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Tropical Storm IVETTE Forecast Discussion Number 20

2016-08-07 16:36:34| National Hurricane Center (East Pacific)

Issued at 800 AM PDT SUN AUG 07 2016 000 WTPZ45 KNHC 071436 TCDEP5 TROPICAL STORM IVETTE DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102016 800 AM PDT SUN AUG 07 2016 Ivette generated a new burst of deep convection around the time of the last advisory, and that burst has been persisting. However, satellite data show that the center remains partially exposed to the southwest of this cloud mass due to strong southwesterly vertical wind shear. An overnight ASCAT pass showed at least 35-kt winds, and the initial intensity estimate is held at 40 kt since the cloud pattern is as organized or perhaps slightly better than 6 hours ago. The future for Ivette looks bleak. The cyclone is forecast to encounter even stronger southwesterly shear in the next few days, along with increasingly drier air and marginal sea surface temperatures. These factors suggest that Ivette's time as a tropical cyclone would likely come to a close sooner rather than later, and the official forecast calls for remnant low status in 36 hours in agreement with the global models. The new intensity forecast is identical to the previous one and is in agreement with the bulk of the intensity guidance, with dissipation shown in 2 days. Ivette has been maintaining a west-northwestward motion of 290/10. This general motion should continue today as the cyclone is steered by the flow on the south side of a subtropical ridge. A westward and west-southwestward change in the cyclone's heading is likely once Ivette becomes a shallower cyclone in about 24 hours. The new forecast track is hardly changed from the previous one, and is near the multi-model conensus. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 17.2N 138.4W 40 KT 45 MPH 12H 08/0000Z 17.7N 139.6W 35 KT 40 MPH 24H 08/1200Z 18.3N 141.3W 30 KT 35 MPH 36H 09/0000Z 18.5N 143.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 09/1200Z 18.3N 145.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 10/1200Z...POST-TROP/REMNT LOW $$ Forecaster Kimberlain

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Tropical Storm JAVIER Forecast Discussion Number 2

2016-08-07 16:33:36| National Hurricane Center (East Pacific)

Issued at 1000 AM CDT SUN AUG 07 2016 000 WTPZ41 KNHC 071433 TCDEP1 TROPICAL DEPRESSION ELEVEN-E DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112016 1000 AM CDT SUN AUG 07 2016 The cloud pattern of the depression has not become any better organized since earlier today. There is little evidence of banding features at this time, although upper-level outflow is fairly well defined over the northern semicircle of the cyclone. The intensity is held at 30 kt based on Dvorak classifications from TAFB and SAB as well as the lack of any surface observations of tropical-storm- force winds. Aside from some land interaction with southwestern Mexico today, the cyclone will move over warm waters and in a low shear environment, which should allow for strengthening. However, since the system is currently broad and poorly organized, only gradual intensification is anticipated. The official intensity forecast is the same as the previous one and very close to the latest SHIPS guidance. Since the center is not yet well-defined, there is significant uncertainty in the initial motion, which is estimated to be 300/9 kt. The depression is expected to move around the southwestern periphery of a mid-tropospheric high pressure system for the next day or two, and then turn toward the right ahead of a trough near southern California. The official track forecast is similar to that from the last advisory and in close agreement with the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 18.7N 105.0W 30 KT 35 MPH 12H 08/0000Z 19.5N 106.5W 35 KT 40 MPH 24H 08/1200Z 20.7N 108.0W 40 KT 45 MPH 36H 09/0000Z 21.7N 109.1W 45 KT 50 MPH 48H 09/1200Z 22.8N 110.2W 50 KT 60 MPH 72H 10/1200Z 25.2N 112.1W 35 KT 40 MPH 96H 11/1200Z 27.5N 113.0W 25 KT 30 MPH...POST-TROP/INLAND 120H 12/1200Z...DISSIPATED $$ Forecaster Pasch

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Tropical Depression ELEVEN-E Forecast Discussion Number 1

2016-08-07 10:55:14| National Hurricane Center (East Pacific)

Issued at 400 AM CDT SUN AUG 07 2016 000 WTPZ41 KNHC 070854 TCDEP1 TROPICAL DEPRESSION ELEVEN-E DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112016 400 AM CDT SUN AUG 07 2016 The low pressure area near the southwestern coast of Mexico has become better defined overnight, and there is sufficient convective organization to classify the system as a tropical depression. Although the convection near the center has recently decreased, there are several curved bands around the outer portion of the circulation. Recent land-based observations indicate that brisk southeasterly winds are occurring along the immediate coast of Mexico, and ship H9LA reported a minimum pressure of 1004.9 mb and 31 kt southerly winds early in the evening. Based on these data, the initial wind speed is estimated to be 30 kt. The forecast track of the depression takes it over very warm water during the next couple of days, but moderate easterly shear and interaction with the mountainous terrain of southwestern Mexico should mean only slight strengthening today. Additional modest intensification is expected tonight and Monday, before the system nears the southern portion of the Baja California peninsula in about 48 hours. After that time, interaction with land and a more stable airmass should cause weakening, and the cyclone is forecast to dissipate near or over the central Baja California peninsula in 4 to 5 days. The NHC intensity forecast is in good agreement with the SHIPS guidance, which is a little above the dynamical models. Since the tropical cyclone is still in its formative stage, the initial motion estimate is a highly uncertain 290/9 kt. The depression is forecast to turn northwesterly by late Sunday as it moves around the southwestern portion of a strong mid-level ridge centered over the south-central United States. In 3 to 4 days, a deepening mid-level trough off the west coast of the United States should cause the cyclone to turn north-northwestward or northward. The track guidance is in good agreement and the NHC forecast lies near the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 18.0N 104.3W 30 KT 35 MPH 12H 07/1800Z 19.0N 105.8W 35 KT 40 MPH 24H 08/0600Z 20.3N 107.4W 40 KT 45 MPH 36H 08/1800Z 21.3N 108.7W 45 KT 50 MPH 48H 09/0600Z 22.4N 110.0W 50 KT 60 MPH 72H 10/0600Z 24.6N 112.0W 35 KT 40 MPH 96H 11/0600Z 27.0N 113.0W 25 KT 30 MPH...INLAND 120H 12/0600Z...DISSIPATED $$ Forecaster Brown

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Tropical Storm IVETTE Forecast Discussion Number 19

2016-08-07 10:38:34| National Hurricane Center (East Pacific)

Issued at 200 AM PDT SUN AUG 07 2016 000 WTPZ45 KNHC 070838 TCDEP5 TROPICAL STORM IVETTE DISCUSSION NUMBER 19 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102016 200 AM PDT SUN AUG 07 2016 Convection has redeveloped on the northern side of Ivette, although the center remains partially exposed. An ASCAT-A pass at 6Z revealed maximum winds of 35-40 kt, and since thunderstorm activity has increased markedly since that time, the initial wind speed is kept at 40 kt. Ivette is forecast to gradually spin down over the next few days due to cooling waters, strong shear and entrainment of dry air aloft. A strong surface high over the central Pacific should cause an enhanced gradient on the northern side of Ivette, similar to Howard's synoptic situation last week. Thus, Ivette will probably have an extended weakening phase, and the official forecast reflects this situation, ending up a little higher than the previous advisory at day 2 and 3. The global models continue to show the system opening up into a trough by day 4. The storm remains on track and is moving 290/10 kt. Ivette should gradually turn westward and west-southwestward over the next few days as it becomes a shallow remnant low. No significant changes were made to the previous forecast, and the new NHC track prediction continues to be positioned only a small distance south of the model consensus. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 16.9N 137.3W 40 KT 45 MPH 12H 07/1800Z 17.4N 138.6W 35 KT 40 MPH 24H 08/0600Z 18.0N 140.3W 30 KT 35 MPH 36H 08/1800Z 18.4N 141.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 09/0600Z 18.4N 143.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 10/0600Z 17.5N 148.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 11/0600Z...DISSIPATED $$ Forecaster Blake

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Tropical Storm IVETTE Forecast Discussion Number 18

2016-08-07 04:34:03| National Hurricane Center (East Pacific)

Issued at 800 PM PDT SAT AUG 06 2016 000 WTPZ45 KNHC 070233 TCDEP5 TROPICAL STORM IVETTE DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102016 800 PM PDT SAT AUG 06 2016 Visible and infrared satellite imagery indicate that all of Ivette's deep convection has been sheared away by moderate-to-strong southwesterly vertical wind shear, leaving the low-level circulation center fully exposed more than 80 n mi southwest of any convection. Satellite intensity estimate from TAFB and SAB have decreased as a result, and the latest UW-CIMSS intensity estimate is T2.7/39 kt. Allowing for some vortex spin down since the previous advisory intensity of 45 kt, the initial intensity has been lowered to 40 kt for this advisory. Ivette has continued to move west-northwestward, or 290/10 kt. This general motion should continue for the next 36 hours or so while the cyclone moves toward a weakness in the subtropical ridge around 139W-140W longitude. After that time, however, Ivette is expected to be a vertically shallow remnant low pressure system that will be steered westward and then west-southwestward by the low-level tradewind flow. The new NHC track forecast is essentially just an extension of the previous advisory track and lies a little south of the multi-model consensus TVCN due to more rapid weakening than previously expected. Ivette still has a very robust low-level circulation and is moving over near-28C SSTs, so redevelopment of deep convection seems likely tonight after 0600Z during the convective maximum period, which should allow the cyclone to retain tropical storm status. However, by 24 hours and beyond, strong southwesterly shear of 25 kt or more, along with considerably drier mid-level air and SSTs of around 26C, should cause any remaining convection to dissipate. As a result, Ivette is forecast to become a remnant low pressure system by 36 hours, with dissipation expected by 96 hours, if not sooner. The official intensity forecast closely follows a blend of the SHIPS and LGEM intensity model solutions. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 16.7N 136.4W 40 KT 45 MPH 12H 07/1200Z 17.2N 137.7W 35 KT 40 MPH 24H 08/0000Z 17.9N 139.3W 30 KT 35 MPH 36H 08/1200Z 18.4N 140.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 09/0000Z 18.5N 142.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 10/0000Z 17.9N 146.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 11/0000Z...DISSIPATED $$ Forecaster Stewart

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