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Hurricane Katia Forecast Discussion Number 14

2017-09-09 04:36:38| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Fri Sep 08 2017 000 WTNT43 KNHC 090236 TCDAT3 Hurricane Katia Discussion Number 14 NWS National Hurricane Center Miami FL AL132017 Issued by the NWS Weather Prediction Center College Park MD 1000 PM CDT Fri Sep 08 2017 Satellite imagery shows Katia has become much less organized over the past several hours with a shrinking area of warming cloud tops. The weakening of Katia could be due to drier air wrapping around the cyclone's western side, which was noted in satellite-based layered precipitable water products. Reconnaissance aircraft has reported a significant northeast tilt of the circulation with height, a sign of southwesterly vertical wind shear. The initial wind speed has been decreased to 65 knots based on a blend of subjective Dvorak estimates from TAFB and SAB and is close to SFMR wind observations from Air Force reconnasissance aircraft currently sampling the storm. Katia is currently making landfall north of Tecolutla, Mexico. Rapid weakening is expected from here on out, and Katia is forecast to dissipate over the rugged terrain of the Sierra Madre mountains on Saturday. Katia has made a turn to the west-southwest at 6 kt. The official track forecast remains consistent with the previous advisory. The weakening hurricane is expected to continue moving west-southwest until dissipation. Very heavy rains associated with Katia are expected to affect eastern Mexico. These rains will likely cause life-threatening flash floods and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 20.6N 97.2W 65 KT 75 MPH 12H 09/1200Z 20.2N 97.9W 40 KT 45 MPH...INLAND 24H 10/0000Z 19.7N 98.9W 25 KT 30 MPH...DISSIPATED $$ Forecaster Roth/Lamers

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Hurricane Irma Forecast Discussion Number 39

2017-09-08 23:00:29| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Fri Sep 08 2017 000 WTNT41 KNHC 082100 TCDAT1 Hurricane Irma Discussion Number 39 NWS National Hurricane Center Miami FL AL112017 500 PM EDT Fri Sep 08 2017 Latest data from an Air Force Hurricane Hunter plane a few hours ago indicate that Irma's intensity continues to fluctuate, and the winds are estimated at 135 kt. The last minimum central pressure was 925 mb. Another reconnaissance plane will check Irma soon. The environment is favorable for Irma to maintain its category 4 status, and only unpredictable eyewall replacement cycles could result in intensity fluctuations during the next 48 hours. The interaction of the hurricane's circulation with Cuba will probably not result in any relevant change in intensity. In summary, the NHC forecast brings Irma near south Florida as a category 4 hurricane. After landfall, interaction with land and an increase in wind shear should induce gradual weakening. Satellite images and radar fixes from Cuba indicate that Irma has slowed down and is now moving toward the west or 280 degrees at about 10 kt. The hurricane should continue on this track for the next 12 hours to 24 hours, and this track will bring the core of Irma very close to the north coast of Cuba. After that time, Irma should reach the southwestern edge of the subtropical high and begin to move toward the northwest and north-northwest toward the Florida peninsula. The precise moment of this turn is still uncertain, and that is why NHC emphasizes that nobody should focus on the exact track of the center. This afternoon's NHC forecast was again adjusted a little bit westward following the trend of the ECMWF model and both the HFIP corrected consensus and the FSU Superensemble. In fact, these 3 aids continued to be tightly packed. KEY MESSAGES: 1. Irma will continue to bring life-threatening wind, storm surge, and rainfall hazards to portions of the Bahamas and the north coast of Cuba, especially over the adjacent Cuban Keys, through Saturday. 2. Irma is expected to make landfall in Florida as an extremely dangerous major hurricane, and will bring life-threatening wind impacts to much of the state regardless of the exact track of the center. 3. There is the danger of life-threatening storm surge inundation in southern Florida and the Florida Keys during the next 36 hours, where a Storm Surge Warning is in effect. The threat of significant storm surge flooding along the southwest coast of Florida has increased, and 8 to 12 feet of inundation above ground level is possible in this area. This is a life-threatening situation. Everyone in these areas should take all actions to protect life and property from rising water and follow evacuation instructions from local officials. 4. Irma is expected to produce very heavy rain and inland flooding. Total rain accumulations of 8 to 15 inches, with isolated amounts of 20 inches are expected over the Florida Keys and much of the Florida peninsula through Tuesday night. The highest amounts are expected over the eastern Florida peninsula and upper Florida Keys. Irma will likely bring periods of heavy rain to much of Georgia, South Carolina, and western North Carolina early next week, including some mountainous areas which are more prone to flash flooding. All areas seeing heavy rainfall from Irma will experience a risk of flooding and flash flooding. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 22.1N 76.5W 135 KT 155 MPH 12H 09/0600Z 22.4N 78.2W 135 KT 155 MPH 24H 09/1800Z 23.0N 79.9W 135 KT 155 MPH 36H 10/0600Z 24.1N 81.0W 140 KT 160 MPH 48H 10/1800Z 25.7N 81.5W 125 KT 145 MPH 72H 11/1800Z 30.6N 83.0W 50 KT 60 MPH...INLAND 96H 12/1800Z 35.0N 85.9W 25 KT 30 MPH...INLAND 120H 13/1800Z 35.6N 87.0W 20 KT 25 MPH...POST-TROP/INLAND $$ Forecaster Avila

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Hurricane Katia Forecast Discussion Number 13

2017-09-08 22:51:09| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Fri Sep 08 2017 000 WTNT43 KNHC 082051 TCDAT3 Hurricane Katia Discussion Number 13 NWS National Hurricane Center Miami FL AL132017 Issued by the NWS Weather Prediction Center College Park MD 400 PM CDT Fri Sep 08 2017 Satellite imagery continues to show Katia becoming better organized with the formation of a small, cloud-filled eye this afternoon. The initial wind speed has been increased to 90 knots based on the subjective Dvorak estimates from both TAFB and SAB. Another reconnaissance plane is expected to arrive in a few hours to check on the winds of Katia. Additional strengthening is possible prior to landfall, and Katia could still become a major hurricane, but there is only about 6 hours left for this to occur. After landfall, rapid weakening is expected, and Katia is forecast to dissipate over the rugged terrain of the Sierra Madre mountains between 24 and 36 hours. Katia has moved westward during the day, but a longer-term motion is still west-southwestward at 6 kt. The official track forecast was shifted to the north near landfall due to the more westerly track this afternoon. The new forecast then resumes a more southwesterly track based on northerly mid/upper-level flow seen on infrared imagery ahead of the storm and model guidance. In addition to a dangerous storm surge and hurricane-force winds, very heavy rains associated with Katia are expected to affect eastern Mexico. These rains will likely cause life-threatening flash floods and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 21.0N 96.5W 90 KT 105 MPH 12H 09/0600Z 20.8N 97.3W 85 KT 100 MPH...INLAND 24H 09/1800Z 20.0N 98.0W 30 KT 35 MPH...INLAND 36H 10/0600Z...DISSIPATED $$ Forecaster Bann/Blake

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Hurricane Jose Forecast Discussion Number 14

2017-09-08 22:42:58| National Hurricane Center (Atlantic)

Issued at 500 PM AST Fri Sep 08 2017 000 WTNT42 KNHC 082042 TCDAT2 Hurricane Jose Discussion Number 14 NWS National Hurricane Center Miami FL AL122017 500 PM AST Fri Sep 08 2017 Jose's satellite presentation continues to impress. A nearly perfectly symmetric CDO surrounds a clear eye, and there is still no sign of weakening due to shear associated with the outflow of Hurricane Irma. Since the earlier reconnaissance flight, Dvorak intensity estimates have actually increased, however they are still lower than what the plane found. The initial intensity has been held at 130 kt, out of respect of the earlier in-situ observations, but given the current cloud pattern, this could be conservative. Another reconnaissance flight this evening will give a better estimate of the intensity. Internal dynamics are still expected to be the primary factor in the intensity for the next 12 hours or so. After that, all of the intensity guidance continues to show weakening throughout the forecast, though it is worth noting that Jose has already exceeded all previous forecasts. The NHC forecast continues to follow the trend of the models, but is a little above the consensus for most of the forecast period. Given the small size of the inner-core of Jose, if the shear does finally increase, weakening could occur at a faster rate than indicated. The global models have come into very good agreement on the track of Jose for the next 2 days, and there is finally a high degree of confidence in that part of the forecast. The eye of Jose should turn toward the northwest tonight and pass just east of Barbuda on Saturday. Beyond 48 h, the extent to which an approaching mid-level trough will cause the hurricane to turn toward the north, and eventually toward the east still varies from model to model, however the model spread has decreased. Both the GFS and ECMWF show Jose being left behind by the trough at some point and trapped in light steering flow. The forecast continues to split these two models, and is very close to the previous official forecast. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 16.6N 58.3W 130 KT 150 MPH 12H 09/0600Z 17.3N 60.0W 125 KT 145 MPH 24H 09/1800Z 18.4N 61.9W 120 KT 140 MPH 36H 10/0600Z 19.9N 64.0W 115 KT 130 MPH 48H 10/1800Z 21.7N 66.0W 105 KT 120 MPH 72H 11/1800Z 24.9N 68.8W 95 KT 110 MPH 96H 12/1800Z 27.0N 68.5W 90 KT 105 MPH 120H 13/1800Z 28.0N 66.5W 80 KT 90 MPH $$ Forecaster Zelinsky

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Hurricane Jose Forecast Discussion Number 13

2017-09-08 16:56:57| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Fri Sep 08 2017 000 WTNT42 KNHC 081456 TCDAT2 Hurricane Jose Discussion Number 13 NWS National Hurricane Center Miami FL AL122017 1100 AM AST Fri Sep 08 2017 An Air Force Hurricane Hunter plane, the first so far into Jose, found the hurricane was much stronger than previously estimated. A standard 90 percent reduction of the 146-kt peak flight-level wind at 700 mb yields an intensity estimate of about 130 kt, which is the basis for the initial intensity. In the short term, Jose is in a fairly favorable environment. Although the SHIPS-diagnosed shear is near 20 kt, the hurricane is small enough that it has thus far remained sheltered from the upper-level outflow of Hurricane Irma to the west. Internal dynamics will therefore most likely be the driving factor of Jose's intensity for the next day or so. After that time, all of the intensity guidance forecasts weakening, perhaps assuming that eventually the shear will begin to affect the hurricane. Due to the very high initial intensity of Jose, the intensity forecast is quite a bit higher than the model consensus, even after adjusting for the initial intensity. However, the NHC forecast still follows the model trend of steady weakening beyond 24 hours. The aircraft data also indicated that the center of Jose is a little farther south than previously estimated. Because of that, the NHC track forecast has been shifted slightly south and west of the previous one. Otherwise, there is no significant change to the track forecast, and Jose is still expected to turn northwest before reaching the Leeward Islands on Saturday, as the subtropical ridge begins to retreat eastward. There is fairly good agreement between the global models for the first 48 h. After that, it is still unclear if Jose will begin to move east with an approaching mid-latitude mid-level trough, or if it will remain trapped in light steering flow. As a course of least regret, my forecast splits the difference between these scenarios and shows a slow northeastward motion at day 5. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 16.3N 57.1W 130 KT 150 MPH 12H 09/0000Z 16.8N 59.0W 130 KT 150 MPH 24H 09/1200Z 17.7N 61.0W 125 KT 145 MPH 36H 10/0000Z 19.0N 62.9W 120 KT 140 MPH 48H 10/1200Z 20.6N 65.0W 110 KT 125 MPH 72H 11/1200Z 24.2N 68.3W 95 KT 110 MPH 96H 12/1200Z 26.4N 68.6W 85 KT 100 MPH 120H 13/1200Z 28.0N 67.5W 85 KT 100 MPH $$ Forecaster Zelinsky

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