TS Irma: Weakening Over Central Florida

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srainhoutx
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Praying that trough over the Eastern half of the United States digs a tad deeper and bit further East protecting Florida from the full wrath of Irma.

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Hurricane Irma Discussion Number 33...Corrected
NWS National Hurricane Center Miami FL AL112017
500 AM AST Thu Sep 07 2017

Corrected to modify Key Messages to reflect the issuance of a
hurricane warning for the northwestern Bahamas.

Irma has become a little less organized during the past few hours.
Data from an Air Force reserve Hurricane Hunter aircraft near 0500
UTC indicated that the central pressure had risen to 921 mb and
that the winds had decreased both at the 700 mb flight-level and in
surface estimates from the Stepped Frequency Microwave Radiometer.
Since that time, the eye has become cloud filled and the central
convection has become somewhat ragged. The initial intensity is
lowered to 155 kt, and this could be a little generous. The next
aircraft is scheduled to reach Irma around 1200 UTC.

The initial motion is 290/15. The hurricane is currently being
steered by the subtropical ridge to the north, and for the next
48 h or so this motion is expected to continue with a decrease in
the forward speed. After 48 h, a mid- to upper-level trough
digging into the eastern United States is expected to create a
break in the ridge and allow Irma to turn northward. The timing of
the turn is the most important question and one still filled with
uncertainty. The UKMET, UK Ensemble mean, and the NAVGEM are the
models showing the latest turn, and they forecast Irma to move into
the southeastern Gulf of Mexico and near the west coast of the
Florida Peninsula. The ECMWF and ECMWF Ensemble mean are in the
middle of the model pack and show Irma moving over the southeastern
portion of the Florida Peninsula. The GFS, Canadian, and GFS
Ensemble mean show the earliest turn and show Irma moving east of
the coast of Florida toward the southeastern United States. The
new forecast track will best follow the ECMWF, as well as the
Florida State Superensemble and the HFIP Corrected Consensus, and
it calls for the center to move over portions of the southeastern
Florida Peninsula between 72-96 h and then across the Atlantic into
southern South Carolina by 120 h. Users are again reminded not to
focus on the exact track since the average NHC track errors at days
3, 4, and 5 are about 120, 175, and 225 miles, respectively.

Irma should remain in warm-water, and a low shear environment for
about the next three days, and thus is expected to remain a strong
hurricane, most likely Category 5 or 4. Fluctuations in intensity
are likely during the time due to internal eyewall replacement
cycles. The large-scale models suggest that shear could increase
starting at about 72 hr. However, due to the uncertainty as to
whether this will happen, the intensity forecast keeps Irma at
category 4 strength until landfall in Florida. The 96-120 h points
now have a lower intensity due to the forecast of shear and land
interaction, but Irma is still expected to be a hurricane when it
reaches the southeastern United States.

Since Irma is moving away from Puerto Rico and the radars there, the
hourly position estimates are discontinued after this advisory.


KEY MESSAGES:

1. Irma is a potentially catastrophic category 5 hurricane and will
bring life-threatening wind, storm surge, and rainfall hazards to
the northern coast of Hispaniola today, the Turks and Caicos
tonight, and the Bahamas tonight through Saturday.

2. A hurricane watch is in effect much of Cuba. Irma is likely to
bring dangerous wind, storm surge, and rainfall to portions of these
areas on Friday and Saturday.

3. The threat of direct hurricane impacts in Florida over the
weekend and early next week continues to increase. Hurricane
watches will likely be issued for portions of the Florida Keys and
the Florida peninsula later this morning.


FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 20.0N 68.3W 155 KT 180 MPH
12H 07/1800Z 20.7N 70.5W 150 KT 175 MPH
24H 08/0600Z 21.7N 73.1W 145 KT 165 MPH
36H 08/1800Z 22.3N 75.5W 140 KT 160 MPH
48H 09/0600Z 22.8N 77.4W 135 KT 155 MPH
72H 10/0600Z 24.5N 80.0W 130 KT 150 MPH
96H 11/0600Z 28.5N 80.5W 105 KT 120 MPH
120H 12/0600Z 33.0N 81.0W 75 KT 85 MPH...INLAND

$$
Forecaster Beven/Brennan
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09072017 5 AM AST Irma102752_5day_cone_no_line_and_wind.png
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srainhoutx
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The Florida Keys and portions of Southern Florida are now under Hurricane Watches...

Hurricane Irma Discussion Number 34
NWS National Hurricane Center Miami FL AL112017
1100 AM AST Thu Sep 07 2017

The eye on satellite continues to be quite distinct, and data from
an Air Force reconnaissance plane indicate that the initial
intensity is 150 kt. The central pressure remains near 921 mb.

The environment along the future track of Irma is favorable for the
hurricane to maintain most of its current intensity, although some
fluctuations are likely due to eyewall replacement cycles which
are difficult to predict. There are no obvious reasons why Irma
will not remain a powerful hurricane for the next 3 days while
approaching Florida. Thereafter, an increase in the wind shear could
lead to gradual weakening, but Irma is expected to remain a
major hurricane until landfall occurs.

The best estimate of the initial motion is toward the west-northwest
or 290 degrees at 14 kt. Irma is being steered by the flow around
the south side of the subtropical ridge, but in 2 to 3 days, the
hurricane will be located on the southwestern edge of the
aforementioned ridge, and a turn to the northwest and north-
northwest should then begin. There has been no change in the
guidance which is still quite clustered and brings the core
of Irma very near the southeast Florida coast in about 3 days.
The NHC forecast, which is similar to the previous one, is very
close to the multi-model consensus and the HFIP corrected consensus
HCCA. The later has been performing very well during Irma.


KEY MESSAGES:

1. Irma is a potentially catastrophic category 5 hurricane and will
continue to bring life-threatening wind, storm surge, and rainfall
hazards to the northern coast of Hispaniola today. These hazards
will spread across the Turks and Caicos tonight and the Bahamas
tonight through Saturday.

2. A hurricane watch is in effect for much of Cuba. Irma is likely
to bring dangerous wind, storm surge, and rainfall to portions of
these areas on Friday and Saturday.

3. The threat of dangerous major hurricane impacts in Florida
continues to increase. A hurricane watch has been issued for south
Florida, the Florida Keys, Lake Okeechobee, and Florida Bay. This
watch will likely be expanded northward later today. Residents in
these areas should heed any advice given by local officials.

4. A storm surge watch has also been issued for portions of south
Florida and the Florida Keys. This means there is the possibility of
life-threatening inundation from rising water moving inland from the
coastline during the next 48 hours in these areas. The Potential
Storm Surge Flooding Map depicts a reasonable worst-case scenario -
the amount of inundation that has a 10 percent chance of being
exceeded. Because the Flooding Map is based on inputs that extend
through 72 hours, it best represents the flooding potential in the
watch area.

5. The chance of direct impacts is increasing in portions of
Georgia, South Carolina, and North Carolina, but it is too early to
specify the magnitude and location of the impacts.

FORECAST POSITIONS AND MAX WINDS

INIT 07/1500Z 20.4N 69.7W 150 KT 175 MPH
12H 08/0000Z 21.1N 71.7W 145 KT 165 MPH
24H 08/1200Z 21.9N 74.2W 140 KT 160 MPH
36H 09/0000Z 22.5N 76.5W 135 KT 155 MPH
48H 09/1200Z 23.1N 78.4W 135 KT 155 MPH
72H 10/1200Z 25.5N 80.0W 125 KT 145 MPH
96H 11/1200Z 30.1N 80.6W 105 KT 120 MPH
120H 12/1200Z 35.0N 82.0W 50 KT 60 MPH...INLAND

$$
Forecaster Avila
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09072017 11 AM AST Irma 154730_5day_cone_no_line_and_wind.png
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Ptarmigan
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Irma is still a Category 5 hurricane today. :shock: :o
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Ptarmigan
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Princess Juliana airport in St Maarten devastated by Hurricane Irma
http://www.news.com.au/travel/travel-up ... 9700e381cc

The airport is leveled. :shock: :o
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Texaspirate11
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all too heartbreaking...I have a friend who lives on turks & caicos.
Just because you're disabled, you don't have to be a victim
Be Weather Aware & Prepared!
Barbara Jordan Winner in Media
Disability Integration Consultant
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srainhoutx
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I am very concerned for old friends and neighbors in the Lower Keys this morning as well of one of our very own old KHOU Weather Forum Members/Meteorologists Matt Moreland (Meteorologist In Charge/NWS Key West). I chatted briefly yesterday with Matt and he is still concerned that some of those Hard Headed old Conch's are not taking Harvey seriously and are going to evacuate. The highest point on Key West is what is known as Solares Hill just East of Duval Street and North of Truman, if you know Key West the general above sea level elevation is generally 4 to 6 feet. They are expecting a 5 to 10 foot storm surge. It's not any better as you travel up the Keys toward Marathon, Tavernier and Key Largo. The biggest fear is that the 7 Mile Bridge from Marathon to Big Pine Key will be destroyed as well as the highest Bridge in the Keys at Long Key. There are a couple of draw bridges along the Keys as well. US 1 is a two lane Road that runs from just S of Key Largo all the way to Key West. All the Electrical Power comes from a single High Voltage line from the Southern Peninsula as well as their water supply. They will experience the impacts of Irma first. So my concern is great.

Hurricane Irma Discussion Number 37
NWS National Hurricane Center Miami FL AL112017
500 AM EDT Fri Sep 08 2017

Microwave images and data from an Air Force Reserve Hurricane
Hunter aircraft indicate that Irma is currently undergoing an
eyewall replacement cycle. A recent GMI overpass showed an 50 nmi
wide outer eyewall, with the inner eyewall weakening. The
Hurricane Hunter aircraft reported peak 700-mb winds of 147 kt in
the outer eyewall near 0500 UTC, and maximum SFMR winds were in the
125-130 kt range. Based on these data, the initial intensity is
reduced to 135 kt.

Irma is forecast to remain in a favorable warm water, light shear
environment for the next 36-48 h. The intensity guidance shows a
slow weakening during this time, but Irma is expected to remain at
least a Category 4 hurricane until landfall in Florida. After
landfall, a fairly quick decay in maximum winds is expected due to
land interaction and increased shear, although Irma's large wind
field is likely to still produce hurricane-force winds over a large
area. There are two caveats to the intensity forecast. First, some
additional weakening could occur during the eyewall replacement,
followed by re-intensification as the cycle completes. Second, the
ECMWF, UKMET, and NAVGEM forecast a track over or close to the
coast of Cuba that is not currently a part of the track forecast.
If this occurs, Irma could be weaker than currently forecast along
the later parts of the track.

The initial motion is west-northwestward or 285/14. Irma should
maintain this general trajectory for the next 24-36 h as it moves
along the southwestern side of the subtropical ridge. After that
time, the guidance is in good agreement that the ridge should break
and allow Irma to turn north-northwestward to northward. There
remains some spread between the models on when the turn will occur,
with the GFS/Canadian being on the eastern side of the guidance and
the UKMET/NAVGEM on the left side. The ECMWF, Florida State
Superensemble, and the HFIP Corrected consensus are in the middle
of the guidance envelope, and the new track forecast is in best
agreement with those models. Overall, the new forecast track is
similar to the previous forecast, with minor westward adjustments
at 36 and 48 h.


KEY MESSAGES:

1. Irma is an extremely dangerous Category 4 hurricane and will
continue to bring life-threatening wind, storm surge, and rainfall
hazards to the Turks and Caicos Islands and the Bahamas through
Saturday. Heavy rainfall is still possible across portions of
Hispaniola through today. Hurricane conditions will also spread
over portions of the north coast of Cuba, especially over the
adjacent Cuban Keys through Saturday.

2. Severe hurricane conditions are expected over portions of the
Florida peninsula and the Florida Keys beginning Saturday night.
Irma is likely to make landfall in southern Florida as a dangerous
major hurricane, and bring life-threatening storm surge and wind
impacts to much of the state. A Hurricane Warning is in effect for
southern Florida, the Florida Keys, Lake Okeechobee, and Florida
Bay, while Hurricane Watches have been issued northward into central
Florida.

3. A Storm Surge Warning is in effect for southern Florida and the
Florida Keys. A Storm Surge Warning means there is a danger of
life-threatening inundation, from rising water moving inland from
the coastline, during the next 36 hours. This is a life-threatening
situation. Persons located within these areas should take all
necessary actions to protect life and property from rising water and
the potential for other dangerous conditions. Promptly follow
evacuation and other instructions from local officials. A Storm
Surge Watch has been issued north of the Storm Surge Warning area
for portions of the central Florida coast.

4. There is a chance of direct impacts in portions of Georgia,
South Carolina, and North Carolina, but it is too early to specify
the magnitude and location of these impacts.

FORECAST POSITIONS AND MAX WINDS

INIT 08/0900Z 21.7N 73.8W 135 KT 155 MPH
12H 08/1800Z 22.1N 75.7W 135 KT 155 MPH
24H 09/0600Z 22.6N 77.8W 135 KT 155 MPH
36H 09/1800Z 23.3N 79.4W 135 KT 155 MPH
48H 10/0600Z 24.5N 80.4W 130 KT 150 MPH
72H 11/0600Z 28.0N 81.5W 90 KT 105 MPH...INLAND
96H 12/0600Z 33.0N 84.0W 40 KT 45 MPH...INLAND
120H 13/0600Z 36.0N 87.0W 25 KT 30 MPH...INLAND

$$
Forecaster Beven
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unome
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from UWSSEC - CIMSS Tropical Cyclone group briefing on Hurricane Irma - Sep. 7, 2017
(SSEC, CIMSS and AOS staff) https://twitter.com/UWSSEC/status/905857900458934272

it's about 50 min, but worth the time - great info: https://youtu.be/H0gGNgFSPjE
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Good morning, I have not been around as I have had my hands full Moderatimg the Storn2k site. It's been a stressful, almost nauseating few days (weeks) for me. I'm a proud Florida native with friends and family spread out all over the state. Wednesday morning I texted everyone I know in Monroe, Miami--Dade, and Broward to just get out. Some left and some stayed.

I do believe the NHC has a good handle on this, track-wise, but may be a bit too conservative with the LF intensity. At this point all we can do is pray and hope for the best for our friends down there.
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DoctorMu
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Irma is back to a CAT 5 after eyewall replacement. Possibly interaction with the mountains of Cuba *could* reduce her to CAT 4 before landfall. She's resilient.

The current path could indeed swamp the Keys and cut off electricity and water - could be uninhabitable for weeks to months.

The Everglades may have to take one for the team. Even so, the surge in Miami and winds in Ft. Meyers would be highly destructive. Just a 25-50 mi wobble could be the difference. Looks like there's potential for the storm to head up I75 to Gainesville, Atlanta, and Nashville. Our son will be at a conference at Georgia Tech, his alma mater. Tuesday morning could be a little rough, but the on-campus structures are sturdy. Food on board, and travel will be unnecessary until Irma passes through.
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Watching the weather channel. Why are people playing on the beach and smiling and laughing and jumping in the surf? These are the folks that will have to be rescued or one of the fatalities you read about. :(
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mckinne63 wrote:Watching the weather channel. Why are people playing on the beach and smiling and laughing and jumping in the surf? These are the folks that will have to be rescued or one of the fatalities you read about. :(
I do not get that either.
Last edited by Ptarmigan on Sat Sep 09, 2017 4:35 pm, edited 1 time in total.
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DoctorMu
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Irma still refusing to turn, but weakening over the sugar cane fields of Cuba. Storms this size create their own bubble. Will she defy steering currents? She's not going for the trough, yet.
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DoctorMu
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Is it a wobble or turn and ejection off the Cuban coast?

Image
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Has Irma started the turn yet?
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Appears so.
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Hurricane Irma looking well defined on radar 95 miles SE of Key West.
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Ounce wrote:Appears so.
Definitely so. Sometime around 00:45 & 01:15?
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DoctorMu
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Irma is headed now NNW towards the Keys, and has regained CAT 4 status:

https://twitter.com/NHC_Atlantic/status ... 9047906304



Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 10th day of the month at 6:00Z
Agency: United States Air Force
Aircraft: Lockheed WC-130J Hercules with reg. number AF96-5302
Storm Number & Year: 11 in 2017
Storm Name: Irma (flight in the North Atlantic basin)
Mission Number: 29
Observation Number: 14 ( See all messages of this type for this mission. )
A. Time of Center Fix: 10th day of the month at 5:42:30Z
B. Center Fix Coordinates: 23°43'N 81°16'W (23.7167N 81.2667W)
B. Center Fix Location: 67 statute miles (108 km) to the SSE (151°) from Key West, FL, USA.
C. Minimum Height at Standard Level: 2,480m (8,136ft) at 700mb
D. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 101kts (~ 116.2mph)
E. Location of the Estimated Maximum Surface Wind Inbound: 10 nautical miles (12 statute miles) to the WSW (254°) of center fix
F. Maximum Flight Level Wind Inbound: From 339° at 113kts (From the NNW at ~ 130.0mph)
G. Location of Maximum Flight Level Wind Inbound: 10 nautical miles (12 statute miles) to the WSW (254°) of center fix
H. Minimum Sea Level Pressure: 930mb (27.47 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 11°C (52°F) at a pressure alt. of 3,051m (10,010ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 19°C (66°F) at a pressure alt. of 3,049m (10,003ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 14°C (57°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape & Diameter: Circular with a diameter of 20 nautical miles (23 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Level: 700mb
O. Navigational Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 1 nautical mile

Remarks Section:
Maximum Outbound and Flight Level Wind: 128kts (~ 147.3mph) which was observed 15 nautical miles (17 statute miles) to the NE (49°) from the flight level center at 5:47:00Z
Dropsonde Surface Wind at Center: From 150° at 5kts (From the SSE at 6mph)
Last edited by DoctorMu on Sun Sep 10, 2017 11:24 am, edited 1 time in total.
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Hurricane Irma Tropical Cyclone Update
NWS National Hurricane Center Miami FL AL112017
910 AM EDT Sun Sep 10 2017

...IRMA MAKES LANDFALL AT CUDJOE KEY IN LOWER FLORIDA KEYS...

The center of Hurricane Irma made landfall at Cudjoe Key in the
lower Florida Keys at 9:10 am EDT. A gust to 106 mph (171 km/h)
was just reported at the National Key Deer Refuge in Big Pine Key.

SUMMARY OF 910 AM EDT...1310 UTC...INFORMATION
----------------------------------------------
LOCATION...24.7N 81.5W
ABOUT 20 MI...30 KM ENE OF KEY WEST FLORIDA
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...929 MB...27.43 INCHES

$$
Forecaster Landsea/Mello
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