KoritheMan's WunderBlog

Tropical weather analysis - July 1, 2013

By: KoritheMan, 4:51 AM GMT on July 01, 2013

Dalila

Tropical Storm Dalila is finally showing some signs of strengthening. As of the latest NHC advisory, the following information was available on the cyclone:

Wind: 45 mph, with higher gusts
Location: 16.8°N 104.4°W
Movement: NW at 10 mph
Pressure: 1001 mb

There have been no recent microwave passes over the center, but infrared satellite pictures suggest a better organized tropical cyclone with an improving central dense overcast structure. In addition, some ill-defined curved bands are evident to the north and west of the center. Upper tropospheric outflow has also become much better established in the western and northern semicircle of the tropical storm, which suggests a decrease in the large-scale vertical shear.



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

Water vapor imagery suggests that the upper low to the west of Dalila has continued to move west away from the cyclone, which has apparently allowed for the upper flow to back to a south-southeasterly direction, as evidenced by the slight expansion of the outflow in the southern semicircle, which was being lambasted by southerly shear 24 hours ago. The current south-southeasterly shear is likely to be less associated with the upper low/trailing trough to the west of Dalila, and more directly connected with a low- to mid-level ridge over the western Caribbean Sea. As a whole, the environment does not look particularly hostile for intensification for the next couple of days, especially since the cyclone is moving parallel to the shear vector, but one can never be too careful with small tricksters like Dalila.

Considering the small size of the cyclone, which will inherently mean greater susceptibility to sudden fluctuations in strength, and the fact that Dalila has been very reluctant to intensify thus far, I have lowered my intensity forecast from yesterday, but still show Dalila becoming a hurricane in about 48 hours, which is still a fair bit above the latest intensity consensus aids. Either way, I will be watching to see if the models win, or if I do.

Dalila remains south of a strong blocking high over the western United States, the same one responsible for the Arizona wildfires and the unfortunate fatalities that have occurred there tonight. The global models suggest that whatever cyclonic scale environment remains to influence Dalila will continue to weaken over the next day or so. At that point, Dalila is expected to come fully under the influence of the western United States ridge, which will cause a turn to the west-northwest and west at later periods. It should be noted that a substantial discrepancy has arisen in the global models today, with the ECMWF and CMC suggesting that Dalila will experience an abrupt turn to the southwest in about 72 hours, while the GFS continues projecting a straight westward motion when the storm nears Socorro Island. I am unsure the exact cause for this apparent division, but if I were to surmise by looking at the 850 mb model fields, it appears that a convectively active ITCZ is forecast to begin pulling Dalila to the south beyond the 72 hour point, possibly aided in part by a modeled disturbance that the models foresee becoming a tropical cyclone in the next 5 - 7 days. I have no real reason to favor one scenario over the other since both are coming from statistically reliable models, so I will split the difference, bring my forecast southward from yesterday, and forecast a much slower westward motion from day three through five. If the division continues, confidence in this forecast will not be particularly high. It should be noted that I am still along the far northern edge of the latest model consensus.

5-day intensity forecast

INITIAL 07/01 0300Z 40 KT 45 MPH
12 hour 07/01 1200Z 45 KT 50 MPH
24 hour 07/02 0000Z 50 KT 60 MPH
36 hour 07/02 1200Z 60 KT 70 MPH
48 hour 07/03 0000Z 70 KT 80 MPH
72 hour 07/04 0000Z 60 KT 70 MPH
96 hour 07/05 0000Z 50 KT 60 MPH
120 hour 07/06 0000Z 40 KT 45 MPH

5-day track forecast



Figure 2.
My 5-day forecast track for Dalila.



NHC storm information


000
WTPZ34 KNHC 010231
TCPEP4

BULLETIN
TROPICAL STORM DALILA ADVISORY NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP042013
800 PM PDT SUN JUN 30 2013

...OUTER RAINBANDS OF DALILA BEGINNING TO MOVE ONSHORE THE
SOUTHWESTERN COAST OF MEXICO...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...16.8N 104.4W
ABOUT 150 MI...245 KM S OF MANZANILLO MEXICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...1001 MB...29.56 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 SOUTHWEST COAST OF MEXICO FROM PUNTA SAN TELMO TO LA FORTUNA

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE SOUTHWEST COAST OF MEXICO FROM NORTH OF LA FORTUNA TO CABO
CORRIENTES

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

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE OF THE
UNITED STATES...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 DALILA WAS
LOCATED NEAR LATITUDE 16.8 NORTH...LONGITUDE 104.4 WEST. DALILA IS
MOVING TOWARD THE NORTHWEST NEAR 10 MPH...17 KM/H. THIS GENERAL
MOTION IS EXPECTED TO CONTINUE TONIGHT AND EARLY MONDAY...FOLLOWED
BY A TURN TOWARD THE WEST-NORTHWEST AT A SLOWER FORWARD SPEED ON
TUESDAY. ON THE FORECAST TRACK...THE CENTER IS EXPECTED TO REMAIN
WELL OFFSHORE THE SOUTHWESTERN COAST OF MEXICO...BUT DALILA IS
STILL EXPECTED TO PRODUCE TROPICAL STORM CONDITIONS WITHIN THE
WARNING AREA ON MONDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/H...WITH HIGHER
GUSTS. GRADUAL STRENGTHENING IS EXPECTED DURING THE NEXT 48 HOURS...
AND DALILA COULD BECOME A HURRICANE ON TUESDAY.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 45 MILES...75 KM
FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1001 MB...29.56 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH THE
COAST WITHIN THE WARNING AREA EARLY MONDAY. TROPICAL STORM
CONDITIONS ARE POSSIBLE IN THE WATCH AREA BY LATE MONDAY.

RAINFALL...DALILA IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS
OF 1 TO 3 INCHES OVER COASTAL PORTIONS OF THE MEXICAN STATES OF
MICHOACAN...COLIMA...AND JALISCO.


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

$$
FORECASTER STEWART



Elsewhere

Elsewhere, there isn't much going in the Atlantic right now, but the tropical wave over the western Caribbean Sea could serve as the catalyst for a modeled tropical cyclone in the eastern Pacific well to the south of Mexico in 5 - 7 days. The majority of the models, including the GFS and even the ECMWF develop this system, so it is of note. If it were to get a name, it would be called "Erick".

2013 Pacific hurricane season Tropical Storm Dalila

Updated: 4:55 AM GMT on July 01, 2013

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Tropical weather analysis - June 29, 2013

By: KoritheMan, 2:48 AM GMT on June 30, 2013

Tropical Depression Four-E

Tropical Depression Four-E has formed today from what was previously Invest 96E. As of the latest NHC advisory, the following information was posted on the storm:

Wind: 35 mph, with higher gusts
Location: 13.7°N 103.0°W
Movement: N at 10 mph
Pressure: 1006 mb

Deep convection associated with the cyclone is exhibiting some distinct curvature, with a prominent curved band in the northern semicircle; if this band wraps around the center more strongly, we could have a tropical storm in a few hours.



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

The upper low seen in water vapor imagery to the west of the depression is still evident today, although I don't see much evidence of shear judging by the cloud pattern. In fact, analysis of upper wind data from the University of Wisconsin CIMSS laboratory suggests that the cyclone has built an anticyclone above its surface center; this is confirmed in the global model forecast fields also, and is evident on the general cloud pattern as well. Since the upper low appears to be moving slowly westward away from the depression, there should be no unexpected influences of vertical shear for the next few days. Later in the period, the CMC and NAVGEM hint that the anticyclone may become dislodged from the cyclone center and impart a little bit of westerly shear; coupled with progressively cooler waters during the day four and five period, and the anticipated outcome should be weakening.

Given the small size of the cyclone, it is more prone than normal to intensify fluctuations, in this case upward. While none of the 0z intensity guidance predicts a hurricane, it is my expectation that the small size of the cyclone will allow it to intensify rather quickly beyond 24 hours as an inner core becomes established. If said core develops quickly, rapid intensification could occur in the short-term. At the risk of being incorrect, my intensity forecast is considerably higher than all of the available intensity guidance, forecasting a peak of 80 kt in 72 hours, which is just shy of Category 2 strength.

The cyclone remains in an area of large-scale upper cyclonic flow between an upper low and trailing mid- to upper-level trough to its west, and another such low over the Gulf of Mexico; an upper cyclone is also seen over the upper midwest diving southward, which will help to reinforce the weakness in this region. The global models maintain this general flow pattern for the next couple of days, which is expected to allow the cyclone to continue moving generally northward to northwestward toward the southwest coast of Mexico. While some of the outlying statistical guidance forecasts a landfall, the reliable guidance suggests that the cyclone will remain well offshore. This is my expectation for now, but the ECMWF and GFDL have been showing the depression getting rather close to the coast, which suggests the pattern is relatively fragile. Beyond 48 hours, the depression is expected to gradually smooth back into a west-northwest to westward motion as it comes under the influence of a building low- to mid-level ridge to the north. This is in good agreement with the model guidance, which remains tightly clustered except for some differences in the forward speed, particularly as the cyclone nears Socorro Island late in the period.

Because of the possibility of the system getting dangerously close to the coast, interests in southwestern Mexico should carefully monitor the progress of the depression over the next few days. Regardless of whether or not the system makes landfall, heavy rain, gusty winds, and dangerous sea conditions will overspread this area over the next few days.

Because of the possibility of the cyclone getting uncomfortably close to the coast, tropical storm watches and warnings have been issued for a portion of the southwest coast of Mexico (see below).


5-day intensity forecast

INITIAL 06/30 0300Z 30 KT 35 MPH
12 hour 06/30 1200Z 35 KT 40 MPH
24 hour 07/01 0000Z 45 KT 50 MPH
36 hour 07/01 1200Z 55 KT 65 MPH
48 hour 07/02 0000Z 70 KT 80 MPH
72 hour 07/03 0000Z 80 KT 90 MPH
96 hour 07/04 0000Z 65 KT 75 MPH
120 hour 07/05 0000Z 50 KT 60 MPH

5-day track forecast



Figure 2. My 5-day forecast track for Tropical Depression Four-E.

NHC storm information

000
WTPZ34 KNHC 300236
TCPEP4

BULLETIN
TROPICAL DEPRESSION FOUR-E ADVISORY NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL EP042013
800 PM PDT SAT JUN 29 2013

...NEW TROPICAL DEPRESSION FORMS...
...TROPICAL STORM WARNING ISSUED FOR A PORTION OF THE SOUTHWEST
COAST OF MEXICO...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...13.7N 103.0W
ABOUT 305 MI...485 KM SW OF ACAPULCO MEXICO
ABOUT 375 MI...605 KM SSE OF MANZANILLO MEXICO
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES


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

THE GOVERNMENT OF MEXICO HAS ISSUED A TROPICAL STORM WARNING FROM
PUNTA SAN TELMO TO MANZANILLO.

THE GOVERNMENT OF MEXICO HAS ISSUED A TROPICAL STORM WATCH FROM
NORTH OF MANZANILLO TO LA FORTUNA.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE SOUTHWEST COAST OF MEXICO FROM PUNTA SAN TELMO TO MANZANILLO

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE SOUTHWEST COAST OF MEXICO FROM NORTH OF MANZANILLO TO LA
FORTUNA

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

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE OF THE
UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 PM PDT...0300 UTC...THE CENTER OF TROPICAL DEPRESSION FOUR-E
WAS LOCATED NEAR LATITUDE 13.7 NORTH...LONGITUDE 103.0 WEST. THE
DEPRESSION IS MOVING TOWARD THE NORTH NEAR 10 MPH...17 KM/H. A
GRADUAL TURN TOWARD THE NORTH-NORTHWEST IS EXPECTED BY LATE
SUNDAY...FOLLOWED BY A TURN TOWARD THE NORTHWEST ON MONDAY. ON THE
FORECAST TRACK...THE CENTER IS EXPECTED TO PASS CLOSE TO THE
SOUTHWEST COAST OF MEXICO IN THE TROPICAL STORM WARNING AREA ON
MONDAY.

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 ON SUNDAY.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB...29.71 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO FIRST REACH THE
COAST WITHIN THE WARNING AREA EARLY MONDAY. TROPICAL STORM
CONDITIONS ARE POSSIBLE IN THE WATCH AREA BY LATE MONDAY.

RAINFALL...THE DEPRESSION IS EXPECTED TO PRODUCE TOTAL RAIN
ACCUMULATIONS OF 1 TO 3 INCHES OVER COASTAL PORTIONS OF THE MEXICAN
STATES OF MICHOACAN...COLIMA...AND JALISCO.


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

$$
FORECASTER BRENNAN

2013 Pacific hurricane season Tropical Depression Four-E

Updated: 2:49 AM GMT on June 30, 2013

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Tropical weather analysis - June 29, 2013

By: KoritheMan, 6:22 AM GMT on June 29, 2013

Invest 96E

A small but well-defined area of low pressure located several hundred miles south of the southern coast of Mexico is showing obvious signs of organization, and could become a tropical depression on Saturday.

Convection has significantly weakened over the last 6-12 hours, but this is probably a diurnal fluctuation.



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

While there have been no recent scatterometer passes over the disturbance, an ASCAT pass around 17z suggested that the surface circulation was becoming better defined in the surface wind field. There have also been no reliable microwave passes over the last several hours either, and the ones we did get provided little coverage to the internal organization of the system, and were thus of little use. While it is difficult to determine precisely the existence of a possible closed surface low pressure center using only nighttime satellite imagery, low cloud vectors on the shortwave infrared satellite channel strongly suggest that the circulation has consolidated since the time of the ASCAT pass (which actually showed that the south side of the gyre was destitute of westerly winds), and based on the cloud lines and organization of the cloud pattern, I strongly believe that the circulation associated with this system is now closed off.

Environmental conditions are seemingly favorable for intensification, possibly significant; the SHIPS and all of the global models forecast an environment of weak upper tropospheric vertical shear over the budding disturbance throughout the forecast period, and they even suggest a large and highly amplified upper-level anticyclone will accompany the system during this time. The only immediate impediment to development I see is that the system is still embedded in the monsoon trough, but this will become irrelevant if the circulation is truly closed off, or in the process of doing so. Also, I see evidence of a small upper low/cyclonic shear axis on water vapor imagery about 5 degrees west and north of Invest 96E. The GFS correctly recognized the presence of this low, but suggests that it should move slowly westward away from the disturbance. Understanding that there actually is evidence of this low and its associated cyclonic vorticity moving westward on a gradual basis, I believe the model forecasts of low shear; however, it is possible that this low will impart some modest southerly shear to the disturbance during the next 24 hours given its orientation and position relative to the surface vortex associated with 96E. Any shear should not be enough to prohibit development, and a southerly shear vector is not all that detrimental for a northward-moving system. In about four days, the system is expected to cross the 26C isotherm and should begin to weaken at that time, with more rapid weakening anticipated at day five.

The large-scale steering environment surrounding this low consists of a broad trough associated with the aforementioned upper low. The global models suggest the consequent weakness in the ridge will stick around for about 48 hours, at which time the model forecast fields show a low- to mid-level ridge building to the north of the tropical cyclone over southern Mexico. This is expected to cause the system to gradually bend to the west-northwest and west with time. Based on the pattern, I anticipate a track similar to Hurricane Beatriz in 2011, although probably a little farther offshore; there is enough margin for error, however, that interests along the southern coast of Mexico should carefully monitor the progress of what will very likely be a small but decent hurricane by the time it reaches its closest approach to the coast.

Regardless of whether or not the system makes landfall, periodic episodes of heavy rain and gusty winds will lash portions of southern Mexico over the next several days. In addition, dangerous rip currents and high waves will accompany the system.

Probability of development in 48 hours: 90%



Elsewhere

Elsewhere, a vigorous tropical wave is moving through the Windward Islands and southeastern Caribbean Sea. While this wave is very well-defined in the surface wind field and is rather unusual for June, upper-level winds are not expected to permit development; given the well-marked wave signature, however, I would watch for the possibility of development in the western Caribbean or the eastern Pacific in the next 7 days.

By the way, the presence of this wave further validates the numerous forecasts of a hyperactive season from the many forecasting agencies.

2013 Pacific hurricane season Invest 96E

Updated: 6:23 AM GMT on June 29, 2013

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Tropical weather analysis - June 25, 2013

By: KoritheMan, 2:15 AM GMT on June 26, 2013

Cosme

Hurricane Cosme continues to spin harmlessly out to sea. As of the latest NHC advisory, the following information was available on the storm:

Wind: 80 mph, with higher gusts
Location: 17.9°N 112.4°W
Movement: WNW at 17 mph
Pressure: 985 mb
Category: 1 (Saffir-Simpson Hurricane Wind Scale)

While an eye is not readily apparent in infrared satellite images, it has been periodically visible on visible satellite images during the day today, and satellite estimates have been hovering to as high as 80 kt during the past several hours. A recent SSMIS overpass just after 0z suggested that an intense ring of convection around the eye was becoming better defined, with the eyewall about 75% closed; the latest available infrared satellite images confirm a similar structure, with tightly-knit banding wrapping around what seems to periodically be a faint warm spot. It should be noted that the latest ATCF update puts Cosme at 75 kt, so we will see if that is confirmed with the upcoming advisory from the National Hurricane Center.



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

The outflow pattern is much more established today, suggesting a sharp decrease in shear over Cosme. While vertical shear is forecast to remain light throughout the next five days, with a large anticyclone moving in tandem with the tropical cyclone, Cosme is about to cross the 26C isotherm; waters drop off rapidly after that, so the hurricane has likely peaked in intensity, and weakening is expected to begin soon. The models -- statistical and all -- agree on this rather abrupt weakening trend. Given the meager thermodynamic environment, my forecast is in agreement with the one from the National Hurricane Center, and shows Cosme becoming a remnant low in about three days. I feel confident, however, that the remnant low-level cloud swirl will continue to carry near gale force winds with it for several days after dissipation due to the forecast low shear environment and the accompanying large anticyclone responsible for it in the model fields. When Cosme's post-tropical remnants reach the longitude of the Hawaiian Islands next week, the models suggest increasing westerly shear associated with the mid-oceanic trough will begin to affect the system, which should stifle any regeneration attempts as Cosme moves into warmer water near those islands.

Synoptic data suggests that Cosme remains south of a mid-level ridge which appears to be strengthening based on trends in water vapor imagery and large-scale data. This is consistent with the pattern furnished by the global models, which show Cosme turning westward during the next 24-36 hours as it weakens and becomes steered by the low-level flow. The large upper low off the coast of the Pacific northwest is already in the process of lifting off to the northwest as a large blocking high develops over the western United States; once again, this has been the forecast from the global models all along, which seem to be doing rather well in resolving the subtleties of the pattern. Confidence in the forecast track is high due to continued strong agreement amongst the model suite. While not explicitly shown by all of the guidance, there are some hints that Cosme's remnants could turn southwestward near the end of the forecast period, so I took the liberty of showing this.

5-day intensity forecast

INITIAL 06/26 0300Z 70 KT 80 MPH
12 hour 06/26 1200Z 75 KT 85 MPH
24 hour 06/27 0000Z 65 KT 75 MPH
36 hour 06/27 1200Z 45 KT 50 MPH
48 hour 06/28 0000Z 35 KT 40 MPH
72 hour 06/29 0000Z 30 KT 35 MPH...POST-TROPICAL/REMNANT LOW
96 hour 06/30 0000Z 30 KT 35 MPH...POST-TROPICAL/REMNANT LOW
120 hour 07/01 000Z 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW

5-day track forecast




Figure 2. My 5-day forecast track for Cosme.

2013 Pacific hurricane season Hurricane Cosme

Updated: 2:22 AM GMT on June 26, 2013

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Tropical weather analysis - June 24, 2013

By: KoritheMan, 12:58 PM GMT on June 24, 2013

Cosme

Tropical Storm Cosme formed during the overnight hours from what was formerly Tropical Depression Three-E. As of the latest NHC advisory (2:00 AM PDT), the following information was available on the cyclone:

Wind: 40 mph, with higher gusts
Location: 12.8°N 105.2°W
Movement: NW at 10 mph
Pressure: 1003 mb

Cosme consists of a rather large ball of very cold convection. There continue to be no significant banding features, and my best guess looking at the cloud pattern is that the cyclone is battling a little bit of northeasterly shear. Looking at upper wind analyses from the University of Wisconsin CIMSS website, there doesn't appear to be a substantial anticyclone over Cosme, and it's actually probably a little bit displaced to the north based on the outflow pattern in the northern semicircle.



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

Identifying the location of the cyclone center hasn't been easy for me this morning, as the most recent microwave pass was around 3z, and there aren't yet any visible satellite pictures available to gauge the low cloud lines. An ASCAT pass around 4z suggested that the low-level center was a little above 13N, which would tend to agree well with satellite imagery this morning if one were to carefully analyze it. My best guess is that the center is somewhere along the northern portion of the coldest convection, which was the case last night as well.

It appears that the majority of vertical shear over Cosme is below the outflow layer, although not completely. The global models tend to have more difficulty in resolving forecasts of mid-tropospheric shear as opposed to upper-tropospheric shear, based on my personal experience as a forecaster, so I didn't rely too heavily on the guidance in the short-term. Assuming these conditions will abate soon, Cosme should continue to at least slowly strengthen. I am still going to bring Cosme to hurricane strength, but it only has about 48 hours before the SHIPS model and real time SST fields suggest that the tropical storm will approach cooler waters, waters which rapidly drop off beyond 72 hours. Interestingly, all of the global models show a large anticyclone moving more or less in tandem with Cosme throughout the forecast period, growing considerably in size from the one in Cosme's vicinity now. Out of deference to that and the light shear pattern it would cause, I anticipate the vortex will carry strong winds for longer than would be expected for a system over cold water. Having said all of that, Cosme is still expected to become a remnant low at the end of the forecast period, and it could occur a little sooner if the forecast anticyclone doesn't strengthen and collocate with the cyclone as forecast.

Cosme remains south of a weak low- to mid-level ridge over southern Mexico. Water vapor imagery shows a sharp upper-level cyclone off the Pacific northwest, with a much larger cyclone located several hundred miles to the northwest of that one. The global models insist that this entire zone, particularly the larger low, will move southeastward and maintain the weakness in the subtropical ridge for another 36-48 hours. This should continue the current northwestward motion of Cosme. Beyond that time, zonal flow is forecast to gradually broaden and deepen to the north of Cosme, which should cause a turn back to the west-northwest and west near the end of the period as the cyclone weakens and becomes steered by the low-level environmental easterlies. Some acceleration is shown at days four and five due to the anticipated strengthening of the low-level ridge to the north of Cosme at those times. The models remain in excellent agreement, and the forecast track is thus of high confidence. However, there may be some fits and wobbles in the storm relative motion over the next day or so as the cyclone strengthens. My belief is that the low-level center will attempt to straddle along to the right ever so slightly during the next 12-24 hours, as the cyclone vortex attempts to compensate for the large burst of convection comprising the vortex. Thus, my forecast track is a little to the right of the National Hurricane Center for the next 24 hours, but gradually smooths into agreement after that.

Cosme may bring enhanced shower activity to portions of Hawaii during the next 7 - 10 days, but it will not reach the longitude of those islands as a tropical cyclone due to cool waters and strong westerly shear.

5-day intensity forecast

INITIAL 06/24 1200Z 35 KT 40 MPH
12 hour 06/25 0000Z 45 KT 50 MPH
24 hour 06/25 1200Z 50 KT 60 MPH
36 hour 06/26 0000Z 60 KT 70 MPH
48 hour 06/27 1200Z 65 KT 75 MPH
72 hour 06/28 1200Z 45 KT 50 MPH
96 hour 06/29 1200Z 35 KT 40 MPH
120 hour 06/30 1200Z 30 KT 35 MPH...POST-TROPICAL/REMNANT LOW

5-day track forecast



Figure 2. My 5-day forecast track for Cosme.

2013 Pacific hurricane season Tropical Storm Cosme

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Tropical weather analysis - June 23, 2013

By: KoritheMan, 1:17 AM GMT on June 24, 2013

Tropical Depression Three-E

Tropical Depression Three-E formed today from what was previously Invest 94E. As of the latest NHC advisory, the following information was available on the system:

Wind: 35 mph, with higher gusts
Location: 12.0°N 103.7°W
Movement: Stationary
Pressure: 1005 mb

After sputtering a bit this afternoon, convection has increased over the center of the depression, and the cyclone appears to be getting better organized. A 1600 UTC ASCAT pass suggested light winds near the circulation center, but that was well before the current convective burst.



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

Other than the large size of the depression, which currently is more reminiscent of monsoon depressions in the western Pacific, environmental conditions appear quite favorable for strengthening, with the SHIPS analyzing relative humidity values at 87% as of 18z. In addition, the global models are unanimous in intensifying and expanding the current upper-level anticyclone developing over the tropical cyclone, which should result in an environment of even lower vertical wind shear. It appears probable that the cyclone will become at least a minimal hurricane, and there remains a chance of more rapid organization if the system develops an inner core. Beyond 48 hours, the depression is expected to move into cooler water, which will offset an environment of continued low shear, and should lead to weakening, with more rapid weakening anticipated near the end of the period. The models remain consistent on this general scenario, with very little important differences.

The depression is located south of a narrow mid-level ridge. Satellite images earlier in the day indicated little movement, but recent fixes suggest a more definite motion to the west-northwest, likely at least in part due to the low-level center following the recent convective burst, which is typical of developing systems in this stage. With a more definite movement established, there appears to be little ongoing deviation to the steering pattern forecast by the global models, and the cyclone is forecast to move west-northwest to northwest over the next few days before gradually turning back to the west near the end of the period. The global models remain in good agreement on this scenario, particularly for a system still in its formative stages. The first 24 hours of my forecast track could well be too far to the left if the depression is moving farther to the right than I'm thinking, or if there is a greater weakness to the north.

The cyclone is not a threat to land.

5-day intensity forecast

INITIAL 06/24 0000Z 30 KT 35 MPH
12 hour 06/24 1200Z 35 KT 40 MPH
24 hour 06/25 0000Z 45 KT 50 MPH
36 hour 06/25 1200Z 55 KT 65 MPH
48 hour 06/26 0000Z 65 KT 75 MPH
72 hour 06/27 0000Z 45 KT 50 MPH
96 hour 06/28 0000Z 35 KT 40 MPH
120 hour 06/29 0000Z 30 KT 35 MPH...POST-TROPICAL/REMNANT LOW

5-day track forecast



Figure 2. My 5-day forecast track for Tropical Depression Three-E.



Invest 95E

An area of low pressure located several hundred miles west of Tropical Depression Three-E continues to produce disorganized showers and thunderstorms that sprawl. Visible satellite images suggest that the circulation associated with this disturbance has become less-defined today, and significant development is not anticipated. Indeed, easterly shear appears to be already increasing in association with Tropical Depression Three-E. The global models suggest the circulation will become absorbed into the larger circulation associated with our developing tropical cyclone to the east in a few days.



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

Probability of development in 48 hours: 10%

I will hold off on mentioning the potential for Atlantic development in early July, since there are still a lot of uncertainties, and because little change has been noted in the global models.

2013 Pacific hurricane season Tropical Depression Three-E Invest 95E

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Tropical weather analysis - June 23, 2013

By: KoritheMan, 5:06 AM GMT on June 23, 2013

Invest 94E

An area of low pressure located several hundred miles south-southwest of Acapulco, Mexico continues to gradually become better organized. A burst of very cold convection, up to about -80C, has developed over the last several hours, but careful analysis of satellite and microwave data suggests that the low-level center is along the far northeastern side of the convection; additionally, last light visible satellite images suggest that the circulation may not be fully closed off, although it is steadily becoming better defined, and I suspect it will accomplish this feat tomorrow.



Figure 1. Latest infrared satellite image of Invest 94E. Image credit: NOAA's Satellite Services Division (SSD).

The northwesterly shear that has been afflicting the system over the past few days continues to decrease, with a small anticyclone developing over the system as diagnosed by University of Wisconsin CIMSS data. The global models strengthen this anticyclone and move it tandem with 94E over the next few days, a pattern which is conducive for at least steady strengthening. Most of the intensity guidance takes this system to hurricane strength, and I anticipate this low will become at least a minimal hurricane, with an outside chance of a peak closer to 85 kt, the lower end of the Category 2 threshold. In about three days, the system is forecast to approach cooler waters, which should initiate a weakening trend despite a low shear environment. This is in good agreement with the dynamical models.

Invest 94E is currently situated to the south of a weak low- to mid-level ridge over southern Mexico. Water vapor imagery and steering data from UW-CIMSS indicate that a substantial weakness is extant along the western extension of the ridge along 110 to 115W. While this weakness may temporarily fill and prevent the system from going too far northward in the short-term, a well-defined upper cold low and trailing upper trough off the coast of Washington is forecast by all of the models to move southeastward and reinforce the weakness over the southwestern United States over the next several days, which is expected to cause the low to move west-northwest to northwest over the next few days. Near the end of the forecast period, the upper cyclone is forecast to retrograde westward, which, combined with 94E's expected rapid weakening at that time, should allow for a gradual turn back toward the west in the low-level flow. This is also in excellent agreement with the global model depictions at those times. It is possible that 94E could eventually cross into the Central Pacific basin, but the chances of it reaching Hawaii as a tropical cyclone are probably 2%. It may eventually increase local shower activity across the islands, however.

Additional development is anticipated under favorable environmental conditions, and this low will likely become a tropical cyclone on Sunday.

This system is not expected to threaten any land areas.

Probability of development in 48 hours: 90%



Invest 95E

Another area of low pressure is located several hundred miles west of Invest 94E. Satellite and microwave data suggest that the circulation associated with this low is well-defined, and there is a convective burst near the center.



Figure 2. Latest infrared satellite image of Invest 95E. Image credit: NOAA's Satellite Services Division (SSD).

There is also a fair amount of subsidence comprising the near-storm environment, which has likely been the largest inhibiting factor to development since the circulation is well-defined. However, the diurnal convective maximum period is coming up in the next 6 to 8 hours, and there is potential for a sharp increase in convective organization during that period. Lacking any knowledge or foresight to know definitively whether or not that will be the case, I feel the best thing to do is to increase the development potential to 40%, a little higher than the National Hurricane Center's, but lower than I could go given the sharp definition of the surface circulation with this system.

Regardless of development, easterly shear is forecast by all the global models to increase sharply in about 48-60 hours as upper-level outflow from developing 94E, by then a tropical cyclone, impinges upon the system from the east. At that point, weakening is anticipated as the system orbits around the larger circulation associated with 94E/Cosme.

95E is in a very weak steering environment, and will likely move erratically northeastward or eastward before gradually gaining more eastward momentum as 94E's developing circulation begins to influence it more strongly. This system is not a threat to any land areas.

Probability of development in 48 hours: 40%



Still watching the Gulf of Mexico/western Atlantic for possible tropical development during the first week of July

Although the last several runs of the operational GFS have dropped the Gulf of Mexico tropical cyclone it was showing for a slew of its runs, its respective ensembles still forecast a decrease in surface pressures across the Gulf of Mexico during the first week of July; presumably, this is due to the upward MJO pulse enhancing convective activity in the eastern north Pacific.

While the timing of this event is still uncertain (due to the models not knowing how to handle the MJO surge), what's important is that modeled predictions have been consistent with lower pressures across that area during that general timeframe.

There have been back and forth solutions amongst the various runs of the GFS, with the majority of them indicating a hit on the northern Gulf Coast over the last several days under a progressive upper pattern. However, the operational has recently begun showing a west-northwest track into central Mexico under a building ridge over the southern United States; studying the model fields carefully, this change of heart appears to be because the GFS now wants to develop the system a couple days later, which, under the progressive pattern alluded to above, allows for the trough over the central plains to lift out and block any further northward progress of the modeled system.

Again, what's important isn't the track, or even the intensity; it's the fact that the upward MJO will be arriving in our area of the world soon, and will very likely generate an area of disturbed weather somewhere in the western Atlantic -- as of now, probably the Gulf of Mexico based on continued model predictions.

2013 Atlantic hurricane season 2013 Pacific hurricane season Invest 94E Invest 95E

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Tropical weather analysis - June 21, 2013

By: KoritheMan, 4:15 AM GMT on June 22, 2013

Invest 94E

An area of low pressure centered several hundred miles south-southwest of Acapulco, Mexico is producing disorganized showers and thunderstorms.



Figure 1. Latest infrared satellite image of Invest 94E. Image credit: NOAA's Satellite Services Division (SSD).

The system is compromised of an elongated convective band to the south, and these bands appear to be attempting to wrap cyclonically into the low-level center. An earlier scatterometer pass showed a broad surface circulation with some evidence of westerly winds on the south side of the gyre. There is still a little northwesterly shear over the low as suggested by the cloud pattern inferred from satellite imagery, but these winds appear to be relaxing, and are less than they were yesterday. There is evidence on water vapor imagery of the subtropical jet lifting northward progressively, so this leads credibility to the model forecasts of a decrease in shear. This low has potential for development into a tropical depression during the next day or two as it moves slowly westward for the next 36-48 hours before turning west-northwest toward a weakness in the subtropical high near 115W. It should be emphasized that many of the dynamical models show some sort of binary interaction between this low and another low several hundred miles to the west, a situation which could easily throw a wrench into the track forecast.


Most of the intensity models bring this system to a Category 1 hurricane, and there is a possibility it could get a little stronger before moving into cooler water in four days, but that will depend on how fast it organizes over the next 24 hours.

Probability of development in 48 hours: 70%

Invest 95E

The area of low pressure I alluded to above has been tagged "Invest 95E" by the National Hurricane Center. This low is located about 750 miles south-southwest of the southern tip of Baja California.



Figure 2. Latest infrared satellite image of Invest 95E. Image credit: NOAA's Satellite Services Division (SSD).

Shower activity near this system is almost nonexistent, but scatterometer and satellite data suggest that the surface circulation associated with this system is fairly robust, although still rather broad. With the subtropical jet lifting north, there is not much evidence of vertical shear over the system, and the main issue with organization at the moment appears to be dry air and the broad nature of the circulation envelope. Otherwise, all systems are a go for gradual development of this low as it moves slowly westward to the south of a distant and weak mid-level ridge over the western United States.

In about four days, most of the models show some sort mutual interaction with Invest 94E. Given that 94E appears to be the more organized of the two, it is likely that 95E will dance around that system while gradually weakening, not the other way around. If the system doesn't interact strongly with 94E, it could get close to hurricane status, particularly since it will have about a day more over warm water than 94E.

Probability of development in 48 hours: 30%



Gulf of Mexico development possible during the first week of July

The GFS and its respective ensemble members have consistently shown lower pressures across the southern Gulf of Mexico/northwestern Caribbean area during the next 7 - 10 days, presumably in response to an increase in atmospheric moisture associated with the upward MJO pulse, which right now is enhancing convection in the eastern Pacific. Given the model forecasts of two tropical cyclones out of this pattern in the Pacific (a situation that actually has some evidence in the form of two invests), and the consistency of these models to forecast the upward MJO pulse into the western Atlantic sometime during the first week of July, I am inclined to believe there is a good possibility of a tropical cyclone forming out of this in the Atlantic later on.

The track of such a hypothetical system is still highly uncertain, and the pattern over the United States during that time is progressive, which often causes disagreement amongst the models as they struggle to resolve the pattern. This is the case now, with the majority of the GFS ensembles sending this system westward toward Mexico. The operational, however, has been consistent in bringing the modeled storm to the northern Gulf Coast from the Texas/Louisiana border to the western Florida panhandle in the long range. Again, don't focus on the exact track of a system we don't have yet, but based on the pattern in the models, there is a definite window of opportunity for whatever does develop (if anything) to move northward toward the northern Gulf Coast, which would be consistent with climatology as well. How strong such a system might get is just as uncertain, but given the upper wind pattern I see on the GFS, and extrapolating it to the time of the modeled storm, there is potential for a minimal hurricane. There is still evidence of upper tropospheric shear, particularly on the southwest quadrant of this system in the isobaric fields on the models, so if it does develop it will probably not be able to rapidly intensify, but it should be stronger than Barry.

While there is disagreement between the ensembles and the operational GFS, my experience as a 5 year forecaster have shown me that in the vast majority of cases, the operational tends to perform better in terms of track than the ensembles do, particularly when there is a sharp disagreement between the two like there is now. Recent examples include the GFS ensemble forecasts of a turn to the northern Gulf Coast with Hurricane Nate in 2011, when the operational insisted on a landfall in Mexico; and Hurricane Gustav in 2008, when the ensembles were all over the place from Pensacola to Houston. Once again, the operational won out on a landfall in Louisiana.

Regardless of whether or not this modeled system develops, it shows that the western Atlantic will soon become a spot for possible develop as pressures start to lower with the arrival of the upward MJO, which can once again be seen enhancing convection over the Pacific -- even the western Pacific, with several invests and a tropical storm.

2013 Pacific hurricane season Invest 94E Invest 95E 2013 Atlantic hurricane season

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Tropical weather analysis - June 19, 2013

By: KoritheMan, 3:44 AM GMT on June 20, 2013

Barry

Tropical Storm Barry continues to move across the extreme southern Bay of Campeche on path toward a landfall in the Mexican state of Veracruz. As of the latest NHC advisory, the following information was available on the storm:

Wind: 45 mph, with higher gusts
Location: 19.6°N 95.8°W
Movement: W at 6 mph
Pressure: 1005 mb

There is still a little bit of time for Barry to strengthen before landfall, as the cyclone is not expected to move inland until Thursday morning. Although the underlying heat content of the Bay of Campeche is currently not very large, Barry is a small enough tropical cyclone so that upwelling will not be a significant factor despite its steadily decreasing forward motion. The latest run of the LGEM, historically shown to be a reliable model, takes Barry up to 45 kt before landfall, with some of the outlying guidance even suggesting an intensity near 50 kt. I am at the upper end of the intensity consensus given the notoriously positive effect of the Bay of Campeche in spinning up storms. It should be noted that there is a weakness in the western end of the mid-level ridge over the Gulf of Mexico, a phenomenon that appears to be caused by a digging mid- to upper-level trough over Texas and northern Mexico. If Barry moves north of the forecast track and continues to decelerate, it would spend more time over water and could have a narrow window to become a hurricane; this is considered an outlier scenario for now.



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

Barry is currently south of a narrow mid-level ridge over the northern Gulf of Mexico, with a westward extension of this ridge into central Texas. The global models maintain this general flow pattern until landfall, which suggests the tropical storm's direction of motion will not change much.

Estimating the location and position of Barry has been an arduous task this evening, to say the least. The circulation is small and was thus not well-resolved by an SSMIS pass just before 0z. The radar site at Alvarado is currently not operational, and there has been no recent scatterometer pass over the cyclone. My best guess is what the National Hurricane Center is saying; that the center is along the south side of an ongoing burst of deep convection, likely the beginnings of a central dense overcast. There could still be some jumps to the north as the convection expands in coverage and intensity.

Barry appears to have slowed down a little more, but once again that is fairly difficult to judge. A slight additional decrease in forward speed, perhaps to as slow as 4 mph, is expected as Barry comes under the influence of the aforementioned mid-level trough, which is already eroding the ridge. A general westward path, however, is still anticipated until the cyclone dissipates in about a day.

The primary threat with Barry continues to be heavy rains of 4 to 8 inches over portions of eastern Mexico, primarily Veracruz. Locally higher amounts may occur. These rains will likely cause flash flooding and mudslides over the next few days.

5-day intensity forecast

INITIAL 06/20 0300Z 40 KT 45 MPH
12H 06/20 1200Z 50 KT 60 MPH...INLAND
24H 06/21 0000Z 30 KT 35 MPH...INLAND
36H 06/21 1200Z 25 KT 30 MPH...INLAND
48H 06/22 0000Z...DISSIPATED

5-day track forecast



Figure 2. My 5-day forecast track for Barry.

NHC storm information

000
WTNT32 KNHC 200238
TCPAT2

BULLETIN
TROPICAL STORM BARRY ADVISORY NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL022013
1000 PM CDT WED JUN 19 2013

...BARRY POISED TO BRING HEAVY RAINS TO SOUTHERN MEXICO...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.6N 95.8W
ABOUT 40 MI...60 KM NE OF VERACRUZ MEXICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 6 MPH...9 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...
* PUNTA EL LAGARTO TO TUXPAN MEXICO

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 BARRY WAS
LOCATED NEAR LATITUDE 19.6 NORTH...LONGITUDE 95.8 WEST. BARRY IS
MOVING TOWARD THE WEST NEAR 6 MPH...9 KM/H. A GENERAL WESTWARD
TRACK WITH A DECREASE IN FORWARD SPEED IS EXPECTED TONIGHT AND
THURSDAY. ON THE FORECAST TRACK...THE CENTER IS FORECAST TO
REACH THE COAST IN THE STATE OF VERACRUZ THURSDAY MORNING.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/H...WITH HIGHER
GUSTS. NO SIGNIFICANT STRENGTHENING IS EXPECTED BEFORE LANDFALL...
AND WEAKENING WILL OCCUR AFTER THE CENTER CROSSES THE COAST ON
THURSDAY.

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

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


HAZARDS AFFECTING LAND
----------------------
RAINFALL...BARRY IS EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS
OF 3 TO 5 INCHES WITH MAXIMUM AMOUNTS OF 10 INCHES ACROSS PORTIONS
OF SOUTHERN MEXICO. THESE RAINS COULD CAUSE LIFE-THREATENING FLASH
FLOODING AND MUD SLIDES...ESPECIALLY IN MOUNTAINOUS AREAS.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH THE COAST
WITHIN THE WARNING AREA OVERNIGHT.


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

$$
FORECASTER BROWN

2013 Atlantic hurricane season Tropical Storm Barry

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Tropical weather analysis - June 18, 2013

By: KoritheMan, 3:21 AM GMT on June 19, 2013

Tropical Depression Two

Tropical Depression Two continues to pose a rainfall threat for Mexico. As of the 11:00 PM advisory from the NHC, the following information was available on the cyclone:

Wind: 30 mph, with higher gusts
Location: 18.9°N 92.7°W
Movement: WNW at 12 mph
Pressure: 1007 mb

Some bands of deep convection are redeveloping over the Bay of Campeche to the north of the center, which suggests the system is still hanging on from a convective standpoint. There have been no recent scatterometer passes over the circulation, but a blend of surface observations, satellite imagery, and radar data suggests the circulation is over water near Ciudad del Carmen; however, there is a lot of uncertainty in this estimate given the broad nature of the circulation.



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

There is excellent agreement amongst the dynamical models as to where the depression will track throughout the remainder of its existence, which should be about two to three days. The current narrow mid-level trough over the northern Gulf Coast is in the process of lifting out as per 0z soundings, with backing noted above 500 mb. There is still some southwesterly flow below that level, but extrapolation of current trends on water vapor imagery suggest that this temporal weakness should quickly fill. In the meantime, there appears to be enough of a weakness in the Gulf of Mexico ridge to keep the cyclone moving with at least a semblance of a northerly component, but a more solid and definite westward turn is forecast over the next 12-24 hours as the ridge to the north of the tropical cyclone strengthens.

While the global models suggest a slowing of the forward speed prior to landfall, this seems a little unrealistic to me given current trends, and it is not immediately clear what would cause such a change. My forecast is thus a little faster than the model consensus. After landfall, the cyclone is forecast to slow down as it gets stuck over the Sierra Madre mountain range.

There is the potential for the system to become a tropical storm prior to landfall, although the upper flow over the Bay of Campeche is one that consists of at least modest southwesterly shear, which may inhibit significant intensification. Then again, the normally enhancing effect of the mountains in this area is generally unappreciated, so there's always that little bit.

Regardless of whether or not the cyclone strengthens, the primary concern is heavy rainfall and flash flooding, particularly over areas of elevated/mountainous terrain.

5-day intensity forecast

INITIAL 06/19 0300Z 25 KT 30 MPH...OVER WATER
12 hour 06/19 1200Z 30 KT 35 MPH
24 hour 06/20 0000Z 35 KT 40 MPH...APPROACHING THE COAST
36 hour 06/20 1200Z 25 KT 30 MPH...INLAND
48 hour 06/21 0000Z 20 KT 25 MPH...INLAND
72 hour 06/22 0000Z...DISSIPATED

5-day track forecast



Figure 2. My 5-day forecast track for Tropical Depression Two.

NHC storm information

000
WTNT32 KNHC 190248
TCPAT2

BULLETIN
TROPICAL DEPRESSION TWO ADVISORY NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL AL022013
1000 PM CDT TUE JUN 18 2013

...TROPICAL DEPRESSION MOVES OVER THE SOUTHERN BAY OF
CAMPECHE...
...TROPICAL STORM WATCH ISSUED FOR A PORTION OF SOUTHERN MEXICO...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...18.9N 92.7W
ABOUT 60 MI...100 KM WNW OF CIUDAD DEL CARMEN MEXICO
ABOUT 120 MI...195 KM ENE OF COATZACOALCOS MEXICO
MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES


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

THE GOVERNMENT OF MEXICO HAS ISSUED A TROPICAL STORM WATCH FROM
PUNTA EL LAGARTO WESTWARD TO BARRA DE NAUTLA.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* PUNTA EL LAGARTO TO BARRA DE NAUTLA MEXICO

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE WITHIN 24 TO 36 HOURS.

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 DEPRESSION TWO
WAS LOCATED NEAR LATITUDE 18.9 NORTH...LONGITUDE 92.7 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST-NORTHWEST NEAR 12 MPH...19
KM/H. A TURN TOWARD THE WEST AND A DECREASE IN FORWARD SPEED ARE
EXPECTED DURING THE NEXT 24 HOURS. ON THE FORECAST TRACK...THE
CENTER OF THE DEPRESSION WILL MOVE OVER THE SOUTHERN BAY OF
CAMPECHE TONIGHT AND WEDNESDAY AND REACH THE COAST IN THE
STATE OF VERACRUZ WEDNESDAY NIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 30 MPH...45 KM/H...WITH HIGHER
GUSTS. SOME SLIGHT STRENGTHENING IS POSSIBLE DURING THE NEXT DAY
OR SO...AND THE DEPRESSION COULD BE NEAR TROPICAL STORM STRENGTH
WHEN IT APPROACHES THE COAST OF MEXICO.

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


HAZARDS AFFECTING LAND
----------------------
RAINFALL...THE DEPRESSION IS EXPECTED TO PRODUCE TOTAL RAINFALL
ACCUMULATIONS OF 3 TO 5 INCHES WITH MAXIMUM AMOUNTS OF 10 INCHES
ACROSS PORTIONS OF GUATEMALA...THE YUCATAN PENINSULA AND SOUTHERN
MEXICO. THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODING AND
MUDSLIDES...ESPECIALLY IN MOUNTAINOUS AREAS.

WIND...TROPICAL STORM FORCE WINDS ARE POSSIBLE IN THE WATCH AREA
BY LATE WEDNESDAY.

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

$$
FORECASTER BROWN

2013 Atlantic hurricane season Tropical Depression Two

Permalink

Tropical weather analysis - June 7, 2013

By: KoritheMan, 7:42 AM GMT on June 07, 2013

Andrea

Tropical Storm Andrea made landfall in the Florida Big Bend region just south of Steinhatchee early Thursday evening. At the time of landfall, Andrea was a 55 kt tropical storm. It has since weakened as it's moved overland, and the following information was available on the tropical cyclone on the latest NHC intermediate advisory:

Wind: 45 mph, with higher gusts
Location: 31.3°N 81.7°W
Movement: NE at 19 mph
Pressure: 996 mb

Satellite and radar data suggest that Andrea looks rather sickly, at least from the standpoint of a tropical cyclone. There is little convection near the center, with all of the associated precipitation in bands well to the north and east of the center due to a highly baroclinic environment characterized by dry air coming off the Gulf of Mexico, southwesterly shear of about 30 kt, and slight cold air advection as denoted by AMSU temperature data and 0z cyclone phase diagrams from FSU, with a notable elongation and deterioration of Andrea's warm core, particularly above 500 mb. Even the low-level warm core appears to be increasingly shallow, and the majority of the analyzed global model forecasts on the cyclone phase diagram page show Andrea more closely straddling the line of a cold core low; the cyclone also appears to be getting collocated beneath a developing upper low as per water vapor imagery. Although this low was not particularly evident in 0z upper air soundings over the southeastern United States, it must be noted that those observations were taken several hours ago, before the upper low had gained appreciable definition in water vapor imagery. With this in mind, it is likely that Andrea will become post-tropical within the next 6-12 hours, if it has not already done so.



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

There have been no reports of tropical storm force winds on land, and very few over the western Atlantic. However, NOAA buoy 41008, located just offshore the Georgia coast about 30 miles east of Andrea recently reported a sustained wind of 35 kt gusting to 46 kt, so Andrea hangs on as a tropical storm for now. Any tropical storm force winds will likely continue to be confined to offshore waters in strong convective bands feeding off the warm Atlantic waters.

Although the models suggest there will be baroclinic forcing over Andrea and its post-tropical remnants for the next five days, I anticipate a short-term decrease in the winds as dry air further erodes the inner core convection (and I use that term rather loosely) and Andrea adapts to its new environment. Beyond that time, I expect a very gradual increase in strength as Andrea races across the north Atlantic and interacts with the core of the mid-latitude westerlies. It should be noted that timing intensification episodes with tropical cyclones in baroclinic environments is rather difficult, and subject to large errors.

Regardless of the technical status of the system, heavy rainfall and possible flooding is expected as Andrea or its extratropical remnants slide up the United States east coast, particularly to the left of the center, as is typical with extratropical lows. The tornado threat appears marginal at best, with upper air data showing very little in the way of veering winds with height. Nevertheless, as Andrea permeates inland and low-level shear increases, the tornado threat should correspondingly increase over the Carolinas and portions of the mid-Atlantic as well. It is possible that if enough cold air is generated into the cyclone circulation after extratropical transition, the tornado threat could be marginalized due to a stable airmass.

Storm surge flooding should be minimal since most areas along the path are experiencing offshore flow.

The track forecast is very straightforward, and Andrea is forecast to continue accelerating northeastward, then turn eastward near the Canadian Maritimes as it orbits around the south side of a large extratropical low over the north Atlantic. A slowing of the forward speed and a turn to the northwest is expected at day five as post-tropical Andrea begins to interact more strongly with the extratropical low.

5-day intensity forecast

Initial 06/07 0600Z 40 KT 45 MPH...INLAND
12 hour 06/07 1800Z 35 KT 40 MPH...POST-TROPICAL/EXTRATROPICAL
24 hour 06/08 0600Z 40 KT 45 MPH...POST-TROPICAL/EXTRATROPICAL
36 hour 06/08 1800Z 40 KT 45 MPH...POST-TROPICAL/EXTRATROPICAL
48 hour 06/09 1800Z 40 KT 45 MPH...POST-TROPICAL/EXTRATROPICAL
72 hour 06/10 1800Z 40 KT 45 MPH...POST-TROPICAL/EXTRATROPICAL
96 hour 06/11 1800Z 40 KT 45 MPH...POST-TROPICAL/EXTRATROPICAL
120 hour 06/12 18000Z 45 KT 50 MPH...POST-TROPICAL/EXTRATROPICAL

5-day track forecast



Figure 2. My 5-day forecast track for Andrea.

NHC storm information
000
WTNT31 KNHC 070539
TCPAT1

BULLETIN
TROPICAL STORM ANDREA INTERMEDIATE ADVISORY NUMBER 6A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL012013
200 AM EDT FRI JUN 07 2013

...ANDREA MOVING NORTHEASTWARD A LITTLE FASTER...

SUMMARY OF 200 AM EDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...31.3N 81.7W
ABOUT 65 MI...100 KM SSW OF SAVANNAH GEORGIA
ABOUT 145 MI...235 KM SW OF CHARLESTON SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NE OR 45 DEGREES AT 19 MPH...31 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...
* FLAGLER BEACH FLORIDA TO CAPE CHARLES LIGHT VIRGINIA
* PAMLICO AND ALBEMARLE SOUNDS
* LOWER CHESAPEAKE BAY SOUTH OF NEW POINT COMFORT

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 200 AM EDT...0600 UTC...THE CENTER OF TROPICAL STORM ANDREA WAS
LOCATED NEAR LATITUDE 31.3 NORTH...LONGITUDE 81.7 WEST. ANDREA HAS
INCREASED ITS FORWARD SPEED AND IS NOW MOVING TOWARD THE NORTHEAST
NEAR 19 MPH...31 KM/H. THIS GENERAL MOTION IS EXPECTED TO CONTINUE
FOR THE NEXT COUPLE OF DAYS WITH AN ADDITIONAL INCREASE IN FORWARD
SPEED. ON THE FORECAST TRACK...THE CENTER OF ANDREA WILL CONTINUE
TO MOVE OVER SOUTHEAST GEORGIA THIS MORNING AND THEN MOVE NEAR THE
EAST COAST OF THE UNITED STATES THROUGH SATURDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/H...WITH HIGHER
GUSTS. THESE WINDS ARE CONFINED TO RAINBANDS PRIMARILY OVER WATER
TO THE EAST OF THE CENTER. LITTLE CHANGE IN STRENGTH IS FORECAST
DURING THE NEXT 48 HOURS...AND ANDREA IS EXPECTED TO LOSE TROPICAL
CHARACTERISTICS LATER TODAY.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140 MILES...220
KM...MAINLY OVER WATER TO THE EAST OF THE CENTER.

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

HAZARDS AFFECTING LAND
----------------------
RAINFALL...ANDREA IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS OF
3 TO 6 INCHES OVER EASTERN GEORGIA...EASTERN SOUTH CAROLINA AND
EASTERN NORTH CAROLINA...WITH ISOLATED MAXIMUM AMOUNTS AROUND 8
INCHES POSSIBLE. TOTAL RAIN ACCUMULATIONS OF 2 TO 4 INCHES ARE ALSO
EXPECTED ALONG THE EASTERN SEABOARD FROM EASTERN VIRGINIA TO
EASTERN MAINE. ADDITIONAL RAIN TOTALS OF 1 TO 3 INCHES ARE EXPECTED
IN OUTER BANDS OVER THE SOUTHERN FLORIDA PENINSULA AND THE FLORIDA
KEYS.

STORM SURGE...THE COMBINATION OF STORM SURGE AND THE TIDE WILL CAUSE
NORMALLY DRY AREAS NEAR THE COAST TO BE FLOODED BY RISING WATERS.
THE WATER COULD REACH THE FOLLOWING HEIGHTS ABOVE GROUND IF THE
PEAK SURGE OCCURS AT THE TIME OF HIGH TIDE...

FLAGLER BEACH NORTH TO CAPE CHARLES LIGHT...1 TO 2 FT

THE DEEPEST WATER WILL OCCUR ALONG THE IMMEDIATE COAST. SURGE-
RELATED FLOODING DEPENDS ON THE RELATIVE TIMING OF THE SURGE AND
THE TIDAL CYCLE...AND CAN VARY GREATLY OVER SHORT DISTANCES. FOR
INFORMATION SPECIFIC TO YOUR AREA...PLEASE SEE PRODUCTS ISSUED BY
YOUR LOCAL NATIONAL WEATHER SERVICE OFFICE.

WIND...TROPICAL STORM CONDITIONS WILL GRADUALLY SPREAD NORTHEASTWARD
IN THE WARNING AREA ALONG THE U.S. EAST COAST DURING THE NEXT 24
HOURS.

TORNADOES...A COUPLE OF TORNADOES ARE POSSIBLE OVERNIGHT OVER
COASTAL PORTIONS OF GEORGIA...SOUTH CAROLINA...AND NORTH CAROLINA.
A FEW TORNADOES ARE POSSIBLE ON FRIDAY FROM EASTERN SOUTH CAROLINA
NORTHWARD TO COASTAL VIRGINIA.

NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 AM EDT.

$$
FORECASTER AVILA



Invest 92L

A vigorous tropical wave over the central Atlantic several hundred miles east of the Lesser Antilles has been displaying some rather persistent convection over the last two days, and scatterometer passes throughout those days suggested that the wave possessed a well-defined surface circulation and tropical storm force winds in squalls. The wave has since become disorganized as it encounters a belt of climatological westerly winds on the south side of the Tropical Upper Tropospheric Trough (TUTT) over the Greater Antilles.



Figure 3. Latest infrared satellite image of Invest 92L. Image credit: NOAA's Satellite Services Division (SSD).

These winds are expected to prohibit any development, although based on the tenacity of the wave, it is possible the southern portion may attempt to slide westward, cross Central America, and develop into Tropical Storm Cosme in the east Pacific in the next 7 - 10 days. None of the models currently show this, it's just kind of an educated guess based on my personal experiences as a five year weather forecaster, and also experience writing personal Tropical Cyclone Reports (TCRs).

It should be noted that it is highly unusual to have tropical waves possessing such vigorous convection and low-level wind circulations in June, and these events are normally precursors to an extremely active Atlantic hurricane season, perhaps a signal that the MDR is more conducive than normal to tropical cyclogenesis in those years. The most recent example of this was a strong tropical wave that nearly became a tropical cyclone east of the Lesser Antilles in June of 2010. Although this wave did not develop, the 2010 season went on to produce 19 named storms, 12 hurricanes, and 5 major hurricanes. Other examples include 2003, 1995, 1989, and 1979.

I feel that even though 92L did not develop, it came close enough that it meets the above criterion. Barring an unlikely El Nino, 2013 will likely go down in history as another very active Atlantic hurricane season.

2013 Atlantic hurricane season Tropical Storm Andrea Invest 92L

Updated: 7:52 AM GMT on June 07, 2013

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Tropical weather analysis - June 6, 2013

By: KoritheMan, 5:30 AM GMT on June 06, 2013

Andrea

Tropical Storm Andrea formed in the east-central Gulf of Mexico today from what was previously Invest 91L. As of the latest NHC advisory, pending the upcoming intermediate update, the following information was available on the cyclone:

Wind: 40 mph, with higher gusts
Location: 26.0°N 86.3°W
Movement: N at 6 mph
Pressure: 1002 mb

Andrea is a typical early June tropical cyclone, with much of the associated weather to the east and northeast of the center due to continued vertical shear. Since the center is still in its formative stages, the movement of the cyclone is a little difficult to determine even with a slew of microwave fixes available to me, but my best estimate is that Andrea is beginning to turn to the right, although I am uneasy about calling it a full on northeastward movement just yet.

A burst of deep convection has recently developed close to the low-level center, although the center itself still remains displaced to the southwest edge of the convective cloud shield due to about 25 kt of southwesterly vertical wind shear induced by an amplifying shortwave trough over the Ohio Valley. While the shear could decrease a little (indeed, the transition from a uniform westerly flow to a more dominant southwesterly upper-level wind regime over the last 24 hours probably contributed to the organization episode we saw on Tuesday) before Andrea makes landfall, dry air is still a major inhibiting factor, and Andrea will not possess the classically organized appearance found in tropical cyclones later in the season.



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

Based on a strong consensus amongst the dynamical models, landfall is anticipated along the Florida Big Bend region in the vicinity of Cedar Key Thursday evening, although it could occur a little sooner or later depending on the exact arrival of the aforementioned trough. Also, perhaps needless to say, where the center makes landfall will be of little consequence in this particular case, because again, Andrea is not well-organized, is battling shear, and thus has most of the associated weather well-removed to the east and northeast of the low-level center.

Little significant change in strength is forecast prior to landfall, although a little strengthening is forecast out of respect for the convective burst. It is possible Andrea could get a little stronger than forecast due to enhanced baroclinic forcing from the approaching trough, a situation which has helped tropical cyclones intensify in the past (Michael in 2000 and Charley in 2004 to name two).

In about 36-48 hours, the global models show the cyclone vortex approaching an area of even greater baroclinic influence as it comes closer to the axis of the upper trough; thus, extratropical transition is forecast in about 48 hours, although it could occur a little sooner. Thereafter, Andrea is forecast to orbit along the south side of an extratropical low over the north Atlantic, and I presume there will be enough baroclinic forcing to keep Andrea a non-tropical gale center throughout the forecast period subsequent to extratropical transition.

It should be accentuated that the primary threat associated with Andrea remains the potential for heavy rains and flash flooding, and I expect an additional 3 to 6 inches of rain with localized amounts of 10 inches across much of the Florida peninsula and Florida Keys over the next several days. Doppler radar data already shows a large area of offshore precipitation slowly edging ashore, although relatively dry air over the Gulf of Mexico may initially inhibit these rains from reaching their full potential.

There is also the threat for isolated tornadoes over the Florida peninsula through the next 24-36 hours, although environmental conditions do not favor a substantial tornado outbreak. However, there have been a couple of tornado warnings and relatively impressive radar signatures associated with rotating thunderstorms within rainbands associated with Andrea's outer circulation across the Miami area over the last couple of hours. Any tornadoes triggered by the cyclone are likely to be weak and short-lived.

Storm surge flooding can also be anticipated in areas of onshore flow, with about 2 to 4 feet expected across the Big Bend region, with 1 to 2 feet south of Tampa.


5-day intensity forecast

Initial 0300Z 06/06 35 KT 40 MPH
12 hour 1200Z 06/06 35 KT 40 MPH
24 hour 0000Z 06/07 40 KT 45 MPH...INLAND
36 hour 1200Z 06/07 40 KT 45 MPH...OVER WATER
48 hour 0000Z 06/08 40 KT 45 MPH...POST-TROPICAL/EXTRATROPICAL
72 hour 0000Z 06/09 35 KT 40 MPH...POST-TROPICAL/EXTRATROPICAL
96 hour 0000Z 06/10 35 KT 40 MPH...POST-TROPICAL/EXTRATROPICAL
120 hour 0000Z 06/11 35 KT 40 MPH...POST-TROPICAL/EXTRATROPICAL

5-day track forecast



Figure 2. My 5-day track forecast for Andrea.

NHC storm information

000
WTNT31 KNHC 060234
TCPAT1

BULLETIN
TROPICAL STORM ANDREA ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL012013
1000 PM CDT WED JUN 05 2013

...HEAVY RAIN OCCURRING ALONG THE WEST COAST OF FLORIDA AS ANDREA
MOVES NORTHWARD...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...26.0N 86.3W
ABOUT 270 MI...430 KM WSW OF TAMPA FLORIDA
ABOUT 270 MI...430 KM SSW OF APALACHICOLA FLORIDA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...N OR 10 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 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 WEST COAST OF FLORIDA FROM BOCA GRANDE TO OCHLOCKNEE RIVER

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* FLAGLER BEACH FLORIDA TO SURF CITY NORTH CAROLINA

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

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1000 PM CDT...0300 UTC...THE CENTER OF TROPICAL STORM ANDREA WAS
LOCATED NEAR LATITUDE 26.0 NORTH...LONGITUDE 86.3 WEST. ANDREA IS
MOVING TOWARD THE NORTH NEAR 6 MPH...9 KM/H. A TURN TOWARD THE
NORTHEAST AND AN INCREASE IN FORWARD SPEED ARE EXPECTED OVERNIGHT
AND THURSDAY...FOLLOWED BY A FURTHER INCREASE IN FORWARD SPEED
THURSDAY NIGHT AND FRIDAY. ON THE FORECAST TRACK...THE CENTER OF
ANDREA WILL REACH THE COAST OF THE FLORIDA BIG BEND AREA THURSDAY
EVENING AND THEN MOVE FROM SOUTHEASTERN GEORGIA ACROSS SOUTHEASTERN
SOUTH CAROLINA AND EASTERN NORTH CAROLINA THURSDAY NIGHT AND
FRIDAY.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 40 MPH...65 KM/H...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 48
HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140 MILES...220 KM
FROM THE CENTER. NOAA BUOY 42003 RECENTLY REPORTED A WIND GUST OF 42
MPH...68 KM/H.

THE ESTIMATED MINIMUM CENTRAL PRESSURE...BASED ON DATA FROM NOAA
BUOY 42003...IS 1002 MB...29.59 INCHES.


HAZARDS AFFECTING LAND
----------------------
STORM SURGE...THE COMBINATION OF A STORM SURGE AND THE TIDE WILL
CAUSE NORMALLY DRY AREAS NEAR THE COAST TO BE FLOODED BY RISING
WATERS. THE WATER COULD REACH THE FOLLOWING HEIGHTS ABOVE GROUND
IF THE PEAK SURGE OCCURS AT THE TIME OF HIGH TIDE...

TAMPA BAY NORTHWARD TO APALACHICOLA...2 TO 4 FT
FLORIDA WEST COAST SOUTH OF TAMPA BAY...1 TO 2 FT

THE DEEPEST WATER WILL OCCUR ALONG THE IMMEDIATE COAST NEAR AND TO
THE SOUTH OF THE LANDFALL LOCATION. SURGE-RELATED FLOODING DEPENDS
ON THE RELATIVE TIMING OF THE SURGE AND THE TIDAL CYCLE...AND CAN
VARY GREATLY OVER SHORT DISTANCES. FOR INFORMATION SPECIFIC TO
YOUR AREA...PLEASE SEE PRODUCTS ISSUED BY YOUR LOCAL NATIONAL
WEATHER SERVICE OFFICE.

RAINFALL...ANDREA IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS OF
3 TO 6 INCHES OVER MUCH OF THE FLORIDA PENINSULA...EASTERN PARTS OF
THE FLORIDA PANHANDLE...AND SOUTHEASTERN GEORGIA...WITH ISOLATED
MAXIMUM AMOUNTS OF 8 INCHES POSSIBLE. TOTAL RAIN ACCUMULATIONS OF
2 TO 4 INCHES ARE ALSO EXPECTED OVER EASTERN SOUTH CAROLINA AND
EASTERN NORTH CAROLINA.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO FIRST REACH THE
COAST WITHIN THE WARNING AREA BY THURSDAY AFTERNOON...MAKING OUTSIDE
PREPARATIONS DIFFICULT OR DANGEROUS. TROPICAL STORM CONDITIONS ARE
POSSIBLE IN THE WATCH AREA THURSDAY NIGHT AND FRIDAY.

TORNADOES...A FEW TORNADOES ARE POSSIBLE OVER THE FLORIDA PENINSULA
TONIGHT THROUGH THURSDAY...WITH THE GREATEST POTENTIAL EXPECTED ON
THURSDAY.


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

$$
FORECASTER BRENNAN

2013 Atlantic hurricane season Tropical Storm Andrea

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Tropical weather analysis - June 5, 2013

By: KoritheMan, 6:15 AM GMT on June 05, 2013

Invest 91L

A weak area of low pressure over the central Gulf of Mexico continues to produce widespread disorganized showers and thunderstorms to the east of the low.

Convection continues to wax and wane, with a current burst going off about two degrees east of the estimated center location. However, CIMSS analyses diagnoses about 25 kt of westerly shear over the disturbance, which in combination with a very subsident airmass over the western Gulf of Mexico (as denoted on water vapor imagery) is preventing the convection from becoming persistent or organized. Bands of heavy showers and embedded thunderstorms continue to train over western and central Cuba, the Florida Keys, and portions of south Florida in the deep southerly flow of tropical moisture associated with the eastern periphery of this tenacious circulation. These showers are being enhanced primarily by diffluent flow associated with a departing shortwave trough over the western Atlantic.



Figure 1. Latest infrared satellite image of Invest 91L. Image credit: NOAA's Satellite Services Division (SSD).

The global models have come into better agreement on the shear relaxing -- at least a little -- in the next 24 hours, which, if true, could allow the system to gain some organization as it approaches the west coast of Florida. So far, however, the shear has been slow to decrease, although there is some evidence that the strongest westerly flow has been gradually shifting northward over the last day or so. The environment never looks particularly anticyclonic in the models, though, even for the normally aggressive GFS.

At the moment, the low-level circulation still looks broad and very ill-defined, with only one report of a northwest wind, which came from the ship PHQW located about 100 miles off the northwestern coast of the Yucatan Peninsula. However, surface pressures remain relatively low in the area, and some tropical or subtropical development is still possible if the shear relaxes. Even if it does so, relative humidity values in the Gulf of Mexico are rather low as noted above, and this extremely dry airmass will continue to be a problem for Invest 91L even if the shear relaxes. The low is currently embedded in a highly confluent environment, and water vapor imagery has even suggested the formation of a weak upper low near the vortex at times.

If the ongoing burst of convection near the center can persist long enough to moisten the surrounding environment and potentially wrap around some portions of the center, we may see an increased probability of development Wednesday morning. However, this burst could just as easily die off given the hostile environment over the Gulf of Mexico, and I would like to see some persistence before going crazy, particularly considering the time of night (diurnal convective maximum).

The steering pattern remains weak, with the system situated between a mid-level ridge over northwestern Mexico and a building ridge over the southeastern United States (denoted by 0z upper air data, water vapor imagery, and CIMSS steering layer analyses), which is allowing for only a slight northward component of motion. Actually, the orientation of the ridge appears such that the low actually seems to be moving west of north, closer to northwest at this hour, although that is admittedly hard to gauge with such a disorganized circulation envelope. It is worth noting that the lower-tropospheric flow pattern in the global model forecast fields appears to go in line with this, and it is possible that we will see a trend more toward the northwest -- or at least west of north -- over the next 24-36 hours before the arrival of a secondary trough into the Ohio Valley, which is the one the models forecast will recurve the system toward peninsular Florida.

My forecast reasoning has not changed over the last two days, and I still anticipate 91L making landfall along the Big Bend region near Cedar Key. Even assuming the current westward motion is not illusory, I still don't see this system getting much farther west than Tallahasee at landfall. After landfall, which is forecast to occur sometime on Friday, the global models suggest rapid acceleration and extratropical transition as the system moves over or just off the United States east coast.

Regardless of development, locally heavy rains and associated flooding will continue over portions of western and central Cuba, the Florida Keys, and southern and central Florida over the next several days. These rains could gradually spread northward and affect the northern Florida peninsula and perhaps the Big Bend region as well.

Probability of development in 48 hours: 40%

2013 Atlantic hurricane season

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Tropical weather analysis - June 4, 2013

By: KoritheMan, 5:35 AM GMT on June 04, 2013

Invest 91L

A large area of disturbed weather extending from the southern Gulf of Mexico into the Florida Straits continues in association with Invest 91L. While areal surface observations indicate that the circulation associated with this system is better defined than yesterday, it is still broad and poorly-defined. The biggest change since yesterday is that the cyclonic envelope encompassing the system appears to have shrunk a little, and I am not being greeted by multiple low-level swirls. Any associated convection remains well east of the center due to persistent westerly shear.



Figure 1. Latest infrared satellite of Invest 91L. Image credit: NOAA's Satellite Services Division (SSD).

Besides the shear, dry air continued to be a problem, with a rather large area of subsidence noted over the Gulf of Mexico on water vapor imagery; in fact, one can even see the stable airmass with satellite imagery, which doesn't always happen. The combination of the shear and subsidence has delayed the intensification process, with no convection over the low-level center. Until this happens, any strengthening of the low will be very gradual, and it is entirely possible that this low never becomes a tropical or subtropical cyclone.

The models continue to want to relax the upper flow over the Gulf, but it never really becomes meridional (south to north), which is what we would want to see for a northward-moving system in a strong shear environment. There are also some notable discrepancies between the models with both the forward motion of the low, and the timing of the upper-level shear; the GFS builds a narrow anticyclone over the disturbance in about 36-48 hours; the CMC suggests a more favorable upper pattern, with a tighter anticyclone persisting until the system reaches the coast; finally, the NAVGEM shows an environment that is more diffluent than anticyclonic, and is a little slower with how fast the shear is going to relax. While a blend of these solutions is preferable, I tend to side with the NAVGEM with a less anticyclonic environment given current trends and model forecasts of shortwave troughing over the Ohio Valley on Thursday, which could keep a little bit of shear over the disturbance.

The models still haven't latched onto a well-defined center as evidenced by multiple swirls seen in their respective 850 mb vorticity fields, but the synoptic pattern portrayed by those models supports a turn toward the western coast of Florida; I favor the Cedar Key area at the moment, although where this system ultimately makes landfall is irrelevant, since it will be a rather lopsided system, with most of the associated weather to the east of the center due to westerly shear. The timing of landfall is still uncertain, but right now I would favor Friday afternoon.

It should perhaps be noted that there appears to be enough low-level ridging over the western Atlantic that this system could move a little more west before the anticipated northeastward turn begins; this is supported by current satellite trends, which show what I suspect to be the center moving just a little west of due north. At this time, areas west of Tallahassee getting directly impacted appear minimal, unless you count subsident flow on the back side of the system.

Regardless of development, locally heavy rains and possible flooding are expected to continue over portions of western Cuba, the Florida Keys, and south Florida over the next several days, particularly in bands of rain enhanced by strongly diffluent flow aloft, which is, at the moment, how the system is keeping its convection. This system is likely to be a prodigious rain-producer for peninsular Florida, with as much as 3 to 6 inches possible through the weekend.

Probability of development in 48 hours: 30%

2013 Atlantic hurricane season Invest 91L

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Tropical weather analysis - June 3, 2013

By: KoritheMan, 7:09 AM GMT on June 03, 2013

Invest 91L

An area of disorganized showers and thunderstorms over the northwestern Caribbean Sea, southern Gulf of Mexico, and the Florida Straits is associated with a poorly-defined surface trough. The National Hurricane Center made the decision to designate this system as "Invest 91L" yesterday (Sunday).

Animation of shortwave infrared satellite imagery, which typically works well with identifying cyclonic cloud swirls at night, reveals a broad and highly disorganized system. I can work out two swirls; the most prominent one is not far from the coast of northeastern Yucatan, and another is closer to Cozumel, which appears to be a more transient feature. Surface observations show no important wind shifts giving any indication of a developing surface low in this area, nor are there any indications of falling pressures. Hence, whatever rotation is identified on satellite imagery is entirely mid-level, and it is likely that the system will continue to consist of multiple mid-level cloud swirls as new centers attempt to form underneath any persistent bursts of convection.



Figure 1. Latest infrared satellite image of Invest 91L. Image credit: NOAA's Satellite Services Division (SSD).

Wind shear analyses -- per the University of Wisconsin CIMSS laboratory -- show about 30 kt of shear over the disturbance, which could be considered consistent with high cloud motion vectors on water vapor imagery (and even standard satellite imagery). The global models have somewhat differing solutions on how the shear pattern is going to evolve as the system moves into the Gulf of Mexico in the next few days, but they all agree that the environment never becomes particularly favorable for any significant tropical development. In addition, water vapor imagery shows an abundance of mid-level dry air over the Gulf of Mexico, which will also tend to discourage development with time. Nevertheless, there is enough suggestion in the global model shear fields to make me believe that the environment over the Gulf could become favorable enough for at least some very slow development. I would give 91L a 40% chance of eventually becoming a tropical cyclone sometime in the next five days. It is not uncommon for early June disturbances to struggle and sometimes never develop into tropical cyclones at all.

As for track, the global models are in excellent agreement, surprisingly so for a system lacking a well-defined surface center. They predict a gentle path toward western Florida, with landfall in about four or five days. There is some nonzero potential for 91L to come more west and impacts areas of the central Gulf Coast, as the models show the trough over the eastern United States lifting out in the next day or so, giving way to mid-level ridging across the southeastern United States. There would be a narrow 36-48 hour opportunity for the system to drift westward before getting pulled northeast by a stronger shortwave trough forecast to move into the upper midwest late Wednesday into Thursday. Of note, I should admonish that any such chance of a more westward motion is highly unlikely, and also strongly conditional; all of the global model vorticity fields show more ridging below 500 mb, concentrated more at the 850-700 mb level. In other words a stronger system in this scenario would have a hard time getting very far to the west, since the trough is deeper at 500 mb and above. One thing supporting the potential for a westward turn is that the system is forecast to remain highly elongated and sheared due to model predictions of strong westerly shear over the Gulf.

I do not want to mislead anyone; the synoptic strongly favors Florida, and I would place the odds of the central Gulf Coast impacted by this in any meaningful fashion at about 10%.

In the meantime, this system is expected to drift slowly northward.

Regardless of development, locally heavy rainfall will occur over portions of western Cuba during the next couple of days, which could lead to local flooding.

Probability of development in 48 hours: 20%

2013 Atlantic hurricane season Invest 91L

Updated: 7:15 AM GMT on June 03, 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.