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Tropical Storm EARL Forecast Discussion Number 12

2016-08-05 10:37:19| National Hurricane Center (Atlantic)

Issued at 400 AM CDT FRI AUG 05 2016 000 WTNT45 KNHC 050837 TCDAT5 TROPICAL STORM EARL DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052016 400 AM CDT FRI AUG 05 2016 Satellite imagery, along with Mexican surface and radar data, shows that the center of Earl is now near the southern coast of the Bay of Campeche west-southwest of Ciudad del Carmen. The associated convection is poorly organized, although radar data shows bands of low-topped showers that are not currently apparent in infrared imagery. There are no recent observations near the area of maximum winds over the Bay of Campeche, so the initial intensity is held at 35 kt based on continuity from the previous advisory. The initial motion is 285/10. A large mid-level ridge near the northern Gulf of Mexico coast should lead to a continued west-northwestward to westward motion for the next 48 hours or so, with this motion taking the center of Earl along the coast of the Bay of Campeche into mainland Mexico. The new forecast track is similar to the previous track and lies just north of the various consensus models. The center of Earl should emerge over the Bay of Campeche later today before final landfall in mainland Mexico. However, significant strengthening is not expected due to the proximity to land and the current level of disorganization. After landfall, Earl should weaken and dissipate over the mountains of central and eastern Mexico. The main threat from Earl continues to be heavy rains over a large portion of Central America and southeastern Mexico, and the combination of Earl with a broader-scale low-level cyclonic gyre over the area enhances the rainfall potential. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 18.4N 92.8W 35 KT 40 MPH 12H 05/1800Z 18.5N 94.3W 35 KT 40 MPH...OVER WATER 24H 06/0600Z 18.7N 95.8W 35 KT 40 MPH...INLAND 36H 06/1800Z 18.9N 97.2W 25 KT 30 MPH...INLAND 48H 07/0600Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm IVETTE Forecast Discussion Number 11

2016-08-05 10:36:49| National Hurricane Center (East Pacific)

Issued at 200 AM PDT FRI AUG 05 2016 000 WTPZ45 KNHC 050836 TCDEP5 TROPICAL STORM IVETTE DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102016 200 AM PDT FRI AUG 05 2016 There has been little change in the convective organization of Ivette overnight. The low-level center remains exposed to the west and northwest of a loosely curved band of thunderstorms, due to westerly to northwesterly shear. Subjective and objective Dvorak T-numbers are all near T3.0, which yields an initial wind speed of 45 kt. Although the shear is not very strong, it appears the small size of the cyclone and perhaps some nearby dry mid-level air in combination with the shear have prevented intensification during the past day. The GFS-based SHIPS guidance indicates that the shear will decrease during the next 24 hours or so, but the ECMWF model shows a continuation of some upper-level westerlies over Ivette. Because of these differences in the expected upper-level winds, the NHC intensity forecast is more uncertain than normal. The updated intensity forecast calls for some slight strengthening during the next 36 hours, but it is lower than the previous advisory, and it is closest to the IVCN intensity consensus. After 48 h, increasing southwesterly shear and cooler SSTs should cause a fairly rapid spin down of Ivette, and the cyclone is likely to become a remnant low in 4 to 5 days. The tropical storm is moving westward or 275/12 kt. Ivette should turn west-northwestward in 12 to 24 hours as a deepening mid- to upper-level trough to the north of the Hawaiian Islands weakens the western portion of the subtropical ridge. After day 3, Ivette is forecast to turn back westward after it weakens and is steered by the low-level easterly trades. There remains high confidence in the track forecast since the dynamical models continue to be in good agreement. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 14.9N 129.7W 45 KT 50 MPH 12H 05/1800Z 15.2N 131.2W 45 KT 50 MPH 24H 06/0600Z 15.8N 133.1W 50 KT 60 MPH 36H 06/1800Z 16.4N 134.8W 55 KT 65 MPH 48H 07/0600Z 17.2N 136.5W 55 KT 65 MPH 72H 08/0600Z 18.5N 139.5W 40 KT 45 MPH 96H 09/0600Z 19.0N 142.7W 30 KT 35 MPH 120H 10/0600Z 18.8N 146.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Tropical Storm EARL Forecast Discussion Number 11

2016-08-05 04:46:48| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT THU AUG 04 2016 000 WTNT45 KNHC 050246 TCDAT5 TROPICAL STORM EARL DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052016 1000 PM CDT THU AUG 04 2016 Somewhat surprisingly, Earl has maintained tropical storm intensity this evening. Observations from Ciudad del Carmen indicated a wind gust to 46 kt at 2348 UTC during heavy squalls, and the initial intensity is held at 35 kt. Since the forecast track takes the center along the Bay of Campeche coast or just offshore during the next 24 hours, this could allow the cyclone to at least maintain its strength on Friday. Based on the new official intensity forecast, a tropical storm warning has been issued for the southern Bay of Campeche coast of Mexico. In 36 hours or so, the center of Earl should move inland for good over south-central Mexico, and the system is forecast to dissipate in about 48 hours. Earl jogged to the west-northwest over the past several hours and the initial motion is estimated to be 285/9 kt. A large mid-level ridge near the northern Gulf of Mexico coast should induce a continued west-northwestward to westward motion through the forecast period. The official track forecast is close to the most recent multi-model consensus. The main threat from Earl continues to be heavy rains over a large portion of Central America and southeastern Mexico, and the combination of Earl with a broader-scale low-level cyclonic gyre over the area enhances the rainfall potential. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 18.1N 91.7W 35 KT 40 MPH 12H 05/1200Z 18.4N 93.3W 35 KT 40 MPH...INLAND 24H 06/0000Z 18.7N 95.2W 35 KT 40 MPH...INLAND 36H 06/1200Z 18.9N 96.7W 30 KT 35 MPH...INLAND 48H 07/0000Z 19.5N 98.0W 20 KT 25 MPH...POST-TROP/INLAND 72H 08/0000Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm IVETTE Forecast Discussion Number 10

2016-08-05 04:45:18| National Hurricane Center (East Pacific)

Issued at 800 PM PDT THU AUG 04 2016 000 WTPZ45 KNHC 050245 TCDEP5 TROPICAL STORM IVETTE DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102016 800 PM PDT THU AUG 04 2016 Though it may sound like a broken record, Ivette still is struggling to intensify and is showing the detrimental effects of vertical shear. The low-level center appears to be on the northwest side of the small area of cold cloud tops, consistent with some west-northwesterly shear as shown in the SHIPS diagnostics and the CIMSS analyses. Yet, the deep-layer vertical shear is only 5-10 kt, which usually is conducive for intensification. Perhaps it is because of the small size of Ivette - tropical-storm-force winds only out to 60 nm at most - which makes it more susceptible to relatively small amounts of shear. A blend of the TAFB, SAB, and CIMSS Dvorak current intensity estimates gives 45 kt, which is unchanged from the previous advisory. An earlier ASCAT scatterometer pass confirmed the small size of Ivette. Ivette has about two days left to intensify under what appear to be conducive environmental conditions. After a couple days, the SSTs cool and the low-level moisture decreases, but still at levels that could support intensification. By days four and five, however, the vertical shear should reach at least 20 kt due to an upper-level trough approaching Ivette. Gradual to steady intensification is thus expected to about 36-48 hours with gradual to steady weakening thereafter. The NHC intensity forecast is closest to a blend of the SHIPS statistical technique and the COAMPS regional dynamical model and is slightly less than that predicted in the previous advisory. Given the poor intensity forecasts thus far, this prediction has a large uncertainty. Ivette is moving toward the west at 12 kt, primarily being steered by the deep-layer subtropical ridge extending westward out of Mexico. The tropical cyclone should begin bending toward the west-northwest in a couple days as it attempts to round the western periphery of the ridge. By day four or five, Ivette should turn back toward the west as the decaying system is advected in the low-level tradewind flow. All of the reliable models are in close agreement and the NHC track forecast - based upon the TVCN track consensus - is nearly unchanged. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 14.8N 128.7W 45 KT 50 MPH 12H 05/1200Z 14.9N 130.3W 50 KT 60 MPH 24H 06/0000Z 15.3N 132.2W 55 KT 65 MPH 36H 06/1200Z 15.9N 134.0W 60 KT 70 MPH 48H 07/0000Z 16.6N 135.7W 60 KT 70 MPH 72H 08/0000Z 18.0N 138.6W 50 KT 60 MPH 96H 09/0000Z 18.7N 142.0W 40 KT 45 MPH 120H 10/0000Z 19.0N 146.0W 30 KT 35 MPH $$ Forecaster Landsea

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Tropical Storm IVETTE Forecast Discussion Number 9

2016-08-04 22:34:23| National Hurricane Center (East Pacific)

Issued at 200 PM PDT THU AUG 04 2016 000 WTPZ45 KNHC 042034 TCDEP5 TROPICAL STORM IVETTE DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102016 200 PM PDT THU AUG 04 2016 Vertical shear over Ivette is gradually decreasing, and the low-level center is now embedded beneath a persistent CDO feature. A recent ASCAT pass indicated that maximum winds are now near 45 kt, which is supported by an average of subjective and objective satellite intensity estimates. Ivette may finally be starting the gradual intensification trend that has been forecast, and the intensity guidance indicates that strengthening should continue for the next 48 hours while sea surface temperatures are warm and vertical shear is low. Most of the models continue to keep Ivette below hurricane strength, but the NHC intensity forecast still makes the cyclone a hurricane in 48 hours, which is supported by the Florida State Superensemble and the SHIPS model. After 48 hours, increasing shear and lower oceanic heat content should cause fast weakening through day 5. The ASCAT pass was useful in helping to reposition Ivette's center, and the initial motion estimate is now 270/12 kt. The subtropical ridge to the north of the cyclone is forecast to steer Ivette westward for the next 24 hours. Thereafter, a break in the ridge to the northeast of Hawaii should cause the cyclone to turn west-northwestward and decelerate. The updated NHC track forecast is adjusted a little southward during the first 3 days to account for the refinement of the initial position. Otherwise, it lies very close to the multi-model consensus in the middle of a tightly packed guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 14.7N 127.3W 45 KT 50 MPH 12H 05/0600Z 14.8N 129.1W 50 KT 60 MPH 24H 05/1800Z 15.0N 131.2W 55 KT 65 MPH 36H 06/0600Z 15.5N 133.0W 60 KT 70 MPH 48H 06/1800Z 16.1N 134.7W 65 KT 75 MPH 72H 07/1800Z 17.4N 137.8W 60 KT 70 MPH 96H 08/1800Z 18.5N 141.0W 45 KT 50 MPH 120H 09/1800Z 19.0N 144.0W 35 KT 40 MPH $$ Forecaster Berg

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