CSU and TSR continue to predict a near-average hurricane season

By: Dr. Jeff Masters , 3:18 PM GMT on August 04, 2009

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A tropical disturbance embedded in the Intertropical Convergence Zone (ITCZ), near 9N 35W, is moving west at about 15 mph. The heavy thunderstorm activity associated with this tropical wave has changed little over the past 24 hours, and remains disorganized. This morning's QuikSCAT pass showed a moderate wind shift, but nothing resembling an organized surface circulation. Top winds were in the 20 - 30 mph range. Strong easterly winds are creating about 20 knots of wind shear over the wave, which is marginally conducive for development. The disturbance is about 300 miles south of the Saharan Air Layer (SAL), so dust and dry air should not hinder development over the next few days.

Given the disturbance's current lack of organization, combined with the presence of 20 knots of wind shear, any development should be slow to occur. The forecast wind shear along the storm's path over the next five days is predicted to remain at or below 20 knots, which should allow some slow development. Sea surface temperatures (SSTs) will warm from about 28°C to 29°C as the storm progresses westward. The GFS model has been indicating some development is possible in several of its runs over the past few days, but has not been consistent with this prediction. None of the other models show any development of the system. NHC is giving the disturbance a low (less than 30% chance) of developing into a tropical depression over the next two days, which is a good forecast. The GFS and ECMWF models predict the system will be approaching the northern Lesser Antilles Islands by Sunday. Both models forecast the development of a band of very high wind shear just to the north of the islands at that time, so the long-range survival of anything that might manage to develop is in doubt.

CSU forecast team continues to predict an average hurricane season
A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued August 4 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 10 named storms, 4 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 83% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 15 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step down from their June forecast, which called for 11 named storms, 5 hurricanes, and 2 intense hurricanes. Their April forecast called for 12 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (27% chance, 31% chance is average) and the Gulf Coast (26% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane (37%; 42% is average).

The forecasters noted that while sea surface temperature anomalies have increased in the tropical Atlantic and surface pressures have fallen in recent weeks, which normally would favor higher hurricane activity, the presence of El Niño conditions in the Eastern Pacific should counteract these influences. They forecast that the current weak El Niño event will strengthen to a moderate event by September:

El Niño events tend to be associated with increased levels of vertical wind shear and decreased levels of Atlantic hurricane activity. Tropical Atlantic sea surface temperatures anomalies have warmed somewhat since our early June prediction and surface pressures have fallen somewhat. But, the negative influences of El Niño-induced strong Caribbean Basin and Main Development Region vertical wind shear typically dominate over surface pressure and sea surface temperature in the tropical Atlantic.



Figure 1. Change in Sea Surface Temperature anomaly (in °C) between July 2009 and May 2009. Most of the tropical Atlantic has warmed, relative to normal, over the past 2 months. Image credit: NOAA/ESRL.

Analogue years
The CSU team picked four previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: weak to moderate El Niño conditions, and average tropical Atlantic and far northern Atlantic SSTs. Those four years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 1965, which had Category 3 Betsy that hit New Orleans; 1963, which had Category 4 Hurricane Flora that devastated Cuba; and 1957, which didn't have any hurricanes that hit hit land during the peak part of hurricane season. The mean activity for these four years was 9 named storms, 4 hurricanes, and 2 intense hurricanes--almost the same as the 2009 CSU forecast.

How accurate are the August forecasts?
The August forecasts by the CSU team have historically offered a skill of 45 -62% higher than a "no-skill" forecast using climatology (Figure 2). However, they are using a new forecast scheme this year, so it is difficult to judge how skillful this year's forecast might be.


Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed at Colorado State University (CSU) by Dr. Bill Gray's team (colored squares) and Tropical Storm Risk, Inc. (TSR, colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

August 2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) also issued a new forecast today, and have increased their numbers by 20% from their June and July forecasts. TSR is also calling for a near-average season, predicting 12.6 named storms, 6.5 hurricanes, 2.8 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 103% of average. Their June forecast called for 10.9 named storms, 5.2 hurricanes, 2.2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 72% of average. The storm numbers are slightly above the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TSR predicts a 40% chance of an above-average season, 44% chance of a near-average season, and a 19% chance of a below-average season, as defined by ACE index. TSR rates their skill level as 51% above chance at forecasting the number of named storms, 60% skill for hurricanes, and 44% skill for intense hurricanes. These are far higher skill numbers than the June ones: 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.

TSR projects that 3.8 named storms will hit the U.S., with 1.6 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these August forecasts for U.S. landfalls is 25% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.1 named storms, 0.5 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites one main factor for their increased forecast: higher sea surface temperatures than expected over the tropical Atlantic, due to the fact that the trade winds over the Atlantic should be slower than originally anticipated. Faster than average trade winds create less spin for developing storms, and allow the oceans to cool down, due to increased mixing of cold water from the depths and enhanced evaporational cooling.

The CSU and TSR groups are done making forecasts for the coming hurricane season, but NOAA is still due to put out an August update.

I'll have an update on Wednesday.
Jeff Masters

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1322. IKE
Quoting futuremet:


Not for long bud...



We'll see what happens.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
post 1319.
The 'weal' you are seeing is the result of a beating-up from adverse conditions.
It's called "storm abuse".
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Quoting IKE:


If we make it through August with a favorable MJO coming....with 0-0-0, I'll be shocked.




Props. It has shown nothing substantial all season. When it starts showing healthy looking systems, I'll bite.


I was looking at the CIMSS shear map. There is no way any blob can make it through....the Caribbean or north of about 20N, from 70W on east. Up to 50 knots of westerly shear.

The GOM looks favorable with low shear. Mostly dry though.


Not for long bud...

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i might be wrong and stand to be corrected.
iam seeing a small cyclonic turning near 11N 34 W. Looking at the QS of the area this morning it appears there might be a weak surface refletion
Member Since: August 22, 2006 Posts: 0 Comments: 2600
1318. IKE
Quoting CycloneOz:
Question: What if we get through August without a named storm? Will September get an auto-downcast or a ramp up forecast based on a 0,0,0 August?


If we make it through August with a favorable MJO coming....with 0-0-0, I'll be shocked.


Quoting Tropicsweatherpr:
I am with Ike about ECMWF being the #1 model in 2009.


Props. It has shown nothing substantial all season. When it starts showing healthy looking systems, I'll bite.


I was looking at the CIMSS shear map. There is no way any blob can make it through....the Caribbean or north of about 20N, from 70W on east. Up to 50 knots of westerly shear.

The GOM looks favorable with low shear. Mostly dry though.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Good Morning.
At 11n 61w, it is overcast, and very still. The sea is totally flat.
Typical August weather.
But no weather to speak of, in the entire Atlantic? Thats strange. Good. But strange.
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Question: The deeper we go into August, how likely is it that we'll get a sneaky stealth Cat V storm like '92s Andrew as the first named storm of the season?
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I am with Ike about ECMWF being the #1 model in 2009.
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"INVEST" is not a quantifiable stage of development...it's a subjective designation which allows forecasters to engage certain tools...
Member Since: August 13, 2007 Posts: 0 Comments: 10479
{{POOF}}

Still there is strong 850mb turning according to CIMMS @ 11N30W which will be entering an area of lower wind shear in the next 24hrs.

IKE's favorite CMC & GFS do something with this area and the NoGaps & UKMET are hinting at the possibility of something in the area as well. I would assume this area would be 90L since it is a different entity than 99L. What else is there to watch?
Question: What if we get through August without a named storm? Will September get an auto-downcast or a ramp up forecast based on a 0,0,0 August?
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FELICIA would be a Major soon.
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1308. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT WED AUG 5 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER BLAKE

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Alot of models out here

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting IKE:


Just keep watching the ECMWF throughout the season.


You have a point there. But remember the ECMWF developed this feature at 3 points. But the otherwise the model is doing well.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1305. WxLogic
Well... as expected... it was able gain some convection from DMAX. It's also higher in LAT (As it has assisted the ITCZ on going moving up to), unfortunately not enough energy associated with it at Mid levels to help it develop like 2 days ago.

Even though it does not have the backing anymore of NHC for development. I'll give it a 15% chance of at least reaching INVEST before it encounters some hostile environment that won't be strong enough to fend off.
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Quoting HadesGodWyvern:
Japan Meteorological Agency
Tropical Cyclone Warning #15
TROPICAL STORM GONI (T0907)
15:00 PM JST August 5 2009, Tropical Storm Goni (992 hPa) located at 21.9N 112.2E has 10 minute sustained winds of 35 knots with gusts of 50 knots. The storm is reported as almost stationary

RMSC Dvorak Intensity: T2.5

Gale-force Winds
================
120 NM from the center

Forecast and Intensity
=========================
24 HRS: 21.7N 111.5E - Tropical Depression

---
heh pressure is falling again.. cyclone center is still near the coast


Thankfully it swept wide right and Macau and western Guangdong got the worst of it. A fair bit of moderate rain and wind last night locally and another rain band just moved in.

Wondering if Goni will start to get sucked back east in to the draft of Morakot and we'll get a second shot of Goni. (and frankly I'm glad I'm not in the path of Morakot)
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Well, well, well.

The wave that came off of Africa a few days ago, the one that "looked great and had the best chance for development so far this season"...has gone "POOF."

It's is August 5th, and still we sit at 0,0,0.

Models are not developing anything, and it could be many more days to pass before something does.

This could be a great moment in time for another poem! :)

Have a GREAT 0,0,0 day...it's AUGUST 2009! :)
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1302. IKE
Quoting futuremet:


Well, for this run...


Just keep watching the ECMWF throughout the season.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1301. IKE
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SAN JUAN PR
417 AM AST WED AUG 5 2009

.SYNOPSIS...A TUTT WITH AXIS ACROSS THE MONA PASSAGE IS TO EVOLVE
INTO A CLOSED LOW OVER HISPANIOLA BY THU. MEANWHILE...TROPICAL
WAVE ALONG 55W TO MOVE ACROSS THE ISLANDS ON THU. STRONG
SUBTROPICAL RIDGE TO BUILD SW INTO THE ERN CARIBBEAN FOR THE
WEEKEND.

&&

.DISCUSSION...LOCAL AREA WILL BE ON THE EAST SIDE OF TUTT AXIS
THIS AFTERNOON WHICH TYPICALLY IS A FAVORABLE PLACE OF CONVECTION.
HOWEVER...MOISTURE REMAINS MODEST AT BEST WITH PWAT VALUES AROUND
1.65 INCHES. WHILE THERE WILL STILL BE CONVECTION ON THE WEST THIS
AFTERNOON WIDESPREAD EXCESSIVE AMTS ARE NOT EXPECTED.

TROPICAL WAVE ALONG 55W IS FCST TO CROSS THE AREA ON THU. ALTHOUGH
NO DEEP CONVECTIVE ACTIVITY IS ASSOCIATED WITH THIS WAVE AT THE MOMENT
WAVE IS LIKELY TO GET MORE ACTIVE AS IT APPROACHES PR/USVI AS IT
BEGINS TO INTERACT WITH EAST SIDE OF TUTT LOW FCST TO EVOLVE
ACROSS HISPANIOLA. ALTHOUGH AN INCREASE IN CONVECTIVE CONVERAGE IS
ANTICIPATED WITH THIS WAVE VERTICAL SHEAR WILL REMAIN TOO STRONG
ACROSS THE ERN CARIBBEAN PROHIBITIVE OF TC FORMATION.

BEHIND THE WAVE A WIND SURGE WILL FOLLOW WITH HAZE AND DUST
LIKELY FOR THE WEEKEND. STRONG MID-UPPER LVL RIDGING WILL BUILD ACROSS
THE ERN CARIBBEAN FOR FRI AND SAT LIKELY PUTTING A LID ON
CONVECTION. WAS TEMPTED TO LOWER POPS FOR FRI AND SAT AS AIR MASS
LOOKS BONE DRY.
IN ANY CASE...EXCELLENT BEACH WX EXPECTED FOR THE
WEEKEND.

REST OF THE TROPICAL ATLC REMAINS QUIET WITH NO THREAT AREAS TO
DISCUSS.


Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Weather456:


yea, the GFS has her moving over the islands as a TD, possibly a a weak TS.


I think a minimal cane or a strong TS will impact Hawaii. The models strengthen it each run.
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Tropical wave in the CATL has finally left the ITCZ. Let us see what it does today.
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Quoting WPBHurricane05:


But, Felicia might threaten Hawaii next week.



yea, the GFS has her moving over the islands as a TD, possibly a a weak TS.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting IKE:


The only model that shows anything before Aug. 15th is the CMC. Shows a TS heading west in the EATL.

I said no named-storm through Aug. 15th. Until the ECMWF shows something, I'm not believing it.




0-0-0.


Well, for this run...
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Quoting Elena85Vet:
Hey, who took the yellow circle?


The NHC giveth and taketh away.
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1295. WxLogic
Morning...
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If the 2010 hurricane season is active, I bet you some folkes here will forget the pessimistic attitude they had in 2009.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
1293. MahFL
The blob is alive....also further north, out of the ITZ ?
It could develop better now.
Someone call Mayor Nagan !
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Quoting leftovers:
why care about the epac no one but fish will ever care. i sure aint waisting my computer space downloading stuff. our atlantic itz low is gone but looks like the energy is transfering to a spot that might be more favorable


But, Felicia might threaten Hawaii next week.

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1291. IKE
Quoting futuremet:



lol Ike

I hope you right. August 15th is a little too aggressive.

I am going for August 10-12


The only model that shows anything before Aug. 15th is the CMC. Shows a TS heading west in the EATL.

I said no named-storm through Aug. 15th. Until the ECMWF shows something, I'm not believing it.


Quoting WeatherStudent:


Yup, that'll probably come from Ike, first thing tomorrow morning, you'll see.


0-0-0.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Hey, who took the yellow circle?
Member Since: August 18, 2008 Posts: 0 Comments: 628

Good morning 456

Felicia looks impressive

GFS model gives still hurrican CAT very near to Hawai coast.

Other models as TS

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Quoting IKE:


And I got raked over the coals by someone over my comment.

I see the yellow circle is gone.

I guess the wishcasters can now head back into hiding until the real season starts.

GFS...wrong.
CMC...wrong.



lol Ike

I hope you right. August 15th is a little too aggressive.

I am going for August 10-12
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1287. IKE
00Z ECMWF shows plenty of action in the east-PAC and continues to show nothing significant in the Atlantic through August 15th.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1286. Patrap
Dont wanna be an American Invest
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morning
The area of interest associated with a tropical wave in the eastern atlantic, has lost most of the convection .the trough/tropical wave is now reduced to an area of mid cyclonic turning near 9N 37W. the wave is moving west at 15 MPH. although the area is devoid of any significant convection, it has been able to mentain it's structure. the wave /trough is under 5-10 knots of vertical wind shear and warm SST near 29 deg C. although the wave still has potential to develop, it will be difficult because of the dry air to the west and north of the system which might preclude any form of organisation. this wave could be the precursor of things to come,and may have paved the way for the two strong waves. one is at 5 deg W and the other over central africa.this could be the period that the GFS has been predicting for increase cyclogenesis. it is also the time frame when the MJO is forecast for an upward pulse in the atlantic. we just have to wait. one should still keep an eye on the CATL wave since it still has a mid level structure and in in the tropics things can change so quickly.
Member Since: August 22, 2006 Posts: 0 Comments: 2600
Quoting clwstmchasr:
Just checked out the topics for the first time since yesterday morning. I was expecting to see an invest and instead our AOI is gone. I can't believe that the first week of August is almost gone and still not a single storm.


Yea, it does. But where you fall, you get up dust off yourself and keep going. Ana will will eventually come, most likely with the next MJO. Also the season is not a dud or the seasonal forecasts would of gone down alot more. They know something most of us know here.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Good Morning all!

Normal Season Still Expected; Hurricane Felicia; Tropical Update
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1282. IKE
Quoting IKE:


I'm not seeing much spin anymore.


And I got raked over the coals by someone over my comment.

I see the yellow circle is gone.

I guess the wishcasters can now head back into hiding until the real season starts.

GFS...wrong.
CMC...wrong.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting CybrTeddy:


I lol'ed at the 'government seeding' to dissipate tropical cyclones conspiracy someone put here. Got a hoot out of that.


1244: Why did you laugh, agreed not applicable to this year, its SAL and shear that are affecting waves right now, but seeding did occur in the 70's, does work but affects subsequent years rain patterns.
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24 HRS: 15.1N 131.2W - 105 knots (SSHS-3 Cyclone)

impressive 120mph 200km/h
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1277. HadesGodWyvern (Mod)
National Hurricane Center
Tropical Cyclone Advisory #7
SEVERE TROPICAL CYCLONE FELICIA (EP082009)
9:00 AM UTC August 5 2009
====================================

At 6:00 AM UTC, Hurricane Felicia (970 hPa) located at 13.4N 128.2W or 1190 NM west-southwest of of the southern tip of Baja California Peninsula has sustained winds of 90 knots with gusts of 105 knots. The cyclone is reported as moving west-northwest at 10 knots.

Hurricane-force Winds
====================
30 NM from the center

Gale/Storm-force Winds
===============
75 NM from the center

Forecast and Intensity
======================
12 HRS: 14.1N 129.5W - 100 knots (SSHS-3 Cyclone)
24 HRS: 15.1N 131.2W - 105 knots (SSHS-3 Cyclone)
48 HRS: 17.1N 134.6W - 90 knots (SSHS-2 Cyclone)
72 HRS: 18.5N 139.0W - 75 knots (SSHS-1 Cyclone)
Member Since: May 24, 2006 Posts: 50 Comments: 44731





Felicia has now a clear eye.
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1275. HadesGodWyvern (Mod)
METEO FRANCE
Eastern Atlantic
High Sea Forecast

Tropical wave along 24/26W and south of 17N moving westward at 10
kts.

Surface trough along 30/31W from 5N to 16N, moving slowly westward.

Heat low 1008 in west of Mauritania along 20N.

ITCZ along 12N 16W 13N 24W 08N 32W 10N 50W.
Member Since: May 24, 2006 Posts: 50 Comments: 44731
Quoting casadunlap:
Hurricane FELICIA is shown to reach CAT 3 but then slow to a tropical storm by the weekend when it approaches Hawaii. What would cause the storm to decrease? It seems there would be ample energy/warm water to feed Felicia.


Vertical shear.
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1273. HadesGodWyvern (Mod)
Joint Typhoon Warning Center

Tropical Cyclone Warning #7
==============================
At 6:00 AM UTC, Tropical Storm NINE (MORAKOT) located at 22.8N 132.2E or 325 NM southeast of Okinawa (Japan) has sustained winds of 55 knots with gusts of 70 knots. The cyclone is reported as moving west at 10 knots.

Significant wave height associated with 09W is 19 feet

---
now who is being conservative with how strong a cyclone is.
Member Since: May 24, 2006 Posts: 50 Comments: 44731
Hurricane FELICIA is shown to reach CAT 3 but then slow to a tropical storm by the weekend when it approaches Hawaii. What would cause the storm to decrease? It seems there would be ample energy/warm water to feed Felicia.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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