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Tropical Storm IVETTE Forecast Discussion Number 4

2016-08-03 16:32:38| National Hurricane Center (East Pacific)

Issued at 800 AM PDT WED AUG 03 2016 000 WTPZ45 KNHC 031432 TCDEP5 TROPICAL STORM IVETTE DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102016 800 AM PDT WED AUG 03 2016 Ivette's convective pattern is gradually improving, with a band lying to the west of a central cluster of deep convection. However, recent microwave data still shows the low-level center displaced to the northeast of the deepest convection due to some shear. Dvorak intensity estimates are T3.0/45 kt from SAB and T2.5/35 kt from TAFB; the initial intensity is therefore raised to 40 kt. Sea surface temperatures are expected to be 27-28C for the next 96 hours, while the vertical shear affecting the cyclone is forecast to gradually diminish over the next couple of days. These conditions would seem to support steady or even fast strengthening. Surprisingly, the SHIPS, LGEM, GFDL, and HWRF models only intensify Ivette to near the hurricane threshold. Given the seemingly favorable environment, the NHC official forecast is above all of the main intensity models, with the exception of COAMPS-TC, and it does not deviate from the peak intensity indicated in the previous advisory. Slightly lower SSTs and increasing shear are likely to cause some weakening by days 4 and 5. A strong subtropical ridge extending westward from northern Mexico is causing Ivette to move quickly west-northwestward at 285/15 kt. The ridge is expected to remain entrenched north of Ivette for the next three days, putting the cyclone on a westward heading but with a gradually decreasing forward speed. By days 4 and 5, Ivette could gain a little more latitude due to a break in the ridge that will develop northeast of the Hawaiian Islands. There is high confidence in the future track of Ivette due to a tightly clustered model envelope, and the NHC track forecast is mainly an update of the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 14.6N 120.4W 40 KT 45 MPH 12H 04/0000Z 15.0N 122.7W 45 KT 50 MPH 24H 04/1200Z 15.2N 125.6W 55 KT 65 MPH 36H 05/0000Z 15.4N 128.3W 65 KT 75 MPH 48H 05/1200Z 15.6N 130.8W 70 KT 80 MPH 72H 06/1200Z 16.5N 135.1W 80 KT 90 MPH 96H 07/1200Z 18.0N 138.5W 75 KT 85 MPH 120H 08/1200Z 19.0N 141.5W 65 KT 75 MPH $$ Forecaster Berg

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Tropical Storm EARL Forecast Discussion Number 4

2016-08-03 10:50:08| National Hurricane Center (Atlantic)

Issued at 500 AM EDT WED AUG 03 2016 000 WTNT45 KNHC 030849 TCDAT5 TROPICAL STORM EARL DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052016 500 AM EDT WED AUG 03 2016 Microwave imagery since 01Z indicates that Earl has formed a mid-level eye, and ASCAT data near 02Z and 03Z suggests that the circulation center has reformed to the south of the previous forecast track underneath the eye feature. Satellite intensity estimates from TAFB and SAB are 55 kt, and that will be the initial intensity. A NOAA Hurricane Hunter aircraft is currently enroute to investigate Earl. The latest satellite imagery suggests that the track excursion caused by the reformation is over, and that Earl is resuming a westward motion of 280/12. A large subtropical ridge centered over the southern United States should steer Earl generally westward to west-northwestward for the next 3-4 days, with the cyclone moving near the Bay Islands of Honduras in 12-18 hours, near or over Belize and the southern Yucatan Peninsula of Mexico in about 24 hours, and over southeastern Mexico and possibly the Bay of Campeche thereafter. The new forecast track is similar to, but south of, the previous track based mainly on the initial position, and it lies a little to the south of the various consensus models. Earl is expected to remain in a light to moderate vertical wind shear environment over very warm sea surface temperatures until landfall. This combination should allow continued strengthening, and the forecast intensity at landfall has been increased slightly from the previous advisory based on the SHIPS and LGEM models. Weakening will occur after landfall as the cyclone passes over southeastern Mexico. The new forecast track has Earl spending less time over the Bay of Campeche than the previous track, so the new intensity forecast shows less re-intensification than the previous forecast. A hurricane watch or warning could be required for the Bay Islands of Honduras later today due to the new forecast track being closer to the islands. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 16.1N 83.7W 55 KT 65 MPH 12H 03/1800Z 16.5N 85.5W 60 KT 70 MPH 24H 04/0600Z 17.0N 87.9W 70 KT 80 MPH 36H 04/1800Z 17.5N 90.3W 45 KT 50 MPH...INLAND 48H 05/0600Z 18.1N 92.4W 30 KT 35 MPH...INLAND 72H 06/0600Z 19.0N 96.0W 35 KT 40 MPH...INLAND 96H 07/0600Z 19.0N 100.0W 20 KT 25 MPH...INLAND 120H 08/0600Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm HOWARD Forecast Discussion Number 12

2016-08-03 10:46:07| National Hurricane Center (East Pacific)

Issued at 200 AM PDT WED AUG 03 2016 000 WTPZ44 KNHC 030845 TCDEP4 TROPICAL STORM HOWARD DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092016 200 AM PDT WED AUG 03 2016 Deep convection associated with Howard has continued to decrease and become separated from the low-level center overnight. Several microwave overpasses since the previous advisory and recent ASCAT data have been extremely helpful in locating the center, which is displaced well south of the remaining area of cold cloud tops. The initial wind speed has been reduced to 40 kt, which is based on the scatterometer data that revealed 35 to 40 kt winds over the northeastern portion of the circulation. Howard is moving west-northwestward or 290/13 kt. The track forecast philosophy remains the same as the previous advisory. The tropical storm should move west-northwestward to the south of a subtropical ridge today, then turn westward by Thursday as the cyclone weakens and comes under the influence of the low-level easterly trades. The model guidance is in good agreement on this scenario, but has generally shifted southward at days 4 and 5. The NHC track has been adjusted accordingly, but it remains near the middle of the guidance envelope. The tropical storm should continue to weaken during the next day or so while it moves over cool water and into a drier and more stable environment. Howard is forecast to become a remnant low in 24 to 36 hours, but this could occur sooner if organized deep convection does not redevelop later today. The cyclone will be move over slightly warm waters after 48 hours, but increasing shear and unfavorable thermodynamic conditions should prevent restrengthening. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 20.3N 132.6W 40 KT 45 MPH 12H 03/1800Z 21.0N 134.7W 35 KT 40 MPH 24H 04/0600Z 21.7N 137.5W 30 KT 35 MPH 36H 04/1800Z 22.1N 140.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 05/0600Z 22.3N 143.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 06/0600Z 22.5N 148.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 07/0600Z 22.3N 153.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 08/0600Z 21.8N 158.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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Tropical Storm HOWARD Forecast Discussion Number 11

2016-08-03 04:57:38| National Hurricane Center (East Pacific)

Issued at 800 PM PDT TUE AUG 02 2016 000 WTPZ44 KNHC 030257 TCDEP4 TROPICAL STORM HOWARD DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092016 800 PM PDT TUE AUG 02 2016 Howard is still displaying some convection this evening, but the extent and organization of the convection is diminishing. Correspondingly, the Dvorak classifications are dropping and a blend of the TAFB, SAB, and CIMSS-ADT values indicate the intensity has dropped to around 40-45 kt. 45 kt is used as the initial intensity, though this may be generous given Howard's recent trends. The initial position of Howard has significant uncertainty, as there have been no microwave images available nor has the last-light visible imagery been very illuminating. The initial motion is assessed as 13 kt toward the west-northwest, as the system is primarily being steered by a mid-level ridge to its northeast. The track models are tightly clustered and suggest a gradual turn toward the west at about the same forward speed during the next few days. The NHC track forecast is nearly the same as that from the previous advisory and is based upon the TVCN track model consensus. While the vertical shear should remain relatively low over Howard during the next day and a half, the SSTs that Howard will traverse should get quite cool and the atmosphere dry and stable. At about two days, the SSTs become lukewarm but the shear becomes prohibitive for intensification. Thus it is expected that Howard will gradually weaken, and in about two days lose its deep convection and become a post-tropical cyclone. The NHC intensity forecast is based upon the LGEM and SHIPS statistical/dynamical methods, as the three dynamical hurricane models - HWRF, GFDL, and COAMPS - all unrealistically re-intensify Howard between days three and five. This official forecast calls for slightly weaker intensities than those indicated in the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 20.1N 131.3W 45 KT 50 MPH 12H 03/1200Z 20.9N 133.3W 40 KT 45 MPH 24H 04/0000Z 21.7N 136.1W 40 KT 45 MPH 36H 04/1200Z 22.3N 138.9W 35 KT 40 MPH 48H 05/0000Z 22.6N 141.8W 35 KT 40 MPH...POST-TROPICAL 72H 06/0000Z 23.0N 147.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 07/0000Z 23.0N 152.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 08/0000Z 23.0N 157.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Landsea

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Tropical Storm EARL Forecast Discussion Number 3

2016-08-03 04:56:36| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT TUE AUG 02 2016 000 WTNT45 KNHC 030256 TCDAT5 TROPICAL STORM EARL DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052016 1100 PM EDT TUE AUG 02 2016 Dropsonde data from a NOAA Hurricane Hunter aircraft investigating Earl several hours ago indicated that the central pressure had fallen to 996 mb or even lower. Therefore the intensity was increased to 50 kt. Some higher surface wind speeds were reported from the aircraft's SFMR instrument, but these are believed to have been rain-inflated. The storm is gradually becoming better organized, with some developing banding features seen on satellite images. With low shear and SSTs approaching 30 C along the projected track, additional strengthening is likely and the NHC forecast calls for Earl to become a hurricane prior to landfall. This is in close agreement with the latest SHIPS guidance and only slightly above the model consensus. Weakening will occur after the cyclone makes landfall over Yucatan, and the amount of restrengthening in 2-3 days is highly dependent on how far Earl moves into the southern Bay of Campeche. Based on aircraft and satellite center fixes, the initial motion is estimated to be 280/14 kt. The track forecast reasoning is essentially unchanged from the previous advisory package. A large and nearly stationary mid-tropospheric high pressure system centered over the southern Great Plains should prevent the tropical cyclone from moving significantly northward. The official forecast track is close to the model consensus for the first 48 hours and is a blend of the GFS and ECMWF tracks thereafter, with the former model's track to the north of the latter one. This is fairly similar to the previous NHC forecast. The new intensity forecast has necessitated the issuance of a hurricane warning for the coast of Belize and a portion of the coast of the Yucatan Peninsula of Mexico. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 16.4N 83.0W 50 KT 60 MPH 12H 03/1200Z 16.7N 84.8W 55 KT 65 MPH 24H 04/0000Z 17.1N 87.2W 65 KT 75 MPH 36H 04/1200Z 17.8N 89.6W 50 KT 60 MPH...INLAND 48H 05/0000Z 18.4N 91.8W 30 KT 35 MPH...INLAND 72H 06/0000Z 19.0N 95.5W 40 KT 45 MPH...OVER WATER 96H 07/0000Z 19.5N 99.0W 20 KT 25 MPH...INLAND 120H 08/0000Z...DISSIPATED $$ Forecaster Pasch

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