KoritheMan's WunderBlog

Tropical weather analysis - September 30, 2013

By: KoritheMan, 5:54 AM GMT on September 30, 2013

Tropical Depression Eleven

Tropical Depression Eleven has not strengthened yet, according to the 0300Z NHC advisory:

Wind: 35 mph, with higher gusts
Location: 27.0°N 47.0°W
Movement: ENE at 9 mph
Pressure: 1010 mb

The 6z satellite estimates from TAFB and SAB have not yet culminated, but a recent UW-CIMSS ADT estimate assumes the depression has become a tropical storm. Indeed, the shear does appear to have decreased from earlier, likely because the adjacent upper low that has been afflicting the system is quickly moving north of the cyclone, a process that is altering the upper flow from southwesterly to northwesterly. Though neither are particularly favorable for intensification, water vapor imagery suggests that -- for now -- the shear may actually be assisting in the development of outflow in the western semicircle. The low-level center is rather difficult to locate lacking any recent microwave or scatterometer passes, but with the help of shortwave infrared imagery and continuity, I surmise that it's more or less embedded within the southwestern edge of the convective cloud shield.



Figure 1. Latest infrared satellite image of Tropical Depression Eleven. Image credit: NOAA's Satellite Services Division (SSD).

Although the large-scale environment is hardly ideal, the shear has lessened, so the window for strengthening appears to be upon us. Satellite estimates are beginning to trend upward, and the depression may already be a tropical storm. A couple of scatterometer passes over the last 12 hours indicate that the low-level center associated with the depression is extremely small and rather fragile, so any abrupt increases in shear could quickly dishevel the system. Primarily due to this uncertainty, my forecast will not yet bring the intensity above 40 kt, but I would not be surprised to see the cyclone get a little stronger. Late in the period, there are some signals within the GFS that the 200 mb flow may transition to southwesterly again ahead of another upper-level trough now over the western Atlantic, which could act to shear the depression during that time. The timing and magnitude of this possibility, however, are highly uncertain.

As alluded to above, the center of the depression is not easy to locate this morning. It appears to be within the southwest edge of the convection, and more or less abiding by the latest NHC track, but I am not certain at all in either the location or the motion of the depression, and a few decent microwave passes would certainly be welcome right now. Regardless of the initial status of the cyclone, water vapor imagery shows the upper low that has been providing the primary steering mechanism quickly lifting out, perhaps even a bit faster than I had expected. This requires me to shift my track a little to the left of the National Hurricane Center track, under the assumption that the clockwise loop that I expect the depression to undertake will not be as sharp and theatrical as I was originally thinking. In a few days, another trough is forecast to approach the system and gradually recurve it around the western periphery of a deep-layer ridge over the eastern Atlantic. The model guidance remains in unwavering agreement on the general evolution of the synoptic pattern, and this forecast is thus of high confidence.

Intensity forecast and positions

INITIAL 09/30 0300Z 27.0°N 47.0°W 30 KT 35 MPH
12 hour 09/30 1200Z 27.1°N 46.7°W 35 KT 40 MPH
24 hour 10/01 0000Z 26.9°N 46.5°W 40 KT 45 MPH
36 hour 10/01 1200Z 26.7°N 46.7°W 40 KT 45 MPH
48 hour 10/02 0000Z 27.2°N 46.9°W 40 KT 45 MPH
72 hour 10/03 0000Z 27.8°N 48.1°W 40 KT 45 MPH
96 hour 10/04 0000Z 29.7°N 48.3°W 35 KT 40 MPH
120 hour 10/05 0000Z 31.3°N 44.8°W 30 KT 35 MPH

Track forecast



Figure 2. My forecast track for Tropical Depression Eleven.



Invest 97L

A weak surface trough in the south-central Caribbean about 350 miles south of Jamaica remains poorly-organized. Shower activity is quite limited, surface pressures are not falling, and earlier scatterometer and microwave data during the evening showed that the low-level center is very poorly-defined.



Figure 3. Latest infrared satellite image of Invest 97L. Image credit: NOAA's Satellite Services Division (SSD).

Westerly shear is impacting the system, diagnosed at 20 kt by UW-CIMSS, and this appears to be preventing significant development despite a relatively moist atmospheric column and amply warm sea surface temperatures. The GFS continues to suggest that upper-level winds will gradually improve over the next couple of days, which does actually look supported via a glance at water vapor imagery, which shows mostly northeasterly flow ahead of the system in the wake of a departing trough over the Gulf of Mexico. This seemingly favorable upper flow pattern could allow for some gradual development of this disturbance as it heads northwestward toward the northwestern Caribbean Sea. None of the models currently develop the disturbance, though.

Regardless of development, locally heavy rains and possible flooding will impact portions of Jamaica, the Cayman Islands, and Cuba over the next several days.

Probability of development in 48 hours: 10%

2013 Atlantic hurricane season Tropical Depression Eleven Invest 97L

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Tropical weather analysis - September 29, 2013

By: KoritheMan, 5:55 AM GMT on September 29, 2013

Tropical Depression Eleven

A tropical depression formed over the central Atlantic today from a tropical wave that has been interacting with an upper low for the last several days. As of the first NHC advisory, issued at 0300Z, the following information was available on the storm:

Wind: 35 mph, with higher gusts
Location: 25.2°N 50.2°W
Movement: N at 9 mph
Pressure: 1010 mb



Figure 1. Latest infrared satellite image of Tropical Depression Eleven. Image credit: NOAA's Satellite Services Division (SSD).

Satellite estimates from TAFB and SAB were below tropical storm strength during their initiation at 0z, and a recent UW-CIMSS ADT estimate yields a final T number of only 2.0. Also, the low-level center, while somewhat ill-defined and hard to locate, appears to be exposed to the south of the convection, with the deep convection occurring in a disorganized cluster to the north. There is about 15 kt of southerly shear over the depression; since the depression is moving in the general direction of the shear vector, the effect of this shear should be mitigated to a degree, but since that doesn't appear to be the case, I am presuming that the adjacent upper low is having a greater effect than meets the eye.

I don't see much evidence of a significant decrease in the expected vertical shear in the path of the tropical cyclone, and water vapor imagery shows the upper low to the northwest of the depression moving northeastward more or less in tandem with the trajectory of the depression. As this occurs, the upper flow may shift to southwesterly, a condition that could allow for some slight intensification as the cyclone begins to head northeast to east-northeast under the influence of the cold low during the next 24 hours. After that time, increasing northwesterly shear and more stable air behind the upper low is expected to weaken the cyclone. It is possible the depression could dissipate sooner than forecast, or not strengthen at all.

As alluded to above, the low-level center has been difficult to find tonight, but recent satellite images suggest it may be moving slower and a little to the left of the current NHC prediction, but I am not completely certain of this. A general east-northeast to northeast motion is anticipated over the next 24-36 hours while the cyclone remains embedded in the flow connected to the upper low. Subsequent to that time, the global models show the low and its attendant trough outrunning the storm, leaving it to execute a clockwise loop in this general vicinity, before rounding another weakness created by another trough now moving through the southern United States. Considering that the system is only in its formative stage, and that loops are generally one thing the models struggle immensely with, I am a little surprised there is good agreement on that loop occurring. Of course, the timing and extent of that loop are still in question. My forecast track is pretty similar to the current NHC prediction.

Intensity and forecast positions

INITIAL 09/29 0300Z 25.2°N 50.2°W 30 KT 35 MPH
12 hour 09/29 1200Z 25.9°N 49.8°W 35 KT 40 MPH
24 hour 09/30 0000Z 26.7°N 49.3°W 40 KT 45 MPH
36 hour 09/30 1200Z 27.2°N 48.3°W 40 KT 45 MPH
48 hour 10/01 0000Z 27.1°N 47.7°W 35 KT 40 MPH
72 hour 10/02 0000Z 26.6°N 47.1°W 35 KT 40 MPH
96 hour 10/03 0000Z 27.2°N 48.1°W 30 KT 35 MPH
120 hour 10/04 0000Z 29.8°N 48.1°W 30 KT 35 MPH

Track forecast




Figure 2. My forecast track for Tropical Depression Eleven.



Caribbean disturbance

An area of disturbed weather is producing disorganized convection over the central and eastern Caribbean Sea. The center is still broad, and there appear to be multiple embedded swirls orbiting within the larger cyclonic gyre. Based on the convective pattern and low cloud lines using nighttime infrared imagery, my best guess at the dominant center location is between southwestern Haiti and southeastern Jamaica. There appears to be a little southwesterly shear over the area, but water vapor images suggest that the strongest upper flow is located comfortably west of the system. Actually, I'd go as far as to say that the mid-oceanic trough may be enhancing the outflow pattern, and this disturbance carries with it one of the better outflow patterns I've observed this season, although I suppose that isn't saying much.

Upper-level winds are forecast to gradually improve over the next couple of days as the low heads northwestward toward the northwestern Caribbean Sea. At that time, more significant development is expected. It is too early to determine the potential threat to the Florida peninsula, as well as whether the system develops at all. It should be noted that water vapor imagery shows a large expanse of very dry air over the Gulf of Mexico, which could inhibit development at longer ranges if the system moves in that direction. An alternate scenario is that an upper low over the western Atlantic gradually eases the system northward.

Regardless of development, heavy rains and possible flooding will likely impact portions of Hispaniola, Jamaica, and particularly the Cayman Islands and sections of Cuba over the next several days.

Probability of development in 48 hours: 20%

2013 Atlantic hurricane season Tropical Depression Eleven

Updated: 6:03 AM GMT on September 29, 2013

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Tropical weather analysis - September 18, 2013

By: KoritheMan, 6:05 AM GMT on September 18, 2013

Humberto

Humberto remains a struggling minimal tropical storm as of the latest NHC advisory:

Wind: 40 mph, with higher gusts
Location: 30.8°N 43.3°W
Movement: NNW at 7 mph
Pressure: 1007 mb

The tropical cyclone is not well organized, with the cloud pattern continuing to more closely resemble that of a subtropical cyclone; this has occurred because Humberto became collocated with a weak upper tropospheric cold low about a day ago. Various scatterometer data from several hours ago suggested a radius of maximum winds of at least 75 miles, perhaps more. AMSU temperature profile data shows also that Humberto's warm core has weakened above 500 mb, likely in response to temperature influence from the upper low.



Figure 1. Latest infrared satellite image of Tropical Storm Humberto. Image credit: NOAA's Satellite Services Division (SSD).

Convection has recently increased well to the southeast of the center, but there continues to be no evidence of these showers attempting to wrap into the center, which suggests that Humberto is not going to strengthen right now. Water vapor and UW-CIMSS 200 mb vorticity data does show the upper vortex moving eastward and weakening a bit, and the global models continue to dismantle this feature, completely dissipating it within about 36 hours. This evolution should allow for the storm to begin to strengthen again, although the necessity for vertical temperature rebounding in the wake of the upper cold low may slow the rate of strengthening despite an otherwise favorable environment. I do not currently expect Humberto to become a hurricane, although considering it will be interacting with an upper trough, that scenario is not completely out of the question.

The tropical storm appears that it might have turned to the north, which was well anticipated by the NHC and the models. This general motion should continue for another 24 hours or so before the cyclone begins to accelerate northeastward ahead of the aforementioned frontal trough. The guidance remains in excellent agreement on this scenario, as the synoptic pattern in this area of the Atlantic seems rather straightforward.

It should be noted that the global models are depicting that extratropical cyclogenesis could occur in association with the southern end of the frontal trough in the next couple of days, and that feature could go on to absorb Humberto in about 96 hours, which is shown in my forecast. The models are not handling this new extratropical cyclone and Humberto's consequent reaction to it very well, so confidence in my forecast is not as high as it could be.

Intensity forecast and positions

INITIAL 09/18 0300Z 30.8°N 43.3°W 35 KT 40 MPH
12 hour 09/18 1200Z 31.6°N 43.4°W 35 KT 40 MPH
24 hour 09/19 0000Z 32.9°N 43.4°W 40 KT 45 MPH
36 hour 09/19 1200Z 34.7°N 43.1°W 45 KT 50 MPH
48 hour 09/20 0000Z 37.0°N 40.0°W 50 KT 60 MPH
72 hour 09/21 0000Z 44.9°N 34.9°W 50 KT 60 MPH...POST-TROPICAL/EXTRATROPICAL
96 hour 09/22 0000Z...ABSORBED

Track forecast



Figure 2. My forecast track for Humberto.



Invest 95L

An area of low pressure located over the northern Yucatan Peninsula ("95L") appears primed to develop into a tropical depression over the Bay of Campeche today (Wednesday) or Thursday. For a system that's been overland for many hours, the cloud pattern looks remarkably organized. Deep convection is located near and just to the east of the presumed low-level center, and some banding features are evident within that convection. In fact, the system resembles a weak tropical cyclone in its formative stages, and low cloud motions on shortwave infrared satellite imagery suggest that the low-level center could be closed, although that is hard to gauge with no reliable surface observations to the south of the center to confirm westerly winds.



Figure 3. Latest infrared satellite image of Invest 95L. Image credit: NOAA's Satellite Services Division (SSD).

Given how well-organized 95L already seems to be while over Yucatan, it should not take long for the system to transform itself into a tropical cyclone when it gets over water later today. I personally think development will occur today rather than Thursday, but it could go either way. Upper-level winds over the Gulf appear favorable for additional development, and the system appears likely to become at least a moderate tropical storm during the next couple of days. Until I see how the upper air pattern can evolve over the Gulf in the next few days, I am not willing to speculate on intensity at longer ranges. A lot depends on how strong it gets in the Bay of Campeche, where it is likely to meander for at least a couple of days. A stronger system in that region would likely be able to shunt any westerly shear closer to the US Gulf Coast, which would enhance the window for strengthening. On the other hand, the farther east the system tracks in the Gulf, the stronger the shear could be.

The future track of this system is riddled with a lot of uncertainty. The two most reliable models, the GFS and the ECMWF, have radically different solutions in the eventual trajectory of this low. The GFS continues to show a diffuse area of low pressure going into peninsular Florida with most of the energy going into a cold front forecast to move across the southern United States this weekend, while the 12z ECMWF showed a tropical storm off the coast of central Louisiana in 10 days. The Euro historically has been more reliable with the upper air pattern, so there is that to consider. However, I feel that the Euro may be a little too slow in pulling 95L inland; if it does hit the United States, it certainly shouldn't take 10 days to do so. At the same time, the GFS seems a little unrealistic with the depth and progression of the modeled trough, which appears to be more amplified out west than the model is currently giving it credit for. Given current movement trends on satellite imagery of the disturbance, as well as UW-CIMSS steering data, the more westward solution shown by the Euro seems more plausible, since that model seems to be resolving 95L's internal organization more than the GFS. The 0z run should be most interesting. There is a large degree of uncertainty in the forecast of this system. Areas from southwestern Louisiana to the western Florida peninsula region should monitor the progress of this disturbance over the next week.

Probability of development in 48 hours: 80%


Manuel

A reborn Manuel appears to be getting better organized just off the coast of southwestern Mexico:

Wind: 35 mph, with higher gusts
Location: 23.0°N 107.7°W
Movement: NW at 6 mph
Pressure: 1002 mb

Select satellite estimates are beginning to show Manuel is back up to a low-end tropical storm, with the most recent CIMSS ADT final T number coming in at 2.3, just shy of the 35 kt threshold needed for tropical storm strength. TAFB came in with 2.0 at 0z, while SAB was 1.0. I tend to favor the CIMSS estimate given current convective trends, which suggest increasing banding features to the east of the center, along with a recent increase in central convection directly atop the low-level center's estimated location. Additionally, recent microwave data show that Manuel's inner core region has become much better defined, with a formative eye feature noted on a 0239 SSMIS microwave pass.



Figure 4. Latest infrared satellite image of Tropical Depression Manuel. Image credit: NOAA's Satellite Services Division (SSD).

There appears to be little nearby vertical shear, and Manuel is over 29 to 30C SSTs, so strengthening appears inevitable. Given the rather abrupt increase in the organization of the inner core, Manuel is expected to strengthen at least modestly before reaching the coast, and my forecast shows a peak of 50 kt before landfall in about 48 hours, which is a shade higher than the current NHC prediction. If the inner core continues to become better defined, there is a chance Manuel could become a minimal hurricane, although land interaction may play a negative role with an intensifying system.

After landfall, Manuel is forecast to ingest an extremely dry airmass west of Baja California, as shown on water vapor imagery. The cyclone is forecast to degenerate into a remnant low on day four, and completely dissipate by day five. My forecast track is similar to the current NHC track forecast scheme, which seems supported rather nicely by current synoptic trends over the western United States.

Intensity forecast and positions

INITIAL 09/18 0300Z 23.0°N 107.7°W 30 KT 35 MPH
12 hour 09/18 1200Z 24.5°N 108.3°W 35 KT 40 MPH
24 hour 09/19 0000Z 24.8°N 108.8°W 40 KT 45 MPH
36 hour 09/19 1200Z 25.3°N 109.6°W 50 KT 60 MPH
48 hour 09/20 0000Z 25.4°N 110.1°W 50 KT 60 MPH
72 hour 09/21 0000Z 25.3°N 110.8°W 30 KT 35 MPH...INLAND
96 hour 09/22 0000Z 24.7°N 111.4°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
120 hour 09/23 0000Z...DISSIPATED

Track forecast



Figure 5. My forecast track for Manuel.

2013 Atlantic hurricane season 2013 Pacific hurricane season Tropical Storm Humberto Invest 95L Tropical Depression Manuel

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Tropical weather analysis - September 16, 2013

By: KoritheMan, 6:50 AM GMT on September 16, 2013

Ingrid

Ingrid weakened on Sunday, but remains a minimal hurricane this morning as of the 0600Z NHC intermediate advisory bulletin:

Wind: 75 mph, with higher gusts
Location: 23.2°N 96.9°W
Movement: WNW at 6 mph
Pressure: 989 mb
Category: 1 (Saffir-Simpson Hurricane Wind Scale)

Satellite estimates are varied, ranging from around 3.5 from CIMSS-ADT to 4.5 from TAFB. A blend of those estimates is probably a good idea given such a notable discrepancy, which would still suggest an intensity of about 65 kt; it will be most interesting to see what the next aircraft unearths.

A small area of convection exists near the center, but the majority of the precipitation is located east and southeast of the low-level center due to continued westerly to northwesterly shear.



Figure 1. Latest infrared satellite image of Hurricane Ingrid. Image credit: NOAA's Satellite Services Division (SSD).

I am not immediately sure what the source of this shear is, but water vapor imagery suggests that the slowly amplifying trough over the western United States could be imparting it, perhaps aiding what's left of Manuel's outflow to effectively shear the hurricane. Since the cloud pattern clearly suggests ongoing shear, I imagine the shear will not decrease appreciably until just before landfall, which is forecast to occur in about 12 hours, with an effective margin for error upward or downward. This should prevent significant strengthening of the hurricane until it moves inland, although some slight strengthening prior to landfall cannot be ruled out. An alternate scenario is that continued shear causes Ingrid to weaken to a tropical storm later today.

Ingrid jogged to the northwest late Sunday evening, but has resumed a west-northwestward motion. Although the ridge over the southern United States is slowly weakening, Ingrid is still well within its confines, and the ridge is not expected to completely weaken until after the hurricane moves inland and dissipates. The global models have come into better agreement on the timing of landfall, and my forecast track is similar to what it was yesterday. The circulation is expected to quickly dissipate over the rugged terrain of the Sierra Madre Oriental mountain range after Ingrid makes landfall.

With the observed weakening on Sunday, unless Ingrid unexpectedly reintensifies, the primary hazard remains the potential for very heavy rains, which could cause additional fatalities, especially in areas of mountainous terrain. Interests in the projected path of the system should closely follow the progress of Ingrid, and take precautions to protect life and property as needed. Flooding is amongst the top killers in tropical cyclones.

Intensity forecast and positions

INITIAL 09/17 0300Z 23.2°N 96.9°W 65 KT 75 MPH
12 hour 09/17 1200Z 23.3°N 97.8°W 65 KT 75 MPH...INLAND
24 hour 09/18 0000Z 23.1°N 98.6°W 30 KT 35 MPH...INLAND
36 hour 09/18 1200Z 22.9°N 99.2°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
48 hour 09/19 0000Z...DISSIPATED

Track forecast



Figure 2. My forecast track for Ingrid.

NHC storm information

000
WTNT35 KNHC 160531
TCPAT5

BULLETIN
HURRICANE INGRID INTERMEDIATE ADVISORY NUMBER 15A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102013
100 AM CDT MON SEP 16 2013

...INGRID EXPECTED TO MAKE LANDFALL IN NORTHEASTERN MEXICO LATER
TODAY...


SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...23.2N 96.9W
ABOUT 95 MI...150 KM NE OF TAMPICO MEXICO
ABOUT 70 MI...115 KM SE OF LA PESCA MEXICO
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...989 MB...29.21 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* CABO ROJO TO LA PESCA

A HURRICANE WATCH IS IN EFFECT FOR...
* NORTH OF LA PESCA TO BAHIA ALGODONES

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* NORTH OF LA PESCA TO RIO SAN FERNANDO
* SOUTH OF CABO ROJO TO TUXPAN

PREPARATIONS TO PROTECT LIFE AND PROPERTY IN THE HURRICANE WARNING
AREA SHOULD BE RUSHED TO COMPLETION.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 100 AM CDT...0600 UTC...THE CENTER OF HURRICANE INGRID WAS
LOCATED NEAR LATITUDE 23.2 NORTH...LONGITUDE 96.9 WEST. INGRID IS
MOVING TOWARD THE WEST-NORTHWEST NEAR 6 MPH...9 KM/H...AND A TURN
TO THE WEST IS EXPECTED LATER TODAY...FOLLOWED BY A TURN TO THE
WEST-SOUTHWEST TONIGHT. ON THE FORECAST TRACK...THE CENTER OF
INGRID SHOULD BE VERY NEAR THE COAST OF MEXICO WITHIN THE HURRICANE
WARNING AREA BY THIS AFTERNOON.

MAXIMUM SUSTAINED WINDS ARE NEAR 75 MPH...120 KM/H...WITH HIGHER
GUSTS. SOME SLIGHT STRENGTHENING IS POSSIBLE BEFORE THE CENTER
REACHES THE COAST. WEAKENING WILL BEGIN ONCE INGRID MOVES OVER
LAND.

HURRICANE-FORCE WINDS EXTEND OUTWARD UP TO 15 MILES...30 KM...FROM
THE CENTER...AND TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 105
MILES...165 KM...MAINLY TO NORTHEAST AND SOUTHEAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB...29.21 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...INGRID IS EXPECTED TO PRODUCE 10 TO 15 INCHES OF RAIN
OVER A LARGE PART OF EASTERN MEXICO...WITH ISOLATED AMOUNTS OF 25
INCHES POSSIBLE...ESPECIALLY IN AREAS OF MOUNTAINOUS TERRAIN. THESE
RAINS ARE LIKELY TO RESULT IN LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES.

WIND...TROPICAL STORM CONDITIONS ARE BEGINNING TO SPREAD OVER THE
COAST WITHIN THE WARNING AREAS. HURRICANE CONDITIONS ARE EXPECTED
TO REACH THE COAST WITHIN THE HURRICANE WARNING AREA LATER THIS
MORNING.

STORM SURGE...A DANGEROUS STORM SURGE WILL RAISE WATER LEVELS BY AS
MUCH AS 2 TO 4 FEET ABOVE NORMAL TIDE LEVELS ALONG THE IMMEDIATE
COAST NEAR AND TO THE NORTH OF WHERE THE CENTER OF INGRID MAKES
LANDFALL. NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE
AND DESTRUCTIVE WAVES.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...400 AM CDT.

$$
FORECASTER PASCH



Invest 94L

An area of low pressure associated with the remnants of Humberto continue to churn aimlessly in the central Atlantic well away from land. Convection has increased again, but any futile attempt to wrap into the well-defined low-level center is quickly shunted by strong westerly shear associated with an upper-level trough to the northwest of the system. There is evidence of this trough weakening, and upper-level winds are forecast to improve considerably over the next 24 to 48 hours, and Humberto could regenerate into a tropical cyclone at any point during that period, probably closer to the latter range.

The system appears to be moving due westward, possibly due to a lack of convection over the center; but since it was moving west-northwest since dissipation a couple of days ago, it's more likely the result of a temporary restrengthening of the subtropical ridge. The large-scale pattern still favors a gradual northward turn, followed by a northeastward motion into the westerlies.



Figure 3. Latest infrared satellite image of Invest 94L. Image credit: NOAA's Satellite Services Division (SSD).

Probability of development in 48 hours: 90%



More Gulf of Mexico development possible next week

The operational GFS and the GFS ensembles are starting to latch onto the idea of an area of disturbed weather/low pressure area forming in the Bay of Campeche in association with an area of showers and cloudiness in the western Caribbean Sea. The ECMWF has been showing something similar as well.

The track of such a system is uncertain. The GFS ensembles portray a pattern that does not appear amplified, and such situations can allow for pretty much anything. The 0z run of the GFS also suggests that this disturbed weather hypothetical could be rather large and monsoonal in nature, probably originating at least in part from the large cyclonic envelope of low pressure encompassing Ingrid and Manuel, with some contribution from the western Caribbean system. This system appears poised to be large and complex, and those large systems with multiple embedded swirls tend to be the most difficult to predict, sadly.

I see potential for several solutions with this, including:

- Another strike on saturated Mexico, creating another flood situation there.

- A northward turn toward the northern or central Gulf Coast.

- A northward-moving system that gradually turns east-northeast toward western Florida; Hurricane Gordon of 2000 would be a fitting analogy.

I am not sure which of these solutions is most viable at the moment; a lot will depend on how the large-scale pattern over the United States evolves in the next few days. One thing to keep in mind is that the synoptic flow over the country, especially over the central United States, has been a little more amplified than progressive, which could throw a wrench into any speculation of various track forecasts if it persists.

Hurricane Ingrid Invest 94L 2013 Atlantic hurricane season

Updated: 6:59 AM GMT on September 16, 2013

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Tropical weather analysis - September 15, 2013

By: KoritheMan, 5:45 AM GMT on September 15, 2013

Ingrid

The following was posted on Ingrid during the 0600Z NHC intermediate advisory:

Wind: 85 mph, with higher gusts
Location: 22.2°N 95.2°W
Movement: NNW at 7 mph
Pressure: 986 mb
Category: 1 (Saffir-Simpson Hurricane Wind Scale)

The satellite presentation of Ingrid is a little ragged looking, with the outflow remaining flat in the western semicircle, signaling that some westerly to southwesterly shear continues to affect the hurricane. This is likely the result of a negative interaction between Ingrid and strengthening Tropical Storm Manuel, located off the Pacific coast of southern Mexico, probably no more than about 300 miles from Ingrid.



Figure 1. Latest infrared satellite image of Hurricane Ingrid. Image credit: NOAA's Satellite Service Division (SSD).

Once Manuel moves inland and weakens within the next 12 hours, the shear over Ingrid should decrease, and an upper-level anticyclone should slowly build over the hurricane. Such a pattern favors significant intensification all the way up to landfall, and my forecast is a little higher than the National Hurricane Center, showing Ingrid becoming a 90 kt Category 2 just as it moves inland in 36 hours; however, it is certainly possible that Ingrid could become a major hurricane before landfall. The circulation is forecast to quickly weaken over the rugged terrain of central Mexico after landfall, with complete dissipation shown in 72 hours, if not sooner.

Lacking any concrete data, Ingrid's movement tonight is a little hard for me to determine, but based on careful analysis of shortwave infrared imagery, the hurricane still seems to be moving roughly north-northwest. However, I note that this estimate is rather uncertain, and if I'm wrong, and Ingrid is actually moving more northwest, my forecast tonight could be a little too far to the east. However, water vapor imagery shows a sharp upper-level trough over the western United States beginning to erode the western periphery of the ridge over the southern United States, which could lend some credibility to my forecast. The guidance has trended north between 18 and 0z, and have been trending in that general direction for much of the day on Saturday. I don't see much evidence of the ridge rebuilding over the southern United States like the National Hurricane Center suggests, although perhaps they see something I don't. Still, with a building mid-level ridge over the eastern Gulf of Mexico, Ingrid should not make much northward progress before beginning the anticipated westward turn. My forecast track is a little to the north of the current NHC forecast. A southward motion is shown after landfall to be in agreement with the model consensus.

Hurricane warnings are up for a portion of the coast, and interests within this area should pay extra attention to Ingrid, and complete preparations to protect life and property.

Excessive rainfall from Ingrid and Manuel remains a serious threat.

Intensity forecast and positions

INITIAL 09/15 0300Z 22.0°N 95.0°W 75 KT 85 MPH
12 hour 09/15 1200Z 22.7°N 95.5°W 80 KT 90 MPH
24 hour 09/16 0000Z 23.5°N 96.5°W 85 KT 100 MPH
36 hour 09/16 1200Z 23.7°N 97.8°W 90 KT 105 MPH...INLAND
48 hour 09/17 0000Z 23.4°N 99.1°W 50 KT 60 MPH...INLAND
72 hour 09/18 0000Z 22.9°N 99.8°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
96 hour 09/19 0000Z...DISSIPATED

Track forecast



Figure 2. My forecast track for Ingrid.



NHC storm information

000
WTNT35 KNHC 150543
TCPAT5

BULLETIN
HURRICANE INGRID INTERMEDIATE ADVISORY NUMBER 11A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102013
100 AM CDT SUN SEP 15 2013

...INGRID EXPECTED TO MAKE LANDFALL ON MONDAY...


SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...22.2N 95.2W
ABOUT 175 MI...280 KM E OF TAMPICO MEXICO
ABOUT 200 MI...320 KM ESE OF LA PESCA MEXICO
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...986 MB...29.12 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* CABO ROJO TO LA PESCA

A HURRICANE WATCH IS IN EFFECT FOR...
* NORTH OF LA PESCA TO BAHIA ALGODONES

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* NORTH OF LA PESCA TO RIO SAN FERNANDO
* SOUTH OF CABO ROJO TO TUXPAN

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN 36 HOURS.
PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO
COMPLETION.

A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE
WITHIN THE WATCH AREA...IN THIS CASE WITHIN 36 HOURS.

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

INTERESTS ELSEWHERE ALONG THE REMAINDER OF THE GULF COAST OF EASTERN
MEXICO SHOULD MONITOR THE PROGRESS OF INGRID.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 100 AM CDT...0600 UTC...THE CENTER OF HURRICANE INGRID WAS
LOCATED NEAR LATITUDE 22.2 NORTH...LONGITUDE 95.2 WEST. INGRID IS
MOVING TOWARD THE NORTH-NORTHWEST NEAR 7 MPH...11 KM/H. A TURN
TOWARD THE NORTHWEST IS EXPECTED LATER THIS MORNING...FOLLOWED BY A
TURN TOWARD THE WEST BY EARLY MONDAY. ON THE FORECAST TRACK...
INGRID SHOULD REACH THE COAST OF MEXICO WITHIN THE HURRICANE WARNING
AREA EARLY MONDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 85 MPH...140 KM/H...WITH HIGHER
GUSTS. SOME ADDITIONAL STRENGTHENING IS FORECAST BEFORE LANDFALL.

HURRICANE-FORCE WINDS EXTEND OUTWARD UP TO 35 MILES...55 KM...FROM
THE CENTER...AND TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 90
MILES...150 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 986 MB...29.12 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...INGRID IS EXPECTED TO PRODUCE 10 TO 15 INCHES OF RAIN
OVER A LARGE PART OF EASTERN MEXICO...WITH ISOLATED AMOUNTS OF 25
INCHES POSSIBLE...ESPECIALLY IN AREAS OF MOUNTAINOUS TERRAIN. THESE
RAINS ARE LIKELY TO RESULT IN LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES.

WIND...HURRICANE CONDITIONS ARE EXPECTED TO REACH THE HURRICANE
WARNING AREA EARLY MONDAY...WITH TROPICAL STORM CONDITIONS EXPECTED
BY LATE SUNDAY. HURRICANE CONDITIONS ARE POSSIBLE IN THE HURRICANE
WATCH AREA EARLY MONDAY.

STORM SURGE...A DANGEROUS STORM SURGE WILL RAISE WATER LEVELS BY AS
MUCH AS 3 TO 5 FEET ABOVE NORMAL TIDE LEVELS ALONG THE IMMEDIATE
COAST NEAR AND TO THE NORTH OF WHERE THE CENTER OF INGRID MAKES
LANDFALL. NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE
AND DESTRUCTIVE WAVES.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...400 AM CDT.

$$
FORECASTER PASCH



Invest 94L

The remnants of Humberto are located in the central Atlantic well away from any land areas. Satellite images show that the low-level circulation is still very well-defined, and some disorganized convection has been persisting about 75 miles northeast of the center. The current shearing environment is forecast to abate over the next 48 hours, at which time Humberto will likely regenerate into a tropical cyclone. I still think Humberto will become a hurricane again as it interacts with an upper-level trough in four or five days.



Figure 3. Latest infrared satellite image of Invest 94L. Image credit: NOAA's Satellite Services Division (SSD).

Probability of development in 48 hours: 70%



Manuel

Tropical Storm Manuel continues to strengthen as it approaches the coast of southern Mexico. As of the latest NHC advisory, the following information was available on the cyclone:

Wind: 70 mph, with higher gusts
Location: 17.5°N 102.5°W
Movement: NNW at 7 mph
Pressure: 985 mb

While an eye is not readily apparent on satellite images, microwave data throughout the last several hours have shown a strengthening of the inner core region, with a well-defined eye and developing eyewall. I suspect Manuel will be a hurricane soon, if it is not one already; given the small size of the circulation and tight inner core region, any eye that attempts to manifest on conventional satellite images will likely be rather small.



Figure 4. Latest infrared satellite image of Tropical Storm Manuel. Image credit: NOAA's Satellite Services Division (SSD).

Environmental conditions appear conducive for strengthening up until landfall, with light shear, high relative humidity values, and very low vertical shear. Since I feel Manuel is going through a period of rapid intensification, my forecast shows the cyclone reaching 75 kt prior to moving inland within the next 12 hours. After landfall, the circulation is forecast to quickly decay.

Manuel made a jog to the right between 21 and 0z, but appears to have resumed a more definitive north-northwestward motion. Manuel should continue moving in that general direction until landfall as it is steered by a weakening subtropical ridge over the southern United States. After landfall, the cyclone is forecast to turn west-northwestward and dissipate.

It is possible that Manuel could emerge into the Gulf of
California in three or four days, but it remains to be seen whether or not it can regenerate in such a state.

Extreme rainfall will lash much of eastern Mexico as Manuel combines with Ingrid to produce a highly dangerous flash flood situation there.

Intensity forecast and positions

INITIAL 09/15 0300Z 17.2°N 102.3°W 60 KT 70 MPH
12 hour 09/15 1200Z 18.1°N 102.5°W 75 KT 85 MPH...AT THE COAST
24 hour 09/16 0000Z 19.3°N 103.5°W 45 KT 50 MPH...INLAND
36 hour 09/16 1200Z 20.0°N 104.7°W 30 KT 35 MPH...POST-TROPICAL/REMNANT LOW
48 hour 09/17 0000Z...DISSIPATED

Track forecast



Figure 5. My forecast track for Manuel.

NHC storm information


000
WTPZ33 KNHC 150544
TCPEP3

BULLETIN
TROPICAL STORM MANUEL INTERMEDIATE ADVISORY NUMBER 7A
NWS NATIONAL HURRICANE CENTER MIAMI FL EP132013
1100 PM PDT SAT SEP 14 2013

...MANUEL DOUSING PORTIONS OF SOUTHWESTERN MEXICO...


SUMMARY OF 1100 PM PDT...0600 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.5N 102.5W
ABOUT 40 MI...65 KM SSW OF LAZARO CARDENAS MEXICO
ABOUT 155 MI...255 KM SE OF MANZANILLO MEXICO
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NNW OR 345 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* LAZARO CARDENAS TO MANZANILLO

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* ACAPULCO TO EAST OF LAZARO CARDENAS

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN THE NEXT
12 HOURS. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE
RUSHED TO COMPLETION.

INTERESTS ELSEWHERE IN SOUTHWESTERN MEXICO SHOULD MONITOR THE
PROGRESS OF MANUEL.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 PM PDT...0600 UTC...THE CENTER OF TROPICAL STORM MANUEL WAS
LOCATED NEAR LATITUDE 17.5 NORTH...LONGITUDE 102.5 WEST. MANUEL IS
MOVING TOWARD THE NORTH-NORTHWEST NEAR 7 MPH...11 KM/H...AND THIS
GENERAL MOTION SHOULD CONTINUE FOR THE NEXT DAY OR TWO. ON THE
FORECAST TRACK...MANUEL WILL BE APPROACHING THE COAST OF
SOUTHWESTERN MEXICO WITHIN THE HURRICANE WARNING AREA EARLY SUNDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 70 MPH...110 KM/H...WITH HIGHER
GUSTS. SOME ADDITIONAL STRENGTHENING IS POSSIBLE...AND MANUEL
COULD BE A HURRICANE WHEN IT MAKES LANDFALL ON SUNDAY.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 275 MILES...445 KM
FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 985 MB...29.09 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...MANUEL IS EXPECTED TO PRODUCE 10 TO 15 INCHES OF RAIN
OVER PORTIONS OF THE MEXICAN STATES OF OAXACA AND GUERRERO...WITH
ISOLATED MAXIMUM AMOUNTS OF 25 INCHES POSSIBLE. THESE RAINS ARE
LIKELY TO RESULT IN LIFE-THREATENING FLASH FLOODS AND MUD SLIDES...
ESPECIALLY IN MOUNTAINOUS TERRAIN.

WIND...TROPICAL STORM CONDITIONS ARE OCCURRING IN PORTIONS OF THE
WARNING AREA. HURRICANE CONDITIONS ARE EXPECTED TO REACH PORTIONS
OF THE HURRICANE WARNING AREA EARLY SUNDAY.

STORM SURGE...A STORM SURGE IS EXPECTED TO PRODUCE COASTAL FLOODING
NEAR AND TO THE EAST OF WHERE THE CENTER OF MANUEL MAKES LANDFALL.
NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE AND
DESTRUCTIVE WAVES.

SURF...SWELLS GENERATED BY MANUEL ARE AFFECTING PORTIONS OF THE
COAST OF MEXICO BETWEEN THE GULF OF TEHUANTEPEC AND MANZANILLO.
THESE SWELLS ARE EXPECTED TO CONTINUE FOR THE NEXT COUPLE OF
DAYS...AND WILL CAUSE LIFE-THREATENING SURF AND RIP CURRENT
CONDITIONS. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER OFFICE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...200 AM PDT.

$$
FORECASTER BERG/PASCH

2013 Atlantic hurricane season Hurricane Ingrid Invest 94L Tropical Storm Manuel 2013 Pacific hurricane season

Updated: 5:48 AM GMT on September 15, 2013

Permalink

Tropical weather analysis - September 13, 2013

By: KoritheMan, 3:52 AM GMT on September 14, 2013

Humberto

Humberto continues to rapidly weaken as of the 0300Z NHC advisory:

Wind: 45 mph, with higher gusts
Location: 24.8°N 33.0°W
Movement: W at 9 mph
Pressure: 999 mb

Humberto has been devoid of deep convection for about 12 hours, and satellite estimates are falling as quickly as traditional Dvorak constraints allow.



Figure 1. Latest infrared satellite image of Tropical Storm Humberto. Image credit: NOAA's Satellite Services Division (SSD).

Analyses from University of Wisconsin CIMSS show that Humberto is embedded in an environment of very strong southwesterly shear, about 40 kt, caused by a sharp and unusually deep upper trough located to the west of the system. This shear was well advertised by the global models ever since the cyclone's inception, although Humberto's response to it perhaps was not. While not explicitly shown in my personal intensity forecast, the lack of convection suggests the likelihood that Humberto will degenerate into a remnant low at anytime, which is consistent with the latest NHC advisory. However, I am trying to maintain some continuity, and also accounting for the potential influence of the diurnal convective maximum period in combination with upper diffluence with the aforementioned trough. My feeling, however, is that my current forecast will be incorrect, and the upper flow is probably too strongly sheared, enough to counteract the upper diffluent flow.

In a few days, the GFS shows 200 mb winds in front of the system improving considerably, so reintensification is shown later in the period, and Humberto is expected to become a hurricane again by day five. Given the large size of the circulation connected with Humberto, it is highly likely that it will regenerate and/or restrengthen later when the upper flow improves.

The cyclone is south of a well-established mid-level ridge near the Azores. In a couple of days, the guidance shows Humberto rounding the western periphery of this ridge in advance of a shortwave trough in the westerlies. My forecast package today is not too different from my previous ones.

Note that the forecast times given below were based on the 2100Z NHC advisory; the 0300Z advisory was not furnished until I was done writing this.

Intensity forecast and positions

INITIAL 09/13 2100Z 25.0°N 32.1°W 45 KT 50 MPH
12 hour 09/14 0600Z 25.5°N 34.6°W 35 KT 40 MPH
24 hour 09/14 1800Z 26.3°N 37.3°W 30 KT 35 MPH
36 hour 09/15 0600Z 27.1°N 39.5°W 30 KT 35 MPH
48 hour 09/15 1800Z 27.8°N 41.3°W 30 KT 35 MPH
72 hour 09/16 1800Z 30.2°N 44.3°W 40 KT 45 MPH
96 hour 09/17 1800Z 32.6°N 45.3°W 55 KT 65 MPH
120 hour 09/18 1800Z 36.8°N 44.7°W 70 KT 80 MPH

Track forecast



Figure 2. My forecast track for Humberto.



Ingrid

Tropical Storm Ingrid continues to meander in the southern Bay of Campeche. As of the 0300Z NHC advisory, the following information was posted on the cyclone:

Wind: 60 mph, with higher gusts
Location: 19.3°N 95.2°W
Movement: Stationary
Pressure: 993 mb

Ingrid was on a strengthening trend earlier today, with reconnaissance sampling suggesting an increase in winds. Since the departure of the aircraft, the satellite signature has not changed much; convection has increased near the center, but the center is still not quite collocated with the deepest convection, as denoted in recent microwave data. This is likely due to moderate southwesterly shear associated with a weak upper trough over northern Mexico and outflow from Tropical Storm Manuel in the Pacific.



Figure 3. Latest infrared satellite image of Tropical Storm Ingrid. Image credit: NOAA's Satellite Services Division (SSD).

Since the synoptic situation favors the shear decreasing, Ingrid is forecast to continue strengthening. As the upper environment over the cyclone improves more markedly in 36-48 hours, a quicker pace of intensification is anticipated, and Ingrid is forecast to be an intensifying Category 1 hurricane at landfall. This is predicated upon the track being farther north, however, and closer to the GFS, so if that turns out to be incorrect, Ingrid will not have as much time over water. However, Manuel is a position relative to Ingrid that favors a more uniform southerly flow than a uniform southeasterly flow, which could allow for Ingrid to move a little more northward during the next 24 hours before it initiates the westward turn. After landfall, Ingrid is forecast to quickly weaken over the mountainous terrain of eastern Mexico.

Although Ingrid is still moving in fits and wobbles, the cyclone is expected to turn northward soon, which is supported by both the GFS and ECMWF. The primary difference in the models appears to be how much time Ingrid has over water, with the GFS showing more time over water, while the ECMWF pulls Ingrid in a little faster. Once again, my forecast favors the GFS, although perhaps not quite as far north. My forecast track is fairly similar to the NHC advisory, but a little farther north.

While high winds will be a concern for coastal areas and mountainous regions just inland if Ingrid becomes a hurricane as forecast, I want to continue to emphasize that the primary threat is torrential rainfall and excessive flooding across a large section of eastern Mexico as Ingrid combines with Tropical Storm Manuel to deliver a one two punch to the region. Interests in the area should monitor Ingrid very carefully, and take the necessary precautions to protect life and property.

Note that the forecast times given below were based on the 0000Z NHC special advisory; the 0300Z advisory was not furnished until I was done writing this.

Intensity forecast and positions

INITIAL 09/14 0000Z 19.2°N 95.3°W 50 KT 60 MPH
12 hour 09/14 1200Z 19.6°N 95.3°W 55 KT 65 MPH
24 hour 09/15 0000Z 20.4°N 95.4°W 60 KT 70 MPH
36 hour 09/15 1200Z 21.3°N 95.4°W 65 KT 75 MPH
48 hour 09/16 0000Z 22.7°N 96.3°W 75 KT 85 MPH
72 hour 09/17 0000Z 22.9°N 98.6°W 40 KT 45 MPH...INLAND
96 hour 09/18 0000Z 23.0°N 100.5°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
120 hour 09/19 0000Z...DISSIPATED

Track forecast



Figure 4. My forecast track for Ingrid.

NHC storm information

000
WTNT35 KNHC 140255
TCPAT5

BULLETIN
TROPICAL STORM INGRID ADVISORY NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102013
1000 PM CDT FRI SEP 13 2013

...INGRID STATIONARY OVER THE SOUTHWESTERN GULF OF MEXICO...
...FORECAST TO STRENGTHEN AND BEGIN MOVING NORTHWARD...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.3N 95.2W
ABOUT 65 MI...105 KM E OF VERACRUZ MEXICO
ABOUT 185 MI...295 KM SE OF TUXPAN MEXICO
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...STATIONARY
MINIMUM CENTRAL PRESSURE...993 MB...29.32 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WATCH IS IN EFFECT FOR...
* NORTH OF CABO ROJO TO LA PESCA

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* COATZACOALCOS TO CABO ROJO

A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE
WITHIN THE WATCH AREA. A WATCH IS TYPICALLY ISSUED 48 HOURS
BEFORE THE ANTICIPATED FIRST OCCURRENCE OF TROPICAL-STORM-FORCE
WINDS...CONDITIONS THAT MAKE OUTSIDE PREPARATIONS DIFFICULT OR
DANGEROUS.

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN THE
NEXT 12 TO 24 HOURS.

INTERESTS ELSEWHERE ALONG THE COAST OF EASTERN MEXICO SHOULD MONITOR
THE PROGRESS OF THIS SYSTEM.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1000 PM CDT...0300 UTC...THE CENTER OF TROPICAL STORM INGRID WAS
LOCATED NEAR LATITUDE 19.3 NORTH...LONGITUDE 95.2 WEST. INGRID IS
CURRENTLY STATIONARY. HOWEVER...A NORTHWARD DRIFT IS EXPECTED TO
BEGIN OVERNIGHT AND EARLY SATURDAY...FOLLOWED BY A FASTER MOTION
TOWARD THE NORTHWEST BY EARLY SUNDAY...AND A TURN TOWARD THE
WEST-NORTHWEST BY LATE SUNDAY. ON THE FORECAST TRACK...INGRID WILL
BE VERY CLOSE TO THE COAST OF MEXICO IN THE TROPICAL STORM WARNING
AREA DURING THE NEXT DAY OR SO...AND APPROACH THE COAST IN THE
HURRICANE WATCH AREA ON SUNDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH...95 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...
AND INGRID IS EXPECTED TO BECOME A HURRICANE BY SUNDAY.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 80 MILES...130 KM
FROM THE CENTER. A JOINT U.S. EPA AND MEXICAN GOVERNMENT WEATHER
STATION IN VERACRUZ HARBOR RECENTLY REPORTED A WIND GUST OF 41
MPH...66 KM/H.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 993 MB...29.32 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...INGRID IS EXPECTED TO PRODUCE 10 TO 15 INCHES OF RAIN
OVER A LARGE PART OF EASTERN MEXICO...WITH ISOLATED AMOUNTS OF 25
INCHES POSSIBLE...ESPECIALLY IN AREAS OF MOUNTAINOUS TERRAIN. THESE
RAINS ARE LIKELY TO RESULT IN LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH PORTIONS OF
THE COAST WITHIN THE TROPICAL STORM WARNING OVERNIGHT AND SATURDAY.
HURRICANE CONDITIONS ARE POSSIBLE IN THE HURRICANE WATCH AREA BY
LATE SUNDAY...WITH TROPICAL STORM CONDITIONS POSSIBLE BY SUNDAY
MORNING.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...100 AM CDT.
NEXT COMPLETE ADVISORY...400 AM CDT.

$$
FORECASTER BRENNAN



Manuel

Tropical Storm Manuel continues to head toward the coast of Mexico. As of the latest NHC advisory, the following information was posted on the cyclone:

Wind: 45 mph, with higher gusts
Location: 15.3°N 102.5°W
Movement: W at 6 mph
Pressure: 996 mb

Satellite and microwave data suggest that the small tropical cyclone has gained some strength this evening. Recent microwave data showed the beginnings of a primitive eye feature, and these features appeared to be only slightly displaced in the vertical between the lower and middle troposphere. In addition, recent satellite data shows deep convection consolidating around that feature. Banding features are increasing in every direction except the north, with the most tightly-knit banding found in the eastern semicircle.



Figure 5. Latest infrared satellite image of Tropical Storm Manuel. Image credit: NOAA's Satellite Services Division (SSD).

While Manuel is experiencing a little bit of northeasterly to easterly shear, the GFS/SHIPS algorithm forecasts the winds to decrease over the next 24 hours, which should allow for some strengthening up until the cyclone makes landfall in about 36 hours. Assuming Ingrid doesn't pull a surprise and rapidly intensify, the outflow associated with the latter cyclone should not be an inhibiting factor to Manuel's own intensification. My forecast identical to the 0300Z NHC one, bringing Manuel up to 55 kt just prior to landfall; given the small radius of maximum winds and tight inner core region, however, I would not be surprised to see Manuel become a hurricane before hitting the coast.

The tropical storm's motion has been a little hard for me to judge this evening; a couple of microwave passes suggested a slow north-northwestward drift over the last several hours, but conventional satellite data suggests little motion, which is something that is a little hard to judge with strictly infrared imagery. In either case, Manuel should soon turn northwest to north-northwest and make landfall along the southern coast of Mexico. The guidance is in good agreement with this scenario, although there appears to have been a slight westward shift in the guidance envelope between 18 and 0z. My forecast is pretty similar to the National Hurricane Center one, with the primary steering mechanism for Manuel being a distant mid-level ridge over Texas and northern Mexico. The circulation of Ingrid should not interfere too strongly with Manuel's movement, if at all.

After landfall, the circulation is forecast to quickly fall apart.

The primary hazard from Manuel is the potential for extreme rainfall and flash flooding over a large portion of eastern Mexico as the large cyclonic envelope in which Manuel and Ingrid are embedded help the two cyclones contribute to heavy rainfall.

Intensity forecast and positions

INITIAL 09/14 0300Z 15.3°N 102.5°W 40 KT 45 MPH
12 hour 09/15 1200Z 16.1°N 102.9°W 45 KT 50 MPH
24 hour 09/16 0000Z 17.2°N 103.1°W 50 KT 60 MPH
36 hour 09/16 1200Z 18.2°N 103.3°W 55 KT 65 MPH
48 hour 09/17 0000Z 20.0°N 103.5°W 30 KT 35 MPH...INLAND
72 hour 09/18 0000Z...DISSIPATED

Track forecast



Figure 6. My forecast track for Manuel.

NHC storm information


000
WTPZ33 KNHC 140249
TCPEP3

BULLETIN
TROPICAL STORM MANUEL ADVISORY NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL EP132013
800 PM PDT FRI SEP 13 2013

...MANUEL NEARLY STATIONARY...
...EXPECTED TO TURN NORTH-NORTHWESTWARD ON SATURDAY...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...15.3N 102.5W
ABOUT 190 MI...300 KM S OF LAZARO CARDENAS MEXICO
ABOUT 280 MI...455 KM SSE OF MANZANILLO MEXICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...SW OR 225 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...996 MB...29.41 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* ACAPULCO TO PUNTA SAN TELMO

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN 24
TO 36 HOURS.

INTERESTS ELSEWHERE IN SOUTHWESTERN MEXICO SHOULD MONITOR THE
PROGRESS OF MANUEL.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 PM PDT...0300 UTC...THE CENTER OF TROPICAL STORM MANUEL WAS
LOCATED NEAR LATITUDE 15.3 NORTH...LONGITUDE 102.5 WEST. MANUEL IS
NEARLY STATIONARY...AND SOME ERRATIC MOTION COULD OCCUR TONIGHT. A
GRADUAL TURN TOWARD THE NORTH-NORTHWEST WITH AN INCREASE IN FORWARD
SPEED IS EXPECTED ON SATURDAY. ON THE FORECAST TRACK...MANUEL
SHOULD BE VERY NEAR THE COAST OF SOUTHWESTERN MEXICO WITHIN THE
WARNING AREA BY LATE SATURDAY OR EARLY SUNDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/H...WITH HIGHER
GUSTS. GRADUAL STRENGTHENING IS FORECAST DURING THE NEXT 36 HOURS
UNTIL MANUEL MAKES LANDFALL.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 60 MILES...95 KM
FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB...29.41 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...MANUEL IS EXPECTED TO PRODUCE 10 TO 15 INCHES OF RAIN
OVER PORTIONS OF THE MEXICAN STATES OF OAXACA AND GUERRERO...WITH
ISOLATED MAXIMUM AMOUNTS OF 20 INCHES POSSIBLE. THESE RAINS ARE
LIKELY TO RESULT IN LIFE-THREATENING FLASH FLOODS AND MUDSLIDES...
ESPECIALLY IN MOUNTAINOUS TERRAIN.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO BEGIN IN PORTIONS
OF THE WARNING AREA BY MID-DAY SATURDAY.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...1100 PM PDT.
NEXT COMPLETE ADVISORY...200 AM PDT.

$$
FORECASTER STEWART

2013 Atlantic hurricane season 2013 Pacific hurricane season Tropical Storm Humberto Tropical Storm Ingrid Tropical Storm Manuel

Updated: 4:00 AM GMT on September 14, 2013

Permalink

Tropical weather analysis - September 13, 2013

By: KoritheMan, 7:14 AM GMT on September 13, 2013

Gabrielle

Gabrielle continues as a minimal tropical storm as of the 0300Z NHC advisory:

Wind: 40 mph, with higher gusts
Location: 35.1°N 67.7°W
Movement: NNE at 10 mph
Pressure: 1008 mb

Gabrielle's tenacity is most commendable, as convection has erupted again tonight. However, cold as the burst is, the general trend has been for the nightly convective resurgence to be short-lived and a little less organized each time. Gabrielle's vortex will continue to gradually spin down as the cyclone traverses an environment of southwesterly shear and mid-level dry air.



Figure 1. Latest infrared satellite image of Tropical Storm Gabrielle. Image credit: NOAA's Satellite Services Division (SSD).

Although a little more convection is possible tonight as the circulation interacts with diffluent flow associated with a nearby frontal trough, Gabrielle is still expected to lose its status as a tropical storm sometime on Friday. After that time, the global models suggest that the circulation will become embedded within the frontal zone, and Gabrielle is thus shown losing its identity in 24 hours.

The cyclone is accelerating north-northeastward ahead of a cold front over the eastern United States. Little deviation from this motion is expected until absorption occurs within a day or so.

Intensity forecast and positions

INITIAL 09/13 0300Z 35.1°N 67.7°W 35 KT 40 MPH
12 hour 09/13 1200Z 40.5°N 64.1°W 30 KT 35 MPH
24 hour 09/14 0000Z...ABSORBED BY FRONTAL ZONE

Track forecast



Figure 2. My forecast track for Gabrielle.



Humberto

Humberto continues as a hurricane as of the 0300Z NHC advisory:

Wind: 80 mph, with higher gusts
Location: 23.4°N 29.7°W
Movement: NNW at 12 mph
Pressure: 984 mb
Category: 1 (Saffir-Simpson Hurricane Wind Scale)

The convective pattern has become rather asymmetric, with the low-level center on the western edge of the convection. Satellite estimates are starting to plummet, with final T numbers from SAB coming in at 4.0 as of 0600Z. UW-CIMSS analysis suggests about 25 kt of southwesterly shear afflicting Humberto, which is expected to further increase as the hurricane moves in tandem with a large upper-level trough over the central Atlantic. In about three or four days, there are hints within the GFS upper tropospheric fields that the shear could decrease over the cyclone, which could potentially allow for some restrengthening prior to recurvature.



Figure 3. Latest infrared satellite image of Hurricane Humberto. Image credit: NOAA's Satellite Services Division (SSD).

Due to uncertainties and inconsistencies within the GFS as to how fast the shear will decrease, no abrupt intensification is being shown, although several of the runs from the GFS and ECMWF over the last several days have brought Humberto back to hurricane strength, which is a viable possibility if the shear relaxes.

The hurricane is about to make a sharp turn to the left, which has been well advertised in the global models since the cyclone's conception; this is in response to a rebuilding of the mid-tropospheric ridge over the Azores. In a few days, Humberto is forecast to begin recurving around the western periphery of this feature in advance of the same upper-level trough recurving Gabrielle. The guidance is in good agreement with this scenario, and my forecast is just a little to the right of the 0300Z NHC prediction, particularly at longer ranges.

Intensity forecast and positions

INITIAL 09/13 0300Z 23.4°N 29.7°W 70 KT 80 MPH
12 hour 09/13 1200Z 24.6°N 30.7°W 65 KT 75 MPH
24 hour 09/14 0000Z 25.2°N 34.1°W 55 KT 65 MPH
36 hour 09/14 1200Z 25.9°N 35.4°W 50 KT 60 MPH
48 hour 09/15 0000Z 27.1°N 39.0°W 45 KT 50 MPH
72 hour 09/16 0000Z 29.3°N 42.0°W 45 KT 50 MPH
96 hour 09/17 0000Z 31.6°N 44.7°W 50 KT 60 MPH
120 hour 09/18 0000Z 35.3°N 44.3°W 60 KT 70 MPH

Track forecast



Figure 4. My forecast track for Humberto.



Tropical Depression Ten

Tropical Depression Ten continues to meander over the southern Bay of Campeche. As of the 0600Z NHC intermediate advisory, the following information was posted on the cyclone:

Wind: 35 mph, with higher gusts
Location: 19.8°N 94.2°W
Movement: W at 2 mph
Pressure: 1003 mb

Satellite estimates suggest the system is still a tropical depression, but that was in lieu of an ongoing convective burst near and to the east of the center. Recent satellite data shows a considerable increase in convective banding to the east of the center, which appears to be trying to wrap into the cyclone circulation. I fully expect the depression will become a tropical storm within the next 6 to 12 hours.



Figure 5. Latest infrared satellite image of Tropical Depression Ten. Image credit: NOAA's Satellite Services Division (SSD).

I find intensity forecasting for Bay of Campeche cyclones rather frustrating. Moderate southwesterly shear has kept the convection east of the low-level center since genesis, and it still appears to be doing that. However, the upper low producing this shear is seen along the coast of south Texas moving southwestward, and the GFS suggests this feature will slowly weaken over the next 48 hours, which should provide an environment of lighter shear, with an anticyclone expected to form over the depression after the cold low departs. While this would normally portend significant strengthening, the cyclone will have only about a day or so left over water at that point if the more speedy guidance trend proves to be correct, which could limit rapid intensification. In addition, the quasi-stationary motion of the depression implies a possibility of upwelling, a situation that also weakened Hurricane Nate in a similar location two years ago. Since the underlying heat content in the location of the depression is not particularly steep, it is certainly possible that the system will struggle for the next few days until it begins to gain forward momentum.

Due to the improving upper-level conditions, I am going to show the system becoming a hurricane prior to crossing the Mexican coast near Tampico. If it turns out that cold water upwelling isn't a problem, my forecast could be conservative.

There have been no reconnaissance passes since Thursday afternoon, but recent satellite and microwave data suggest that the depression has been meandering, and even the 2 mph westward motion assigned by the NHC operationally might be a little generous. The dynamical models show little movement over the next 36-48 hours. Between the GFS and ECMWF, the latter is a little faster with letting the depression get a move on; at this point, either scenario could verify, but I tend to side a little more with the GFS in the short-term due to a developing tropical disturbance in the east Pacific off the coast of southern Mexico, which could combine with the mid-level ridge over the western United States to provide little net motion to the tropical cyclone.

In general, the guidance has trended faster at the 0z cycle, with the depression moving inland about a half a day quicker than in earlier runs. My forecast track is a little slower than the GFS and ECMWF, but on the same general heading, showing a gradual northwestward motion ensuing as the cyclone gains momentum, followed by an abrupt west-northwest turn just as the system runs into the coast.

A very serious flood threat is possible over a large stretch of eastern Mexico over the next several days as the depression combines with another tropical disturbance in the east Pacific to generate torrential rains. Interests in this area should carefully monitor the progress of the depression.

Intensity forecast and positions

INITIAL 09/13 0600Z 19.8°N 94.2°W 30 KT 35 MPH
12 hour 09/13 1800Z 19.7°N 94.2°W 35 KT 40 MPH
24 hour 09/14 0600Z 19.6°N 94.2°W 40 KT 45 MPH
36 hour 09/14 1800Z 19.6°N 94.5°W 45 KT 50 MPH
48 hour 09/15 0600Z 19.7°N 94.7°W 55 KT 65 MPH
72 hour 09/16 0600Z 21.4°N 95.5°W 70 KT 80 MPH
96 hour 09/17 0600Z 23.5°N 98.1°W 50 KT 60 MPH...INLAND
120 hour 09/18 0600Z 24.0°N 99.0°W 25 KT 30 MPH...INLAND

Track forecast



Figure 6. My forecast track for Tropical Depression Ten.

NHC storm information

000
WTNT35 KNHC 130543
TCPAT5

BULLETIN
TROPICAL DEPRESSION TEN INTERMEDIATE ADVISORY NUMBER 2A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102013
100 AM CDT FRI SEP 13 2013

...TROPICAL DEPRESSION DRIFTING WESTWARD...
...LIFE-THREATENING FLOODING EXPECTED OVER PARTS OF EASTERN
MEXICO...


SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...19.8N 94.2W
ABOUT 135 MI...215 KM ENE OF VERACRUZ MEXICO
ABOUT 225 MI...360 KM ESE OF TUXPAN MEXICO
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 2 MPH...4 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* COATZACOALCOS TO BARRA DE NAUTLA

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 100 AM CDT...0600 UTC...THE CENTER OF TROPICAL DEPRESSION TEN
WAS LOCATED NEAR LATITUDE 19.8 NORTH...LONGITUDE 94.2 WEST. THE
DEPRESSION IS DRIFTING TOWARD THE WEST NEAR 2 MPH...4 KM/H...AND A
SLOW AND ERRATIC MOTION OVER THE FAR SOUTHERN GULF OF MEXICO IS
EXPECTED DURING THE NEXT COUPLE OF DAYS.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...AND
THE DEPRESSION IS EXPECTED TO BECOME A TROPICAL STORM LATER TODAY.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB...29.62 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...THE DEPRESSION IS EXPECTED TO PRODUCE 10 TO 15 INCHES OF
RAIN OVER A LARGE PART OF EASTERN MEXICO...WITH ISOLATED AMOUNTS
AROUND 25 INCHES POSSIBLE...ESPECIALLY IN AREAS OF MOUNTAINOUS
TERRAIN. THESE RAINS ARE LIKELY TO RESULT IN LIFE-THREATENING FLASH
FLOODS AND MUD SLIDES.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO FIRST REACH THE
COAST WITHIN THE WARNING AREA LATER TODAY.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...400 AM CDT.

$$
FORECASTER BEVEN

2013 Atlantic hurricane season Tropical Storm Gabrielle Hurricane Humberto Tropical Depression Ten

Permalink

Tropical weather analysis - September 11, 2013

By: KoritheMan, 7:32 AM GMT on September 11, 2013

Gabrielle

Tropical Storm Gabrielle continues to move just west of Bermuda. As of the 0600Z NHC intermediate advisory, the following information was available on Gabrielle:

Wind: 60 mph, with higher gusts
Location: 32.2°N 65.3°W
Movement: NNW at 8 mph
Pressure: 1009 mb



Figure 1. Latest infrared satellite image of Tropical Storm Gabrielle. Image credit: NOAA's Satellite Services Division (SSD).

The satellite signature is not impressive, with all of the remaining shower activity displaced at least 75 miles to the east of the low-level center due to about 25 kt of southwesterly shear as diagnosed by the University of Wisconsin CIMSS laboratory. If convection does not return soon, Gabrielle could degenerate into a remnant low later today, as noted in the latest NHC forecast discussion. Considering the diurnal convective maximum period is fast approaching and the cyclone has nothing to show for it, this may occur sooner rather than later.

My forecast generously allows Gabrielle to live for another 36 hours as a tropical cyclone, but I would not be surprised in the slightest if this were to occur much, much sooner.

Bermuda has been reporting sustained tropical storm force winds for the last several hours. These winds could continue for the next 12 hours or so even without the assistance of convection, as the low-level circulation is quite vigorous. Interests there should continue to monitor Gabrielle until it has safely passed.

In about 96 hours, the global models show Gabrielle's low-level vortex elongating and becoming absorbed by a frontal trough forecast to move offshore the eastern United States in a couple of days.

Gabrielle is temporarily being steered by a low- to mid-level ridge near Bermuda, as the large scale flow to the north of the island has become zonal as an upper low over the Bahamas retrogrades to the west. In a couple of days, the global models show another trough, now over the northern United States, moving offshore the east coast, which is expected to accelerate Gabrielle northeastward to north-northeastward. The guidance is in good agreement, although there has been another westward shift during the first 24-36 hours while the tropical storm gets steered by the ridge. Gabrielle is forecast to lose tropical characteristics in about 72 hours, if it doesn't completely lose its identity before then.

Intensity forecast and positions

INITIAL 09/11 0600Z 32.2°N 65.3°W 50 KT 60 MPH
12 hour 09/11 1800Z 33.1°N 66.1°W 45 KT 50 MPH
24 hour 09/12 0600Z 34.3°N 66.8°W 40 KT 45 MPH
36 hour 09/12 1800Z 37.0°N 66.0°W 35 KT 40 MPH
48 hour 09/13 0600Z 41.9°N 63.8°W 30 KT 35 MPH...POST-TROPICAL/REMNANT LOW
72 hour 09/14 0600Z 48.4°N 56.5°W 30 KT 35 MPH...POST-TROPICAL/EXTRATROPICAL
96 hour 09/15 0600Z...ABSORBED BY FRONTAL ZONE

Track forecast



Figure 2. My forecast track for Gabrielle.

NHC storm information

NHC storm information


000
WTNT32 KNHC 110551
TCPAT2

BULLETIN
TROPICAL STORM GABRIELLE INTERMEDIATE ADVISORY NUMBER 11A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013
200 AM AST WED SEP 11 2013

...CENTER OF GABRIELLE PASSING WEST-SOUTHWEST OF BERMUDA...
...TROPICAL STORM CONDITIONS TO CONTINUE THROUGH WEDNESDAY
MORNING...


SUMMARY OF 200 AM AST...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...32.2N 65.3W
ABOUT 40 MI...65 KM WSW OF BERMUDA
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NNW OR 345 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* BERMUDA

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 200 AM AST...0600 UTC...THE CENTER OF TROPICAL STORM GABRIELLE
WAS LOCATED NEAR LATITUDE 32.2 NORTH...LONGITUDE 65.3 WEST.
GABRIELLE IS MOVING TOWARD THE NORTH-NORTHWEST NEAR 8 MPH...13 KM/H.
THIS GENERAL MOTION IS EXPECTED TO CONTINUE WITH A DECREASE IN
FORWARD SPEED TODAY. ON THE FORECAST TRACK...THE CENTER OF
GABRIELLE IS EXPECTED TO MOVE AWAY FROM BERMUDA LATER TODAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH...95 KM/H...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 48
HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 115 MILES...185 KM
FROM THE CENTER. AN ELEVATED STATION AT COMMISSIONERS POINT ON
BERMUDA RECENTLY REPORTED A WIND GUST OF 56 MPH...90 KM/H.

THE MINIMUM CENTRAL PRESSURE JUST REPORTED BY AN AIR FORCE RESERVE
HURRICANE HUNTER AIRCRAFT IS 1009 MB...29.80 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS WILL CONTINUE ON BERMUDA THROUGH
THIS MORNING.

RAINFALL...GABRIELLE IS EXPECTED TO PRODUCE RAINFALL AMOUNTS OF
2 TO 4 INCHES OVER BERMUDA...WITH ISOLATED MAXIMUM TOTALS OF 6
INCHES POSSIBLE.

STORM SURGE...A STORM SURGE OF 2 TO 3 FEET ABOVE NORMAL TIDE LEVELS
IS EXPECTED ON BERMUDA. IN ADDITION...ROUGH SURF CONDITIONS WILL
CONTINUE TO AFFECT BERMUDA TODAY.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 AM AST.

$$
FORECASTER BEVEN


Humberto

Humberto remains just under hurricane status as of the 0300Z NHC advisory:

Wind: 70 mph, with higher gusts
Location: 15.4°N 28.4°W
Movement: NW at 7 mph
Pressure: 995 mb

After looking a little ragged earlier on Tuesday, Humberto is making a bit of a comeback this morning, likely in response to instability enhancement caused by the diurnal convective maximum. Convection has increased over the center, and microwave data suggests a better defined inner core region; on the other hand, conventional satellite images still do not suggest the presence of an eye. Satellite estimates are hovering between 3.5 and 4.0 depending on the agency you pick, and Humberto may tie or surpass the record for the latest-forming first hurricane since Hurricane Gustav of 2002, which became a hurricane near 1200 UTC 11 September. Keep in mind that this formation is the latest after the advent of aerial reconnaissance in 1944, and a major hurricane in October of 1905 finally became the first hurricane of the year on October 8; also, 1907 and 1914 did not have hurricanes at all.



Figure 3. Latest infrared satellite image of Tropical Storm Humberto. Image credit: NOAA's Satellite Services Division (SSD).

Humberto still remains over reasonably warm water and in an environment of seemingly low shear. As long as dry air does not interfere again, the cyclone should become a hurricane very soon. It no longer appears that a period of rapid intensification into a major hurricane is unlikely, and Humberto is forecast to cross the 26C isotherm in about 24 hours, after which time intensification is expected to be halted. Simultaneously, the GFS shows an abrupt increase in southwesterly shear in response to a large upper-level trough over the central Atlantic, an evolution which is forecast to cause Humberto to steadily weaken, and possibly even rapidly weaken.

Humberto turned northwestward on Tuesday, and appears to still be moving along that general heading as it rounds the western periphery of a deep-layer ridge centered near the Azores. The guidance remains in good agreement on the synoptic evolution, with Humberto forecast to turn sharply back to the west-northwest or west near the end of the period as it escapes the influence of any large-scale cyclonic flow capable of creating an amplified weakness in the subtropical ridge. It is unlikely Humberto makes it to the United States coast even with the projected westward turn, as it will be moving across a region of ocean where few storms historically make the crossing successfully.

My forecast track is similar to the one from the National Hurricane Center.

Intensity forecast and positions

INITIAL 09/11 0300Z 15.4°N 28.4°W 60 KT 70 MPH
12 hour 09/11 1200Z 16.3°N 29.1°W 65 KT 75 MPH
24 hour 09/12 0000Z 17.9°N 29.5°W 75 KT 85 MPH
36 hour 09/12 1200Z 20.0°N 29.7°W 75 KT 85 MPH
48 hour 09/13 0000Z 21.6°N 30.1°W 70 KT 80 MPH
72 hour 09/14 0000Z 23.3°N 32.5°W 55 KT 65 MPH
96 hour 09/15 0000Z 24.7°N 35.3°W 45 KT 50 MPH
120 hour 09/16 0000Z 25.3°N 39.6°W 35 KT 40 MPH

Track forecast



Figure 4. My forecast track for Humberto.


Invest 93L

An area of low pressure is moving across northern Belize. Although shower activity is currently not well organized, the GFS shows a very favorable upper-level environment over the Bay of Campeche, which would favor development of a tropical cyclone in that region as the low moves over water in the next 24 hours.



Figure 5. Latest infrared satellite image of Invest 93L. Image credit: NOAA's Satellite Services Division (SSD).

The models made a northward shift in Tuesday's cycles, with the 18z run of the GFS showing a landfall in south Texas, while the 12z NAVGEM showed a hurricane heading toward the central Gulf Coast. The NAVGEM is historically unreliable, but a model never postulates possibilities without reason. The most likely scenario is for a landfall in eastern or northeastern Mexico, but there is enough fragility in the pattern over the United States that this system could still pull northward to Texas or extreme western Louisiana (more likely Texas if the more northerly projections ensued). If the ECMWF starts trending more northward as well, the more northern solution will have to be considered more than a remote possibility. The northward turn is possible if a trough amplifying over the western United States moves eastward quicker than the models are showing. The modeled trough is not forecast to arrive in the central United States until around four or five days, and a lot change in that time. It also depends on where a definite center forms in the Bay of Campeche, and also how slow the system moves while in the Bay of Campeche.

Regardless of development, heavy rains and flooding are possible over portions of the Yucatan Peninsula, Belize, Guatemala, and eastern Mexico over the next several days, especially in mountainous areas.

Probability of development in 48 hours: 30%

2013 Atlantic hurricane season Tropical Storm Gabrielle Tropical Storm Humberto Invest 93L

Updated: 7:54 AM GMT on September 11, 2013

Permalink

Tropical weather analysis - September 9, 2013

By: KoritheMan, 12:35 AM GMT on September 10, 2013

Humberto

Tropical Storm Humberto continues to gradually intensify in the eastern Atlantic. As of the 2100Z NHC advisory bulletin, the following information was available on the storm:

Wind: 50 mph, with higher gusts
Location: 13.7°N 25.3°W
Movement: W at 12 mph
Pressure: 1002 mb

While the satellite presentation looks impressive, with an abundance of deep convection, recent microwave and scatterometer data suggest that the low-level center remains along the northeastern edge of the convection, a direct symptom of northeasterly shear. Satellite estimates have not changed appreciably, with a recent UW-CIMSS raw ADT number coming in at 3.0. The shear is customary of systems in this portion of the Atlantic, and as Humberto becomes more distant to the axis of the deep-layer ridge centered over the Azores, the shear should lessen, with the GFS amplifying a large 200 mb anticyclone over the surface center. Such a wind pattern normally portends significant intensification, and as long as Humberto remains over sufficiently warm water, it should respond to that pattern by strengthening.



Figure 1. Latest infrared satellite image of Tropical Storm Humberto. Image credit: NOAA's Satellite Services Division (SSD).

My forecast still calls for a peak of 80 kt between 36 and 48 hours; thereafter, the cyclone is forecast to cross the 26C isotherm, encounter more stable air, and increasing southwesterly shear associated with a large upper trough. Weakening is thus shown beyond 48 hours, although the large size of the circulation will probably not allow for a rapid decay. Although sea surface temperatures warm slightly along the projected track at the end of the period, I don't see how Humberto can reintensify at those ranges in an environment characterized by southwesterly to westerly shear. It is possible that Humberto could experience a brief episode of rapid intensification tomorrow if an inner core becomes established, and there is still a chance of the cyclone reaching major hurricane status.

Synoptic data suggest that Humberto is south of a well-established subtropical ridge near or over the Azores. Water vapor imagery shows an upper low over the central Atlantic between Bermuda and the Azores moving southeastward, and another such low and attendant trough a few hundred miles west of the coast of Portugal moving southward. These two features are forecast to interact and create a large weakness in the western extent of the subtropical ridge, allowing Humberto to turn sharply northwestward to north-northwestward in the next 24-36 hours. At days four and five of the forecast, I anticipate the cyclone sharply turning back toward the west-northwest as mid-level ridging rebuilds to the north. The models continue to be in agreement with this, increasing confidence in the forecast.

Intensity forecast and positions

INITIAL 09/09 2100Z 13.7°N 25.3°W 45 KT 50 MPH
12 hour 09/09 0600Z 13.8°N 27.1°W 50 KT 60 MPH
24 hour 09/10 1800Z 14.4°N 28.6°W 65 KT 75 MPH
36 hour 09/11 0600Z 17.1°N 29.3°W 75 KT 85 MPH
48 hour 09/11 1800Z 18.5°N 29.6°W 80 KT 90 MPH
72 hour 09/12 1800Z 22.1°N 30.2°W 70 KT 80 MPH
96 hour 09/13 1800Z 24.9°N 31.4°W 60 KT 70 MPH
120 hour 09/14 1800Z 25.9°N 35.3°W 50 KT 60 MPH

Track forecast



Figure 2. My forecast track for Humberto.



Invest 92L

An area of low pressure, associated with the remnants of Gabrielle, is located about 350 miles south of Bermuda. Convection has increased significantly during the diurnal minimum, which could be a sign that the system is attempting to regenerate. Based on microwave and earlier visible satellite data, the low-level circulation, albeit small, appears well-defined, and only a slight increase in the organization of the convection would result in the reformation of a tropical cyclone. For now though, the data suggests that the center is clearly to the west of the convection due to continued southwesterly to westerly shear. The GFS shows the upper flow remaining only marginally favorable, but the diffluence associated with such a flow might allow for enough convective sustenance to see Gabrielle regenerate despite the shear.

This system is expected to begin moving northeast ahead of a frontal zone over the western Atlantic.

Probability of development in 48 hours: 50%



Bay of Campeche development possible late in the week

The GFS and ECMWF show a tropical cyclone developing in the southwestern Bay of Campeche in about four or five days; the GFS is about a day faster with development. In either case, the upper flow pattern on the GFS is very favorable for the development and intensification of a tropical cyclone, with the possibility existing that the system could become a hurricane.

There is a window of opportunity for the system to move northward into Texas or Louisiana as a trough amplifies over the southern United States this weekend, but it will depend on the depth of the trough, the latitude of formation, and the vertical depth of the modeled tropical cyclone.

I assume this system comes from the tropical wave currently over the Yucatan Peninsula. This system is already generating deep convection in the western Caribbean, indicating some potency to the wave.


Regardless of development, heavy rains and possible flooding is expected over portions of eastern Mexico later this week.

2013 Atlantic hurricane season Tropical Storm Humberto Invest 92L

Permalink

Tropical weather analysis - September 9, 2013

By: KoritheMan, 5:40 AM GMT on September 09, 2013

Tropical Depression Nine

Tropical Depression Nine formed from the strong tropical wave we've tracked over west Africa for the past couple days. As of the latest NHC advisory, the following information was available on the storm:

Wind: 35 mph, with higher gusts
Location: 13.3°N 22.3°W
Movement: W at 12 mph
Pressure: 1005 mb

Satellite estimates suggest that the cyclone remains a tropical depression, and a partial ASCAT pass a couple hours ago did not give any indication that the winds have increased to tropical storm force. However, convection has increased in coverage and extent, and is quite deep, so the winds should catch up shortly. Based on the ASCAT data, the circulation center is presumed to be somewhere along the eastern portion of the convective canopy, due to about 15 kt of northeasterly shear as analyzed by the SHIPS and UW-CIMSS.



Figure 1. Latest infrared satellite image of Tropical Depression Nine. Image credit: NOAA's Satellite Services Division (SSD).

The shear is forecast to lessen by the GFS over the next 12-24 hours, which should permit a quicker pace of intensification after that time. While the statistical intensity guidance is normally very inconsistent and incredibly wrong, the SHIPS and LGEM projections of the cyclone flirting with major hurricane status in a few days is definitely not out of the question, with the large-scale environment and location remarkably similar to the one Hurricane Fred in 2009 experienced its rapid intensification episode in. Beyond 72 hours, the depression is forecast to cross the 26C isotherm and encounter increasing southwesterly shear associated with an upper-level trough over the central Atlantic, which is anticipated to result in a gradually weakening cyclone at that point. It should be noted that the horizontal circulation envelope associated with the depression appears rather large, so it may not decay as fast as we would ordinarily expect with a system in similar conditions to the ones being projected in the models.

In the interim, conditions appear conducive for a relatively swift rate of intensification, with rapid intensification even a possibility if the depression can establish an inner core. My forecast is higher than the one from the National Hurricane Center, but below the more bullish SHIPS/LGEM guidance, which generally have not done particularly well with Atlantic tropical cyclones this year. Tentatively, I show the cyclone reaching the upper end of Category 1 intensity in about 72 hours, but there is a chance the cyclone could rapidly intensify to a major hurricane at anytime within the next 48-72 hours.

The depression is anchored to the south of a strong and persistent deep-layer ridge that is centered over the Azores. This ridge has not budged in the last six hours, and I don't expect it to over the next 24-36 hours, so I indicate a primarily westward motion during that portion of the forecast. Beyond that time, an upper low seen on water vapor imagery near 31.5°N 44.3°W is expected to retrograde southeastward and begin eroding the western portion of the ridge; this evolution is expected to turn the cyclone toward the north-northwest along or just east of 30W. At day five, the GFS and ECMWF show mid-level ridging reestablishing its dominance to the north of the depression, so a turn back to the northwest is forecast at that time, although I am not going to show quite as sharp a westward turn as those two models, which actually portray a more definitive west-northwest motion. My forecast follows very closely the 0z TVCE model consensus.

A tropical storm warning is in effect for the Cape Verde Islands due to the uncertainties in the evolution of the cyclone's wind field as it intensifies. Interests there should carefully monitor the progress of this tropical cyclone. Heavy rains, flash flooding, and mudslides will be a concern regardless of whether tropical storm force winds reach the archipelago; the rains could be especially prodigious over areas of mountainous terrain.

Intensity forecast and positions

INITIAL 09/09 13.2°N 21.9°W 0300Z 30 KT 35 MPH
12 hour 09/09 13.3°N 23.7°W 1200Z 35 KT 40 MPH
24 hour 09/10 13.4°N 25.4°W 0000Z 45 KT 50 MPH
36 hour 09/10 13.7°N 27.5°W 1200Z 55 KT 65 MPH
48 hour 09/11 15.2°N 28.3°W 0000Z 75 KT 85 MPH
72 hour 09/12 18.9°N 29.4°W 0000Z 80 KT 90 MPH
96 hour 09/13 21.2°N 30.1°W 0000Z 70 KT 80 MPH
120 hour 09/14 23.3°N 31.7°W 0000Z 60 KT 70 MPH

Track forecast



Figure 2. My forecast track for Tropical Depression Nine.

NHC storm information

000
WTNT34 KNHC 090536
TCPAT4

BULLETIN
TROPICAL DEPRESSION NINE INTERMEDIATE ADVISORY NUMBER 2A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092013
200 AM AST MON SEP 09 2013

...DEPRESSION VERY CLOSE TO BECOMING A TROPICAL STORM...


SUMMARY OF 200 AM AST...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...13.3N 22.3W
ABOUT 140 MI...220 KM SE OF PRAIA CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE SOUTHERN CAPE VERDE ISLANDS OF MAIO...SANTIAGO...FOGO...AND
BRAVA

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN THE
NEXT 12 TO 24 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 200 AM AST...0600 UTC...THE CENTER OF TROPICAL DEPRESSION NINE
WAS LOCATED NEAR LATITUDE 13.3 NORTH...LONGITUDE 22.3 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST NEAR 12 MPH...19 KM/H...AND
THIS GENERAL MOTION SHOULD CONTINUE TODAY. A TURN TOWARD THE
WEST-NORTHWEST WITH A DECREASE IN FORWARD SPEED IS EXPECTED BY
TUESDAY. ON THE FORECAST TRACK...THE CENTER OF THE DEPRESSION
SHOULD PASS SOUTH OF THE CAPE VERDE ISLANDS THIS AFTERNOON AND
TONIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. STRENGTHENING IS EXPECTED DURING THE NEXT 48 HOURS...AND
THE DEPRESSION IS FORECAST TO BECOME A TROPICAL STORM LATER THIS
MORNING.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH THE ISLANDS
OF MAIO AND PRAIA THIS MORNING...AND SPREAD ACROSS THE REMAINDER OF
THE SOUTHERN CAPE VERDE ISLANDS BY THIS AFTERNOON.

RAINFALL...THE DEPRESSION IS EXPECTED TO PRODUCE TOTAL RAINFALL
ACCUMULATIONS OF 3 TO 6 INCHES ACROSS THE SOUTHERN CAPE VERDE
ISLANDS...WITH ISOLATED MAXIMUM AMOUNTS OF 8 INCHES POSSIBLE...
ESPECIALLY IN AREAS OF MOUNTAINOUS TERRAIN. THESE RAINS COULD
PRODUCE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 AM AST.

$$
FORECASTER STEWART

2013 Atlantic hurricane season Tropical Depression Nine

Permalink

Tropical weather analysis - September 7, 2013

By: KoritheMan, 5:40 AM GMT on September 07, 2013

Tropical Depression Eight

The area of low pressure in the southern Bay of Campeche became a tropical depression just as it was crossing the coast around 1800 UTC Friday. As of the 0300Z NHC advisory, the following information was available on the storm:

Wind: 30 mph, with higher gusts
Location: 21.7°N 98.8°W
Movement: SW at 8 mph
Pressure: 1009 mb

The cloud pattern has become increasingly disorganized since landfall, with satellite data suggesting that the circulation has become ill-defined. However, a burst of convection has recently erupted near and along the coastal waters near Tampico, which will continue to cause a heavy rain threat there, along with perhaps some locally gusty winds.



Figure 1. Latest infrared satellite image of Tropical Depression Eight. Image credit: NOAA's Satellite Services Division (SSD).

I don't have much to say about the depression. It appears to be moving pretty much due southwest under a deep-layer ridge located over the central United States. The residual circulation should disintegrate shortly, and the cyclone is expected to become a remnant low very soon, and then completely dissipate in about 24 hours or less. Nevertheless, there is still a vigorous mid-level circulation which will pose a threat for very heavy rainfall and flash flooding over portions of Veracruz, San Luis Potosi, and Tamaulipas even for a couple of days succeeding dissipation.

Any remaining strong winds along the coast and offshore should quickly subside over the next few hours as the circulation moves farther inland and the convection loses its support.

Intensity forecast and positions

INITIAL 09/07 21.7°N 98.8°W 0300Z 25 KT 30 MPH...INLAND
12 hour 09/07 21.1°N 99.5°W 1200Z 20 KT 25 MPH...POST-TROPICAL/REMNANT LOW
24 hour 09/08 0000Z...DISSIPATED

Track forecast



Figure 2. My forecast track for Tropical Depression Eight.



Lorena

Lorena weakens to a tropical depression while it moves just off the coast of southwestern Baja. As of the latest NHC advisory, the following information was available on the storm:

Wind: 35 mph, with higher gusts
Location: 23.1°N 111.5°W
Movement: WNW at 9 mph
Pressure: 1007 mb

Lorena is rapidly becoming disorganized, with satellite and radar data showing a significant deterioration of the convective cloud pattern. Satellite estimates from TAFB and SAB barely support a tropical storm, and the latest CIMSS ADT estimates have been even lower. The remaining convection, quite shallow, is confined to a broken cloud band about 35 to 40 miles southeast of the exposed low-level center. Surface observations and radar data suggest that the center of Lorena is located not far southwest of La Paz, and that the circulation is becoming elongated.



Figure 3. Latest infrared satellite image of Tropical Storm Lorena. Image credit: NOAA's Satellite Services Division (SSD).

Water vapor imagery shows a very dry airmass just ahead of Lorena, which could be partly responsible for the cyclone's rather abrupt decay this evening. In addition, sea surface temperatures are cooling along the forecast track, and the circulation is interacting with land, even with it being just offshore. These factors should continue to weaken Lorena, and the GFS and SHIPS even suggest that southwesterly shear could increase in a couple of days, which will likely be a moot point since Lorena is forecast to be long deceased by that point.

My forecast track is similar to the one from the National Hurricane Center, with the primary steering mechanism for Lorena being the southwestern extent of the strong ridge located over the central United States, the same one steering what's left of Tropical Depression Eight.

Surface observations have not suggested much in the way of strong winds this evening, and Lorena did not make landfall as I had originally predicted. Thus, any remaining tropical storm force winds should stay offshore, probably even in the mountains; the continued lack of convection will also assist in weakening the surface winds.

Locally heavy rainfall and possible isolated flooding will continue over portions of southern and central Baja for the next couple of days, as Lorena is not expected to move much as it enters a region of weak steering currents. This is consistent with the GFS and ECMWF, which both indicate little motion of the dying tropical storm.

Intensity forecast and positions

INITIAL 09/07 0300Z 23.2°N 111.0°W 35 KT 40 MPH
12 hour 09/07 1200Z 23.5°N 111.6°W 30 KT 35 MPH
24 hour 09/08 0000Z 23.7°N 111.8°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
36 hour 09/08 1200Z 23.8°N 112.1°W 20 KT 25 MPH...POST-TROPICAL/REMNANT LOW
48 hour 09/09 0000Z...DISSIPATED

Track forecast



Figure 4. My forecast track for Lorena.

NHC storm information

NHC storm information

000
WTPZ32 KNHC 070532
TCPEP2

BULLETIN
TROPICAL DEPRESSION LORENA INTERMEDIATE ADVISORY NUMBER 8A
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122013
1100 PM PDT FRI SEP 06 2013

...LORENA WEAKENS TO A TROPICAL DEPRESSION NEAR THE SOUTHERN BAJA
CALIFORNIA PENINSULA...


SUMMARY OF 1100 PM PDT...0600 UTC...INFORMATION
-----------------------------------------------
LOCATION...23.1N 111.5W
ABOUT 100 MI...160 KM W OF CABO SAN LUCAS MEXICO
ABOUT 120 MI...195 KM SSE OF CABO SAN LAZARO MEXICO
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

THE GOVERNMENT OF MEXICO HAS DISCONTINUED ALL TROPICAL STORM WATCHES
AND WARNINGS.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 PM PDT...0600 UTC...THE CENTER OF TROPICAL DEPRESSION LORENA
WAS LOCATED NEAR LATITUDE 23.1 NORTH...LONGITUDE 111.5 WEST. LORENA
IS MOVING TOWARD THE WEST-NORTHWEST NEAR 9 MPH...15 KM/H. A
DECREASE IN FORWARD SPEED AND A TURN TO THE NORTH-NORTHWEST ARE
EXPECTED OVER THE WEEKEND. ON THE FORECAST TRACK...THE CENTER OF
LORENA SHOULD REMAIN NEAR THE SOUTHERN BAJA CALIFORNIA PENINSULA
DURING THE NEXT COUPLE OF DAYS.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 35 MPH...55 KM/H...
WITH HIGHER GUSTS. ADDITIONAL WEAKENING IS EXPECTED...AND LORENA
IS FORECAST TO BECOME A REMNANT LOW ON SATURDAY.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB...29.74 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...LORENA IS EXPECTED TO PRODUCE ADDITIONAL RAINFALL
ACCUMULATIONS OF 1 TO 2 INCHES OVER THE SOUTHERN PORTION OF THE
BAJA CALIFORNIA PENINSULA...WITH ISOLATED MAXIMUM AMOUNTS OF 4
INCHES POSSIBLE THROUGH SATURDAY. THESE RAINS COULD PRODUCE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...200 AM PDT.

$$
FORECASTER LANDSEA/AVILA



African tropical wave a threat to develop

A tropical wave over west Africa has the potential to become a tropical depression over the next few days. In fact, the GFS and ECMWF both actually support development in about two or three days. While rare, tropical cyclogenesis with systems just emerging from Africa does happen, with Hurricane Julia in 2010, Tropical Depression Ten in 2011, and Tropical Storm Florence in 2012 being three recent examples. Environmental conditions favor intensification, but the system will be moving northwestward through a latitude where it is statistically unlikely for an impact to the United States.

Heavy rains and gusty winds will likely overspread much of the Cape Verde Islands over the next couple of days as the well-defined wave axis moves off the coast.

Probability of development in 48 hours: 20%

2013 Atlantic hurricane season 2013 Pacific hurricane season Tropical Depression Eight Tropical Depression Lorena

Updated: 5:46 AM GMT on September 07, 2013

Permalink

Tropical weather analysis - September 6, 2013

By: KoritheMan, 6:07 AM GMT on September 06, 2013

Lorena

Tropical Storm Lorena continues to approach southern Baja California. As of the just released NHC intermediate advisory, the following information was posted on the cyclone:

Wind: 40 mph, with higher gusts
Location: 21.0°N 107.8°W
Movement: NW at 13 mph
Pressure: 1005 mb

The 6z satellite estimate should be up soon, but are unavailable as of this writing; the 0z estimates supported a 35 kt tropical storm. Satellite images show a cloud pattern that is a little better organized, with evidence of banding features wrapping into the southern quadrant of the circulation. The low-level center is a little difficult to locate, but based on radar data, microwave, and satellite fixes, I assume that it is on the southwestern side of the convective cloud tops.



Figure 1. Latest infrared satellite image of Tropical Storm Lorena. Image credit: NOAA's Satellite Services Division (SSD).

Lorena is over SSTs of 29-30C, and the near-storm vertical shear appears weak. The cyclone could thus intensify a little prior to making landfall across southern Baja in about 24 hours. The overall guidance envelope has shifted eastward between 18z and 0z, with a track now more clustered over the southern peninsula. My forecast follows this reasoning, showing a landfall in southern Baja in about 24 hours, followed by a gradual northward turn as Lorena rounds the western periphery of a deep-layer ridge anchored over the southwestern United States. The global model fields suggest that the low-level remnants of Lorena will shear off from the mid-level center, with the former heading west back into the open Pacific, while the latter streams northward ahead of a deep-layer trough off the west coast of the United States. My forecast track shows a considerable slowing of the forward speed in response to this likelihood. It is also possible that Lorena could dissipate sooner than forecast.

The primary threat in connection with Lorena is heavy rainfall; waters off this section of Baja are rather warm, and the deep convection seen on satellite imagery reflects that. These rains are likely to cause flash flooding and mudslides, and people in the region should carefully follow the progress of Lorena. The heavy rain threat may stream northward into the southwestern United States in a few days once the cyclone shears off. Winds to tropical storm force, especially in the mountains, are also possible.

Intensity forecast and positions

INITIAL 09/06 0300Z 20.4°N 107.6°W 35 KT 40 MPH
12 hour 09/06 1200Z 21.8°N 108.8°W 40 KT 45 MPH
24 hour 09/07 0000Z 23.3°N 109.8°W 40 KT 45 MPH...INLAND
36 hour 09/07 1200Z 24.1°N 110.6°W 30 KT 35 MPH...INLAND
48 hour 09/08 0000Z 24.7°N 111.1°W 25 KT 30 MPH...INLAND
72 hour 09/09 0000Z 24.9°N 111.1°W 20 KT 25 MPH...POST-TROPICAL/REMNANT LOW
96 hour 09/10 0000Z...DISSIPATED

Track forecast



Figure 2. My forecast track for Lorena.

NHC storm information

000
WTPZ32 KNHC 060546
TCPEP2

BULLETIN
TROPICAL STORM LORENA INTERMEDIATE ADVISORY NUMBER 4A
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122013
1100 PM PDT THU SEP 05 2013

...LORENA CONTINUES AS A TROPICAL STORM PARALLELING THE MEXICAN
COAST...


SUMMARY OF 1100 PM PDT...0600 UTC...INFORMATION
-----------------------------------------------
LOCATION...21.0N 107.8W
ABOUT 145 MI...235 KM WNW OF CABO CORRIENTES MEXICO
ABOUT 190 MI...305 KM SE OF CABO SAN LUCAS MEXICO
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NW OR 325 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* BAJA CALIFORNIA SUR FROM AGUA BLANCA TO BUENAVISTA

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* BAJA CALIFORNIA SUR NORTH OF AGUA BLANCA TO SANTA FE

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN THE
NEXT 24 TO 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE WITHIN THE NEXT 36 TO
48 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 PM PDT...0600 UTC...THE CENTER OF TROPICAL STORM LORENA WAS
LOCATED NEAR LATITUDE 21.0 NORTH...LONGITUDE 107.8 WEST. LORENA IS
MOVING TOWARD THE NORTHWEST NEAR 13 MPH...20 KM/H...AND THIS MOTION
IS EXPECTED TO CONTINUE THROUGH FRIDAY MORNING. A SLOWER
NORTHWESTWARD MOTION IS EXPECTED TO BEGIN LATE FRIDAY...FOLLOWED BY
A TURN TOWARD THE NORTH-NORTHWEST BY LATE SATURDAY. ON THE FORECAST
TRACK...THE CENTER OF LORENA WILL APPROACH THE SOUTHERN BAJA
CALIFORNIA PENINSULA ON FRIDAY AND THEN BE NEAR OR OVER LAND BY
SATURDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS POSSIBLE DURING THE NEXT 24 HOURS OR
SO. WEAKENING IS FORECAST TO BEGIN BY FRIDAY NIGHT OR SATURDAY
WHEN LORENA BEGINS TO INTERACT WITH LAND.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 80 MILES...130 KM
NORTHEAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...LORENA IS EXPECTED TO PRODUCE TOTAL RAINFALL
ACCUMULATIONS OF 3 TO 5 INCHES OVER THE SOUTHWEST COAST OF MEXICO
AND THE SOUTHERN PORTION OF THE BAJA CALIFORNIA PENINSULA...WITH
ISOLATED MAXIMUM AMOUNTS OF 10 INCHES POSSIBLE. THESE RAINS COULD
PRODUCE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.

WIND...TROPICAL STORM FORCE WINDS ARE EXPECTED TO BEGIN IN THE
WARNING AREA FRIDAY AFTERNOON AND COULD CONTINUE THROUGH SATURDAY.
TROPICAL STORM FORCE WINDS ARE POSSIBLE IN THE WATCH AREA SATURDAY.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...200 AM PDT.

$$
FORECASTER LANDSEA/AVILA



Invest 99L

An area of low pressure is producing a large area of cloudiness and thunderstorms over the southern Bay of Campeche. Satellite, surface, and earlier reconnaissance data suggest that the system lacks a well-defined center of circulation. However, a tropical depression or tropical storm could still form before the system moves inland over eastern Mexico later today.

Regardless of development, very heavy rain and flash flooding will impact the state of Veracruz over the next couple of days.

Probability of development in 48 hours: 50%

Tropical Storm Lorena Invest 99L 2013 Atlantic hurricane season 2013 Pacific hurricane season

Permalink

Tropical weather analysis - September 4, 2013

By: KoritheMan, 6:51 AM GMT on September 04, 2013

Invest 97L

A tropical wave accompanied by a broad low pressure system is located in the eastern Caribbean about midway between Dominica and Puerto Rico. Satellite images show an increase in convection at this hour, but it is quite difficult to locate the actual low-level center, which appears to be rather poorly-defined. Upper-level outflow is restricted along the east side of the wave axis, implying some southeasterly shear; this means that although the large-scale cyclonic flow in this area is lessening (and thus the shear), the consequent upper-level anticyclone is not quite collocated with the tropical wave.



Figure 1. Latest infrared satellite image of Invest 97L. Image credit: NOAA's Satellite Services Division (SSD).

Although the shear is improving as water vapor imagery shows the TUTT weakening, the broad nature of the circulation could be an inhibiting factor, not to mention interaction with Hispaniola over the next day or two. One interesting meteorological factor that I didn't notice a few days ago, is the area of convection to the east of the Lesser Antilles, which appears to be connected with another tropical wave. The global models hinted the other day at a vorticity lobe heading westward and another one heading northward. I ignored it then, considering it an interesting triviality but with little bearing on reality; however, it seems they might have been onto something with those predictions after all. It will be most difficult to pinpoint the evolution of this wave over the next several days, and its possible influence on 97L in front of it. I believe the tropical wave is one of the reasons why the models have shown an abrupt recurve with this system after it passes Hispaniola; I surmise that the cyclonic flow associated with the tropical wave interacts with a trough over the western Atlantic to help pull 97L northward out to sea ahead of the trough. While I would expect some convective deepening of the secondary tropical wave over the next 12-24 hours, the global models show the upper low centered north of the system that has been responsible for providing the diffluence and lifting mechanism for thunderstorm development retreating northwestward and weakening, a conclusion that is already supported by water vapor analysis. With this in mind, there should be no real influence on 97L's track from the secondary tropical wave unless it unexpectedly becomes a tropical cyclone, which seems unlikely in the face of 20 to 30 kt of northwesterly shear north of the Greater Antilles as shown in the GFS fields.

This is one of the more complex situations I've had to forecast, and I could certainly be wrong. I don't generally defy a consensus, but I think the models are deepening 97L too fast, and are also overestimating the influence of the tropical wave to the east. My personal expectation is that 97L will move west-northwest into the Dominican Republic -- a bit to the west of where the currently clustered guidance is -- and then proceed slowly west-northwestward. At that point, either it recurves near or east of Bermuda, or it continues westward toward the Bahamas and south Florida under increased mid-level ridging behind the trough. Some of the GFS ensemble members have started to offer support for the more westward track once the system emerges into the Atlantic north of the Dominican Republic, and the 0z ECMWF shows the system moving westward into the central Bahamas before deepening and turning northward. The pattern in either direction (ridging or troughing) is rather fragile, and I cannot confidently say what will happen at this stage The trough seen carving out over the western Atlantic, I feel, does not possess enough amplitude to dig far enough south to recurve 97L nearly as sharp as the models are saying. Indeed, there has actually been a noticeable westward shift in the dynamical guidance envelope over the last 24 hours, particularly at longer ranges, which reflects my current thinking.

Regardless of development, heavy rains and possible flash flooding will impact portions of Puerto Rico and Hispaniola over the next couple of days, particularly along mountainous areas. Wind gusts to tropical storm force may also spread over the higher elevations of those regions.

Probability of development in 48 hours:
30%



Invest 99E

An area of low pressure centered off the southwest coast of Mexico a few hundred miles south of Manzanillo is generating some showers and thunderstorms. While satellite data suggests that the circulation is gradually becoming better-defined, the associated convection has not been deep or persistent. If there is a significant blowup of organized thunderstorms over the center tonight due to the diurnal convective maximum period, we could see a tropical cyclone form tomorrow. However, the system is forecast to reach cooler waters in about three days, arresting development after then.



Figure 2. Latest infrared satellite image of Invest 99E. Image credit: NOAA's Satellite Services Division (SSD).

This disturbance is expected to move west-northwestward while staying offshore mainland Mexico or Baja.

Probability of development in 48 hours: 50%

2013 Atlantic hurricane season 2013 Pacific hurricane season Invest 97L Invest 99E

Updated: 6:57 AM GMT on September 04, 2013

Permalink

Tropical weather analysis - September 2, 2013

By: KoritheMan, 9:29 AM GMT on September 02, 2013

Invest 97L

A tropical wave accompanied by a broad surface low pressure system is located just north of Barbados. After a significant increase in convection Sunday afternoon, the associated shower activity has dwindled significantly. A new burst of convection is affecting Barbados, but this is south of the analyzed low-level vortex, centered near 14.0N 59.9W; this is supported by doppler radar data from Barbados as well.



Figure 1. Latest infrared satellite imaged of Invest 97L. Image credit: NOAA's Satellite Services Division (SSD).

Surface observations suggest that the circulation associated with the tropical wave axis is not particularly well-defined, and the system still lacks significant vorticity above 700 mb, although I note there has been a substantial improvement in the 700 mb vorticity compared to 24 hours ago, likely due to the convective burst we saw Sunday helping to amplify the wave axis.

There doesn't appear to be a whole lot of shear in the near-storm environment, which would ordinarily portend strengthening. However, MIMIC-TPW from the University of Wisconsin CIMSS shows some mid-level dry air to the north of the system, associated with the backside of the mid-oceanic trough over the Greater Antilles region, which the wave could entrain over the next day or two. In addition, the system is headed to the eastern Caribbean, which has widely been dubbed as a hurricane graveyard, disrupting or destroying even well-developed tropical cyclones. So even though the large-scale environment around and ahead of the system is characterized by weak vertical shear, I expect the subsident flow aloft will continue to promote sinking air and discourage organized thunderstorms from forming along the wave axis.

The track forecast is of low confidence. There has been a progressive poleward shift in the guidance over the last several cycles, with the 6z dynamical guidance even farther east than the 0z envelope was, showing a northwestward motion across Puerto Rico, across the Dominican Republic, and into the central Bahamas. There will be some weak shortwave energy moving across the western Atlantic over the next few days, the first impulse being a trailing shortwave from an upper low moving through Toronto; in addition, two upper tropospheric cold lows are seen spinning to the north of the system on water vapor imagery; one southeast of Bermuda, and the other over eastern Haiti. In theory, this would promote at least a slight poleward component of motion to the tropical wave, but satellite images and official ATCF center fixes continue to indicate a due west motion, and the system has not gained latitude in about 24 hours. The more westward motion would make sense given the convectionless state of the system, which isn't doing particularly well even with the advent of the diurnal convective maximum. Given this, and the fact that I see no evidence of any large-scale weakness to the north of the system on UW-CIMSS tropospheric steering data or water vapor imagery, I am a little confused as to why the dynamical guidance turns the system almost immediately west-northwestward and then northwestward. A track across Puerto Rico seems extremely unlikely to me, and I would anticipate a significant westward shift in the guidance today. I normally don't diverge against a guidance consensus, but the center is still not particularly well-defined, and the forecast component of motion is clearly not realistic considering current happenings, so I am inclined to discount this consensus for now.

I still see a few possibilities for the ultimate track of this system:

- It heads westward into Central America or Mexico as a weak tropical wave

- It heads west-northwestward while passing near or over the south coast of Hispaniola, and eventually finds its way into the southern Gulf of Mexico, possibly as a hurricane

- It heads northwestward while passing over Hispaniola, then proceeds up through the Bahamas and possibly the United States east coast

Given current trends discouraging any significant development in the near-term, I favor the middle track, but the Bahamas solution could happen if the upper lows to the north of the system exert a greater poleward influence than anticipated, and also if convection reforms and persists. I would consider the Central America solution an enormous outlier with little chance of actually occurring.

The upper wind environment is forecast to be quite favorable for intensification when the wave is forecast to enter the western Caribbean Sea in about 5 or 6 days. Assuming things pan out that way, we would have to watch it very carefully. An alternate scenario is that the system becomes too disrupted by the Greater Antilles to ever redevelop, similar to Chantal.

Regardless of development, locally heavy rain and gusty winds -- perhaps to tropical storm force -- are expected over portions of the Windward Islands over the next day or so.

Probability of development in 48 hours: 30%



Kiko

Kiko weakens to a tropical depression as of the 0900Z NHC advisory:

Wind: 35 mph, with higher gusts
Location: 22.7°N 116.3°W
Movement: NNW at 5 mph
Pressure: 1005 mb

Satellite classifications are plummeting as fast as the Dvorak rules allow, and Kiko is a well-defined swirl of low- to mid-level clouds devoid of deep convection. Since the cyclone has lacked deep convection for many hours, it is presumed that it will degenerate into a remnant low later today.



Figure 2. Latest infrared satellite image of Tropical Depression Kiko. Image credit: NOAA's Satellite Services Division (SSD).

Kiko is already over cool waters, and is expected to continue moving across marginal waters; in combination with a meager thermodynamic environment, Kiko is expected to continue to weaken. Most of the guidance loses the circulation in the next 36-48 hours, and my forecast follows suit.

Kiko is on the south side of a low- to mid-level ridge over the southwestern United States. There has been no appreciable change to the steering philosophy or synoptic pattern, with the shallow cyclone forecast to continue moving slowly north-northwestward with a gradual decrease in forward speed. The GFS and ECMWF show Kiko remaining nearly stationary beyond 24 hours, so it is possible even this forecast is a little too enthusiastic on the forward speed spectrum.

Intensity forecast and positions

INITIAL 09/02 0900Z 22.7°N 116.3°W 30 KT 35 MPH
12 hour 09/02 1800Z 23.2°N 117.5°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
24 hour 09/03 0600Z 23.4°N 117.6°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
36 hour 09/03 1800Z 23.6°N 117.8°W 20 KT 25 MPH...POST-TROPICAL/REMNANT LOW
48 hour 09/04 0600Z...DISSIPATED

Track forecast



Figure 3. My forecast track for Kiko.

2013 Atlantic hurricane season 2013 Pacific hurricane season Invest 97L Tropical Depression Kiko

Updated: 9:35 AM GMT on September 02, 2013

Permalink

Tropical weather analysis - September 1, 2013

By: KoritheMan, 6:20 AM GMT on September 01, 2013

Invest 96L

A large tropical wave is over the eastern Atlantic just east of the Cape Verde Islands. Although this system is producing a large cyclonic wind shift as evidenced by surface observations from the Cape Verde Islands, the associated shower activity has continued to diminish this evening. Waters will continue to cool from this point on as the wave moves west-northwestward across the eastern Atlantic at 15 to 20 mph over the next few days, and vertical shear will be increasing during this time as well. I no longer anticipate tropical development from this wave. However, it will likely spread locally heavy rains and gusty winds over much of the Cape Verde archipelago during the next 24 hours.



Figure 1. Latest infrared satellite images of Invest 96L. Image credit: NOAA's Satellite Services Division (SSD).

Probability of development in 48 hours: 0%



Invest 97L

Another tropical wave is located a few hundred miles east of the Windward Islands. While satellite images suggest that convection has increased over the last several hours, the actual low-level center is much farther to the west, away from the convection and devoid of anything impressive. Surface observations and data from yesterday's NOAA G-IV mission suggest that the wave likely has a broad closed surface wind circulation; interestingly, CIMSS vorticity data indicates that the wave is actually rather poorly-defined above 850 mb, which is typically the opposite of what occurs with these westward-moving easterly waves.



Figure 2. Latest infrared satellite image of Invest 97L. Image credit: NOAA's Satellite Services Division (SSD).

Although upper-level winds are not currently favorable for development due to southwesterly shear, the GFS shows the upper wind environment over the Caribbean gradually improving over the next several days, which could allow for some long-range development in the western Caribbean Sea. Based on the pattern, my feeling is that the tropical wave will continue westward through the Caribbean. I am not sure whether it will turn northwestward near Hispaniola, continue westward, or turn west-northwestward in that vicinity. The model field suggest a shortwave trough over the western Atlantic at about the time the wave will be traversing the central Caribbean Sea, but it looks to be fairly shallow, with a fairly progressive synoptic flow regime over that portion of the basin, which would not allow the trough to stick around for long before being replaced by mid-level ridging aloft. Since the upper wind environment will not significantly improve until the longitude of Jamaica or points thereabouts, and also taking into consideration the typical trade wind hurdles found in much of the Caribbean, it is my expectation that the wave will remain weak enough to take a more westward track toward the vicinity of Jamaica and Cuba at longer ranges, although this is uncertain. Upper diffluence associated with a small upper low seen on water vapor imagery spinning to the north of Hispaniola may favor enhanced convective activity as the wave moves westward over the next few days, particularly along the northern portion of the wave axis, which could possibly allow a more poleward component of motion to develop. When the wave is expected to be in the western Caribbean in four or five days, the GFS shows the upper air environment improving, with the shear easing up quite a bit in that area, so this will need to be watched carefully at longer ranges.

In the interim, the wave will spread locally heavy rains and gusty winds over portions of the Lesser Antilles during the next couple of days.

Probability of development in 48 hours: 10%



Kiko

Tropical Storm Kiko is flirting with hurricane status as of the 0300Z NHC advisory:

Wind: 70 mph, with higher gusts
Location: 20.0°N 115.8°W
Movement: N at 7 mph
Pressure: 993 mb

The convective pattern seems to have improved a little since the advent of the last official NHC advisory bulletin, with conventional satellite images suggesting strong convective banding wrapping around the northern and western portions of what appears to be a small warm spot -- perhaps an eye. The 0z satellite classifications still do not quite support hurricane strength, with the highest being a 3.5 from TAFB; however, I note that the standard Dvorak derivatives don't seem to be working particularly well for this system, which developed rather rapidly during the day Saturday.



Figure 3. Latest infrared satellite image of Tropical Storm Kiko. Image credit: NOAA's Satellite Services Division (SSD).

The northerly shear that was seen yesterday appears to have abated, although the high cloud motion vectors cause me to surmise, with good reason, that there may be some northwesterly shear starting to restrict the outflow on the western periphery of the cyclone circulation. This appears to be caused by a small but well-defined upper cold low located not far north of Kiko on water vapor imagery. This feature is forecast to move essentially in tandem with Kiko, which could keep some shearing on the system. Nevertheless, Kiko still has about another 18-24 hours before it reaches waters cooler than 26C, and since the shear does not appear prohibitively strong yet, I will forecast a peak of 70 kt in 24 hours, a marginal Category 1 hurricane. Beyond that time, cooler waters and increasing southwesterly shear is anticipated to cause weakening, with a more rapid propensity to that end shown later in the forecast period before Kiko completely dies in 96 hours.

Kiko appears to have jogged to the east of the 0300Z NHC forecast track by about 20 or 30 miles over the last couple of hours, tracking east of north, but the latest microwave fixes suggest that the cyclone has resumed a more definitive northward motion. Given that there still appears to be a sizable ridge north of the system, Kiko is expected to move west of north over the next couple of days, before turning closer to a northwest direction at the end of the forecast period. If the vortex lives to see 96 hours and beyond, the GFS and ECMWF suggest that it will shear apart and drift slowly southward in the low-level flow. My forecast track is a little to the right of the National Hurricane Center forecast, particularly early on, to account for the more eastward deviation from that respective track.

Intensity forecast and positions

INITIAL 09/01 0300Z 20.0°N 115.8°W 60 KT 70 MPH
12 hour 09/01 1200Z 20.5°N 115.7°W 65 KT 75 MPH
24 hour 09/02 0000Z 21.1°N 115.8°W 70 KT 80 MPH
36 hour 09/02 1200Z 21.7°N 115.9°W 60 KT 70 MPH
48 hour 09/03 0000Z 22.5°N 116.2°W 45 KT 50 MPH
72 hour 09/04 0000Z 22.8°N 116.3°W 30 KT 35 MPH...POST-TROPICAL/REMNANT LOW
96 hour 09/05 0000Z...DISSIPATED

Track forecast



Figure 4. My forecast track for Kiko.

2013 Atlantic hurricane season 2013 Pacific hurricane season Invest 96L Invest 97L Tropical Storm Kiko

Updated: 6:21 AM GMT on September 01, 2013

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About KoritheMan

I'm just a 22 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.