197
FXUS62 KKEY 210842
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
442 AM EDT TUE JUL 21 2026
..NEW DISCUSSION, MARINE, AVIATION
KEY MESSAGES
- TROPICAL STORM BERTHA IS LOCATED ACROSS THE NORTHEASTERN GULF,
AND THE NATIONAL HURRICANE CENTER CONTINUES TO ISSUE ADVISORIES.
THIS SYSTEM POSES NO THREAT TO THE FLORIDA KEYS.
- HEAT INDICES MAY APPROACH 108 TO 110 DEGREES EACH AFTERNOON FOR
SOME FLORIDA KEYS ISLAND COMMUNITIES.
- SAHARAN AIR LAYER PLUMES WILL TRANSIT THE AREA THROUGH AT LEAST
MID WEEK, LIMITING RAIN AND THUNDER CHANCES.
DISCUSSION
ISSUED AT 442 AM EDT TUE JUL 21 2026
CIMSS PRODUCTS SHOWS TROPICAL STORM BERTHA CONTINUES TO SLOWLY
CHURN NORTHWESTWARD ACROSS THE NORTHEASTERN GULF WHILE TWO RIDGES
REMAIN IN PLAY ON EITHER SIDE OF IT. ALSO, BROAD TROUGHING REMAINS
IN PLACE ACROSS THE NORTHEAST AND THE MID-ATLANTIC. THIS IS
LEAVING BERTHA IN A VERY WEAK STEERING FLOW ENVIRONMENT. AT
THE SURFACE, THE WESTERN FLANK OF THE RIDGE OVER THE ATLANTIC
CONTINUES TO HOLD ON JUST ENOUGH TO INFLUENCE OUR WINDS. MARINE
OBSERVATION PLATFORMS SURROUNDING THE ISLAND CHAIN ARE RECORDING
SOUTHEAST TO SOUTH BREEZES OF 10 TO 15 KNOTS. KBYX RADAR HAS NOT
DETECTED ANY SHOWER ACTIVITY FOR THE LAST FEW HOURS. GOES 19
NIGHTTIME MICROPHYSICS IMAGERY SHOWS PARTLY CLOUDY SKIES
THROUGHOUT THE KEYS WITH SOME HIGH LEVEL CLOUDS ALONG WITH LOW
LEVEL CUMULUS. TEMPERATURES ALONG THE ISLAND CHAIN ARE IN THE MID
80S AND DEW POINTS ARE IN THE MID TO UPPER 70S.
FORECAST
TROPICAL STORM BERTHA WILL CONTINUE TO RUN THE HEADLINES FOR THE
NEXT FEW DAYS AS IT ONLY SLOWLY TRAVERSES ACROSS THE NORTH GULF
COAST. HOWEVER, THIS SYSTEM POSES NO RISK TO THE FLORIDA KEYS.
WITH THAT SAID, THE WESTERN PERIPHERY OF AN ATLANTIC RIDGE WILL
CONTINUE TO BE THE DOMINANT FEATURE FOR THE KEYS SENSIBLE WEATHER.
OVERALL, SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE
THROUGH MUCH OF THE WEEK AS MOISTURE UNDULATIONS MOVE THROUGH THE
REGION, EXCEPT FOR TODAY WHERE WE HAVE REMOVED RAIN CHANCES.
LATEST INDICATIONS ARE FOR DRY AIR TO REMAIN DOMINANT TODAY ALONG
WITH SOME RESIDUAL SAHARA DUST STILL OVER THE REGION. OUTSIDE OF
THE SLIGHT RAIN CHANCES, SEASONABLY TO SLIGHTLY ABOVE NORMAL
TEMPERATURES ARE EXPECTED TO CONTINUE THROUGH THE WEEK. DAYTIME
HIGHS WILL BE NEAR 90 DEGREES AND OVERNIGHT LOWS IN THE LOWER TO
MID 80S. DEW POINTS WILL CONTINUE TO BE TROPICAL AND STEAMY
RESULTING IN HEAT INDEX VALUES OF 105 TO 110 DEGREES. MAKE SURE TO
CONTINUE TO TAKE BREAKS AND STAY HYDRATED! PEAKING AND LULLING
GENTLE TO MODERATE SOUTHEAST TO SOUTH BREEZES ARE EXPECTED THROUGH
MID WEEK BEFORE SHIFTING MORE TO THE EAST TO SOUTHEAST FOR LATE
WEEK AND INTO THE WEEKEND. OCCASIONALLY, BREEZES MAY DECREASE TO
LIGHT TO GENTLE.
GUIDANCE CONTINUES TO SHOW SIGNS OF ANOTHER TROPICAL UPPER
TROPOSPHERIC TROUGH (TUTT) CELL MOVING SWIFTLY WESTWARD TO WEST-
SOUTHWESTWARD FOR MID TO LATE WEEK. IT CONTINUES TO LOOK LIKE IT
WILL CROSS THE BAHAMAS SOMETIME WEDNESDAY NIGHT AND THEN CUBA
AROUND THURSDAY BEFORE CONTINUING TO MOVE TOWARDS THE YUCATAN BY
THE WEEKEND. LATEST GUIDANCE HAS SHOWN A SLIGHT NUDGE NORTHWARD
WITH THIS TUTT, THEREFORE, WE HAVE INCREASED THE FORECAST TO
REPRESENT CHANCES OF SHOWERS AND THUNDERSTORMS FOR THURSDAY NIGHT
AND FRIDAY.
MARINE
ISSUED AT 442 AM EDT TUE JUL 21 2026
THERE ARE CURRENTLY NO WATCHES, WARNINGS, OR ADVISORIES ACROSS THE
FLORIDA KEYS COASTAL WATERS. FROM SYNOPSIS, AS OF 5 AM EDT,
TROPICAL STORM BERTHA WAS CENTERED OVER THE NORTHEASTERN GULF
WATERS. BERTHA IS EXPECTED TO CONTINUE MOVING SLOWLY TO THE
NORTHWEST OR WEST-NORTHWEST TODAY, FOLLOWED BY A TURN TO THE WEST
BY THE MIDDLE PART OF THE WEEK. ON THE FORECAST TRACK, TS BERTHA
WILL MOVE NEAR OR ALONG THE NORTHERN GULF COAST DURING THE NEXT
SEVERAL DAYS. CLOSER TO HOME, AN ATLANTIC RIDGE OF HIGH PRESSURE
WILL EXTEND TO THE FLORIDA PENINSULA FOR THE NEXT SEVERAL DAYS.
MODERATE BREEZES WILL SLACKEN TO MAINLY GENTLE THIS AFTERNOON.
THEREAFTER, BREEZES WILL CONTINUE TO PEAK OVERNIGHT AND LULL
DURING THE DAY THROUGH FRIDAY.
AVIATION
(06Z TAFS)
ISSUED AT 442 AM EDT TUE JUL 21 2026
VFR CONDITIONS ARE EXPECTED TO PERSIST AT BOTH EYW AND MTH
TERMINALS THROUGH THE TAF PERIOD. NEAR SURFACE WINDS ARE EXPECTED
TO REMAIN SOUTHEAST TO SOUTH THIS MORNING BEFORE SHIFTING TO EAST
TO SOUTHEAST THIS AFTERNOON AND EVENING. DRY WEATHER IS EXPECTED
TO PREVAIL THROUGHOUT MUCH OF THE KEYS TODAY.
CLIMATE
ON THIS DAY IN 2017, THE DAILY RECORD WARM LOW TEMPERATURE OF 85F
WAS RECORDED IN KEY WEST. TEMPERATURE RECORDS FOR KEY WEST DATE
BACK TO 1872.
ON THIS DAY IN 2023, THE DAILY RECORD WARM LOW TEMPERATURE OF 85F
WAS RECORDED IN MARATHON. TEMPERATURE RECORDS FOR MARATHON DATE
BACK TO 1951.
PRELIMINARY POINT TEMPS/POPS
KEY WEST 90 84 90 84 / 0 10 10 10
MARATHON 90 82 90 82 / 0 10 10 10
KEY WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GM...NONE.
PUBLIC/MARINE/FIRE...MJV
AVIATION/NOWCASTS....MJV
DATA ACQUISITION.....MJV
VISIT US ON THE WEB AT WEATHER.GOV/KEY
FOLLOW US ON FACEBOOK AND X AT:
WWW.FACEBOOK.COM/NWSKEYWEST
WWW.X.COM/NWSKEYWEST
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page