding surface high pressure cell over the Atlantic and lower pressures over the Yucatan Channel and southwestern Gulf Basin. As such, winds will be highest over western zones where Small Craft Should Exercise Caution. A Small Craft Advisory may be needed by tonight for some of these zones. && .AVIATION... (00Z TAFS) Issued at 255 AM EDT Sun Jun 16 2024 VFR conditions will prevail at both EYW and MTH through the TAF period. Near surface winds will be east to southeast and be near 10 knots increasing to 10 to 15 knots late morning. && .CLIMATE... On this day in 1906, a Category One Hurricane moved slowly to the north-northeast crossing what is now the Seven Mile Bridge. Instrumentation in Key West recorded a minimum pressure of 29.62" and a peak wind of 42 mph. && .PRELIMINARY POINT TEMPS/POPS... Key West 87 81 88 82 / 20 20 30 30 Marathon 88 81 88 82 / 20 20 30 30 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...Kasper Aviation/Nowcasts....AP Data Acquisition.....AP Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest