Gulf Distubance 91L More Organized, Headed Towards Florida

By: Dr. Jeff Masters , 5:21 PM GMT on June 05, 2013

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Tropical disturbance 91L in the Southeast Gulf of Mexico has gotten more organized over the past day, and the Hurricane Hunters are scheduled to fly their first mission of 2013 this afternoon to see if the storm is becoming a tropical depression. Buoy 42003 near the heaviest thunderstorms of 91L measured sustained winds of 33 mph, gusting to 41 mph this morning at 2 am EDT. Satellite loops show a lopsided storm, with a large area of heavy thunderstorms on the east side of a center of circulation that is trying to develop at the edge of a region of dry air that covers the entire Central and Western Gulf of Mexico. This dry air is due to a trough of low pressure whose upper level winds are also creating moderate wind shear of 15 - 20 knots. Wind shear is forecast to rise to the high range, by Thursday, and 91L is forecast to make landfall along the northern Gulf Coast of Florida on Thursday evening, so the system has a short window of time to intensify. NHC is giving the disturbance a 50% chance of developing into a tropical cyclone. I put these odds higher, at 60%. If it does develop, it will be difficult for 91L to get any stronger than a 45 mph tropical storm in the Gulf of Mexico. Regardless of whether or not 91L develops into a tropical depression, heavy rains will be the storm's main threat. A swath from Florida to New England can expect 2 - 4" of rain. A few isolated EF-0 tornadoes will also be possible along the northern Florida Gulf Coast. A storm surge of 1 - 3 feet is predicted for Cedar Key, Florida, and rip currents will be a risk for swimmers who brave the high surf. Fort Pickens, located in Gulf Islands National Seashore on a barrier island offshore from Pensacola, Florida, has been closed to visitors due to the approaching storm. A single 2-lane road vulnerable to storm surges runs to Fort Pickens. Officials want to prevent a repeat of the situation that occurred in September 2011, when Tropical Storm Lee pushed a storm surge over the road that blocked it with sand and debris, trapping numerous campers and visitors in Fort Pickens.

The storm is getting caught up in a trough of low pressure that will pull it quickly to the north-northeast beginning on Thursday, with the center expected to move over coastal North Carolina on Friday afternoon, and over Massachusetts on Friday night. If 91L does manage to become a tropical storm before making landfall on Thursday, it will quickly degenerate into a regular extratropical low pressure system before moving up the East Coast.


Figure 1. Latest satellite image of Invest 91L.


Figure 2. Predicted precipitation for the 7-day period ending June 12, 2013 from the NWS/NCEP. A swath of 2 - 4" of rain is expected from Florida to New England from 91L.

Jeff Masters

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Yepper... looks closed.

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Renumber should come soon folks
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679. flsky
Isn't it the case that the radar image on the tropical page (on this website) under the Invest 91L heading stays centered on the low? If so, it looks like it is moving east
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that loooks north and northwest to me
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Looks closed to me.
Member Since: November 24, 2005 Posts: 635 Comments: 26562
Current Convective Forecast for tomorrow..



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Winds dropping off quick now

Time: 20:45:30Z
Coordinates: 25.3167N 86.8833W
Acft. Static Air Press: 984.1 mb (~ 29.06 inHg)
Acft. Geopotential Hgt: 181 meters (~ 594 feet)
Extrap. Sfc. Press: 1004.7 mb (~ 29.67 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 52° at 35 knots (From the NE at ~ 40.2 mph)
Air Temp: 23.1°C (~ 73.6°F)
Dew Pt: 20.6°C (~ 69.1°F)
Peak (10s) Flt. Lvl. Wind: 35 knots (~ 40.2 mph)
SFMR Peak (10s) Sfc. Wind: 25 knots (~ 28.7 mph)
SFMR Rain Rate: 1 mm/hr (~ 0.04 in/hr)
Member Since: June 24, 2012 Posts: 0 Comments: 1534
the COC IS HERE
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HMMMM!
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gonna get some mesocyclone storms soon..
Link
Member Since: October 29, 2010 Posts: 0 Comments: 169
If TS Andrea is declared before landfall, then we reach one storm out of the normal June-July 1.7 average before June 10th........Interesting start to the season.
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Quoting WxLogic:
We'll see if it finds the center on this pass.


I don't think it's going to make too much difference to me. I'm on the west cost of Florida about an hour north of Tampa Bay and I've been getting pounding by rain for the past two days. Every couple of hours it just streams in and dumps on me. Speaking of... there it goes.
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Waiting to see if its closed.
Member Since: June 24, 2012 Posts: 0 Comments: 1534
Member Since: November 6, 2010 Posts: 11 Comments: 7877
looks like the classic june east lopsided weak storm. what chance do you give it of becoming andrea
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Quoting TylerStanfield:

Clarification, recon needs to find this..


Well... it looks elongated, there may not be any quite yet... but as the pressure drops it will become inevitable.
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I said early this morning that tonight and into tomorrow morning is the best chance this thing has to develop before it begins its transition into an extra-tropical low.
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Quoting Gearsts:
Dmin
Yep...Its also starting to have that classic squashed bird look we have seen over the years.
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System is already spawning low-topped supercells in Florida.

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Quoting TropicalAnalystwx13:
Needs north and northwest winds.

Clarification, recon needs to find this..
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Quoting MiamiHurricanes09:
1004.7mb readings.


204500 2521N 08654W 9838 00183 0047 +230 +208 055035 035 026 000 00
204530 2519N 08653W 9841 00181 0047 +231 +206 052035 035 025 001 00

No evidence of west winds though.

Recon one update away from clarifying if we have west winds or not...
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Needs north and northwest winds.
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I think 91L will be upgraded to a 1003-1004 mb 40-45 mph TS Andrea by the time the HH mission is over, just my take.
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Quoting BaltimoreBrian:


Do you think it is more likely that the low will close off before landfall in ~36 hours or stay open?


should have baroclinic processes beginning to get injected by then... but what do i know
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We'll see if it finds the center on this pass.
Member Since: August 14, 2008 Posts: 4 Comments: 4934
1004.7 and 1005mb
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Quoting washingtonian115:
Well I guess no Andrea then :).Oh we'll we still have another 5 months to go.


dont short change me, its still about 6
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Effective on or about Tuesday, July 16, 2013, beginning with the
1200 Coordinated Universal Time (UTC) run, the National Centers
for Environmental Prediction (NCEP) will upgrade the HWRF
Princeton Ocean Model (POM) coupled system.


Excerpt:

The FY2013 HWRF model will be implemented on NCEP’s new Weather
and Climate Operational Supercomputing System (WCOSS), scheduled
to become the operational machine by July 16, 2013. A separate
TIN will be issued announcing the operational switch to the WCOSS
system. In the event that switch date is changed, this TIN will
be modified to reflect that change in implementation date.
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Quoting Levi32:


The absolute pressure doesn't matter at all. The pressure gradient does. At some point the winds have to respond to the pressure field, but if the gradient is weak, it won't necessarily be a closed circulation. 91L's new center has almost no pressure gradient to the west, because the larger gyre is there with pressures near 1008mb, so there may be no true northerly winds yet.


Do you think it is more likely that the low will close off before landfall in ~36 hours or stay open?
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really elongated from east to west
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.
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Quite a few sea turtles have already nested very low on the beach at Longboat Key this year. With tides 1-3 feet higher than normal we will likely lose some/all of them. Such a shame.
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Quoting 7544:


dont u think they should have waited to drop the rain totals for se fla as it looks like this will be goin more east than expected


Latest models agree with a Central Florida landfall. But anywhere from 3-6 inches is likely with locally 8'' in S Florida. But it deepens on how much moisture is on the system south end. Its still lashing the Yucatan and western Cuba with rain as we speak.
Member Since: May 28, 2013 Posts: 0 Comments: 348
Quoting Levi32:


The absolute pressure doesn't matter at all. The pressure gradient does. At some point the winds have to respond to the pressure field, but if the gradient is weak, it won't necessarily be a closed circulation. 91L's new center has almost no pressure gradient to the west, because the larger gyre is there with pressures near 1008mb, so there may be no true northerly winds yet.


There's a familiar name. Hi Levi.
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646. 7544
Quoting nrtiwlnvragn:
Center relocation shifted early models eastward....

and more south too might go even further south and east imo
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Quoting Autistic2:
How low can the pressure go before it HAS to be closed. I remember two years ago the NHC could not find a closed low in an Atlantic invest approaching the islands but went to TS assuming that the HH missed the low twice. It think that was about 1002.


I believe that was irene... they found 60 mph on north side in that one.
Quoting MiamiHurricanes09:
1004.7mb readings.


204500 2521N 08654W 9838 00183 0047 +230 +208 055035 035 026 000 00
204530 2519N 08653W 9841 00181 0047 +231 +206 052035 035 025 001 00

No evidence of west winds though.


much better than we thought... still not good enough.
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Quoting Autistic2:
How low can the pressure go before it HAS to be closed. I remember two years ago the NHC could not find a closed low in an Atlantic invest approaching the islands but went to TS assuming that the HH missed the low twice. It think that was about 1002.


The absolute pressure doesn't matter at all. The pressure gradient does. At some point the winds have to respond to the pressure field, but if the gradient is weak, it won't necessarily be a closed circulation. 91L's new center has almost no pressure gradient to the west, because the larger gyre is there with pressures near 1008mb, so there may be no true northerly winds yet.
Member Since: November 24, 2005 Posts: 635 Comments: 26562
Miami Local Channel 7 is reporting wind gusts to 67 mph on the NE of center by HH aircraft
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Well I guess no Andrea then :).Oh we'll we still have another 5 months to go.
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25.5 north 87 west is my guess on where the COC is. not an extremely impressive circulation
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Quoting notanotherwrong:
dont panic folks just a baby storm gonna put down some rain not to bad


Even "baby" storms that put down "some" rain can do a lot of damage when given the right circumstances.
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1004.7mb readings.


204500 2521N 08654W 9838 00183 0047 +230 +208 055035 035 026 000 00
204530 2519N 08653W 9841 00181 0047 +231 +206 052035 035 025 001 00

No evidence of west winds though.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
637. 7544
Quoting Ricki13th:


We will see some Action in Southern Florida as there is moisture coming up from the Yucatan. Worse of the weather will be tonight and on Thursday. Some lingering effects on Friday. 1-4 inches seem about right but could be more though. Chance of some gust winds and POSSIBLY a weak tornado or two there is some shear over Florida the can spark couple here or there.



dont u think they should have waited to drop the rain totals for se fla as it looks like this will be goin more east than expected
Member Since: May 6, 2007 Posts: 0 Comments: 6694
How low can the pressure go before it HAS to be closed. I remember two years ago the NHC could not find a closed low in an Atlantic invest approaching the islands but went to TS assuming that the HH missed the low twice. It think that was about 1002.
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There isn't much to say so far that this is a tropical cyclone, but it does appear to be much closer than we thought it would be this morning to becoming one. Possible that it could become Andrea tonight.
Member Since: July 8, 2005 Posts: 259 Comments: 23619
Quoting DataNerd:


Well. Now we just sit back and see if there is a VDM or not.


So there is a possible Closed Low just need the VDM. So we can crank out some advisories. A couple of storms got classified 30 mins to and hour after 5pm if I remembered carefully.
Member Since: May 28, 2013 Posts: 0 Comments: 348
Center relocation shifted early models eastward.....


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Quoting Dakster:


I should have put my sarcasm: on field... It was a sarcastic response.

Which is why I then looked up the site with all the data on the plane. I was curious myself.


I see. Either way, there are always some around here who could use the random aircraft speed knowledge, ha.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.