Hurricane Season runs from June 1-November 30
[10/10]
689 FXCA62 TJSJ 102018 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 418 PM AST Fri May 10 2024 .SYNOPSIS... Unstable conditions continue to bring the risk of flooding across the local islands through tonight and the weekend. Excessive rainfall over saturated areas will further elevate the risk for flooding, mainly across the interior to northern sections of Puerto Rico. Winds will become southeasterly over the weekend, bringing warmer than usual temperatures. Marine conditions are improving as a northerly swell begins to fade. && .SHORT TERM...Tonight through Sunday... A cluster of showers started to form across the coastal waters between Vieques and St. Croix around 10am this morning, bringing over 2 inches of rain to the eastern tip of the island. After this showers started to form across the interior to northern sections of Puerto Rico and continued through the afternoon. Various areas such as San Juan, Arecibo, and San Sebastian received between 2-4 inches of rain with multiple Flash Flood Warnings issued due to flooding impacts. Winds were generally from the east around 10 mph with seabreeze variations. Abundant moisture and a lingering mid to upper-level trough will continue to bring unstable weather conditions through the weekend. A jet streak segment of the upper-level trough will remain over the islands tonight through Saturday night, which will assist the development of convection meanwhile causing 500mb temperatures to drop. Due to this, rainy conditions with thunderstorms will continue to effect the area with flooding remaining a threat across sections with prolonged or heavy rainfall. The afternoon hours continue to have the best chance of bringing strong showers mainly for the mainland island of Puerto Rico due to diurnal heating and local effects. The light to moderate easterly surface flow, with easterly winds gradually transitioning to south-southeast by Saturday and Sunday, and upper-level westerly wind will allow showers to form across most sections of Puerto Rico with the strongest activity across the interior to northern sections. The weakening of the upper-level trough on Sunday and a reduction of jet wind speeds will allow conditions to slightly improve compared the the previous days. However, there is still a high chance for afternoon convection to bring locally heavy rainfall from slow- moving showers over already saturated soils which will sustain a flooding risk. By tomorrow, due to the southerly component in the wind temperatures may soar into the upper 80s to mid-90s across coastal and other urban areas, while higher elevations could see highs in the upper 70s to mid-80s. With plenty of moisture across the region, heat indices could exceed 102 degrees Fahrenheit, potentially reaching around 108-110 degrees in localized coastal areas of northern Puerto Rico over the weekend. && .LONG TERM...Monday through Friday... /from previous discussion/ No major changes to the long term forecast. Model guidance to suggest a mid- to upper-level ridge building over the region by the start of the workweek, potentially promoting more typical weather with afternoon convection due to diurnal and local effects. Precipitable water (PWAT) values are forecast to generally stay at normal values between 1.5 to near 2.0 inches, through the workweek as patches of moisture advect into the region. ESE winds to start the period will back to become more easterly by late Monday through the rest of the period as a surface high moves into the western Atlantic. Most available moisture should reach up to 850 to 800 mb for the period. The NASA aerosol optical thickness (AOT) guidance continues to suggests the presence of an air mass with Saharan dust particles lingering to start the period, this could extend through the period. Limited Heat Risk (heat indices from 102 to 107 degrees Fahrenheit) or even higher, especially during the daily maximum heating, will persists across several lower elevation sectors of the islands where no significant rain is observed. This diurnal heating, local effects and sea breeze variations will continue to promote up to strong afternoon convection, steered by east-southeast winds on Monday, backing to become more easterly winds for the rest of the workweek, promoting convective activity mainly over sectors of the interior to western half of the Puerto Rico and downwind of the local islands. Above-normal sea surface temperatures can also promote nighttime showers across windward sectors of the islands, patchy fog also forecast for areas of the interior during the early morning hours. && .AVIATION... (18Z TAFS) SHRA and TSRA are resulting in lower ceilings and VRB winds at TJBQ/TJSJ/TJPS where TEMPO MVFR conditions conditions through 21Z. SHRA/TSRA will continue to affect the area, causing mountain obscuration across the Cordillera Central. SFC winds will continue light from the E-SE and VRB near the showers with gusty winds. After 23Z, only VCSH are expected for all the eastern sites. Winds are expected to bcm light at VRB again after 11/03Z. Another round of SHRA/TSRA is forecast for 11/18Z for all the TAF sites. && .MARINE... A surface high pressure across the central Atlantic and a building low in the western Atlantic with allow easterly wind tonight then southeasterly wind through the weekend. Weak pulses of northeasterly swell will begin to fade Atlantic waters and Caribbean Passages over the next few days. Strong showers and thunderstorms over the waters can result in locally higher seas and gusty winds. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ DSR/MMC/RC
