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Tropical Storm Cristina Forecast Discussion Number 8

2020-07-08 16:58:06| National Hurricane Center (East Pacific)

Issued at 900 AM MDT Wed Jul 08 2020 000 WTPZ45 KNHC 081457 TCDEP5 Tropical Storm Cristina Discussion Number 8 NWS National Hurricane Center Miami FL EP052020 900 AM MDT Wed Jul 08 2020 First light satellite images show that the convective organization of Cristina is gradually improving, while banding features are developing across the northern portion of the circulation. The center remains underneath the northeastern side of the main area of convection due to moderate shear, but this shear appears to be diminishing. The initial intensity has been increased to 50 kt, which is a blend of the subjective Dvorak intensity estimates from TAFB and SAB. Cristina turned to the northwest and slowed down to about 10 kt this morning. A turn back toward the west-northwest is expected to occur later today or tonight, and this motion is forecast to continue for the next few days as the cyclone is steered by a large ridge centered over the southwestern United States. Later in the forecast period, a turn to the west is expected as the weakening cyclone becomes steered by the low-level easterlies. The track guidance is tightly clustered, and the NHC forecast lies near the middle of the envelope. The decreasing shear over Cristina combined with warm SSTs and a moist air mass should allow the cyclone to intensify over the next couple of days. After that time, the system will cross over the 26 C isotherm and enter into a drier and more stable atmospheric environment. This should cause a steady weakening trend to begin after 48 h. Although the forecast still shows Cristina as a tropical storm in 5 days, it is possible all of the deep convection would have dissipated by that time. The latest NHC forecast is very close to the intensity consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 14.6N 106.9W 50 KT 60 MPH 12H 09/0000Z 15.4N 108.2W 55 KT 65 MPH 24H 09/1200Z 16.6N 110.1W 65 KT 75 MPH 36H 10/0000Z 17.6N 112.1W 70 KT 80 MPH 48H 10/1200Z 18.5N 114.1W 75 KT 85 MPH 60H 11/0000Z 19.5N 116.5W 70 KT 80 MPH 72H 11/1200Z 20.2N 119.1W 60 KT 70 MPH 96H 12/1200Z 21.0N 124.5W 45 KT 50 MPH 120H 13/1200Z 21.5N 130.5W 35 KT 40 MPH $$ Forecaster Latto

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Tropical Storm Cristina Forecast Discussion Number 7

2020-07-08 10:33:00| National Hurricane Center (East Pacific)

Issued at 300 AM MDT Wed Jul 08 2020 000 WTPZ45 KNHC 080832 TCDEP5 Tropical Storm Cristina Discussion Number 7 NWS National Hurricane Center Miami FL EP052020 300 AM MDT Wed Jul 08 2020 Satellite images indicate that deep convection has been gradually increasing in association with Cristina during the past several hours. However, the storm still lacks banding features and the low-level center is located on the northeastern side of the convection due to moderate wind shear. An ASCAT-B overpass from a few hours ago showed maximum winds of only 30-35 kt in the southeastern quadrant. The initial intensity is held at 40 kt for this advisory blending the ASCAT data with the 3.0/45 kt Dvorak estimates from TAFB and SAB. Cristina is forecast to remain over warm SSTs and in a moist air mass for the next couple of days. These favorable conditions combined with lessening wind shear should promote steady strengthening during the next two days or so. However, beyond that time, Cristina is expected to move over waters cooler than 26 C and into a progressively drier and more stable environment. These negative factors for the cyclone should promote weakening after 48 hours. The new NHC intensity forecast is again nudged downward from the previous one, but it still lies at the high end of the guidance in the short term in case Cristina takes advantage of the generally conducive conditions for intensification. The tropical storm has turned a little to the left recently, but its longer term motion is still west-northwestward at 13 kt. A deep-layer ridge centered over the southwestern U.S. is expected to remain stationary, and that should cause the cyclone to continue moving west-northwestward at about the same forward speed for the next 4 days or so. By the end of the forecast period, a slight turn to the west is forecast as the weakening system is expected to be steered by the low-level flow. The track models are tightly packed, and only minor changes were made to the previous NHC forecast. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 13.9N 106.5W 40 KT 45 MPH 12H 08/1800Z 14.9N 108.0W 50 KT 60 MPH 24H 09/0600Z 16.1N 109.8W 55 KT 65 MPH 36H 09/1800Z 17.1N 111.6W 65 KT 75 MPH 48H 10/0600Z 18.0N 113.4W 75 KT 85 MPH 60H 10/1800Z 19.0N 115.6W 70 KT 80 MPH 72H 11/0600Z 20.0N 118.0W 65 KT 75 MPH 96H 12/0600Z 21.4N 123.6W 50 KT 60 MPH 120H 13/0600Z 21.9N 129.2W 40 KT 45 MPH $$ Forecaster Cangialosi

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Tropical Storm Cristina Forecast Discussion Number 6

2020-07-08 04:37:58| National Hurricane Center (East Pacific)

Issued at 1000 PM CDT Tue Jul 07 2020 000 WTPZ45 KNHC 080237 TCDEP5 Tropical Storm Cristina Discussion Number 6 NWS National Hurricane Center Miami FL EP052020 1000 PM CDT Tue Jul 07 2020 Since the previous advisory, Cristina's well-defined low-level center became briefly exposed for a couple of hours, likely resulting in a slight spin-down of the vortex. However, deep convection has recently redeveloped over and southwest of the center, so the intensity will be held at 40 kt for this advisory, which is a blend of TAFB and SAB subjective satellite classifications, and the most recent downward-trending UW-CIMSS ADT estimate of T2.9/43 kt. The initial motion estimate is 300/13 kt. There is no significant change to the previous forecast track or reasoning. The latest NHC model guidance remains in excellent agreement on Cristina moving west-northwestward south of a nearly stationary deep-layer subtropical ridge for the next 5 days. The new NHC forecast track is a tad north of the previous advisory track, and lies close to the tightly packed simple and corrected consensus models. High-resolution GOES-16 visible satellite imagery indicates that Cristina's center has been moving closer to the center of the synoptic-scale upper-level anticyclone where the vertical wind shear should be lower. The recent burst of deep convection near the center could the beginning stages of more significant strengthening owing to the lower shear, high mid-level humidity near 80 percent, and sea-surface temperatures (SSTs) near 29C. Therefore, steady strengthening is forecast for the next 60 h while the cyclone remains over warm SSTs, and a period of rapid intensification (RI) is still possible during the next couple of days. By 72 h and beyond, however, Cristina will be moving over sub-26 deg C SSTs that will decrease to about 22C by 120 h, with the much cooler water inducing steady weakening on days 4-5. The NHC intensity forecast is similar to the IVCN intensity guidance through 36 hours, and then is slightly higher than the guidance in order to maintain continuity with the previous intensity forecast and also due to the possibility of RI occurring. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 13.8N 105.3W 40 KT 45 MPH 12H 08/1200Z 14.7N 106.7W 50 KT 60 MPH 24H 09/0000Z 15.9N 108.6W 55 KT 65 MPH 36H 09/1200Z 17.0N 110.4W 65 KT 75 MPH 48H 10/0000Z 17.8N 112.2W 75 KT 85 MPH 60H 10/1200Z 18.8N 114.2W 80 KT 90 MPH 72H 11/0000Z 19.8N 116.5W 80 KT 90 MPH 96H 12/0000Z 21.4N 121.6W 65 KT 75 MPH 120H 13/0000Z 22.1N 127.0W 50 KT 60 MPH $$ Forecaster Stewart

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Tropical Storm Cristina Forecast Discussion Number 5

2020-07-07 22:33:53| National Hurricane Center (East Pacific)

Issued at 400 PM CDT Tue Jul 07 2020 667 WTPZ45 KNHC 072033 TCDEP5 Tropical Storm Cristina Discussion Number 5 NWS National Hurricane Center Miami FL EP052020 400 PM CDT Tue Jul 07 2020 Cristina is still being affected by some northeasterly vertical wind shear as visible satellite imagery shows that the center is located near the northeastern edge of the large curved convective band. The various subjective and objective satellite intensity estimates range from 35 to 45 kt, and a recent ASCAT overpass revealed a small area of 35-40 kt wind vectors near the center. Based on these data, the initial intensity is set at 40 kt. The moderate vertical wind shear over the system is forecast to abate over the next 12-24 hours. This, along with SSTs of 28-29C, should allow for strengthening and Cristina is still forecast to become a hurricane in a day or two. Although Cristina has not strengthened as much as anticipated over the past 24 hours, with the more favorable atmospheric conditions anticipated beginning Wednesday, a period of steady to rapid strengthening is still possible. The latest intensity guidance shows a slightly lower peak wind speed than before, so the new NHC intensity forecast has been nudged in that direction. After 72 hours, Cristina will be moving over cooler waters and steady weakening is expected later in the period. Satellite fixes show that Cristina is moving west-northwestward or 305/11 kt. There has been no significant change to the track foreast reasoning. Cristina should continue on a west-northwestward heading over the next several days to the south of a large mid-level ridge over the southwestern United States. The overall track guidance envelop has shifted slightly northward, so the NHC track forecast has been adjusted accordingly. The new track forecast lies between the previous official foreast and the most recent consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 13.0N 103.8W 40 KT 45 MPH 12H 08/0600Z 13.8N 105.3W 45 KT 50 MPH 24H 08/1800Z 15.0N 107.2W 55 KT 65 MPH 36H 09/0600Z 16.1N 109.2W 65 KT 75 MPH 48H 09/1800Z 17.0N 110.9W 75 KT 85 MPH 60H 10/0600Z 18.0N 112.7W 85 KT 100 MPH 72H 10/1800Z 19.0N 114.9W 85 KT 100 MPH 96H 11/1800Z 20.5N 119.8W 70 KT 80 MPH 120H 12/1800Z 21.8N 125.0W 50 KT 60 MPH $$ Forecaster Brown

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Tropical Storm Cristina Forecast Discussion Number 4

2020-07-07 16:48:49| National Hurricane Center (East Pacific)

Issued at 1000 AM CDT Tue Jul 07 2020 000 WTPZ45 KNHC 071448 TCDEP5 Tropical Storm Cristina Discussion Number 4 NWS National Hurricane Center Miami FL EP052020 1000 AM CDT Tue Jul 07 2020 Early morning microwave and first-light visible imagery revealed that the center of Cristina was located well to the east-northeast of previous estimates. The center is now located near the end of a long curved band that goes around portions of its western semicircle. The center position relative to the convection suggests that at least some northeasterly shear is negatively affecting the organization of Cristina and it may not be well vertically aligned yet. Various satellite intensity estimates have increased since the last advisory, but were also based in part on an assumption that the center of Cristina was located farther west, so the initial wind speed has been conservatively held at 35 kt for now. The new NHC track forecast has been adjusted a fair amount to the east of the previous one, mainly due to the updated initial position. That said, the overall thinking behind the forecast has not changed. A mid-level ridge centered over the southwestern U.S. should steer Cristina on a general west-northwestward path through the end of the week. The official forecast is very near the latest multi-model consensus at all forecast times. The shear and some nearby dry air that appear to have inhibited Cristina's organization so far are not expected to persist as negative factors for much longer. All of the models still forecast strengthening, and given the very favorable environment that the cyclone will encounter in a day or two, a period of rapid intensification at some point would not be surprising. The NHC forecast remains near the high end of the guidance envelope, near the HFIP Corrected Consensus. Cristina is forecast to reach cooler waters that will likely lead to weakening over the weekend. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 12.2N 102.8W 35 KT 40 MPH 12H 08/0000Z 12.9N 104.5W 45 KT 50 MPH 24H 08/1200Z 13.9N 106.5W 55 KT 65 MPH 36H 09/0000Z 15.0N 108.4W 65 KT 75 MPH 48H 09/1200Z 15.9N 110.2W 80 KT 90 MPH 60H 10/0000Z 16.9N 112.0W 90 KT 105 MPH 72H 10/1200Z 17.9N 113.8W 90 KT 105 MPH 96H 11/1200Z 19.5N 118.5W 75 KT 85 MPH 120H 12/1200Z 21.0N 123.5W 55 KT 65 MPH $$ Forecaster Zelinsky

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