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Potential Tropical Cyclone Seven Forecast Discussion Number 1
2021-08-13 17:02:17| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Fri Aug 13 2021 000 WTNT42 KNHC 131502 TCDAT2 Potential Tropical Cyclone Seven Discussion Number 1 NWS National Hurricane Center Miami FL AL072021 1100 AM AST Fri Aug 13 2021 A tropical wave and small area of low pressure moving quickly westward across the central tropical Atlantic has been producing bursts of deep convection near and to the west of the wave axis. Scatterometer data from last evening indicated that the system did not quite have a closed circulation, but it is close. In addition, the convective organization has increased a bit since yesterday, with TAFB and SAB providing Dvorak classification of T1.5 and T2.0. Therefore, only an additional slight increase in convective organization and the low-level circulation closing off would make the system a tropical depression, and it could be at tropical storm strength when it approaches the Leeward Islands during the next couple of days. Therefore, advisories are being initiated on the system in order to issue Tropical Storm Watches for portions of the Leeward Islands at this time. Subtropical ridging extending across nearly the entire Atlantic is pushing the low along quickly toward the west, or 280/18 kt. In general this ridging is expected to persist into the middle part of next week. However, around the Sunday-Monday time frame, some mid-level troughing over the western Atlantic could allow the system to gain a little more latitude before it runs into additional ridging located near the east coast of the United States at the end of the forecast period. The GFS, which has perhaps one of the strongest solutions, is a northern outlier and shows the system turning farther into the weak troughing, while the ECMWF has a weaker solution and keeps the system on a westward track across the Lesser and Greater Antilles. At this time, the NHC official forecast lies close to the TVCN and HCCA consensus aids, and it is also relatively close to the ECMWF ensemble mean, which is farther north than its parent model. The biggest negative to the system becoming a tropical cyclone and strengthening is its fast motion of 15-20 kt. However, that motion is expected to gradually decrease in 2 to 3 days. At that same time, deep-layer shear has decreased a bit, and the system will be moving over warmer waters and toward a slightly more moist environment. Therefore, gradual strengthening is anticipated, and the NHC intensity forecast closely follows the HCCA and IVCN consensus aids through 72 hours, up until the system is near Hispaniola. After that time, land interaction is likely to disrupt the circulation, and the official forecast is below the model consensus aids on days 4 and 5. Key Messages: 1. Tropical storm conditions are possible in portions of the Leeward Islands late Saturday or early Sunday, and the risk of tropical storm conditions will spread westward to the Virgin Islands and Puerto Rico late Sunday and Sunday night. 2. Heavy rainfall with this system may produce areas of scattered flash flooding over the northern Leeward Islands Saturday into Sunday. 3. There is a risk of wind and rainfall impacts in portions of Hispaniola, the Turks and Caicos Islands, the southeastern Bahamas, and Cuba next week, and interests in those areas should monitor the progress of this system. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 15.3N 49.3W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 14/0000Z 15.7N 52.0W 30 KT 35 MPH...TROPICAL DEPRESSION 24H 14/1200Z 16.2N 55.9W 35 KT 40 MPH 36H 15/0000Z 16.7N 59.6W 35 KT 40 MPH 48H 15/1200Z 17.2N 63.0W 40 KT 45 MPH 60H 16/0000Z 17.8N 66.0W 40 KT 45 MPH 72H 16/1200Z 18.4N 68.7W 45 KT 50 MPH...OVER HISPANIOLA 96H 17/1200Z 20.0N 73.5W 35 KT 40 MPH...OVER WATER 120H 18/1200Z 23.0N 77.0W 40 KT 45 MPH $$ Forecaster Berg
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Tropical Depression Fred Graphics
2021-08-13 17:01:06| National Hurricane Center (Atlantic)
5-Day Uncertainty Track last updated Fri, 13 Aug 2021 15:01:06 GMT Wind Speed Probabilities last updated Fri, 13 Aug 2021 15:22:58 GMT
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Potential Tropical Cyclone Seven Graphics
2021-08-13 16:56:44| National Hurricane Center (Atlantic)
5-Day Uncertainty Track last updated Fri, 13 Aug 2021 14:56:44 GMT Wind Speed Probabilities last updated Fri, 13 Aug 2021 15:29:05 GMT
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Potential Tropical Cyclone Seven Wind Speed Probabilities Number 1
2021-08-13 16:55:48| National Hurricane Center (Atlantic)
Issued at 1500 UTC FRI AUG 13 2021 000 FONT12 KNHC 131455 PWSAT2 POTENTIAL TROPICAL CYCLONE SEVEN WIND SPEED PROBABILITIES NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072021 1500 UTC FRI AUG 13 2021 AT 1500Z THE CENTER OF POTENTIAL TROPICAL CYCLONE SEVEN WAS LOCATED NEAR LATITUDE 15.3 NORTH...LONGITUDE 49.3 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 30 KTS...35 MPH...55 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) ATLANTIC STANDARD TIME (AST)...SUBTRACT 4 HOURS FROM Z TIME EASTERN DAYLIGHT TIME (EDT)...SUBTRACT 4 HOURS FROM Z TIME CENTRAL DAYLIGHT TIME (CDT)...SUBTRACT 5 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 12Z FRI AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 12Z FRI 00Z SAT 12Z SAT 00Z SUN 12Z SUN 12Z MON 12Z TUE PERIODS TO TO TO TO TO TO TO 00Z SAT 12Z SAT 00Z SUN 12Z SUN 12Z MON 12Z TUE 12Z WED FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT FT LAUDERDALE 34 X X( X) X( X) X( X) X( X) X( X) 3( 3) MARATHON FL 34 X X( X) X( X) X( X) X( X) X( X) 3( 3) GRAND BAHAMA 34 X X( X) X( X) X( X) X( X) X( X) 3( 3) NEW PROVIDENCE 34 X X( X) X( X) X( X) X( X) X( X) 7( 7) ANDROS 34 X X( X) X( X) X( X) X( X) X( X) 9( 9) GREAT EXUMA 34 X X( X) X( X) X( X) X( X) 1( 1) 7( 8) SAN SALVADOR 34 X X( X) X( X) X( X) X( X) 1( 1) 4( 5) MAYAGUANA 34 X X( X) X( X) X( X) X( X) 4( 4) 3( 7) GRAND TURK 34 X X( X) X( X) X( X) 2( 2) 4( 6) 1( 7) CAMAGUEY 34 X X( X) X( X) X( X) X( X) 1( 1) 3( 4) GUANTANAMO BAY 34 X X( X) X( X) X( X) X( X) 2( 2) 3( 5) LES CAYES 34 X X( X) X( X) X( X) X( X) 3( 3) 1( 4) PORT-AU-PRINCE 34 X X( X) X( X) X( X) 2( 2) 8(10) 2(12) CAPE BEATA 34 X X( X) X( X) X( X) 2( 2) 7( 9) 1(10) PUERTO PLATA 34 X X( X) X( X) X( X) 6( 6) 7(13) 1(14) SANTO DOMINGO 34 X X( X) X( X) X( X) 7( 7) 4(11) 1(12) PONCE PR 34 X X( X) X( X) X( X) 11(11) X(11) X(11) AGUADILLA PR 34 X X( X) X( X) 1( 1) 18(19) 1(20) X(20) AGUADILLA PR 50 X X( X) X( X) X( X) 3( 3) X( 3) X( 3) SAN JUAN PR 34 X X( X) X( X) X( X) 11(11) 1(12) X(12) VIEQUES PR 34 X X( X) X( X) 3( 3) 19(22) 1(23) X(23) VIEQUES PR 50 X X( X) X( X) 1( 1) 3( 4) X( 4) X( 4) VIEQUES PR 64 X X( X) X( X) X( X) 1( 1) X( 1) X( 1) SAINT THOMAS 34 X X( X) X( X) 5( 5) 18(23) X(23) X(23) SAINT THOMAS 50 X X( X) X( X) 1( 1) 3( 4) X( 4) X( 4) SAINT CROIX 34 X X( X) X( X) 7( 7) 17(24) X(24) X(24) SAINT CROIX 50 X X( X) X( X) 1( 1) 5( 6) X( 6) X( 6) SAINT CROIX 64 X X( X) X( X) X( X) 1( 1) X( 1) X( 1) SAINT MAARTEN 34 X X( X) 1( 1) 19(20) 6(26) X(26) X(26) SAINT MAARTEN 50 X X( X) X( X) 3( 3) 1( 4) X( 4) X( 4) SABA 34 X X( X) 1( 1) 20(21) 6(27) X(27) X(27) SABA 50 X X( X) X( X) 3( 3) 1( 4) X( 4) X( 4) ST EUSTATIUS 34 X X( X) 1( 1) 22(23) 5(28) X(28) X(28) ST EUSTATIUS 50 X X( X) X( X) 4( 4) X( 4) X( 4) X( 4) ST KITTS-NEVIS 34 X X( X) 1( 1) 22(23) 3(26) X(26) X(26) ST KITTS-NEVIS 50 X X( X) X( X) 4( 4) 1( 5) X( 5) X( 5) ST KITTS-NEVIS 64 X X( X) X( X) 1( 1) X( 1) X( 1) X( 1) BARBUDA 34 X X( X) 2( 2) 24(26) 1(27) X(27) X(27) BARBUDA 50 X X( X) X( X) 3( 3) X( 3) X( 3) X( 3) ANTIGUA 34 X X( X) 2( 2) 23(25) 1(26) X(26) X(26) ANTIGUA 50 X X( X) X( X) 4( 4) X( 4) X( 4) X( 4) GUADELOUPE 34 X X( X) 2( 2) 12(14) 1(15) X(15) X(15) AVES 34 X X( X) X( X) 3( 3) 3( 6) X( 6) X( 6) DOMINICA 34 X X( X) X( X) 3( 3) X( 3) X( 3) X( 3) $$ FORECASTER BERG
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Tropical Depression Fred Forecast Discussion Number 16
2021-08-13 16:51:17| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Fri Aug 13 2021 000 WTNT41 KNHC 131451 TCDAT1 Tropical Depression Fred Discussion Number 16 NWS National Hurricane Center Miami FL AL062021 1100 AM EDT Fri Aug 13 2021 Fred remains disorganized this morning. The low-level center, which is currently over the barrier islands of the north coast of Cuba, is exposed to the northwest of the main convective mass due to moderate southwesterly vertical shear. Reports from Air Force Reserve and NOAA Hurricane hunter aircraft show winds of 25-30 kt to the northeast of the center, so the initial intensity remains 30 kt. The central pressure is 1013 mb based on a combination of aircraft data and surface observations. The center has jogged a bit to the left during the past several hours, which has brought it to the Cuban coast. The longer-term initial motion is 295/10. The cyclone should continue west-northwestward for the next 12-24 h, followed by a turn toward the northwest as Fred approaches the western periphery of the subtropical ridge. This motion should take the center along the northern coast of Cuba today, near the Florida Keys and the southwestern coast of Florida on Saturday, and near or over the coast of the Florida Panhandle Sunday night or Monday. After that, a northward turn is expected as Fred moves into a weakness in the ridge over the southeastern United States. With both the initial position and the track guidance shifting westward since the last advisory, the new forecast track is also nudged a little to the west. The new track is east of the consensus models, especially from 24-60 h, and thus some additional adjustments could occur later today if the current model trends continue. Fred is continuing to experience about 20 kt of westerly or southwesterly vertical wind shear, and these conditions should continue for at least another 24 hours. Between that and land interaction, the intensity forecast calls for only modest strengthening during this time. After that, there is still relatively poor agreement on how much shear Fred will experience as it crosses the eastern Gulf of Mexico, with the ECMWF and the UKMET forecasting less shear than the GFS and CMC global models. Due to the uncertainty, the intensity forecast will keep the previous peak intensity of 45 kt. However, the intensity guidance during this period has trended a little higher, and the 45 kt peak is now a little below the upper edge of the guidance. It should be noted that much of the Florida peninsula is expected to be on the east side of Fred, which is where the heaviest rains, strongest winds, and a chance of tornadoes will be. KEY MESSAGES: 1. Today through Monday, heavy rainfall could lead to areal, urban, small stream, and exacerbated river flooding across southern and central Florida into the Big Bend. From Sunday onward, heavy rain and flood impacts could extend into other portions of the Southeast and into the southern and central Appalachians and Piedmont as Fred interacts with a front in that area. 2. Tropical storm conditions are expected in portions of the Florida Keys on Saturday, where a Tropical Storm Warning is in effect. 3. Tropical storm conditions are possible late Saturday and early Sunday across portions of the west coast of Florida in the Tropical Storm Watch area. The risk of tropical storm conditions will spread northward along the Florida west coast and to the Florida Panhandle Sunday and Monday. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 22.3N 78.4W 30 KT 35 MPH...NEAR COAST OF CUBA 12H 14/0000Z 23.0N 79.7W 30 KT 35 MPH 24H 14/1200Z 24.2N 81.3W 35 KT 40 MPH 36H 15/0000Z 25.6N 82.5W 35 KT 40 MPH 48H 15/1200Z 27.2N 83.6W 40 KT 45 MPH 60H 16/0000Z 28.7N 84.6W 45 KT 50 MPH 72H 16/1200Z 30.2N 85.4W 35 KT 40 MPH...INLAND 96H 17/1200Z 33.0N 86.5W 25 KT 30 MPH...INLAND 120H 18/1200Z 36.5N 86.5W 20 KT 25 MPH...POST-TROP/INLAND $$ Forecaster Beven
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