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Tropical Storm Carlos Forecast Discussion Number 3

2021-06-13 10:36:43| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Sun Jun 13 2021 000 WTPZ43 KNHC 130836 TCDEP3 Tropical Storm Carlos Discussion Number 3 NWS National Hurricane Center Miami FL EP032021 200 AM PDT Sun Jun 13 2021 Infrared and scatterometer satellite data indicate that Carlos remains a compact tropical cyclone. Two ASCAT passes between 0400-0500 UTC revealed a radius of maximum wind of 10-12 nmi and tropical-storm-force winds that only extended outward about 20 nmi. Cloud tops colder than -50C only extend outward about 60 nmi from the center. The earlier ASCAT-A/-B passes contained peak surface wind vectors of 37 kt/40 kt, respectively, so the estimated intensity has been increased to 40 kt for this advisory, which could be a little conservative owing to the small size of the cyclone and possible undersampling of the scatterometer instrument. The initial motion estimate is due west or 270/07 kt. There is little change to the previous NHC track forecast or reasoning. The latest model runs are in good agreement on Carlos turning toward the west-southwest later today, followed by a southwestward motion on Monday and Tuesday as a low- to mid-level ridge to the north of the cyclone builds southward. By day 3, the models diverge significantly when the deep-layer steering currents collapse, followed by possible rapid weakening. The ECMWF weakens Carlos into a shallow remnant low by 72 h, with the shallow vortex then being driven southwestward by a strong low-level ridge to the north and northeast. In contrast, the GFS and some of the other global and regional models keep Carlos stronger and vertically deeper, which results in a ridge to the east lifting the cyclone out toward the north. Given the large spread in the track guidance on days 4 and 5, the new NHC track forecast is similar to but slightly slower than the previous advisory track, and close to a blend of the TVCE and GFEX simple consensus track models. Carlos' small size in combination with the relatively low deep-layer vertical shear of 5-10 kt for the next 36 h or so would normally argue for significant strengthening. However, the cyclone's proximity to very dry mid-level and cooler sea-surface just to its north and northwest is expected to result in the periodic entrainment of stable air for the 72 h or so, resulting in intermittent disruptions of the central deep convection. Thus, little change in strength is forecast during that time. Thereafter, the combination of increasing southwesterly wind shear and sub-27C sea-surface temperatures along the track is expected to induce gradual weakening. The official intensity forecast is similar to the previous advisory, and closely follows the IVCN and HCCA intensity consensus models. FORECAST POSITIONS AND MAX WINDS INIT 13/0900Z 11.9N 125.3W 40 KT 45 MPH 12H 13/1800Z 11.6N 126.1W 45 KT 50 MPH 24H 14/0600Z 11.2N 126.9W 45 KT 50 MPH 36H 14/1800Z 10.7N 127.4W 45 KT 50 MPH 48H 15/0600Z 10.3N 127.7W 45 KT 50 MPH 60H 15/1800Z 10.2N 128.0W 40 KT 45 MPH 72H 16/0600Z 10.6N 128.1W 40 KT 45 MPH 96H 17/0600Z 12.0N 128.2W 35 KT 40 MPH 120H 18/0600Z 14.0N 127.9W 30 KT 35 MPH $$ Forecaster Stewart

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Tropical Storm Carlos Forecast Discussion Number 2

2021-06-13 05:14:39| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Sat Jun 12 2021 000 WTPZ43 KNHC 130313 CCA TCDEP3 Tropical Storm Carlos Discussion Number 2...Corrected NWS National Hurricane Center Miami FL EP032021 800 PM PDT Sat Jun 12 2021 Corrected humidity value in third paragraph. Satellite imagery indicates improved organization this evening as a cold convective burst has expanded over the estimated low-level circulation center. A 2032 UTC AMSR2 microwave pass indicated that underneath this convective burst was also improved convective banding, especially over the southern semicircle. The latest round of Dvorak satellite estimates were T2.0/30 kt from TAFB and T2.5/35 kt from SAB. The most recent UW-CIMSS Advanced Dvorak Technique value was also T2.5/35 kt. Favoring the higher intensity estimates, and assuming some intensification has occurred from the earlier scatterometer passes, Tropical Depression Three-E has been upgraded to Tropical Storm Carlos with an advisory intensity of 35 kt. Carlos appears to be gradually turning leftward and slowing down this evening, with the most recent estimated motion at 270/06 kt. The mid-level ridge north of Carlos is forecast to gradually weaken, shift northward, and then be replaced by a deep-layer trough that will essentially shut down the steering currents near the cyclone after 24 h. Between 36 to 48 h the motion of Carlos is likely to slow to a crawl, generally to the west-southwest. By 72 h, another mid-to-upper level trough digging in from the northwest will finally induce some northerly steering, helping Carlos to gradually accelerate to the north. The latest track forecast is a bit west of the previous NHC forecast owing to the current motion, but remains very close to the HFIP corrected consensus and TCVE track consensus. It should be noted that there remains large spread in the guidance on how quickly Carlos slows down, with the latest GFS forecast slowing down the cyclone almost immediately, while the CMC and ECMWF runs show a much faster track to the west-southwest. The intensity forecast is tricky due to both the small size of the tropical cyclone and also the less than optimal environment surrounding the system. While deep-layer vertical wind shear is only expected to be low to moderate over the next 72 h, mid-level shear out of the north to northwest is a bit higher (15-25 kt) and could occasionally import very dry mid-level air from that direction. In fact, ECMWF-SHIPS mid-level humidity values gradually decrease to under 50 percent in the next 36 h. In addition, the very slow motion of Carlos expected between 24-72 h could potentially upwell cooler sea-surface temperatures than the current 27-28 C values along the forecast track. For this reason, the latest NHC intensity forecast is fairly conservative, forecasting a peak intensity of 45 kt between 24-60 h, which is close to the HFIP corrected consensus and peak intensity of the most recent HWRF run. Thereafter, as the storm begins to gain latitude, increasingly dry, stable air in addition to decreasing sea surface temperatures should lead to gradual weakening beyond 60 h. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 11.9N 124.5W 35 KT 40 MPH 12H 13/1200Z 11.8N 125.5W 40 KT 45 MPH 24H 14/0000Z 11.4N 126.5W 45 KT 50 MPH 36H 14/1200Z 10.8N 127.2W 45 KT 50 MPH 48H 15/0000Z 10.6N 127.4W 45 KT 50 MPH 60H 15/1200Z 10.3N 127.7W 45 KT 50 MPH 72H 16/0000Z 10.3N 128.0W 40 KT 45 MPH 96H 17/0000Z 11.5N 128.1W 35 KT 40 MPH 120H 18/0000Z 13.5N 127.9W 30 KT 35 MPH $$ Forecaster Papin/Pasch

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Tropical Storm Carlos Forecast Discussion Number 2

2021-06-13 04:56:06| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Sat Jun 12 2021 000 WTPZ43 KNHC 130256 TCDEP3 Tropical Storm Carlos Discussion Number 2 NWS National Hurricane Center Miami FL EP032021 800 PM PDT Sat Jun 12 2021 Satellite imagery indicates improved organization this evening as a cold convective burst has expanded over the estimated low-level circulation center. A 2032 UTC AMSR2 microwave pass indicated that underneath this convective burst was also improved convective banding, especially over the southern semicircle. The latest round of Dvorak satellite estimates were T2.0/30 kt from TAFB and T2.5/35 kt from SAB. The most recent UW-CIMSS Advanced Dvorak Technique value was also T2.5/35 kt. Favoring the higher intensity estimates, and assuming some intensification has occurred from the earlier scatterometer passes, Tropical Depression Three-E has been upgraded to Tropical Storm Carlos with an advisory intensity of 35 kt. Carlos appears to be gradually turning leftward and slowing down this evening, with the most recent estimated motion at 270/06 kt. The mid-level ridge north of Carlos is forecast to gradually weaken, shift northward, and then be replaced by a deep-layer trough that will essentially shut down the steering currents near the cyclone after 24 h. Between 36 to 48 h the motion of Carlos is likely to slow to a crawl, generally to the west-southwest. By 72 h, another mid-to-upper level trough digging in from the northwest will finally induce some northerly steering, helping Carlos to gradually accelerate to the north. The latest track forecast is a bit west of the previous NHC forecast owing to the current motion, but remains very close to the HFIP corrected consensus and TCVE track consensus. It should be noted that there remains large spread in the guidance on how quickly Carlos slows down, with the latest GFS forecast slowing down the cyclone almost immediately, while the CMC and ECMWF runs show a much faster track to the west-southwest. The intensity forecast is tricky due to both the small size of the tropical cyclone and also the less than optimal environment surrounding the system. While deep-layer vertical wind shear is only expected to be low to moderate over the next 72 h, mid-level shear out of the north to northwest is a bit higher (15-25 kt) and could occasionally import very dry mid-level air from that direction. In fact, ECMWF-SHIPS mid-level humidity values gradually decrease to under 500ver the next 36 h. In addition, the very slow motion of Carlos expected between 24-72 h could potentially upwell cooler sea-surface temperatures than the current 27-28 C values along the forecast track. For this reason, the latest NHC intensity forecast is fairly conservative, forecasting a peak intensity of 45 kt between 24-60 h, which is close to the HFIP corrected consensus and peak intensity of the most recent HWRF run. Thereafter, as the storm begins to gain latitude, increasingly dry, stable air in addition to decreasing sea surface temperatures should lead to gradual weakening beyond 60 h. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 11.9N 124.5W 35 KT 40 MPH 12H 13/1200Z 11.8N 125.5W 40 KT 45 MPH 24H 14/0000Z 11.4N 126.5W 45 KT 50 MPH 36H 14/1200Z 10.8N 127.2W 45 KT 50 MPH 48H 15/0000Z 10.6N 127.4W 45 KT 50 MPH 60H 15/1200Z 10.3N 127.7W 45 KT 50 MPH 72H 16/0000Z 10.3N 128.0W 40 KT 45 MPH 96H 17/0000Z 11.5N 128.1W 35 KT 40 MPH 120H 18/0000Z 13.5N 127.9W 30 KT 35 MPH $$ Forecaster Papin/Pasch

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Tropical Depression Three-E Forecast Discussion Number 1

2021-06-12 22:46:39| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Sat Jun 12 2021 000 WTPZ43 KNHC 122046 TCDEP3 Tropical Depression Three-E Discussion Number 1 NWS National Hurricane Center Miami FL EP032021 200 PM PDT Sat Jun 12 2021 The disturbance that has been tracked westward for the past several days across the open waters of the the tropical eastern Pacific has finally established a sufficiently well-defined low-level circulation to be designated as Tropical Depression Three-E. Convection increased last night and began to consolidate, while satellite images and microwave data this morning indicated that there was evidence of a well-defined low developing. This was later confirmed by a pair of ASCAT overpasses. These overpasses showed a compact radius of maximum winds. And, although the ASCAT-A data had a few vectors between 30-35 kt, these were not homogeneous and appeared unrepresentative of the system's intensity. In addition, the rather ragged satellite appearance and the Dvorak intensity estimate of 2.0 from SAB are suggestive that this system should be initialized as a 30-kt depression for this advisory. The environment surrounding the depression is moderately conducive for gradual strengthening, with SSTs of 27-28 degrees C, mid-level RH values between 50-60 percent, and vertical wind shear of about 5-10 kt. These conditions are expected to continue for the next 2-3 days. By 72 h, dry air and subsidence are expected to hinder any further intensification and should begin a weakening trend. By late in the forecast period, the system is forecast to cross the 26 degree C isotherm, which should hasten the pace of weakening. The official intensity closely follows the HFIP corrected consensus HCCA, which shows the depression becoming a tropical storm tonight, and levels off its intensity by 48 h, followed by a weakening trend after 60 h. A mid-level ridge to the north of the cyclone is steering it at a somewhat uncertain 275/08 kt. This ridge is forecast by nearly all of the models to weaken over the next couple of days, leaving the depression in a region of very weak steering currents through early next week. A mid-upper level trough digging southward to the northwest of the cyclone should induce a northerly component of motion along with an increase in forward speed by midweek. As said, there is good agreement on the pattern, however, the models vary greatly on how abruptly they slow the system. This is resulting in a track model spread of about 300 n mi by 72 h. The NHC track forecast tries to split the difference by closely following the TVCE and TVCN consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 11.8N 123.6W 30 KT 35 MPH 12H 13/0600Z 11.9N 124.5W 35 KT 40 MPH 24H 13/1800Z 11.7N 125.5W 40 KT 45 MPH 36H 14/0600Z 11.4N 126.1W 45 KT 50 MPH 48H 14/1800Z 11.0N 126.5W 50 KT 60 MPH 60H 15/0600Z 10.8N 126.7W 50 KT 60 MPH 72H 15/1800Z 11.0N 126.9W 45 KT 50 MPH 96H 16/1800Z 12.5N 126.7W 40 KT 45 MPH 120H 17/1800Z 15.2N 126.1W 30 KT 35 MPH $$ Forecaster Latto

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Post-Tropical Cyclone Blanca Forecast Discussion Number 19

2021-06-04 10:33:17| Tropical Depression LIDIA

Issued at 200 AM PDT Fri Jun 04 2021

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