Caribbean disturbance 93L to drench Honduras; 97L disturbance worth watching

By: Dr. Jeff Masters , 3:04 PM GMT on August 18, 2011

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A westward-moving tropical wave in the Central Caribbean a few hundred miles south-southwest of Jamaica, Invest 93L, has continued to increase in organization, and is close to tropical depression status. 93L is a small system, but has built up a respectable area of heavy thunderstorms around its center. A few low-level spiral bands are apparent on satellite imagery, but there is almost no upper-level outflow apparent, and a surface circulation is not obvious. 93L has moistened its environment somewhat over the past day, but dry air is still in evidence around the storm, particularly to the southeast, as seen on water vapor satellite images. Wind shear continues to be low, 5 - 10 knots. There is a hurricane hunter mission scheduled for this afternoon at 2pm EDT to see if a tropical depression is forming.


Figure 1. Morning satellite image of 93L.

Heavy rains from 93L will begin spreading over Northern Honduras and Northeast Nicaragua tonight. The forward motion of 93L will slow to 5 - 10 mph by Friday, so the storm could be a major rain event for Northern Honduras, with rain amounts of 4 - 8 inches likely by the time the storm reaches Belize on Saturday. Heavy rains will spread to Belize and Mexico's Yucatan Peninsula by Friday night or Saturday morning. The latest SHIPS model forecast shows wind shear remaining in the low range and the atmosphere steadily moistening over the next two days, which should allow 93L to reach tropical storm strength. All of the models agree that the ridge of high pressure steering 93L to the west will remain strong, forcing the storm into a landfall Friday in Northeast Honduras, or Saturday near the Belize/Mexico border. It is possible that 93L will have time to intensify into a Category 1 hurricane before then, though landfall as a tropical storm would be more likely, given the dry air that 93L needs to overcome, and the possibility that the storm will pass too close to the northern coast of Honduras. Regardless, heavy rain will be a major threat from 93L. NHC gave 93L an 80% chance of developing into a tropical depression by Saturday morning in their 8am outlook. If 93L does cross the Yucatan Peninsula and enters the Gulf of Mexico, a strong ridge of high pressure should keep the storm moving due west to make a second landfall along the Mexican coast, well south of Texas.


Figure 2. Morning satellite image of the tropical wave 97L midway between the Lesser Antilles and the coast of Africa.

Invest 97L midway between the Lesser Antilles and the coast of Africa
A tropical wave near 14°N 40°W, midway between the Lesser Antilles Islands and the coast of Africa, is moving westward near 15 - 20 mph. This wave, designated 97L by NHC this morning, has little heavy thunderstorm activity associated with it due to dry air, but an impressive amount of large-scale spin is obvious in visible satellite loops. 97L is expected to arrive in the Lesser Antilles Islands by Saturday. Over the past day, all four of our reliable models for predicting tropical storm genesis have predicted that this wave could develop into a tropical depression sometime Saturday through Monday, so 97L needs to be watched carefully. NHC gave 97L a 10% chance of developing into a tropical depression by Saturday morning in their 8am outlook, and it is unlikely that this storm will pose much of a threat to the Lesser Antilles. It will take several days for the storm to overcome the large amount of dry air surrounding it, even though wind shear is a low 5 - 10 knots. By Saturday, the wave will find a moister atmosphere and warmer sea surface temperatures near the northern Lesser Antilles, and more rapid development may occur. However, there is expected to be high wind shear associated with an upper level low pressure system to the north of Puerto Rico at that time, and this wind shear may interfere with development. 97L is expected to take a west-northwest track through the Northeast Caribbean bringing the storm near Puerto Rico by Sunday or Monday. Long-range model runs, which are highly unreliable, foresee that 97L could be a threat to Hispaniola, Eastern Cuba, the Bahamas, and Florida by the middle to end of next week.

Jeff Masters

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Quoting Dennis8:


That is great..I hope he is drinking lots of cold water.! What make you interested in Wx?
check your WU mail.
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Quoting TropicalAnalystwx13:


Me neither, especially since it JUST emerged off Africa and hasn't been through that 24 hour window to see if it dies out or sustains itself.

It IS a well defined tropical wave though, rotation very apparent.



A few GFS runs back there was a fairly intense 500 HPa vortmax developing over the western Sahel..guess that panned out.
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Quoting Levi32:
Well if it looks like a duck...

The GFS and ECMWF do show this feature being robust for a few days before dissipating. This is the one ahead of the "big one" that comes off of Africa in several days, shown to be basically a tropical storm on the GFS and Euro before even leaving the African land mass.




Thanks for triggering a seizure...:/
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1143. Levi32
The GFS and Euro both show almost instantaneous NW motion from 98L, which seems odd given that the Azores High is solidly in place to the northwest. A northward component to the movement could be acquired later, but I would favor a more westward movement to start off with.

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Quoting ProgressivePulse:
I see Harvey and Irene down the line however, 93L will not be one of them IMO.


I think we will see harvey out of 93L, it definitely has the looks of one.
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Quoting ProgressivePulse:
I see Harvey and Irene down the line however, 93L will not be one of them IMO.


93L should be declared a tropical cyclone very soon...Within the next 6-12 hours or less.

IMO.

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Quoting Levi32:


I honestly did not see that coming.
i don't think no one was really paying attention to it.
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Quoting Levi32:
Well if it looks like a duck...

The GFS and ECMWF do show this feature being robust. This is the one ahead of the "big one" that comes off of Africa in several days, shown to be basically a tropical storm on the GFS and Euro before even leaving the African land mass.

Probably our most impressive AEW to date (satellite presentation-wise). Very good 850mb vorticity as well.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Lol...Anyone else think it's funny that we are talking about 93L becoming a tropical cyclone when 98L was just established?
Member Since: July 15, 2006 Posts: 17 Comments: 10159
Quoting Dennis8:
REA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
349 PM CDT THU AUG 18 2011

.DISCUSSION...
YET ANOTHER 100 DEGREE DAY FOR HOUSTON TODAY...NUMBER 18...WITH
VERY WARM TEMPERATURES ACROSS SOUTHEAST TEXAS THIS AFTERNOON. THE
HIGH TEMPERATURE AT OUR OFFICE HAS REACHED 103 DEGREES THIS
AFTERNOON...THE HOTTEST TEMPERATURE WE HAVE SEEN YET THIS YEAR AND
THE THIRD HIGHEST TEMPERATURE RECORDED AT OUR CURRENT OFFICE. A
SLIGHT INCREASE IN MOISTURE TODAY HAS LED TO GREATER CLOUD
COVERAGE AND EVEN A FEW ISOLATED SHOWERS AND THUNDERSTORMS ACROSS
THE REGION. THIS ACTIVITY SHOULD COME TO AN END LATE THIS EVENING
WHEN AFTERNOON HEATING IS LOST.

THE FORECAST REMAINS RELATIVELY UNCHANGED THIS AFTERNOON. THE
RIDGE IS EXPECTED TO FLATTEN OUT OVER THE WEEKEND AND ALLOW FOR
SLIGHTLY COOLER TEMPERATURES ACROSS OUR REGION. RAIN CHANCES
CONTINUE TO LOOK BLEAK AS THE RIDGE BUILDS BACK IN THROUGH EARLY NEXT
WEEK.


Hmmmm? Doesn't this say the opposite about the ridge?

ONGOING WEATHER PATTERN EXPECTED TO CONTINUE. AREA WILL REMAIN
UNDER THE INFLUENCE OF EXPANSIVE SOUTH PLAINS HIGH. TEMPERATURES
WELL ABOVE THE NORM WILL BE MAINTAINED WHILE RAIN CHANCES SHOULD
STAY LIMITED. COULD SEE A WETTER PATTERN DEVELOP TOWARD THE MID
PART OF THE NEW WEEK AS GLOBAL MODELS SHOWING SOME RETROGRADING OF
HIGH AS A DEEP LOW DEVELOPS OVER THE UPPER MIDWEST.


CONTINUE TO WATCH WESTWARD MOVING DISTURBANCE OVER THE CARIBBEAN
WITH NHC CARRYING AN 80 PERCENT CHANCE OF DEVELOPMENT.
Member Since: August 24, 2010 Posts: 0 Comments: 676
1136. DFWjc
Google maps has now added a weather layer .... you even see the storms out in the ocean..

Link
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Do they keep stats on invest life span? Because 93L has got to be right up there.

I would think it's rare to have 93 and 98 at the same time.
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Quoting Tazmanian:




am thinking at lest 40% right now even cod red


I wouldn't rule that out either taz. We'll just have to see how it holds in 24 hours.
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I see Harvey and Irene down the line however, 93L will not be one of them IMO.
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98L looks like a damn EPAC system
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dos any one have the mode runs that go with 98L?
Member Since: May 21, 2006 Posts: 5091 Comments: 114697
From WU

Invest 98
Wind: 30 MPH — Location: 12.6 17.6W — Movement: WNW
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Convective organization finally hints that 93L is a tropical cyclone.

Member Since: July 15, 2006 Posts: 17 Comments: 10159
1127. xcool
WHXX01 KWBC 182103
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
2103 UTC THU AUG 18 2011

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL982011) 20110818 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
110818 1800 110819 0600 110819 1800 110820 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 12.6N 17.6W 12.9N 18.7W 13.5N 20.1W 14.3N 21.7W
BAMD 12.6N 17.6W 13.1N 18.7W 13.8N 19.8W 14.7N 20.8W
BAMM 12.6N 17.6W 13.2N 18.7W 14.0N 19.8W 14.9N 21.1W
LBAR 12.6N 17.6W 13.3N 19.6W 14.4N 21.8W 15.6N 23.7W
SHIP 25KTS 31KTS 40KTS 49KTS
DSHP 25KTS 31KTS 40KTS 49KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
110820 1800 110821 1800 110822 1800 110823 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 15.2N 23.4W 16.7N 27.8W 18.1N 32.9W 19.5N 38.2W
BAMD 15.9N 22.1W 19.1N 26.2W 21.8N 31.1W 23.2N 35.1W
BAMM 16.1N 22.7W 18.4N 27.6W 20.3N 33.8W 22.1N 40.1W
LBAR 16.9N 25.8W 19.8N 29.9W 23.0N 34.2W 25.4N 38.1W
SHIP 55KTS 65KTS 61KTS 53KTS
DSHP 55KTS 65KTS 61KTS 53KTS

...INITIAL CONDITIONS...
LATCUR = 12.6N LONCUR = 17.6W DIRCUR = 285DEG SPDCUR = 12KT
LATM12 = 12.1N LONM12 = 15.3W DIRM12 = 283DEG SPDM12 = 12KT
LATM24 = 11.6N LONM24 = 12.6W
WNDCUR = 25KT RMAXWD = 60NM WNDM12 = 25KT
CENPRS = 1006MB OUTPRS = 1008MB OUTRAD = 300NM SDEPTH = S
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
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Quoting HurricaneGeek:


great! thanks.. the tropics are heating up!



sure is
Member Since: May 21, 2006 Posts: 5091 Comments: 114697
1124. Levi32
Well if it looks like a duck...

The GFS and ECMWF do show this feature being robust for a few days before dissipating. This is the one ahead of the "big one" that comes off of Africa in several days, shown to be basically a tropical storm on the GFS and Euro before even leaving the African land mass.

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1123. Drakoen
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Quoting TropicalAnalystwx13:


Me neither, especially since it JUST emerged off Africa and hasn't been through that 24 hour window to see if it dies out or sustains itself.

It IS a well defined tropical wave though, rotation very apparent.



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wow 98 L .. wouldnt it be funny if 98L becomes named before 93L or 97L
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Quoting Tazmanian:



sure thing

Link


great! thanks.. the tropics are heating up!
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1119. Dennis8
Quoting ncstorm:


The NOGAPS was showing that as a tropical storm soon as it came off of Africa early this week..not surprised at all


Not at all this time of year...this is common. Look at it.
Member Since: August 15, 2008 Posts: 0 Comments: 446
Quoting Dennis8:


Thanks..you are the man



your welcome
Member Since: May 21, 2006 Posts: 5091 Comments: 114697
until there is actually more than an invest out there there is no sense in guessing what may happen in 10 days. we need a cyclone first..
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1115. ncstorm
Quoting TropicalAnalystwx13:
30 MPH, 1006 MB.



The NOGAPS was showing that as a tropical storm soon as it came off of Africa early this week..not surprised at all
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Quoting tropicfreak:


Thanks taz. Expect a new yellow circle in the 8pm TWO, and Harvey or TD 8 at 11pm.




am thinking at lest 40% right now even cod red
Member Since: May 21, 2006 Posts: 5091 Comments: 114697
Quoting Levi32:


I honestly did not see that coming.


Me neither, especially since it JUST emerged off Africa and hasn't been through that 24 hour window to see if it dies out or sustains itself.

It IS a well defined tropical wave though, rotation very apparent.

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Quoting TropicalAnalystwx13:
30 MPH, 1006 MB.



Wow, that's almost the strength of a tropical depression.
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Quoting xcool:
wowww 98L .THANK TAZ





your welcome all
Member Since: May 21, 2006 Posts: 5091 Comments: 114697
1110. Dennis8
Quoting Tazmanian:



sure thing

Link


Thanks..you are the man
Member Since: August 15, 2008 Posts: 0 Comments: 446
Quoting Tazmanian:
if am looking at this right it looks like we have 98L


BEGIN
NHC_ATCF
invest_al982011.invest
FSTDA
R
U
040
010
0000
201108182101
NONE
NOTIFY=ATRP
END
INVEST, AL, L, , , , , 98, 2011, DB, O, 2011081818, 9999999999, , , , , , METWATCH, , AL982011
AL, 98, 2011081718, , BEST, 0, 116N, 126W, 25, 1009, DB, 0, , 0, 0, 0, 0,
AL, 98, 2011081806, , BEST, 0, 121N, 153W, 25, 1007, DB, 0, , 0, 0, 0, 0,
AL, 98, 2011081812, , BEST, 0, 123N, 164W, 25, 1007, DB, 0, , 0, 0, 0, 0,
AL, 98, 2011081818, , BEST, 0, 126N, 176W, 25, 1006, DB, 34, NEQ, 0, 0, 0, 0, 1008, 300, 60, 0, 0, L, 0, , 0, 0, INVEST, S,




invest_al982011.invest 1 KB 8/18/2011 8:57:00 PM


Thanks taz. Expect a new yellow circle in the 8pm TWO, and Harvey or TD 8 at 11pm.

1007 mb pressure? That's quite low for an invest, that has the pressure of a TD.
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have a feeling these next few weeks the blog is going to be in overdrive...
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Harvey and Irene may not play as nice as their counterparts have done so far this season
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Quoting HurricaneGeek:
Post # 1078, Taz...

Can I have a link to that site so I have it for the future?

Thanks.



sure thing

Link
Member Since: May 21, 2006 Posts: 5091 Comments: 114697
This buoy is still way out in front of 97L. I'm thinking TD right now.

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1104. xcool
wowww 98L .THANK TAZ
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Post # 1078, Taz...

Can I have a link to that site so I have it for the future?

Thanks.
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1102. Levi32
Quoting TropicalAnalystwx13:
We have Invest 98L.


I honestly did not see that coming.
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30 MPH, 1006 MB.

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Quoting Tazmanian:
if am looking at this right it looks like we have 98L


BEGIN
NHC_ATCF
invest_al982011.invest
FSTDA
R
U
040
010
0000
201108182101
NONE
NOTIFY=ATRP
END
INVEST, AL, L, , , , , 98, 2011, DB, O, 2011081818, 9999999999, , , , , , METWATCH, , AL982011
AL, 98, 2011081718, , BEST, 0, 116N, 126W, 25, 1009, DB, 0, , 0, 0, 0, 0,
AL, 98, 2011081806, , BEST, 0, 121N, 153W, 25, 1007, DB, 0, , 0, 0, 0, 0,
AL, 98, 2011081812, , BEST, 0, 123N, 164W, 25, 1007, DB, 0, , 0, 0, 0, 0,
AL, 98, 2011081818, , BEST, 0, 126N, 176W, 25, 1006, DB, 34, NEQ, 0, 0, 0, 0, 1008, 300, 60, 0, 0, L, 0, , 0, 0, INVEST, S,
Well that's interesting. Still over Africa:

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting atmoaggie:
Those "low-level clouds" are not necessarily indicate of surface winds. (And very rarely of any utility.)

Just what I've seen in comparing that product against SFMR wind directions, scatterometer, etc.


From NOAA: Combination of visible and infrared using a
three channel technique to make features stand out

Link

I presumed it is to make low-level cloud movement stand out.
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1098. Dennis8
98L ..the big wave off AFRICA
Member Since: August 15, 2008 Posts: 0 Comments: 446
Quoting TropicalAnalystwx13:
We have Invest 98L.



TropicalAnalystwx13 where is 98L?
Member Since: May 21, 2006 Posts: 5091 Comments: 114697
1096. Levi32
Quoting atmoaggie:
doh.

The CH1, CH1, CH4 means it's visible, visible, and IR.
Given the sunglint, the low levels must be visible, not IR.

(Oops, my bad.)

Still don't think it truly depicts surface winds worth a [snip].


I think if you compare the vis and rgb loops side by side, you will see that there is absolutely no difference except for the colorization. It is my understanding that IR sensing is used to detect which of the clouds to color yellow, which are supposed to be low-level clouds. The RGB product is visible, but with a color enhancement designed to make it easier to pick out low-level clouds.
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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.