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Tropical Depression Seven Forecast Discussion Number 3

2021-08-14 04:59:57| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Fri Aug 13 2021 000 WTNT42 KNHC 140259 TCDAT2 Tropical Depression Seven Discussion Number 3 NWS National Hurricane Center Miami FL AL072021 1100 PM AST Fri Aug 13 2021 While Tropical Depression Seven has maintained a irregularly shaped cirrus canopy of deep cold cloud tops near its estimated center, the convection does not appear well organized. Several SSMIS microwave passes between 2011 UTC and 2205 UTC did not reveal much organization under the cirrus, with just a few patches of deeper convection contributing to the larger stratiform region. A helpful ASCAT-B pass at 0030 UTC showed that the center was near the southeastern end of this cirrus canopy, and found peak winds lower than earlier today at only 27 kt. The 0000 UTC subjective Dvorak estimates were T2.5/35 kt from SAB and T2.5/30 kt from TAFB and the most recent objective ADT estimate was in between at T2.2/32 kt. A blend of these data support keeping the initial intensity at 30-kt for this advisory. The small cyclone continues to move quickly off to the west at 280/18 kt. A large low- to mid-level ridge draped across the central and western North Atlantic is expected to maintain the system on a general west-northwest heading, though with gradual deceleration as the ridge is eroded some by a mid- to upper-tropospheric trough. The latest track guidance remains tightly clustered but a bit more poleward through the first 72 hours. Afterwards, more track guidance spread becomes apparent. A quick look at the latest ECMWF ensemble guidance suggest that some of this spread is driven by the forecast intensity of the system, with stronger members taking the cyclone on a more poleward track. For now, the latest NHC track forecast is fairly close to, but a little poleward of the previous track. This track remains close to the HCCA and TVCN consensus aids, and roughly splits the difference between the deterministic GFS and ECMWF model solutions. The intensity forecast is somewhat conflicting. Even though both the GFS & ECMWF based SHIPS guidance depict low 200-850 hPa vertical wind shear between 5-10 knots over the next 48 hours, the depression is also embedded in very dry mid-level air, with 700-500 hPa layer mean relative humidity as low as 44 percent currently in the ECMWF-SHIPS. In addition, the system is moving rapidly westward, and a continued fast motion in the short-term may result in higher westerly mid-level shear which may have a larger than normal effect to a small tropical cyclone in a very dry environment. After 48 hours, vertical wind shear out of the northwest is expected to increase, ahead of a large upper-level trough digging southwestward, upstream of the cyclone. Moreover, land interaction with both Puerto Rico and Hispaniola remains a distinct possibility, especially if the cyclone tracks left of the current forecast track. It is worth noting the latest HWRF run continues to be a extreme outlier with a much higher intensity than the remaining guidance. In fact, much of global model guidance and COAMPS-TC regional hurricane model barely maintains a closed circulation over the next 36-48 hours. I have elected to maintain a very similar forecast to the previous advisory, with peak winds of only 45 kt in 48-60 hours. This forecast remains conservative and is still lower than the SHIPS and HCCA intensity guidance. Key Messages: 1. Tropical storm conditions are expected in portions of the Leeward Islands late Saturday or early Sunday, and are possible over the Virgin Islands and Puerto Rico on Sunday. The risk of strong winds will then spread westward to the Dominican Republic Sunday night and Monday. 2. Heavy rainfall could lead to flash and urban flooding over the Leeward and Virgin Islands. Across Puerto Rico, heavy rainfall may lead to flash, urban and small stream flooding, along with the potential for mudslides. 3. There is a risk of wind and rainfall impacts across Haiti, 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 14/0300Z 15.5N 53.8W 30 KT 35 MPH 12H 14/1200Z 16.0N 56.8W 35 KT 40 MPH 24H 15/0000Z 16.7N 60.3W 35 KT 40 MPH 36H 15/1200Z 17.5N 63.5W 40 KT 45 MPH 48H 16/0000Z 18.3N 66.2W 45 KT 50 MPH...INLAND 60H 16/1200Z 18.9N 68.2W 45 KT 50 MPH...OVER WATER 72H 17/0000Z 19.6N 70.4W 35 KT 40 MPH...INLAND 96H 18/0000Z 21.7N 74.3W 40 KT 45 MPH...OVER WATER 120H 19/0000Z 24.3N 78.6W 40 KT 45 MPH $$ Forecaster Papin/Brown

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Tropical Depression Fred Graphics

2021-08-14 04:52:40| National Hurricane Center (Atlantic)

5-Day Uncertainty Track last updated Sat, 14 Aug 2021 02:52:40 GMT Wind Speed Probabilities last updated Sat, 14 Aug 2021 02:52:40 GMT

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Tropical Depression Fred Forecast Discussion Number 18

2021-08-14 04:51:25| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Fri Aug 13 2021 239 WTNT41 KNHC 140251 TCDAT1 Tropical Depression Fred Discussion Number 18 NWS National Hurricane Center Miami FL AL062021 1100 PM EDT Fri Aug 13 2021 Interaction with land and southwesterly shear has continued to take a toll on Fred this evening. It is very difficult to determine in infrared satellite imagery and recent surface observations from Cuba if a closed circulation still exists, however the system is maintained as a tropical depression for now. Scatterometer data, which should arrive very soon, and reconnaissance aircraft observations on Saturday morning should provide additional information on the system's intensity and structure. The system still appears to be moving moving westward or 280/11 kt. There has been no change to the track forecast reasoning from the previous advisory. The cyclone is approaching the western periphery of a subtropical ridge extending over the western Atlantic, and Fred should turn west-northwestward overnight, and then northwestward on Saturday. The track guidance has again shifted westward, but the shift is not as large as was noted on the previous cycle. The NHC track forecast has been adjusted to the left, closer to the consensus aids, but it still remains to the east of those models. Some additional westward adjustments in subsequent forecasts may be required. As mentioned above, land interaction and southwesterly vertical will limit any attempt of re-organization overnight, however the system is expected to move off the northern coast of Cuba Saturday morning and the global model guidance suggests that a center re-formation could occur over the western portion of the Straits of Florida. The center re-formation shown by the guidance appears to be aided by an area of upper-level diffluent flow to the southeast of an upper-level trough currently located over the eastern Gulf of Mexico. Although only a little strengthening is indicated in the official forecast through 36 hours, the environment could become a little more conducive on Sunday, and the NHC wind speed forecast again calls for gradual strengthening while Fred moves northwestward over the eastern Gulf. The updated intensity forecast is unchanged from the previous advisory and is a blend of the statistical guidance and the HCCA model. The intensity forecast continues to be of lower-than-normal confidence given the current disorganized structure of the system. KEY MESSAGES: 1. Tonight through Monday, heavy rainfall could lead to areal, urban, and small stream flooding impacts, and cause new and renewed 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 the area. 2. Tropical storm conditions are expected in portions of the Lower Florida Keys on Saturday, where a Tropical Storm Warning is in effect. 3. There is a risk of tropical storm conditions in the Florida Panhandle beginning on Monday. Watches may be required for a portion of this area on Saturday. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 22.7N 80.6W 30 KT 35 MPH 12H 14/1200Z 23.4N 81.9W 30 KT 35 MPH...OVER WATER 24H 15/0000Z 24.8N 83.6W 35 KT 40 MPH 36H 15/1200Z 26.3N 85.0W 35 KT 40 MPH 48H 16/0000Z 27.8N 86.0W 40 KT 45 MPH 60H 16/1200Z 29.2N 86.6W 45 KT 50 MPH 72H 17/0000Z 30.6N 86.8W 50 KT 60 MPH...INLAND 96H 18/0000Z 34.0N 86.5W 25 KT 30 MPH...INLAND 120H 19/0000Z 37.5N 84.0W 20 KT 25 MPH...POST-TROP/INLAND $$ Forecaster Brown

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Tropical Depression Seven Wind Speed Probabilities Number 3

2021-08-14 04:50:25| National Hurricane Center (Atlantic)

Issued at 0300 UTC SAT AUG 14 2021 000 FONT12 KNHC 140250 PWSAT2 TROPICAL DEPRESSION SEVEN WIND SPEED PROBABILITIES NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072021 0300 UTC SAT AUG 14 2021 AT 0300Z THE CENTER OF TROPICAL DEPRESSION SEVEN WAS LOCATED NEAR LATITUDE 15.5 NORTH...LONGITUDE 53.8 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 00Z SAT 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 00Z SAT 12Z SAT 00Z SUN 12Z SUN 00Z MON 00Z TUE 00Z WED PERIODS TO TO TO TO TO TO TO 12Z SAT 00Z SUN 12Z SUN 00Z MON 00Z TUE 00Z WED 00Z THU FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT FT PIERCE FL 34 X X( X) X( X) X( X) X( X) X( X) 4( 4) W PALM BEACH 34 X X( X) X( X) X( X) X( X) X( X) 6( 6) FT LAUDERDALE 34 X X( X) X( X) X( X) X( X) X( X) 7( 7) MIAMI FL 34 X X( X) X( X) X( X) X( X) X( X) 4( 4) HOMESTEAD ARB 34 X X( X) X( X) X( X) X( X) X( X) 4( 4) MARATHON FL 34 X X( X) X( X) X( X) X( X) X( X) 6( 6) KEY WEST FL 34 X X( X) X( X) X( X) X( X) X( X) 5( 5) NAPLES FL 34 X X( X) X( X) X( X) X( X) X( X) 5( 5) VENICE 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) 7( 7) NEW PROVIDENCE 34 X X( X) X( X) X( X) X( X) 2( 2) 9(11) ANDROS 34 X X( X) X( X) X( X) X( X) 2( 2) 12(14) ANDROS 50 X X( X) X( X) X( X) X( X) X( X) 3( 3) GREAT EXUMA 34 X X( X) X( X) X( X) X( X) 6( 6) 8(14) SAN SALVADOR 34 X X( X) X( X) X( X) X( X) 5( 5) 5(10) MAYAGUANA 34 X X( X) X( X) X( X) 3( 3) 9(12) 1(13) GRAND TURK 34 X X( X) X( X) X( X) 10(10) 6(16) 1(17) GRAND TURK 50 X X( X) X( X) X( X) 2( 2) 1( 3) X( 3) CAMAGUEY 34 X X( X) X( X) X( X) X( X) X( X) 3( 3) GUANTANAMO BAY 34 X X( X) X( X) X( X) X( X) 2( 2) 2( 4) PORT-AU-PRINCE 34 X X( X) X( X) X( X) 4( 4) 3( 7) X( 7) CAPE BEATA 34 X X( X) X( X) X( X) 4( 4) 1( 5) X( 5) PUERTO PLATA 34 X X( X) X( X) 1( 1) 14(15) 4(19) X(19) PUERTO PLATA 50 X X( X) X( X) X( X) 2( 2) 1( 3) X( 3) SANTO DOMINGO 34 X X( X) X( X) 1( 1) 8( 9) 1(10) X(10) PONCE PR 34 X X( X) X( X) 11(11) 5(16) X(16) X(16) PONCE PR 50 X X( X) X( X) 2( 2) 1( 3) X( 3) X( 3) AGUADILLA PR 34 X X( X) 1( 1) 16(17) 13(30) X(30) X(30) AGUADILLA PR 50 X X( X) X( X) 2( 2) 4( 6) X( 6) X( 6) AGUADILLA PR 64 X X( X) X( X) 1( 1) X( 1) X( 1) X( 1) SAN JUAN PR 34 X X( X) X( X) 16(16) 5(21) X(21) X(21) SAN JUAN PR 50 X X( X) X( X) 3( 3) X( 3) X( 3) X( 3) SAN JUAN PR 64 X X( X) X( X) 1( 1) X( 1) X( 1) X( 1) VIEQUES PR 34 X X( X) 4( 4) 27(31) 2(33) 1(34) X(34) VIEQUES PR 50 X X( X) X( X) 6( 6) 1( 7) X( 7) X( 7) VIEQUES PR 64 X X( X) X( X) 1( 1) X( 1) X( 1) X( 1) SAINT THOMAS 34 X X( X) 9( 9) 25(34) 2(36) X(36) X(36) SAINT THOMAS 50 X X( X) 1( 1) 5( 6) X( 6) X( 6) X( 6) SAINT CROIX 34 X X( X) 10(10) 20(30) 1(31) X(31) X(31) SAINT CROIX 50 X X( X) 1( 1) 5( 6) 1( 7) X( 7) X( 7) SAINT MAARTEN 34 X X( X) 28(28) 4(32) X(32) X(32) X(32) SAINT MAARTEN 50 X X( X) 3( 3) 1( 4) X( 4) X( 4) X( 4) SABA 34 X X( X) 33(33) 3(36) 1(37) X(37) X(37) SABA 50 X X( X) 5( 5) 1( 6) X( 6) X( 6) X( 6) SABA 64 X X( X) 1( 1) X( 1) X( 1) X( 1) X( 1) ST EUSTATIUS 34 X 1( 1) 32(33) 2(35) X(35) X(35) X(35) ST EUSTATIUS 50 X X( X) 5( 5) X( 5) X( 5) X( 5) X( 5) ST KITTS-NEVIS 34 X 1( 1) 30(31) 1(32) X(32) X(32) X(32) ST KITTS-NEVIS 50 X X( X) 4( 4) 1( 5) X( 5) X( 5) X( 5) BARBUDA 34 X 4( 4) 29(33) X(33) X(33) X(33) X(33) BARBUDA 50 X X( X) 4( 4) X( 4) X( 4) X( 4) X( 4) ANTIGUA 34 X 4( 4) 27(31) X(31) X(31) X(31) X(31) ANTIGUA 50 X X( X) 4( 4) X( 4) X( 4) X( 4) X( 4) GUADELOUPE 34 X 3( 3) 11(14) X(14) X(14) X(14) X(14) AVES 34 X X( X) 2( 2) 1( 3) X( 3) X( 3) X( 3) $$ FORECASTER PAPIN/BROWN

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Summary for Tropical Depression Fred (AT1/AL062021)

2021-08-14 04:49:56| National Hurricane Center (Atlantic)

...HEAVY RAINFALL FROM FRED CONTINUES OVER PORTIONS OF CENTRAL CUBA... As of 11:00 PM EDT Fri Aug 13 the center of Fred was located near 22.7, -80.6 with movement W at 12 mph. The minimum central pressure was 1013 mb with maximum sustained winds of about 35 mph.

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