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Hurricane Larry Forecast Discussion Number 11
2021-09-03 10:33:37| National Hurricane Center (Atlantic)
Issued at 500 AM AST Fri Sep 03 2021 000 WTNT42 KNHC 030833 TCDAT2 Hurricane Larry Discussion Number 11 NWS National Hurricane Center Miami FL AL122021 500 AM AST Fri Sep 03 2021 Larry continues to gradually become better organized. Satellite images show a fairly compact central dense overcast feature with an eye occasionally evident. Beyond the inner core, banding features are gradually becoming more distinct, especially to the south of the center. The latest Dvorak classifications at 0600 UTC was 4.5/77 kt from TAFB and SAB, and based on those estimates and the improving trend, the initial intensity is nudged upward to 80 kt. Larry is moving west-northwestward at 17 kt. There has been no change to the track forecast reasoning. A continued westward to west-northwestward motion is expected on Friday and through the weekend as the hurricane remains on the south side of a mid-level ridge. By early next week, Larry is expected to slow down and turn northwestward when it reaches the southwestern periphery of the ridge. The models are in fairly good agreement, and the NHC track forecast lies near the middle of the guidance envelope. This forecast is largely an update of the previous one. The environmental factors appear favorable for steady strengthening during the next few days with wind shear remaining low and mid-level moisture fairly high. The only slightly negative factor is marginally warm 26-27 deg C waters that Larry will be moving over during the next couple of days, which should prevent rapid intensification. All of the models are in general agreement that Larry will become a major hurricane in a day or so with continued strengthening through day 3, and the NHC intensity forecast follows suit. Some weakening is shown by the end of the forecast period when the wind shear could increase a little. This forecast is very similar to the previous one and lies near the high end of the guidance envelope. It should be noted that eyewall replacement cycles are possible, which could cause intensity fluctuations that are challenging to predict. The leading swell front from Larry is expected to reach the Lesser Antilles on Sunday, increasing the risk of life-threatening rip currents and high surf conditions on those islands early next week. Large swells are likely to spread to areas surrounding the western Atlantic later in the week as well. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 14.6N 38.9W 80 KT 90 MPH 12H 03/1800Z 15.2N 41.1W 90 KT 105 MPH 24H 04/0600Z 16.2N 43.8W 100 KT 115 MPH 36H 04/1800Z 17.3N 46.2W 105 KT 120 MPH 48H 05/0600Z 18.6N 48.5W 115 KT 130 MPH 60H 05/1800Z 19.8N 50.5W 120 KT 140 MPH 72H 06/0600Z 21.1N 52.5W 120 KT 140 MPH 96H 07/0600Z 23.8N 55.8W 115 KT 130 MPH 120H 08/0600Z 27.1N 58.9W 110 KT 125 MPH $$ Forecaster Cangialosi
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Hurricane Larry Forecast Advisory Number 11
2021-09-03 10:31:07| National Hurricane Center (Atlantic)
Issued at 0900 UTC FRI SEP 03 2021 000 WTNT22 KNHC 030830 TCMAT2 HURRICANE LARRY FORECAST/ADVISORY NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122021 0900 UTC FRI SEP 03 2021 THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT. HURRICANE CENTER LOCATED NEAR 14.6N 38.9W AT 03/0900Z POSITION ACCURATE WITHIN 20 NM PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 285 DEGREES AT 17 KT ESTIMATED MINIMUM CENTRAL PRESSURE 982 MB MAX SUSTAINED WINDS 80 KT WITH GUSTS TO 100 KT. 64 KT....... 20NE 15SE 0SW 20NW. 50 KT....... 40NE 40SE 20SW 40NW. 34 KT.......130NE 100SE 40SW 120NW. 12 FT SEAS..240NE 180SE 150SW 180NW. 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 14.6N 38.9W AT 03/0900Z AT 03/0600Z CENTER WAS LOCATED NEAR 14.4N 38.2W FORECAST VALID 03/1800Z 15.2N 41.1W MAX WIND 90 KT...GUSTS 110 KT. 64 KT... 25NE 20SE 15SW 25NW. 50 KT... 50NE 40SE 30SW 50NW. 34 KT...140NE 120SE 70SW 120NW. FORECAST VALID 04/0600Z 16.2N 43.8W MAX WIND 100 KT...GUSTS 120 KT. 64 KT... 30NE 20SE 20SW 30NW. 50 KT... 60NE 40SE 40SW 60NW. 34 KT...140NE 120SE 80SW 130NW. FORECAST VALID 04/1800Z 17.3N 46.2W MAX WIND 105 KT...GUSTS 130 KT. 64 KT... 40NE 30SE 30SW 40NW. 50 KT... 60NE 50SE 50SW 60NW. 34 KT...140NE 130SE 90SW 130NW. FORECAST VALID 05/0600Z 18.6N 48.5W MAX WIND 115 KT...GUSTS 140 KT. 64 KT... 50NE 40SE 30SW 40NW. 50 KT... 70NE 60SE 60SW 70NW. 34 KT...140NE 130SE 90SW 130NW. FORECAST VALID 05/1800Z 19.8N 50.5W MAX WIND 120 KT...GUSTS 145 KT. 50 KT... 70NE 60SE 60SW 70NW. 34 KT...140NE 130SE 90SW 130NW. FORECAST VALID 06/0600Z 21.1N 52.5W MAX WIND 120 KT...GUSTS 145 KT. 50 KT... 80NE 70SE 60SW 70NW. 34 KT...140NE 130SE 90SW 130NW. 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 07/0600Z 23.8N 55.8W MAX WIND 115 KT...GUSTS 140 KT. OUTLOOK VALID 08/0600Z 27.1N 58.9W MAX WIND 110 KT...GUSTS 135 KT. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 14.6N 38.9W NEXT ADVISORY AT 03/1500Z $$ FORECASTER CANGIALOSI
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Hurricane Larry Forecast Discussion Number 10
2021-09-03 04:33:58| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Thu Sep 02 2021 000 WTNT42 KNHC 030233 TCDAT2 Hurricane Larry Discussion Number 10 NWS National Hurricane Center Miami FL AL122021 1100 PM AST Thu Sep 02 2021 A series of SSMIS microwave passes earlier this afternoon indicated that Larry may have been starting an eyewall replacement. However, the last pass at 2058 UTC suggested that the eyewall replacement failed, with the western part of the outer eyewall being eroded, possibly by some modest mid-level shear and some dry air, and the tighter inner eyewall trying to re-establish itself. As a result, the convective pattern has reverted back to a small Central Dense Overcast. Subjective Dvorak intensity estimates are now T4.5/77 kt from TAFB and T4.0/65 kt from SAB, and the latest objective estimates range from 72 to 78 kt. Overall these numbers have risen a bit, and Larry's maximum winds are now estimated to be 75 kt. Larry continues moving toward the west but perhaps slightly faster (280/17 kt). There is no change to the track forecast reasoning. A fairly stagnant pattern consisting of a strong mid-level high over the central Atlantic and broad-scale troughing over the eastern United States and western Atlantic should persist through the 5-day forecast period. Larry is therefore forecast to turn toward the west-northwest on Friday and then take on a northwest heading Sunday through Tuesday while it moves around the southwestern periphery of the high. The updated NHC track forecast lies right along the previous forecast and is very close to the various consensus aids. Low shear, gradually increasing sea surface temperatures, and the potential for an upper-level outflow jet to form north of the hurricane during the next 24-48 hours should support continued strengthening. During the first 48 hours, the NHC forecast shows a steady increase of 10 kt every 24 hours, close to the HCCA consensus aids and near the top of the guidance envelope. By days 3 and 4, there continue to be indications that increasing westerly or northwesterly shear could become a factor, and the NHC forecast therefore shows a leveling off of the intensity, with some slight weakening by the end of the forecast period. If Larry becomes a strong hurricane, eyewall replacements would also be a possibility, which would likely lead to difficult-to-forecast fluctuations in intensity. The leading swell front from Larry is expected to reach the Lesser Antilles on Sunday, increasing the risk of life-threatening rip currents and surf conditions on those islands early next week. Large swells are likely to spread to areas surrounding the western Atlantic later in the week as well. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 14.1N 37.5W 75 KT 85 MPH 12H 03/1200Z 14.5N 39.9W 85 KT 100 MPH 24H 04/0000Z 15.3N 42.6W 95 KT 110 MPH 36H 04/1200Z 16.4N 45.2W 105 KT 120 MPH 48H 05/0000Z 17.6N 47.5W 115 KT 130 MPH 60H 05/1200Z 19.0N 49.7W 120 KT 140 MPH 72H 06/0000Z 20.4N 51.8W 120 KT 140 MPH 96H 07/0000Z 22.9N 55.0W 115 KT 130 MPH 120H 08/0000Z 25.9N 58.0W 110 KT 125 MPH $$ Forecaster Berg
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Hurricane Larry Forecast Advisory Number 10
2021-09-03 04:32:58| National Hurricane Center (Atlantic)
Issued at 0300 UTC FRI SEP 03 2021 782 WTNT22 KNHC 030232 TCMAT2 HURRICANE LARRY FORECAST/ADVISORY NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122021 0300 UTC FRI SEP 03 2021 THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT. HURRICANE CENTER LOCATED NEAR 14.1N 37.5W AT 03/0300Z POSITION ACCURATE WITHIN 20 NM PRESENT MOVEMENT TOWARD THE WEST OR 280 DEGREES AT 17 KT ESTIMATED MINIMUM CENTRAL PRESSURE 985 MB MAX SUSTAINED WINDS 75 KT WITH GUSTS TO 90 KT. 64 KT....... 20NE 15SE 0SW 20NW. 50 KT....... 40NE 40SE 20SW 40NW. 34 KT.......130NE 100SE 40SW 120NW. 12 FT SEAS..240NE 180SE 120SW 180NW. 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 14.1N 37.5W AT 03/0300Z AT 03/0000Z CENTER WAS LOCATED NEAR 13.9N 36.7W FORECAST VALID 03/1200Z 14.5N 39.9W MAX WIND 85 KT...GUSTS 105 KT. 64 KT... 25NE 20SE 15SW 25NW. 50 KT... 50NE 40SE 30SW 50NW. 34 KT...140NE 120SE 70SW 120NW. FORECAST VALID 04/0000Z 15.3N 42.6W MAX WIND 95 KT...GUSTS 115 KT. 64 KT... 30NE 20SE 20SW 30NW. 50 KT... 60NE 40SE 40SW 60NW. 34 KT...140NE 120SE 80SW 130NW. FORECAST VALID 04/1200Z 16.4N 45.2W MAX WIND 105 KT...GUSTS 130 KT. 64 KT... 40NE 30SE 30SW 40NW. 50 KT... 60NE 50SE 50SW 60NW. 34 KT...140NE 130SE 90SW 130NW. FORECAST VALID 05/0000Z 17.6N 47.5W MAX WIND 115 KT...GUSTS 140 KT. 64 KT... 50NE 40SE 30SW 40NW. 50 KT... 70NE 60SE 60SW 70NW. 34 KT...140NE 130SE 90SW 130NW. FORECAST VALID 05/1200Z 19.0N 49.7W MAX WIND 120 KT...GUSTS 145 KT. 50 KT... 70NE 60SE 60SW 70NW. 34 KT...140NE 130SE 90SW 130NW. FORECAST VALID 06/0000Z 20.4N 51.8W MAX WIND 120 KT...GUSTS 145 KT. 50 KT... 80NE 70SE 60SW 70NW. 34 KT...140NE 130SE 90SW 130NW. 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 07/0000Z 22.9N 55.0W MAX WIND 115 KT...GUSTS 140 KT. OUTLOOK VALID 08/0000Z 25.9N 58.0W MAX WIND 110 KT...GUSTS 135 KT. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 14.1N 37.5W NEXT ADVISORY AT 03/0900Z $$ FORECASTER BERG
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Hurricane Larry Forecast Discussion Number 9
2021-09-02 22:49:53| National Hurricane Center (Atlantic)
Issued at 500 PM AST Thu Sep 02 2021 000 WTNT42 KNHC 022049 TCDAT2 Hurricane Larry Discussion Number 9 NWS National Hurricane Center Miami FL AL122021 500 PM AST Thu Sep 02 2021 This afternoon, Larry's appearance has evolved from a small central dense overcast to a tightly coiled spiral banding pattern, with these bands wrapping into the estimated center. I finally received a useful SSMIS microwave overpass at 1857 UTC which provided evidence that Larry could be undergoing an eyewall replacement cycle (ERC). The imagery suggests a large outer eyewall is taking shape on the low-level 37-GHz channel, while an inner eyewall fragment is still seen on the mid-level 91-GHz channel. Despite these structural changes, the 1800 UTC subjective Dvorak estimates from TAFB and SAB were unchanged from this morning at CI 4.0/65 kt. In addition, the latest objective intensity estimates from SATCON and ADT have only varied slightly at 73 kt and 74 kt respectively. Taking a blend of the subjective and objective estimates still yields 70 kt for this advisory. Larry continues to move just north of due west, with the latest motion estimated at 280/16 kt. There is not much new to report with the track reasoning, with a large mid-level ridge currently north of Larry expected to steer the hurricane to the west or west-northwest over the next 2-3 days. Over time, the ridge axis is forecast to slowly shift further northeast of Larry's position, allowing the hurricane to gradually gain a more rightward component of motion by the end of the forecast period. In general, the track guidance remains tightly clustered for the first 2-3 days. There was a notable shift west in the latest 12z GFS deterministic track, while the 12z ECMWF shifted ever so slightly right. A quick look at the 12z ECMWF ensemble guidance reveals that the deterministic run is a bit to the northeast of the ensemble mean. The latest NHC track has been shifted slightly to the south and west of the previous track, following the reliable HFIP corrected consensus aid (HCCA) which also shifted a bit south and west this cycle. Once Larry completes the ongoing ERC, significant or even rapid intensification is anticipated. The short-term intensity forecast has been raised a bit more, since it appears more likely the present ERC will finish in the next 6-12 h. The latest NHC intensity forecast now makes Larry a major hurricane by tomorrow night, with further intensification up to Category 4 intensity anticipated by Sunday. Once again, there remains some discrepancy in the vertical wind shear forecast between the GFS- and ECMWF-based SHIPS guidance, with the ECMWF forecasting significantly more southwesterly shear beyond 72 hours. Both guidance tools also indicate a decrease in mid-level relative humidity which, if the shear materializes, could disrupt Larry's inner core structure. Thus, the NHC intensity forecast still shows gradual weakening from 72 to 120 hours. The latest intensity forecast is just a hair above HCCA in the short term, with the intensity forecast most closely following the latest COAMPS-TC (CTCI) guidance in the first three days. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 13.7N 35.8W 70 KT 80 MPH 12H 03/0600Z 14.0N 38.4W 80 KT 90 MPH 24H 03/1800Z 14.7N 41.3W 95 KT 110 MPH 36H 04/0600Z 15.7N 43.9W 105 KT 120 MPH 48H 04/1800Z 16.9N 46.3W 110 KT 125 MPH 60H 05/0600Z 18.3N 48.6W 120 KT 140 MPH 72H 05/1800Z 19.7N 50.6W 120 KT 140 MPH 96H 06/1800Z 22.2N 54.0W 115 KT 130 MPH 120H 07/1800Z 25.1N 57.0W 110 KT 125 MPH $$ Forecaster Papin
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