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Tropical Storm Sally Forecast Discussion Number 8

2020-09-13 16:57:34| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Sun Sep 13 2020 133 WTNT44 KNHC 131457 TCDAT4 Tropical Storm Sally Discussion Number 8 NWS National Hurricane Center Miami FL AL192020 1100 AM EDT Sun Sep 13 2020 Although the center of Sally remains near the northwestern edge of the deep convection, there is a large area of convection and some banding evident over the southeastern portion of the circulation. An Air Force Reserve Hurricane Hunter aircraft investigating the storm this morning reported a peak 850-mb flight-level wind of 62 kt, and believable SFMR winds of around 50 kt, and these data are the basis for the 50-kt initial wind speed. The plane reported minimum pressures in the 996-998 mb range, with the higher value being the most recent information available. Northwesterly shear continues over the cyclone, but this shear is expected to decrease later today and tonight as Sally moves beneath a narrow upper-level ridge axis. This more conducive upper-level pattern is expected to allow the tropical storm to strengthen while it moves over the north-central Gulf of Mexico tonight and Monday. Most of the intensity guidance calls for Sally to become a hurricane in about 24 hours and so does the official forecast. Additional strengthening is expected after that time and Sally could be slightly stronger at landfall than indicated below since it is forecast to reach the coast between the 36 h forecast point and 48 h when it is inland over southeast Louisiana. The NHC intensity forecast is close to the consensus aids through 24 hours and at or just above the SHIPS, LGEM and HFIP corrected consensus aids at 36 and 48 hours. Sally is moving west-northwestward at about 10 kt. The tropical storm should continue on that general heading and speed over the next 12 to 24 hours as it steered around the southern flank of a mid-level ridge. After 24 hours, Sally is expected to be near the western portion of the ridge which should cause the storm to slow down and turn northwestward. The global models have trended toward slightly more ridging over the northern Gulf during the next 24 hours, and the track guidance has edged westward. The NHC track has been adjusted slightly westward and lies near the lastest run of the GFS, but is not as far west as the ECMWF and the various consensus aids. As Sally rounds the ridge in 48 to 72 h, the steering flow is expected to be quite weak, and a slow northward motion is forecast at that time. Afterward, a north-northeastward to northeastward motion should commence as the cyclone moves in that direction ahead of a short-wave trough. Users are reminded to not focus on the exact details of the track or intensity forecasts, as the average NHC track error at 36-48 h is 60-80 miles and the average intensity error is 10-15 mph. In addition, wind, storm surge, and rainfall hazards will extend far from the center. Unfortunately, confidence is increasing that Sally's expected slow forward speed near the Gulf Coast will exacerbate the storm surge and heavy rainfall threats. KEY MESSAGES: 1. An extremely dangerous and life-threatening storm surge is now expected, and a Storm Surge Warning is in effect for areas outside the southeastern Louisiana Hurricane and Storm Damage Risk Reduction System from Port Fourchon, Louisiana to the Mississippi/Alabama border. Residents in these areas should follow any advice given by local officials. 2. Hurricane conditions are expected by late Monday from Grand Isle, Louisiana to Ocean Springs, Mississippi, including Metropolitan New Orleans, with tropical storm conditions likely by Monday. Preparations should be rushed to completion in those areas. 3. Sally is expected to produce flash flooding across southwest and central Florida and prolong existing minor river flooding across west-central Florida through Monday. Widespread significant flash flooding and minor to isolated major river flooding is likely across portions of the central Gulf Coast Monday through the middle of the week, with flooding impacts spreading farther into the Southeast in the middle to late parts of the week. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 27.5N 84.9W 50 KT 60 MPH 12H 14/0000Z 28.0N 86.6W 55 KT 65 MPH 24H 14/1200Z 28.5N 88.2W 65 KT 75 MPH 36H 15/0000Z 28.9N 89.4W 80 KT 90 MPH 48H 15/1200Z 29.7N 90.2W 65 KT 75 MPH...INLAND 60H 16/0000Z 30.3N 90.5W 50 KT 60 MPH...INLAND 72H 16/1200Z 31.5N 90.3W 35 KT 40 MPH...INLAND 96H 17/1200Z 33.6N 88.3W 25 KT 30 MPH...INLAND 120H 18/1200Z 34.8N 83.8W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Summary for Tropical Storm Sally (AT4/AL192020)

2020-09-13 16:57:05| National Hurricane Center (Atlantic)

...SALLY EXPECTED TO STRENGTHEN TONIGHT AND MONDAY... ...LIFE-THREATENING STORM SURGE, HURRICANE-FORCE WINDS AND HEAVY RAINFALL EXPECTED ALONG PORTIONS OF THE NORTHERN GULF COAST STARTING ON MONDAY... As of 11:00 AM EDT Sun Sep 13 the center of Sally was located near 27.5, -84.9 with movement WNW at 12 mph. The minimum central pressure was 998 mb with maximum sustained winds of about 60 mph.

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Tropical Storm Sally Forecast Advisory Number 8

2020-09-13 16:56:41| National Hurricane Center (Atlantic)

Issued at 1500 UTC SUN SEP 13 2020 000 WTNT24 KNHC 131456 TCMAT4 TROPICAL STORM SALLY FORECAST/ADVISORY NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL192020 1500 UTC SUN SEP 13 2020 CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY... THE HURRICANE WARNING ALONG THE COAST OF LOUISIANA HAS BEEN EXTENDED WESTWARD TO MORGAN CITY. A TROPICAL STORM WARNING HAS BEEN ISSUED FOR THE COAST OF LOUISIANA FROM WEST OF MORGAN CITY TO INTRACOASTAL CITY. SUMMARY OF WATCHES AND WARNINGS IN EFFECT... A STORM SURGE WARNING IS IN EFFECT FOR... * PORT FOURCHON LOUISIANA TO THE MISSISSIPPI/ALABAMA BORDER * LAKE PONTCHARTRAIN...LAKE MAUREPAS...AND LAKE BORGNE A HURRICANE WARNING IS IN EFFECT FOR... * MORGAN CITY LOUISIANA TO OCEAN SPRINGS MISSISSIPPI * LAKE PONTCHARTRAIN AND LAKE MAUREPAS INCLUDING METROPOLITAN NEW ORLEANS A STORM SURGE WATCH IS IN EFFECT FOR... * MISSISSIPPI/ALABAMA BORDER TO THE ALABAMA/FLORIDA BORDER A HURRICANE WATCH IS IN EFFECT FOR... * EAST OF OCEAN SPRINGS TO THE ALABAMA/FLORIDA BORDER A TROPICAL STORM WARNING IS IN EFFECT FOR... * EAST OF OCEAN SPRINGS TO INDIAN PASS * INTRACOASTAL CITY LOUISIANA TO WEST OF MORGAN CITY A TROPICAL STORM WATCH IS IN EFFECT FOR... * INDIAN PASS TO OCHLOCKONEE RIVER FLORIDA A STORM SURGE WARNING MEANS THERE IS A DANGER OF LIFE-THREATENING INUNDATION...FROM RISING WATER MOVING INLAND FROM THE COASTLINE...DURING THE NEXT 36 HOURS IN THE INDICATED LOCATIONS. FOR A DEPICTION OF AREAS AT RISK...PLEASE SEE THE NATIONAL WEATHER SERVICE STORM SURGE WATCH/WARNING GRAPHIC...AVAILABLE AT HURRICANES.GOV. THIS IS A LIFE-THREATENING SITUATION. PERSONS LOCATED WITHIN THESE AREAS SHOULD TAKE ALL NECESSARY ACTIONS TO PROTECT LIFE AND PROPERTY FROM RISING WATER AND THE POTENTIAL FOR OTHER DANGEROUS CONDITIONS. PROMPTLY FOLLOW EVACUATION AND OTHER INSTRUCTIONS FROM LOCAL OFFICIALS. A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA. A WARNING IS TYPICALLY ISSUED 36 HOURS BEFORE THE ANTICIPATED FIRST OCCURRENCE OF TROPICAL-STORM-FORCE WINDS...CONDITIONS THAT MAKE OUTSIDE PREPARATIONS DIFFICULT OR DANGEROUS. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION. A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS. A STORM SURGE WATCH MEANS THERE IS A POSSIBILITY OF LIFE- THREATENING INUNDATION...FROM RISING WATER MOVING INLAND FROM THE COASTLINE...IN THE INDICATED LOCATIONS DURING THE NEXT 48 HOURS. FOR A DEPICTION OF AREAS AT RISK...PLEASE SEE THE NATIONAL WEATHER SERVICE STORM SURGE WATCH/WARNING GRAPHIC...AVAILABLE AT HURRICANES.GOV. A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA. A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE WITHIN 12 TO 24 HOURS. TROPICAL STORM CENTER LOCATED NEAR 27.5N 84.9W AT 13/1500Z POSITION ACCURATE WITHIN 25 NM PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 10 KT ESTIMATED MINIMUM CENTRAL PRESSURE 998 MB MAX SUSTAINED WINDS 50 KT WITH GUSTS TO 60 KT. 50 KT....... 30NE 30SE 0SW 0NW. 34 KT....... 60NE 80SE 0SW 20NW. 12 FT SEAS.. 30NE 30SE 0SW 30NW. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 27.5N 84.9W AT 13/1500Z AT 13/1200Z CENTER WAS LOCATED NEAR 27.3N 84.6W FORECAST VALID 14/0000Z 28.0N 86.6W MAX WIND 55 KT...GUSTS 65 KT. 50 KT... 30NE 30SE 0SW 0NW. 34 KT... 90NE 80SE 0SW 40NW. FORECAST VALID 14/1200Z 28.5N 88.2W MAX WIND 65 KT...GUSTS 80 KT. 64 KT... 20NE 0SE 0SW 0NW. 50 KT... 40NE 20SE 0SW 20NW. 34 KT... 90NE 80SE 20SW 70NW. FORECAST VALID 15/0000Z 28.9N 89.4W MAX WIND 80 KT...GUSTS 100 KT. 64 KT... 20NE 10SE 10SW 15NW. 50 KT... 40NE 20SE 20SW 30NW. 34 KT...100NE 80SE 50SW 70NW. FORECAST VALID 15/1200Z 29.7N 90.2W...INLAND MAX WIND 65 KT...GUSTS 80 KT. 64 KT... 20NE 10SE 0SW 10NW. 50 KT... 40NE 30SE 20SW 30NW. 34 KT...100NE 80SE 50SW 60NW. FORECAST VALID 16/0000Z 30.3N 90.5W...INLAND MAX WIND 50 KT...GUSTS 60 KT. 50 KT... 20NE 20SE 0SW 0NW. 34 KT... 60NE 90SE 20SW 40NW. FORECAST VALID 16/1200Z 31.5N 90.3W...INLAND MAX WIND 35 KT...GUSTS 45 KT. 34 KT... 30NE 60SE 20SW 20NW. EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 150 NM ON DAY 4 AND 175 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY OUTLOOK VALID 17/1200Z 33.6N 88.3W...INLAND MAX WIND 25 KT...GUSTS 35 KT. OUTLOOK VALID 18/1200Z 34.8N 83.8W...POST-TROP/REMNT LOW MAX WIND 20 KT...GUSTS 30 KT. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 27.5N 84.9W INTERMEDIATE PUBLIC ADVISORY...WTNT34 KNHC/MIATCPAT4...AT 13/1800Z NEXT ADVISORY AT 13/2100Z $$ FORECASTER BROWN

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Tropical Storm Karina Graphics

2020-09-13 16:55:28| National Hurricane Center (East Pacific)

5-Day Uncertainty Track last updated Sun, 13 Sep 2020 14:55:28 GMT Wind Speed Probabilities last updated Sun, 13 Sep 2020 15:53:15 GMT

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Tropical Storm Karina Forecast Discussion Number 3

2020-09-13 16:53:37| National Hurricane Center (East Pacific)

Issued at 900 AM MDT Sun Sep 13 2020 000 WTPZ41 KNHC 131453 TCDEP1 Tropical Storm Karina Discussion Number 3 NWS National Hurricane Center Miami FL EP162020 900 AM MDT Sun Sep 13 2020 Karina's center is a little bit closer to the deep convection this morning, resulting in intensity estimates increasing slightly. Based on Dvorak estimates of T3.0/45 kt and T2.5/35 kt from TAFB and SAB, respectively, and an overnight SATCON estimate of 42 kt, Karina's initial intensity is assumed to be 40 kt. The moderate northeasterly shear currently affecting the cyclone is not expected to change appreciably during the next few days. However, Karina will remain over ocean waters warmer than 26 degrees Celsius for the next 48 hours, which should allow for a gradual intensification trend during that period. The shear is forecast to lighten up in 3-4 days, but by then Karina will be over colder waters and in a drier, more stable environment, which should induce weakening. Karina is likely to lose all of its deep convection and become a remnant low by the end of the forecast period. The NHC intensity forecast is generally close to the HCCA aid and the IVCN intensity consensus and shows weakening starting a little sooner than before. Karina is moving toward the west-northwest (300/9 kt), south of a mid-level ridge axis which extends from northwestern Mexico southwestward over the Pacific. This ridge should keep Karina on this general heading with a very gradually decreasing forward speed through day 4. Once the cyclone weakens to a remnant low, it is expected to turn westward, steered by lower-level trade winds. No significant changes in the track forecast were required compared to the previous prediction, and the official forecast lies generally close to the multi-model consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 17.6N 114.7W 40 KT 45 MPH 12H 14/0000Z 18.3N 115.8W 45 KT 50 MPH 24H 14/1200Z 19.0N 117.4W 45 KT 50 MPH 36H 15/0000Z 19.7N 119.0W 50 KT 60 MPH 48H 15/1200Z 20.2N 120.4W 55 KT 65 MPH 60H 16/0000Z 20.9N 121.6W 50 KT 60 MPH 72H 16/1200Z 21.7N 122.8W 50 KT 60 MPH 96H 17/1200Z 22.6N 125.2W 35 KT 40 MPH 120H 18/1200Z 22.8N 127.7W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg

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