8 Sep Weather in Cayman & Tropical Report, 2 TS, 1 TD, 1 Dist
8 Sep Sat 2018
Tropical Report
Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sat Sep 8 2018
For the North Atlantic…Caribbean Sea and the Gulf of Mexico:
The National Hurricane Center is issuing advisories on Tropical
Storm Florence, located over the central Atlantic Ocean, on Tropical
Storm Helene, located near the coast of Africa, and on Tropical
Depression Nine, located over the eastern Atlantic.
1. A trough of low pressure is generating disorganized showers over the
western Atlantic near Bermuda. Development of this system, if any,
should be slow to occur before environmental conditions become
unfavorable in a couple of days.
* Formation chance through 48 hours…low…10 percent.
* Formation chance through 5 days…low…10 percent.
Public Advisories on Tropical Storm Helene are issued under WMO
header WTNT33 KNHC and under AWIPS header MIATCPAT3.
Forecast/Advisories on Tropical Storm Helene are issued
under WMO header WTNT23 KNHC and under AWIPS header MIATCMAT3.
Public Advisories on Tropical Depression Nine are issued under
WMO header WTNT34 KNHC and under AWIPS header MIATCPAT4.
Forecast/Advisories on Tropical Depression Nine are issued under WMO
header WTNT24 KNHC and under AWIPS header MIATCMAT4.
Forecaster Beven
HELENE MOVING WESTWARD TOWARD THE SOUTHERN CABO VERDE ISLANDS… …TROPICAL STORM CONDITIONS EXPECTED TO REACH PORTIONS OF THE CABO VERDE ISLANDS TONIGHT
Tropical Storm Helene Discussion Number 4
NWS National Hurricane Center Miami FL AL082018
500 AM AST Sat Sep 08 2018
Helene’s structure appears to be quickly improving this morning.
The initial intensity has been increased to 40 kt based on a blend
of the latest subjective Dvorak intensity estimates and the
UW-CIMSS SATCON. Several microwave passes overnight indicate that
the cyclone has become more vertically aligned, likely due to a
reformation of the center beneath the strongest convection. In
fact, a 0733 UTC SSMIS image shows the early development of a low-
to mid-level eye, which is often a precursor to intensification.
Nearly all of the intensity guidance seems to have picked up on the
improved structure of Helene, and the models show far more
intensification than before, especially through 48 h. Consequently,
a significant change has been made to the intensity forecast, which
now calls for Helene to become a hurricane on Sunday while it is
near the Cabo Verde islands. Once the cyclone passes the islands,
the environment is expected to remain favorable for intensification
for at least 72 h. By the end of the forecast period, all of the
guidance shows some weakening due primarily to increased shear
associated with an approaching mid- to upper-level trough over the
central Atlantic. Given the recent microwave imagery signature, low
shear, and warm SSTs, its possible that the current forecast is
still too conservative, especially for the first 36 h of the
forecast, and further adjustments could be required if it becomes
clear that Helene is intensifying at a faster rate than expected.
Smoothing through the possible reformation of the center, Helene
appears to be moving west with an initial motion around 275/10 kt.
Little change was required to the track forecast, which has been
nudged only slightly south for the first 48 h of the forecast, in
line with the latest track model consensus. A westward motion
should continue for the next couple of days, as Helene is steered
by a mid-level ridge to the north. By day 5, the aforementioned
trough over the central Atlantic should force Helene to turn toward
the northwest.
FORECAST POSITIONS AND MAX WINDS
INIT 08/0900Z 13.7N 19.6W 40 KT 45 MPH
12H 08/1800Z 13.9N 21.2W 50 KT 60 MPH
24H 09/0600Z 14.1N 23.5W 60 KT 70 MPH
36H 09/1800Z 14.7N 26.3W 70 KT 80 MPH
48H 10/0600Z 15.4N 29.3W 75 KT 85 MPH
72H 11/0600Z 17.2N 35.1W 80 KT 90 MPH
96H 12/0600Z 19.0N 39.5W 70 KT 80 MPH
120H 13/0600Z 22.0N 42.5W 65 KT 75 MPH
$$
Forecaster Zelinsky
DEPRESSION EXPECTED TO BECOME A TROPICAL STORM LATER TODAY OVER THE EASTERN TROPICAL ATLANTIC
Tropical Depression Nine Discussion Number 3
NWS National Hurricane Center Miami FL AL092018
500 AM AST Sat Sep 08 2018
The depression continues to be affected by moderate to strong east
to southeasterly vertical wind shear, which has resulted in the
bulk of the deep convection being displaced to the west of the
low-level center. The initial intensity has been held at 30 kt
based on Dvorak satellite intensity estimate of T2.0/30 kt from
both TAFB and SAB.
The depression has been meandering in the same general area for the
past 12-18 h due to being caught in a weakness in the subtropical
ridge. However, recent microwave satellite data suggest that the
cyclone is now moving slowly northwestward. A turn toward the west
is expected to occur later today as a shortwave trough to the north
that has weakened the ridge lifts out, allowing the ridge to fill
back in and build westward to the north of the Lesser Antilles. The
latest NHC model guidance suite remains tightly packed, and the
official forecast track lies down the middle of the envelope near a
blend of the consensus aids TCVA, HCCA, FSSE.
Although the wind shear is forecast to gradually weaken and become
less than 5 kt by 36-48 h, which would favor rapid strengthening,
the airmass that the cyclone is embedded is fairly dry. Since
mid-level humidity values are forecast to decrease from the current
60-percent range down to around 50 percent by 48 hours and beyond,
only modest strengthening is expected during the next 4 days. By day
5, vertical wind shear from the southwest is forecast to increase to
20-25 kt, serving to cap the intensification process. The NHC
intensity forecast is based on a blend of the IVCN and the HCCA
consensus models, and continues to remain below the stronger HWRF
model at days 4 and 5, which makes the cyclone a major hurricane in
78 h.
FORECAST POSITIONS AND MAX WINDS
INIT 08/0900Z 14.3N 35.4W 30 KT 35 MPH
12H 08/1800Z 14.4N 36.1W 35 KT 40 MPH
24H 09/0600Z 14.5N 37.5W 40 KT 45 MPH
36H 09/1800Z 14.7N 39.5W 45 KT 50 MPH
48H 10/0600Z 14.6N 42.0W 55 KT 65 MPH
72H 11/0600Z 14.5N 47.3W 75 KT 85 MPH
96H 12/0600Z 14.6N 52.7W 80 KT 90 MPH
120H 13/0600Z 14.9N 57.2W 80 KT 90 MPH
$$
Forecaster Stewart
FLORENCE FORECAST TO BECOME A HURRICANE BY SUNDAY… …EXPECTED TO BECOME A MAJOR HURRICANE AGAIN EARLY NEXT WEEK
Tropical Storm Florence Discussion Number 36
NWS National Hurricane Center Miami FL AL062018
500 AM AST Sat Sep 08 2018
Although Florence remains a sheared tropical cyclone, satellite
imagery during the past 6 h also indicates that the shear has
started to abate somewhat, which has allowed the dense cirrus
canopy to build back over the previously exposed low-level
circulation center. Furthermore, deep convection with overshooting
cloud tops near -80C and an abundance of lightning activity have
developed very close to the center. Based on these data along with
Dvorak intensity estimates of T3.5/55 kt from TAFB and SAB, the
initial intensity has been raised to 55 kt.
The initial motion estimate is 265/8 kt. The mid-latitude flow
across CONUS and the northern Atlantic is forecast to flatten out
and become more zonal over the next 48 h or so, resulting in the
development of a narrow east-west oriented ridge along 35/36N
latitude. This large-scale feature is expected to steer Florence
in a general westward direction during that time. By days 3-5,
however, the flow across the central and western U.S. is forecast
to buckle and become more meridional as a deep mid-/upper-level
trough over the northeast Pacific pushes inland over the western
U.S., causing downstream ridging over the northeastern U.S. and
northwestern Atlantic. The global models agree on this general
change in the synoptic-scale flow pattern, but they differ
noticeably on where a downstream mid-/upper-level high pressure cell
takes up residence over the Atlantic either to the northwest or
northeast of Bermuda. The farther west/east the high develops will
determine how far west/east Florence will eventually move and
possibly affect the U.S. east coast beyond the 5-day forecast
period. The new official forecast track is close to the previous
advisory track through 48 h, and then was nudged a little to the
left or west of the previous track, which is close to the consensus
model TVCN and is north of the corrected-consensus models FSSE and
HCCA since the bulk of the NHC model guidance lies north of those
latter two models.
The upper-level environment is expected to improve to significantly
during the next 12 h and beyond with the current 20 kt of
southwesterly shear forecast to give way to shear of less than 10
kt. By 72 h and beyond, light shear from the southeast and east
along with the development of strong upper-level outflow jets to
the north of Florence is expected to create an environment that
favors significant and possibly even rapid strengthening. The new
NHC intensity forecast has been increased over the previous advisory
in anticipation of these very favorable dynamical conditions
developing, and now shows Florence becoming a hurricane by Sunday
and a major hurricane in 3 days, followed by additional
strengthening over the very warm Atlantic waters of at least 29 deg
C that are about 2 deg C above normal right now. The consensus
models IVCN and HCCA were closely followed, which are a little
below the FSSE model.
Key Messages:
1. Regardless of Florence’s eventual track, large swells are
affecting Bermuda and will begin to affect portions of the U.S.
East Coast this weekend, resulting in life-threatening surf and rip
currents.
2. The risk of other direct impacts associated with Florence along
the U.S. East Coast next week has increased. However, there is
still very large uncertainty in model forecasts of Florence’s track
beyond day 5, making it too soon to determine the exact location,
magnitude, and timing of these impacts. Interests near and along
the U.S. East Coast should monitor the progress of Florence through
the weekend and ensure they have their hurricane plans in place.
FORECAST POSITIONS AND MAX WINDS
INIT 08/0900Z 24.5N 54.2W 55 KT 65 MPH
12H 08/1800Z 24.6N 55.0W 60 KT 70 MPH
24H 09/0600Z 24.6N 56.0W 65 KT 75 MPH
36H 09/1800Z 24.6N 57.2W 75 KT 85 MPH
48H 10/0600Z 24.9N 59.0W 90 KT 105 MPH
72H 11/0600Z 26.0N 64.0W 105 KT 120 MPH
96H 12/0600Z 28.0N 70.2W 120 KT 140 MPH
120H 13/0600Z 30.9N 75.8W 125 KT 145 MPH
$$
Forecaster Stewart
OLIVIA MOVING WEST-NORTHWESTWARD TOWARD THE CENTRAL PACIFIC BASIN
Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Sat Sep 8 2018
For the eastern North Pacific…east of 140 degrees west longitude:
The National Hurricane Center is issuing advisories on Hurricane
Olivia, located about 1200 miles east of Hilo, Hawaii.
1. Showers and thunderstorms associated with a low pressure system
located about 600 miles south-southwest of the southern tip of the
Baja California peninsula continue to show signs of organization,
and it appears that a tropical depression could be forming. If
this trend continues, then advisories would be initiated on this
system later today. The low is expected to move northwestward at
about 10 mph during the next couple of days, away from the coast of
Mexico.
* Formation chance through 48 hours…high…near 100 percent.
* Formation chance through 5 days…high…near 100 percent.
Forecaster Berg
Global Tropics & Benefits Outlook
Weather in Cayman
SYNOPSIS
Isolated showers and some thunder will continue across the Cayman area for the next 24 hours as the upper level trough interacts with a tropical wave over the Northwest Caribbean. Radar images show isolated showers in and around the Cayman area moving towards the northwest. The National Hurricane Center is issuing advisories on Tropical Storm Florence, Tropical Storm Helene and Tropical Depression 9. These systems pose no threat to the Cayman Islands. For further information please visit www.nhc.noaa.gov.
Humidity: 87% (UP from yesterday)
UV: 11.5 EXTREME (UP from yesterday)
Temperature: Today’s current temperature – See weather forecast top right of website. Yesterday: H 90.5°F L 79.1°F
Wind direction TODAY: E 10-15 mph GC
Wind direction TONIGHT: E 5-10 mph GC
Barometer: 1014.40 mb Steady Rain: Last month: 1.83 in Last 24 hrs 0.81 This month: 2.29 in 0 days since rain 4 rain day in September
2017 Season Total: 62.94 in 2018 Season Total: 26.29 in
Average Yearly Rainfall 56.20 in (Note: National Weather Service 2017 Season Total – measured at Owen Roberts Airport GT – was 59.32 in)
All readings are from SOUTH SOUND.
Average rainfall in September 8.2 in. Average temperature in September: 77°F to 90°F
Sea Temperature in September 84°F
MOON:
2% Waning Crescent
TIDES, SUNRISE, SUNSET, MOON RISE, MOON SET AND MOON PHASE
GRAND CAYMAN SEPTEMBER 2018 – Click to enlarge
LOCAL 5 DAY FORECAST
http://www.weather.gov.ky/portal/page?_pageid=4421,7428393&_dad=portal&_schema=PORTAL
FOR RADAR IMAGE GO TO: http://www.weather.gov.ky/portal/page/portal/nwshome/forecasthome/radar
Also see Weather In Cayman: http://www.weatherincayman.com/
Moon info and graphic:
https://www.timeanddate.com/moon/uk/georgetown
Atlantic satellite image: http://www.intellicast.com/global/satellite/infrared.aspx?region=hiatlsat
Description:
The Global Infrared Satellite image shows clouds by their temperature. Red and blue areas indicate cold (high) cloud tops. Infrared (IR) radiation is electromagnetic radiation whose wavelength is longer than that of visible light, but shorter than that of terahertz radiation and microwaves. Weather satellites equipped with scanning radiometers produce thermal or infrared images which can then enable a trained analyst to determine cloud heights and types, to calculate land and surface water temperatures, and to locate ocean surface features.
Tropical storm data and graphics from National Hurricane Center at: https://www.nhc.noaa.gov/
Weathernerds: https://www.weathernerds.org/
Mikes Weather Page: http://www.spaghettimodels.com/
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