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Old 09-28-2018, 08:13 PM
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28Sept18 2pPDT/4pCDT/5pEDT: Tropical Depression 20E formed 25Sept, became Tropical Storm Rosa off the SW Mexico coast that same day, became a Cat1 Hurricane 26Sept, and became a powerful Cat4 hurricane by 27Sept. Rapid intensification anyone? Estimated winds as of 2pPDT/5pEDT back down to Cat3 120mph(195km/h) sustained, moving NW 6mph(9km/h), pressure 955mb.

Pacific - Rosa forms September 25, 2018-_rosa.jpg

Expected to turn more to the North tonight, then more NNE as we start the upcoming week. Continued weakening expected, may even become a Tropical Storm(winds between 39-73mph) by end of weekend, but has about a day or so with warmer waters to feed off of if it can keep moving before colder waters are upwelled and help weaken it more as well. Hurricane force winds extend out 35miles(55km) from storm center, Tropical Storm force winds extend up to 185miles(295km). Tropical Storm Watches/Warnings may be posted for central/northern Baja region Saturday or Sunday but storm should be quickly weakening as it approaches the coast with such colder waters that region offshore.

Tropical Storm force winds estimated time of arrival (39+mph):
Pacific - Rosa forms September 25, 2018-_02.jpg

Water temps in Celsius (hurricanes don't like below 26/27C):
Pacific - Rosa forms September 25, 2018-_temps.jpg

Intensity Guidance suggest continued weakening:
Pacific - Rosa forms September 25, 2018-_2in.jpg

Higher swells from the storm for parts of Mexico, Baja region, as well as S California next several days, increased rip current threat.

Heavy scattered rain potential will likely be the biggest story with this storm now from N Baja, NW Mexico and SW US states. Flood potential rising.

GFS brings widespread 20-30mph winds across much of Arizona, and very heavy rain into SW, W, Central and N and NE Arizona into SE Utah, and SW, W Denver.
Pacific - Rosa forms September 25, 2018-us_model-en-087-0_modusa_2018092818_129_500_220.png

The NOAA WPC scattered rain totals prediction map:
Pacific - Rosa forms September 25, 2018-wpc_qpf_168h_p.us_sw.png

Euro model brings in winds 15-30ish mph SW Arizona Tuesday, and much less elsewhere, maybe about the same level for just East of Flagstaff, AZ overnight Tuesday into Wednesday. But it keeps the rain more off to the West into Southern Cali and Southern Nevada, SW Utah, NW Arizona early Tuesday morning into Wednesday:
Pacific - Rosa forms September 25, 2018-us_model-en-087-0_modez_2018092812_135_502_220.png

The HWRF hurricane model brings Rosa into SW Arizona Tuesday with heavy scattered rains and a near 1000mb Low pressure system with winds around Tropical Depression level (35-ish mph).
Pacific - Rosa forms September 25, 2018-hwrf.jpg

Official updates for East Pacific basin storms comes from the US National Hurricane Center based in Miami, FL. Updates are issued at 2 & 8am/pmPDT(5 & 11am/pmEDT) (If Watches/Warnings issued then updates are also added at 5 & 11am/pmPDT (2 & 8am/pmEDT) here: https://www.nhc.noaa.gov/?epac

Cone map (Shows: Current storm wind field at storm center(orange: winds 39mph+, red: 74mph+), Classification (Black/white dots with letters: "D" = Depression, "S" = Tropical Storm, "H" = Cat1 or Cat2 Hurricane, "M" = Major Hurricane (Cat3+)), any coastal tropical Watches/Warnings, and the "cone" is where the center of the storm could be over time (it's NOT the size of the storm), effects of the storm can be felt outside this area:
Pacific - Rosa forms September 25, 2018-_01.jpg

Some of the models, the small black numbers are hours from now (ie: 96 = 4 days from now):
Pacific - Rosa forms September 25, 2018-_01models.jpg

Some Satellite imagery sources:
-Tropical Tidbits: https://www.tropicaltidbits.com/sat/
-GOESeast(GOES16): https://www.star.nesdis.noaa.gov/GOES/index.php
-WeatherNerds: https://www.weathernerds.org/satellite/floaters/
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Old 09-29-2018, 06:12 AM
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29Sept18 - 2aPDT/5aEDT - Winds 100mph(155km/h), moving N 9mph(15km/h), pressure 971mb.

Heavy rainfall continues to be the big story with this system. The totals may not seem like much to the Gulf of Mexico region or US East coast, but just a couple inches can cause large scale issues in Baja, NW Mexico, and SW US.

3-6 inches, isolated 10inches Baja to Sonora.
2-4 inches, isolated 6inches Mogollon Rim of Arizona.
1-2 inches isolated 4inches across Desert Southwest, central Rockies and Great Basin.

The exact position of these rains may be adjusted as we get closer to event start early this coming week, so stay aware of situation anywhere in the SW US region.

High risk of flash flooding, debris flows across deserts & mountains.
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Old 09-29-2018, 07:54 PM
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29Sept18 - 5pPDT/8pEDT - Winds 105mph(165km/h), moving N 12mph(19km/h), pressure 968mb.

Tropical Storm Watch (winds 39mph+ possible within 48hours or less) for Baja coast from Punta Abreojos to Cabo San Quintin. Watches/Warnings are time based issuance and if winds could be at Tropical Storm as nears coast then that means it will change to a Warning when closer to event start.

With Watches now posted that means official storm stats and track cone map are updated by the National Hurricane Center (NHC) every 3 hours at (2,5,8,&11am/pmPDT/EDT) here: https://www.nhc.noaa.gov/?epac

Pacific - Rosa forms September 25, 2018-img_3976.png

Flash Flood Watches up for a large portion of SW US:
Pacific - Rosa forms September 25, 2018-img_3978.png
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Old 10-03-2018, 05:59 PM
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2Oct18 8aPDT/11aEDT - Rosa officially dissipated but brought heavy scattered rains into parts of the SW US region. An archive of previous advisories from the NHC can be found here: https://www.nhc.noaa.gov/archive/2018/ROSA.shtml?
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